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Last Updated :2024/08/25

研究者情報

マスター

アカウント（マスター）

  • 氏名

    平野　高司(ヒラノ　タカシ), ヒラノ　タカシ

所属（マスター）

  • 農学研究院　基盤研究部門　生物環境工学分野

所属（マスター）

  • 農学研究院　基盤研究部門　生物環境工学分野

独自項目

syllabus

  • 2021, 地域環境学特論Ⅰ, Advanced Regional Environment I, 修士課程, 農学院, 水土資源利用・保全、大気の循環、エネルギー収支、物質循環、農業生態系
  • 2021, 温暖化影響学総論, Mitigation of Global Warming Effect, 修士課程, 農学院, 炭素循環、窒素循環、陸域生態系、森林、農地、湿地、泥炭地、永久凍土、土壌、植物、微生物、大気、二酸化炭素、亜酸化窒素、メタン、オゾン、施肥、収穫、耕うん、焼畑、植林、再植林、森林改変、森林火災、環境撹乱、熱帯、温帯、北方、水循環、水資源、バイオマスエネルギー、バイオマス製品、環境ガバナンス
  • 2021, 環境と人間, Environment and People, 学士課程, 全学教育, 湿地、泥炭地、湿原生態系、植物、動物、水生生物、タンチョウ、イトウ、保全と再生、水文、土壌、気象、津波、火山噴火、自然災害、水質、農業、土地利用、地球温暖化、熱帯泥炭
  • 2021, 環境化学, Environmental Chemistry, 学士課程, 農学部, 大気・河川・湖沼・海洋・地下水・土壌の汚染、人工公害物質、ミスト、バイオレメディエーション、バイオマス廃棄物の資源化・循環、ＬＣＡ、植物ストレス
  • 2021, 環境と人間, Environment and People, 学士課程, 全学教育, 土壌、水、大気、自然エネルギー、地域、物質循環、Information and communication technology (ICT) と農業生産、作物生産技術、持続的食料生産、農産物の収穫後技術と品質
  • 2021, 情報解析学, Information Analysis, 学士課程, 農学部, 統計学，誤差，相関，確率，分布，検定，推定，分散分析，単回帰分析，多変量解析，重回帰分析，クラスター分析，主成分分析，ベイズ推定
  • 2021, 農業気象学, Agricultural Meteorology, 学士課程, 農学部, 気象学，局地気気候，微気象学，気象災害，作物生産，気候変動

researchmap

プロフィール情報

学位

  • 博士（農学）（1992年 大阪府立大学）

プロフィール情報

  • 姓

    平野, ヒラノ

  • 名

    高司, タカシ

  • ID各種

    200901029666712699

対象リソース

業績リスト

研究キーワード

  • 森林生態系   森林火災   温室効果気体   CO2収支   土地利用変化   蒸発散   エネルギー収支   熱帯泥炭   渦相関法   土壌呼吸   フラックス観測   北方泥炭   微気象学   農業気象学   環境撹乱   

研究分野

  • 環境・農学 / 農業環境工学、農業情報工学
  • 自然科学一般 / 大気水圏科学
  • 環境・農学 / 環境農学
  • 環境・農学 / 環境影響評価
  • 環境・農学 / 環境動態解析

経歴

  • 2006年05月 - 現在 北海道大学 大学院農学院 教授
  • 2001年04月 - 現在 国立環境研究所 客員研究員
  • 2020年04月 - 2024年03月 独立行政法人日本学術振興会 学術システム研究センター 専門研究員
  • 1998年04月 - 2006年04月 北海道大学 大学院農学院 准教授
  • 1995年04月 - 1998年03月 大阪府立大学 農学部 助教授
  • 1993年04月 - 1995年03月 大阪府立大学 農学部 講師
  • 1988年04月 - 1993年03月 大阪府立大学 農学部 助手
  • 1986年04月 - 1988年03月 一般財団法人日本気象協会 技師

学歴

  • 1984年04月 - 1986年03月   北海道大学   大学院農学研究科   農業工学専攻
  • 1981年10月 - 1984年03月   北海道大学   農学部   農業工学科
  • 1980年04月 - 1981年09月   北海道大学   理Ⅰ系

委員歴

  • 2023年10月 - 現在   科学技術振興機構   創発的研究支援事業 アドバイザー
  • 2023年10月 - 現在   日本学術会議   連携会員
  • 2020年08月 - 現在   北海道立総合研究機構   研究評価委員会常任委員
  • 2015年 - 現在   日本学術会議iLEAPS小委員会   委員
  • 2011年 - 現在   日本生物環境工学会   理事   日本生物環境工学会
  • 2008年 - 現在   Agricultural and Forest Meteorology   編集委員
  • 2024年01月 - 2026年12月   マレーシア政府パーム油庁   研究諮問委員会
  • 2024年01月 - 2025年12月   マレーシア政府パーム油庁   Journal of Oil Palm Research 編集委員
  • 2021年09月 - 2023年09月   日本学術会議   特任連携会員
  • 2021年01月 - 2023年03月   日本農業工学会   理事
  • 2019年03月 - 2023年03月   日本農業気象学会   会長
  • 2018年01月 - 2021年12月   マレーシア政府パーム油庁   国際諮問委員会
  • 2018年01月 - 2021年03月   AsiaFlux   副委員長
  • 2014年10月 - 2020年09月   日本学術会議   連携会員
  • 2017年01月 - 2019年12月   マレーシア政府パーム油庁   研究諮問委員会
  • 2017年03月 - 2019年03月   日本農業気象学会   副会長
  • 2006年 - 2017年12月   JapanFlux   委員長   JapanFlux
  • 2002年 - 2017年12月   AsiaFlux   運営委員
  • 2013年03月 - 2017年03月   Journal of Agricultural Meteorology   編集委員長
  • 2012年 - 2016年03月   Journal of Forest Research   編集委員
  • 2010年01月 - 2012年12月   日本農業気象学会   北海道支部支部長   日本農業気象学会
  • 2007年03月 - 2011年03月   日本農業気象学会   総務理事   日本農業気象学会
  • 2009年 - 2010年   日本生物環境工学会   評議員   日本生物環境工学会
  • 2002年03月 - 2006年03月   日本農業気象学会   編集理事
  • 2001年 - 2006年   日本熱帯生態学会   編集委員   日本熱帯生態学会

受賞

  • 2016年06月 尾瀬財団 尾瀬賞
     熱帯泥炭生態系の炭素動態に関するフィールド研究 
    受賞者: 平野 高司
  • 2010年03月 日本農業気象学会 学術賞
     長期フラックス観測に基づく森林生態系の炭素収支に関する研究
  • 1992年07月 日本農業気象学会 奨励賞
     植物葉の光合成への粉じんの影響に関する研究

論文

  • Kanokrat Buareal, Tomomichi Kato, Tomoki Morozumi, Naohisa Nakashima, Kitpanuwat Tanatarakeree, Masahito Ueyama, Takashi Hirano
    Journal of Geophysical Research: Biogeosciences 129 7 2024年07月23日 
    Abstract Wetlands play an essential role in the global greenhouse gas budget via carbon dioxide sequestration as well as methane emission. In recent decades, solar‐induced chlorophyll fluorescence (SIF) has been recognized as a remotely sensed proxy of gross primary productivity (GPP), which generates substrates for methane production. To examine the suitability of SIF for estimation of these two fluxes, we conducted ground tower‐based SIF observation with an ultrafine‐resolution spectroradiometer in conjunction with eddy covariance measurement in a cool‐temperate bog. The daily SIF retrieved in the red (687 nm) and far‐red (760 nm) bands (SIFred and SIFfar‐red, respectively) increased nonlinearly with GPP and linearly with absorbed photosynthetically active radiation (APAR). The relatively weak correlation between apparent SIF yield (ΦSIF = SIF/APAR) and light use efficiency implied that both APAR and plant physiology constrained the SIF emission in this wetland. The SIFred/SIFfar‐red ratio showed a significant negative relationship with vegetation greenness indices, and the similar seasonal variation in SIFred and SIFfar‐red indicated that the SIFred reabsorption effect only weakly influenced the SIFred–GPP relationship. Episodic temporal reduction in the water table did not distinctly influence SIF and ΦSIF. Estimation of the methane emission rate was subtly improved by incorporating SIF, which was substituted for GPP as the methanogenesis substrate, in a multivariable regression analysis together with two environmental factors: soil temperature and water table depth. This study illustrates the potential of both SIFred and SIFfar‐red to monitor GPP and to predict methane emission in wetlands.
  • Nikaan Koupaei‐Abyazani, Iuliia Burdun, Ankur R. Desai, Kristell Hergoualc'h, Takashi Hirano, Lulie Melling, Erin Swails, Angela Che Ing Tang, Guan Xhuan Wong
    Journal of Geophysical Research: Biogeosciences 129 6 2024年06月18日 [査読有り]
     
    Abstract Tropical peatlands store copious amounts of carbon (C) and play a critical role in the global C cycle. However, this C store is vulnerable to natural and anthropogenic disturbances, leading these ecosystems to become weaker C sinks or even net C sources. Variabilities in water table (WT) greatly influence the magnitude of greenhouse gas flux in these biomes. Despite its importance in C cycling, observations of the spatiotemporal dynamics of tropical peatland WT are limited in spatial extent and length. Here, we use in situ WT measurements from tropical peatlands in Indonesia, Malaysia, and Peru to evaluate the satellite‐based Optical Trapezoid Model (OPTRAM). The model uses the pixel distribution in the shortwave infrared transformed reflectance and normalized difference vegetation index (NDVI) space to calculate indices that are then compared against in situ WT data. 30‐m resolution Landsat 7 and Landsat 8 images were utilized for model parameterization. We found OPTRAM to best capture tropical peatland WT dynamics in minimally forested and non‐forested areas (low to intermediate NDVI) (0.7 < R < 1) using the “best pixel” approach (the pixel with the highest Pearson‐R correlation value). In areas with relatively higher NDVI, OPTRAM index did not correlate with WT (average R of −0.04 to 0.24), likely due to trees being less sensitive to WT fluctuations. OPTRAM shows potential for reliably estimating tropical peatland WT without the need for direct measurements, which is challenging due to site remoteness and harsh conditions.
  • Takashi Hirano, Shinjiro Ohkubo, Masayuki Itoh, Hayato Tsuzuki, Ayaka Sakabe, Hidenori Takahashi, Kitso Kusin, Mitsuru Osaki
    Communications Earth & Environment 5 1 1 - 9 2024年04月25日 [査読有り][通常論文]
     
    Abstract The huge carbon stock of tropical peat swamp forest (PSF) in Southeast Asia has been threatened by environmental disturbances due to quasi-periodic El Niño-Southern Oscillation (ENSO) droughts, biomass and peat burning, smoke haze, drainage, and deforestation. Carbon dioxide (CO2) emissions from such disturbances have not been well quantified because of insufficient field data. Therefore, we quantified the ecosystem-scale CO2 balance and examine the disturbance effects from a long-term field experiment for 12–15 years at three PSF sites with different degrees of degradation in Indonesia. Here, we show a drastic change of an undrained PSF from a CO2 sink to a source owing to the transient groundwater lowering by the droughts, a significant decrease in ecosystem photosynthesis due to the radiation attenuation by smoke haze in drought years, and long-lasting CO2 emissions through enhanced peat decomposition by drainage. The impact on CO2 emissions was greater from drainage than drought-induced disturbances.
  • Gavin McNicol, Etienne Fluet‐Chouinard, Zutao Ouyang, Sara Knox, Zhen Zhang, Tuula Aalto, Sheel Bansal, Kuang‐Yu Chang, Min Chen, Kyle Delwiche, Sarah Feron, Mathias Goeckede, Jinxun Liu, Avni Malhotra, Joe R. Melton, William Riley, Rodrigo Vargas, Kunxiaojia Yuan, Qing Ying, Qing Zhu, Pavel Alekseychik, Mika Aurela, David P. Billesbach, David I. Campbell, Jiquan Chen, Housen Chu, Ankur R. Desai, Eugenie Euskirchen, Jordan Goodrich, Timothy Griffis, Manuel Helbig, Takashi Hirano, Hiroki Iwata, Gerald Jurasinski, John King, Franziska Koebsch, Randall Kolka, Ken Krauss, Annalea Lohila, Ivan Mammarella, Mats Nilson, Asko Noormets, Walter Oechel, Matthias Peichl, Torsten Sachs, Ayaka Sakabe, Christopher Schulze, Oliver Sonnentag, Ryan C. Sullivan, Eeva‐Stiina Tuittila, Masahito Ueyama, Timo Vesala, Eric Ward, Christian Wille, Guan Xhuan Wong, Donatella Zona, Lisamarie Windham‐Myers, Benjamin Poulter, Robert B. Jackson
    AGU Advances 4 5 1 - 24 2023年09月06日 [査読有り][通常論文]
     
    Abstract Wetlands are responsible for 20%–31% of global methane (CH4) emissions and account for a large source of uncertainty in the global CH4 budget. Data‐driven upscaling of CH4 fluxes from eddy covariance measurements can provide new and independent bottom‐up estimates of wetland CH4 emissions. Here, we develop a six‐predictor random forest upscaling model (UpCH4), trained on 119 site‐years of eddy covariance CH4 flux data from 43 freshwater wetland sites in the FLUXNET‐CH4 Community Product. Network patterns in site‐level annual means and mean seasonal cycles of CH4 fluxes were reproduced accurately in tundra, boreal, and temperate regions (Nash‐Sutcliffe Efficiency ∼0.52–0.63 and 0.53). UpCH4 estimated annual global wetland CH4 emissions of 146 ± 43 TgCH4 y−1 for 2001–2018 which agrees closely with current bottom‐up land surface models (102–181 TgCH4 y−1) and overlaps with top‐down atmospheric inversion models (155–200 TgCH4 y−1). However, UpCH4 diverged from both types of models in the spatial pattern and seasonal dynamics of tropical wetland emissions. We conclude that upscaling of eddy covariance CH4 fluxes has the potential to produce realistic extra‐tropical wetland CH4 emissions estimates which will improve with more flux data. To reduce uncertainty in upscaled estimates, researchers could prioritize new wetland flux sites along humid‐to‐arid tropical climate gradients, from major rainforest basins (Congo, Amazon, and SE Asia), into monsoon (Bangladesh and India) and savannah regions (African Sahel) and be paired with improved knowledge of wetland extent seasonal dynamics in these regions. The monthly wetland methane products gridded at 0.25° from UpCH4 are available via ORNL DAAC (https://doi.org/10.3334/ORNLDAAC/2253).
  • Rui Hu, Takashi Hirano, Kaho Sakaguchi, Syunpei Yamashita, Rui Cui, Lifei Sun, Naishen Liang
    Soil Biology and Biochemistry 184 109094 - 109094 2023年09月 [査読有り][通常論文]
  • Tomohiro Shiraishi, Ryuichi Hirata, Masato Hayashi, Takashi Hirano
    Scientific Reports 13 1 2023年08月11日 [査読有り][通常論文]
     
    Abstract Borneo has accumulated an abundance of woody carbon in its forests and peat. However, agricultural land conversion accompanied by plantation development, dead wood burning, and peat drying from drainage are major challenges to climate change mitigation. This study aimed to develop a method of estimating carbon dioxide (CO2) emissions from land use change, forest and peat fires, and oxidative peat decomposition, and CO2 uptake from biomass growth across Borneo using remote sensing data from 2001 to 2016. Although CO2 uptake by biomass growth in vast forests has shown a significant increasing trend, an annual net release of 461.10 ± 436.51 (average ± 1 standard deviation) Tg CO2 year−1 was observed. The estimated emissions were predominantly characterized by land use changes from 2001 to 2003, with the highest emissions in 2001. Land use change was evaluated from annual land use maps with an accuracy of 92.0 ± 1.0% (average ± 1 standard deviation). Forest and peat fires contributed higher emissions in 2002, 2006, 2009, 2014, and 2015 compared to other years and were strongly correlated with the Southern Oscillation Indexes. These results suggest that more CO2 may have been released into the atmosphere than previously thought.
  • Shinjiro Ohkubo, Takashi Hirano, Kitso Kusin
    Journal of Hydrology 620 129523 - 129523 2023年05月 [査読有り][通常論文]
  • Chandra S. Deshmukh, Ari P. Susanto, Nardi Nardi, Nurholis Nurholis, Sofyan Kurnianto, Yogi Suardiwerianto, M. Hendrizal, Ade Rhinaldy, Reyzaldi E. Mahfiz, Ankur R. Desai, Susan E. Page, Alexander R. Cobb, Takashi Hirano, Frédéric Guérin, Dominique Serça, Yves T. Prairie, Fahmuddin Agus, Dwi Astiani, Supiandi Sabiham, Chris D. Evans
    Nature 616 7958 740 - 746 2023年04月05日 [査読有り][通常論文]
     
    Abstract Tropical peatlands cycle and store large amounts of carbon in their soil and biomass1–5. Climate and land-use change alters greenhouse gas (GHG) fluxes of tropical peatlands, but the magnitude of these changes remains highly uncertain6–19. Here we measure net ecosystem exchanges of carbon dioxide, methane and soil nitrous oxide fluxes between October 2016 and May 2022 from Acacia crassicarpa plantation, degraded forest and intact forest within the same peat landscape, representing land-cover-change trajectories in Sumatra, Indonesia. This allows us to present a full plantation rotation GHG flux balance in a fibre wood plantation on peatland. We find that the Acacia plantation has lower GHG emissions than the degraded site with a similar average groundwater level (GWL), despite more intensive land use. The GHG emissions from the Acacia plantation over a full plantation rotation (35.2 ± 4.7 tCO2-eq ha−1 year−1, average ± standard deviation) were around two times higher than those from the intact forest (20.3 ± 3.7 tCO2-eq ha−1 year−1), but only half of the current Intergovernmental Panel on Climate Change (IPCC) Tier 1 emission factor (EF)20 for this land use. Our results can help to reduce the uncertainty in GHG emissions estimates, provide an estimate of the impact of land-use change on tropical peat and develop science-based peatland management practices as nature-based climate solutions.
  • Albertus Sulaiman, Mitsuru Osaki, Hidenori Takahashi, Manabu D. Yamanaka, Raden Dwi Susanto, Sawahiko Shimada, Keiji Kimura, Takashi Hirano, Rahmawati Ihsani Wetadewi, Silsigia Sisva, Tsuyoshi Kato, Osamu Kozan, Hideyuki Kubo, Awaluddin Awaluddin, Nobuyuki Tsuji
    Scientific Reports 13 1 939  2023年01月18日 [査読有り][通常論文]
     
    Abstract In general, it is known that extreme climatic conditions such as El Niño and positive Indian Ocean Dipole (IOD+) cause prolonged drought in Indonesia's tropical peatlands so that groundwater levels (GWL) drop and peat is prone to fire. However, 27 years of GWL measurements in Central Kalimantan peat forests show the opposite condition, where the lowest GWL occurs several weeks before El Niño and after IOD+ reaches its peaks. We show that the dropped sea surface temperature anomaly induced by anomalously easterly winds along the southern Java-Sumatra occurs several weeks before the GWL drop to the lowest value. Local rainfall decreased, and GWL dropped sharply by 1.0 to 1.5 m, during the super El Niño events in 1997/98 and 2015, as well as remarkable events of IOD+ in 2019. It is suggested that the tropical peatland ecohydrological system (represented by the GWL), El Niño Southern Oscillation (ENSO), and IOD+ are teleconnected. Hence, monitoring GWL variability of peatland over the IMC is a possibility an alert for extreme climate events associated with El Niño and/or moderate IOD+.
  • Masahito Ueyama, Sara H. Knox, Kyle B. Delwiche, Sheel Bansal, William J. Riley, Dennis Baldocchi, Takashi Hirano, Gavin McNicol, Karina Schafer, Lisamarie Windham‐Myers, Benjamin Poulter, Robert B. Jackson, Kuang‐Yu Chang, Jiquen Chen, Housen Chu, Ankur R. Desai, Sébastien Gogo, Hiroki Iwata, Minseok Kang, Ivan Mammarella, Matthias Peichl, Oliver Sonnentag, Eeva‐Stiina Tuittila, Youngryel Ryu, Eugénie S. Euskirchen, Mathias Göckede, Adrien Jacotot, Mats B. Nilsson, Torsten Sachs
    Global Change Biology 2023年01月11日 [査読有り][通常論文]
  • Wakhid N, Hirano T
    Journal of Oil Palm Research 2022年10月19日 [査読有り][通常論文]
  • Takashi Hirano, Guan Xhuan Wong, Joseph Wenceslaus Waili, Kim San Lo, Frankie Kiew, Edward Baran Aeries, Ryuichi Hirata, Kiwamu Ishikura, Masato Hayashi, Shoko Murata, Tomohiro Shiraishi, Masayuki Itoh, Lulie Melling
    Journal of Agricultural Meteorology 78 4 137 - 146 2022年10月10日 [査読有り][通常論文]
  • M. Helbig, T. Živković, P. Alekseychik, M. Aurela, T. S. El-Madany, E. S. Euskirchen, L. B. Flanagan, T. J. Griffis, P. J. Hanson, J. Hattakka, C. Helfter, T. Hirano, E. R. Humphreys, G. Kiely, R. K. Kolka, T. Laurila, P. G. Leahy, A. Lohila, I. Mammarella, M. B. Nilsson, A. Panov, F. J. W. Parmentier, M. Peichl, J. Rinne, D. T. Roman, O. Sonnentag, E.-S Tuittila, M. Ueyama, T. Vesala, P. Vestin, S. Weldon, P. Weslien, S. Zaehle
    Nature Climate Change 12 8 743 - 749 2022年08月 [査読有り][通常論文]
  • Takashi Hirano, Rui Cui, Lifei Sun, Munemasa Teramoto, Naishen Liang
    PLANT AND SOIL 2022年08月 [査読有り][通常論文]
     
    Purpose Fine roots play an essential role in global carbon cycles, but phenological variations in root function and metabolism are poorly understood. To illustrate the dynamics of fine root function and metabolism in the field, we partitioned root respiration (R-r) into growth (R-g), maintenance (R-m), and ion uptake (R-ion) components using a modified traditional model.Methods A year-round experiment was conducted in a young larch-dominated forest regrowing on bare soil. Soil respiration was measured with a chamber method and partitioned into R-r and heterotrophic respiration by trenching. Fine root biomass and production were measured simultaneously. Using the field data, the model was parameterized, and R-r was further partitioned.Results Annually, R-r (210-253 g C m(-2) yr(-1)) accounts for 45-47% of the total soil respiration. The contribution of fine root R-g, fine root R-m, coarse root R-m, and fine root R-ion were 26-40, 46-51, 10-16, and 12%, respectively. The R-g contribution showed a clear seasonal variation, with a peak in mid-spring and a minimum in early fall, mainly because of different seasonality between fine root production and soil temperature.Conclusion The model parameters were consistent with those from our previous study conducted by the same method in the same site. Thus, we believe that our approach was robust under a relatively simple condition. However, our growth respiration parameter resulting from only field data was much higher than those from laboratory experiments. To further improve our understanding of root respiration, more field data should be accumulated.
  • Maria Strack, Scott J. Davidson, Takashi Hirano, Christian Dunn
    Current Climate Change Reports 8 3 71 - 82 2022年06月13日 [査読有り][招待有り]
  • Masahito UEYAMA, Tomotsugu YAZAKI, Takashi HIRANO, Ryosuke ENDO
    Agricultural and Forest Meteorology 316 108852 - 108852 2022年04月 [査読有り]
  • S. Apers, G. J, M. De Lannoy, A. J. Baird, A. R. Cobb, G. C. Dargie, J. Pasquel, A. Gruber, A. Hastie, H. Hidayat, T. Hirano, A. M. Hoyt, A. J. Jovani‐Sancho, A. Katimon, A. Kurnain, R. D. Koster, M. Lampela, S. P. P. Mahanama, L. Melling, S. E. Page, R. H. Reichle, M. Taufik, J. Vanderborght, M. Bechtold
    Journal of Advances in Modeling Earth Systems 14 3 2022年03月 [査読有り]
  • Net primary production of oil palm plantations on tropical peat
    Wakhid N, Hirano T, Dariah A, Agus F
    Mires and Peat 28 2 1 - 12 2022年 [査読有り][通常論文]
  • Yoshikawa K, Takagi K, Yazaki T, Hirano T, Hayakashi S, Ide R, Oguma H, Hirose Y, Kurihara J
    Journal of Agricultural Meteorology 78 4 223 - 261 2021年10月 [査読有り][通常論文]
     
    Liquid crystal tunable filter (LCTF) can change the transmissible wavelength by changing the applied voltage to the filter, which enables the drastic increase in the observable wavelength resolution in a small size system and is considered to be a powerful tool for the spectral earth observation from flying units or microsatellites. However, there is limited knowledge about its season-long application for the vegetation monitoring and the prediction of the ecosystem photosynthetic capacity. We compared the seasonal variation of spectral reflectance obtained by a LCTF camera with that obtained by a popular spectral radiometer in a cool-temperate young larch plantation in northern Hokkaido, Japan. Then we tried to find the best normalized difference spectral index (NDSI) to explain the seasonal variation of the ecosystem photosynthetic capacity using all pairs of two reflectances observed in the range of wavelength between 500 and 770 nm with 10-nm intervals (28 wavelength bands) by the LCTF. The best NDSI among all combinations (28×27) of two reflectances was NDSI[770, 720] for the maximum gross primary production at light saturation and NDSI[530, 600] for the initial slope of the light-response curve, which reflect the red edge shift owing to the change in the chlorophyll content and relative strength of the light absorbance in the visible red wavelength region compared with that in the green wavelength region, respectively. Predicted daily gross primary production of the plantation using these NDSI agreed well with the observed values. NDSI[530, 600] was better to distinguish each vegetation type of the studied plantation.
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  • Cui R, Hirano T, Sun L, Teramoto M, Liang N
    Journal of Agricultural Meteorology 77 3 167 - 178 2021年07月 [査読有り][通常論文]
     
    Root respiration (R-r) plays a crucial role in the global carbon balance, because R-r accounts for about a half of soil respiration in typical forest ecosystems. Plant roots are different in metabolism and functions according to size. Fine roots, which are typically defined as roots < 2 mm in diameter, perform important ecosystem functions and consequently govern belowground carbon cycles mainly because of their high turnover rates. However, the phenological variation of fine root functions is not well understood yet. To quantitatively examine the fine mot functions, we adopted an approach to partition R-r into growth respiration (R-g) and maintenance respiration (R-m) using a modified traditional model, in which R-s was proportional to root production, and R-m was proportional to root biomass and exponentially related to soil temperature. We conducted a field experiment on soil respiration and fine root biomass and production over a year in a larch-dominated young forest developing on the bare ground after removing surface organic soil to parameterize the model. The model was significantly parameterized using the field data measured in such simplified field conditions, because we could control spatial variation in heterotrophic respiration and contamination from roots other than fine roots. The annual R-r of all roots was 94 g C m(-2) yr(-1) and accounted for 25% of total soil respiration on average. The annual R-r was partitioned into fine root R-g , fine root R-m and coarse root R-m by 30,44 and 26%, respectively; coarse root R-g was presumed to be negligible. Fine root R-g and R-m varied according to the seasonal variations of fine root production and soil temperature, respectively; the contribution of fine root biomass was minor because of its small seasonality. The contribution of R-g to total fine root respiration was lower in the cold season with low production.
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  • 平野高司
    地球環境 26 1-2 57 - 68 2021年 [査読有り][招待有り]
  • Ohkubo S, Hirano T, Kusin K
    Journal of Hydrology 603 126906 - 126906 2021年 [査読有り][通常論文]
  • Irvin J, Zhou S, McNicol G, Lu F, Liu V, Fluet-Chouinard E, Ouyang Z, Knox SH, Lucas-Moffat A, Trotta C, Papale D, Vitale D, Mammarella I, Alekseychik P, Aurela M, Avati A, Baldocchi D, Bansal S, Bohrer G, Campbell DI, Chen J, Chu H, Dalmagro HJ, Delwiche KB, Desai AR, Euskirchen E, Feron S, Goeckede M, Heimann M, Helbig M, Helfter C, Hemes KS, Hirano T, Iwata H, Jurasinski G, Kalhori A, Kondrich A, Lai DYF, Lohila A, Malhotra A, Merbold L, Mitra B, Ng A, Nilsson MB, Noormets A, Peichl M, Rey-Sanchez AC, Richardson AD, Runkle BRK, Schafer KVR, Sonnentag O, Stuart-Ha, entjens E, Sturtevant C, Ueyama M, Valach AC, Vargas R, Vourlitis GL, Ward EJ, Wong GX, Zona D, Alberto MCR, Billesbach DP, Celis G, Dolman H, Friborg T, Fuchs K, Gogo S, Gondwe MJ, Goodrich JP, Gottschalk P, Hortnagl L, Jacotot L, Koebsch L, Kasak K, Maier R, Morin TH, Nemitz E, Oechel WC, Oikawa PY, Ono K, Sachs T, Sakabe A, Schuur EA, Shortt R, Sullivan RC, Szutu DJ, Tuittila ES, Varlagin A, Verfaillie JG, Wille C, Windham-Myers L, Poulter B, Jackson RB
    Agricultural and Forest Meteorology 308-309 108528 - 108528 2021年 [査読有り][通常論文]
  • Wakhid N, Hirano T
    Mires and Peat 27 Article 13  2021年 [査読有り][通常論文]
  • Ohkubo S, Hirano T, Kusin K
    Agricultural and Forest Meteorology 306 108448  2021年 [査読有り][通常論文]
     
    Tropical peat swamp forest is a unique ecosystem rich in carbon and water, accumulating a huge amount of carbon as peat. However, the huge carbon pool has been threatened by oxidative peat decomposition and fire loss mainly because of deforestation and drainage. Fire causes acute carbon dioxide (CO2) emissions through the combustion of biomass and peat. Also, fire should change the CO2 balance of postfire ecosystems. Although it is crucial to quantify CO2 balance even after a fire event to understand the total fire impact, information based on field measurement is lacking. Thus, we had measured eddy CO2 flux above a repeatedly burned degraded peat forest for about 13 years since 2004. The site was a stable CO2 source of 147 290 g C m(-2) yr(-1) for five years after a stand-replacing fire in 2002. Unexpectedly, a moderate-severity fire in 2009 changed the site to a CO2 sink of about 600 g C m(-2) yr(-1). The drastic change would have been caused by a large decrease in the decomposition of plant debris, which had accumulated since the 2002 fire but was burned by the 2009 fire. In contrast, gross primary production (GPP) remained about the same even though vegetation was damaged, mainly because year-round wet conditions caused by a La Nina event promoted the regrowth of hygrophilous herbaceous plants and were favorable to their GPP. The site also had a low-severity fire and was drained in 2014 but did not return to a CO2 source. However, the net ecosystem CO2 uptake after the 2009 fire was insufficient to recover a large amount of fire CO2 emission. If CO2 emissions from four fires in 1999, 2002, 2009 and 2014 are counted, the site is expected to owe an outstanding CO2 debt of 25 kg C m(-2).
  • New inventories of global carbon dioxide emissions through 2 biomass burning in 2001–2018
    Tomohiro Shiraishi, Ryuichi Hirata, Takashi Hirano
    Remote Sensing 13 1914  2021年 [査読有り][通常論文]
  • Kyle B. Delwiche, Sara Helen Knox, Avni Malhotra, Etienne Fluet-Chouinard, Gavin McNicol, Sarah Feron, Zutao Ouyang, Dario Papale, Carlo Trotta, Eleonora Canfora, You-Wei Cheah, Danielle Christianson, M. Carmelita, R. Alberto, Pavel Alekseychik, Mika Aurela, Dennis Baldocchi, Sheel Bansal, David P. Billesbach, Gil Bohrer, Rosvel Bracho, Nina Buchmann, David I. Campbell, Gerardo Celis, Jiquan Chen, Weinan Chen, Housen Chu, Higo J. Dalmagro, Sigrid Denge, Ankur R. Desai, Matteo Detto, Han Dolman, Elke Eichelmann, Eugenie Euskirchen, Daniela Famulari, Thomas Friborg, Kathrin Fuchs, Mathias Goeckede, Sébastien Gogo, Mangaliso J. Gondwe, Jordan, P. Goodrich, Pia Gottschalk, Scott L. Graham, Martin Heimann, Manuel Helbig, Carole Helfter, Kyle S. Hemes, Takashi Hirano, David Hollinger, Lukas Hörtnagl, Hiroki Iwata, Adrien Jacotot, Joachim Jansen, Gerald Jurasinski, Minseok Kang, Kuno Kasak, John King, Janina Klatt, Franziska Koebsch, Ken W. Krauss, Derrick Y, F. Lai, Ivan Mammarella, Giovanni Manca, Luca Belelli Marchesini, Jaclyn Hatala Matthes, Trofim Maximon, Lutz Merbold, Bhaskar Mitra, Timothy H. Morin, Eiko Nemitz, Mats B. Nilsson, Shuli Niu, Walter C. Oechel, Patricia Y. Oikawa, Keisuke Ono, Matthias Peichl, Olli Peltola, Michele L. Reba, Andrew D. Richardson, William Riley, Benjamin R, K. Runkle, Youngryel Ryu, Torsten Sachs, Ayaka Sakabe, Camilo Rey Sanchez, Edward A. Schuur, Karina V, R. Schäfer, Oliver Sonnentag, Jed, P. Sparks, Ellen Stuart-Haëntjens, Cove Sturtevant, Ryan C. Sullivan, Daphne J. Szutu, Jonathan E. Thom, Margaret S. Torn, Eeva-Stiina Tuittila, Jessica Turner, Masahito Ueyama, Alex C. Valach, Rodrigo Vargas, Andrej Varlagin, Alma Vazquez-Lule, Joseph G. Verfaillie, Timo Vesala, George L. Vourlitis, Eric J. Ward, Christian Wille, Georg Wohlfahrt, Guan Xhuan Wong, Zhen Zhang, Donatella Zona, Lisamarie Windham-Myers, Benjamin Poulter, Robert B. Jackson
    Earth System Science Data 13 367 - 3689 2021年 [査読有り]
     
    Abstract. Methane (CH4) emissions from natural landscapes constitute roughly half of global CH4 contributions to the atmosphere, yet large uncertainties remain in the absolute magnitude and the seasonality of emission quantities and drivers. Eddy covariance (EC) measurements of CH4 flux are ideal for constraining ecosystem-scale CH4 emissions, including their seasonality, due to quasi-continuous and high temporal resolution of flux measurements, coincident measurements of carbon, water, and energy fluxes, lack of ecosystem disturbance, and increased availability of datasets over the last decade. Here, we 1) describe the newly published dataset, FLUXNET-CH4 Version 1.0, the first global dataset of CH4 EC measurements (available at https://fluxnet.org/data/fluxnet-ch4- community-product/). FLUXNET-CH4 includes half-hourly and daily gap-filled and non gap-filled aggregated CH4 fluxes and meteorological data from 79 sites globally: 42 freshwater wetlands, 6 brackish and saline wetlands, 7 formerly drained ecosystems, 7 rice paddy sites, 2 lakes, and 15 uplands. Then, we 2) evaluate FLUXNET-CH4 representativeness for freshwater wetland coverage globally, because the majority of sites in FLUXNET-CH4 Version 1.0 are freshwater wetlands and because freshwater wetlands are a substantial source of total atmospheric CH4 emissions; and 3) provide the first global estimates of the seasonal variability and seasonality predictors of freshwater wetland CH4 fluxes. Our representativeness analysis suggests that the freshwater wetland sites in the dataset cover global wetland bioclimatic attributes (encompassing energy, moisture, and vegetation-related parameters) in arctic, boreal, and temperate regions, but only sparsely cover humid tropical regions. Seasonality metrics of wetland CH4 emissions vary considerably across latitudinal bands. In freshwater wetlands (except those between 20° S to 20° N) the spring onset of elevated CH4 emissions starts three days earlier, and the CH4 emission season lasts 4 days longer, for each degree C increase in mean annual air temperature. On average, the onset of increasing CH4 emissions lags soil warming by one month, with very few sites experiencing increased CH4 emissions prior to the onset of soil warming. In contrast, roughly half of these sites experience the spring onset of rising CH4 emissions prior to the spring increase in gross primary productivity (GPP). The timing of peak summer CH4 emissions does not correlate with the timing for either peak summer temperature or peak GPP. Our results provide seasonality parameters for CH4 modeling, and highlight seasonality metrics that cannot be predicted by temperature or GPP (i.e., seasonality of CH4 peak). The FLUXNET-CH4 dataset provides an open-access resource for CH4 flux synthesis, has a range of applications, and is unique in that it includes coupled measurements of important CH4 drivers such as GPP and temperature. Although FLUXNET-CH4 could certainly be improved by adding more sites in tropical ecosystems and by increasing the number of site-years at existing sites, it is a powerful new resource for diagnosing and understanding the role of terrestrial ecosystems and climate drivers in the global CH4 cycle. All seasonality parameters are available at https://doi.org/10.5281/zenodo.4408468. Additionally, raw FLUXNET-CH4 data used to extract seasonality parameters can be downloaded from https://fluxnet.org/data/fluxnet-ch4-community-product/, and a complete list of the 79 individual site data DOIs is provided in Table 2 in the Data Availability section of this document.
  • Sara Helen Knox, Sheel Bansal, Gavin McNicol, Karina Schafer, Cove Sturtevant, Masahito Ueyama, Alex C. Valach, Dennis Baldocchi, Kyle Delwiche, Ankur R Desai, Eugenie Euskirchen, Jinxun Liu, Annalea Lohila, Avni Malhotra, Lulie Melling, William Riley, Benjamin R, K. Runkle, Jessica Turner, Rodrigo Vargas, Qing Zhu, Tuula Alto, Etienne Fluet-Chouinard, Mathias Goeckede, Joe R. Melton, Oliver Sonnentag, Timo Vesala, Eric Ward, Zhen Zhang, Sarah Feron, Zutao Ouyang, Pavel Alekseychik, Mika Aurela, Gil Bohrer, David I. Campbell, Jiquan Chen, Housen Chu, Higo J, Dalmagro, Jordan, P. Goodrich, Pia Gottschalk, Takashi Hirano, Hiroki Iwata, Gerald Jurasinski, Minseok Kang, Franziska Koebsch, Ivan Mammarella, Mats B. Nilsson, Keisuke Ono, Matthias Peichl, Olli Peltola, Youngryel Ryu, Torsten Sachs, Ayaka Sakabe, Jed Sparks, Eeva-Stiina Tuittila, George L Vourlitis, Guan Xhuan Wong, Lisamarie Windham-Myers, Ben Poulter, Robert B. Jackson
    Global Change Biology 27 15 3582 - 3604 2021年 [査読有り][通常論文]
  • Substantial hysteresis in emergent temperature sensitivity of global wetland CH4 emissions
    Kuang-Yu Chang, William J. Riley, Sara H. Knox, Robert B. Jackson, Gavin McNicol, Benjamin Poulter, Mika Aurela, Dennis Baldocchi, Sheel Bansal, Gil Bohrer, David I. Campbell, Alessandro Cescatti, Housen Chu, Kyle B. Delwiche, Ankur R. Desai, Eugenie Euskirchen, Thomas Friborg, Mathias Goeckede, Manuel Helbig, Kyle S. Hemes, Takashi Hirano, Hiroki Iwata, Minseok Kang, Trevor Keenan, Ken W. Krauss, Annalea Lohila, Ivan Mammarella, Bhaskar Mitra, Akira Miyata, Mats B. Nilsson, Asko Noormets, Walter C. Oechel, Dario Papale, Matthias Peichl, Michele L. Reba, Janne Rinne, Benjamin R, K. Runkle, Youngryel Ryu, Torsten Sachs, Karina V, R. Schäfer, Hans Peter Schmid, Narasinha Shurpali, Oliver Sonnentag, Angela C. I. Tang, Margaret S. Torn, Carlo Trotta, Eeva-Stiina Tuittila, Masahito Ueyama, Rodrigo Vargas, Timo Vesala, Lisamarie Windham-Myers, Zhen Zhang, Donatella Zona
    Nature Communications 12 2266  2021年 [査読有り][通常論文]
  • Ohkubo S, Hirano T, Kusin K
    Agricultural and Forest Meteorology 301-302 108348  2021年 [査読有り][通常論文]
     
    Tropical peat swamp forests have been experiencing drastic disturbances, such as deforestation, drainage, and fire. We examined how such disturbances influence albedo, which regulates radiative energy exchange between the terrestrial surface and the atmosphere. We conducted continuous field observations at three sites: undrained forest (UF), drained forest (DF), and drained burned ex-forest (DB), in Central Kalimantan, Indonesia, for over 13 years.Observed albedo was strongly influenced by haze caused by fire because the haze layer covering the canopy has a relatively high reflectance. Under severe haze conditions in October 2015, apparent albedo increased to 0.156, 0.162, and 0.183 at the UF, DF, and DB sites respectively. Mean monthly albedos excluding fire periods were 0.094 +/- 0.005, 0.092 +/- 0.006, and 0.099 +/- 0.017 (mean +/- 1 standard deviation) at the UF, DF, and DB sites respectively. Seasonal fluctuation in albedo at the DB site, where ferns were dominant, was greater than at the UF and DF sites.Albedo at the DF site was significantly lower than that at the UF site from February to August (p < 0.05). At the forest sites the albedo increased as groundwater level decreased. Albedo was higher under high vapor pressure deficit at all sites. At the DB site albedo decreased when the soil surface was water-saturated and patched with puddles, potentially due to the low albedo of open water. The albedo at the DB site was lower than that at the forest sites at the beginning of the observation period. Subsequently, the albedo increased and exceeded those at the UF and DF sites immediately after fire damage in 2009. This could be explained by the expansion of bright-colored ferns and sedges over dark-colored peat soil. According to our results, haze, groundwater level, and vegetation cover significantly influence albedo in tropical peat swamp forests.
  • Ueyama, Masahito, Ichii, Kazuhito, Kobayashi, Hideki, Kumagai, Tomo'omi, Beringer, Jason, Merbold, Lutz, Euskirchen, Eugenie S, Hirano, Takashi, {Belelli Marchesini}, Luca, Baldocchi, Dennis, Saitoh, Taku M., Mizoguchi, Yasuko, Ono, Keisuke, Kim, Joon, Varlagin, Andrej, Kang, Minseok, Shimizu, Takanori, Kosugi, Yoshiko, Bret-Harte, Marion Syndonia (Donie), Machimura, Takashi, Matsuura, Yojiro, Ohta, Takeshi, Takagi, Kentaro, Takanashi, Satoru, Yasuda, Yukio
    Environmental Research Letters 15 084009  2020年02月 [査読有り][通常論文]
  • Ben Bond-Lamberty, Danielle S. Christianson, Avni Malhotra, Stephanie C. Pennington, Debjani Sihi, Amir AghaKouchak, Hassan Anjileli, M. Altaf Arain, Juan J. Armesto, Samaneh Ashraf, Mioko Ataka, Dennis Baldocchi, Thomas Andrew Black, Nina Buchmann, Mariah S. Carbone, Shih-Chieh Chang, Patrick Crill, Peter S. Curtis, Eric A. Davidson, Ankur R. Desai, John E. Drake, Tarek S. El-Madany, Michael Gavazzi, Carolyn-Monika Görres, Christopher M. Gough, Michael Goulden, Jillian Gregg, Omar Gutiérrez del Arroyo, Jin-Sheng He, Takashi Hirano, Anya Hopple, Holly Hughes, Järvi Järveoja, Rachhpal Jassal, Jinshi Jian, Haiming Kan, Jason Kaye, Yuji Kominami, Naishen Liang, David Lipson, Catriona A. Macdonald, Kadmiel Maseyk, Kayla Mathes, Marguerite Mauritz, Melanie A. Mayes, Steve McNulty, Guofang Miao, Mirco Migliavacca, Scott Miller, Chelcy F. Miniat, Jennifer G. Nietz, Mats B. Nilsson, Asko Noormets, Hamidreza Norouzi, Christine S. O’Connell, Bruce Osborne, Cecilio Oyonarte, Zhuo Pang, Matthias Peichl, Elise Pendall, Jorge F. Perez-Quezada, Claire L. Phillips, Richard P. Phillips, James W. Raich, Alexandre A. Renchon, Nadine K. Ruehr, Enrique P, Sánchez-Cañete, Matthew Saunders, Kathleen E. Savage, Marion Schrumpf, Russell L. Scott, Ulli Seibt, Whendee L. Silver, Wu Sun, Daphne Szutu, Kentaro Takagi, Masahiro Takagi, Munemasa Teramoto, Mark G. Tjoelker, Susan Trumbore, Masahito Ueyam, Rodrigo Vargas, Ruth K. Varner, Joseph Verfaillie, Christoph Vogel, Jinsong Wang, Greg Winston, Tana E. Wood, Juying Wu, Thomas Wutzler, Jiye Zeng, Tianshan Zha, Quan Zhang, Junliang Zou
    Global Change Biology 26 12 7268 - 7283 2020年 [査読有り][通常論文]
     
    Globally, soils store two to three times as much carbon as currently resides in the atmosphere, and it is critical to understand how soil greenhouse gas (GHG) emissions and uptake will respond to ongoing climate change. In particular, the soil-to-atmosphere CO(2)flux, commonly though imprecisely termed soil respiration (R-S), is one of the largest carbon fluxes in the Earth system. An increasing number of high-frequencyR(S)measurements (typically, from an automated system with hourly sampling) have been made over the last two decades; an increasing number of methane measurements are being made with such systems as well. Such high frequency data are an invaluable resource for understanding GHG fluxes, but lack a central database or repository. Here we describe the lightweight, open-source COSORE (COntinuous SOil REspiration) database and software, that focuses on automated, continuous and long-term GHG flux datasets, and is intended to serve as a community resource for earth sciences, climate change syntheses and model evaluation. Contributed datasets are mapped to a single, consistent standard, with metadata on contributors, geographic location, measurement conditions and ancillary data. The design emphasizes the importance of reproducibility, scientific transparency and open access to data. While being oriented towards continuously measuredR(S), the database design accommodates other soil-atmosphere measurements (e.g. ecosystem respiration, chamber-measured net ecosystem exchange, methane fluxes) as well as experimental treatments (heterotrophic only, etc.). We give brief examples of the types of analyses possible using this new community resource and describe its accompanying R software package.
  • Kiew F, Hirata R, Hirano T, Wong GX, Aries EB, Kemudang K, Wenceslaus J, Lo KS, Melling L
    Agricultural and Forest Meteorology 295 108189  2020年 [査読有り][通常論文]
  • Environmental controls on methane fluxes in a cool temperate bog
    Ueyama M, Yazaki T, Hirano T, Futakuchi Y, Okamura M
    Agricultural and Forest Meteorology 281 107852  2020年 [査読有り][通常論文]
  • Wong G, Hirata R, Hirano T, Kiew F, Aeries E, Musin K, Waili J, Lo K, Melling L
    Agricultural and Forest Meteorology 282-283 107869  2020年 [査読有り][通常論文]
  • Ishikura K, Hirata R, Hirano T, Okimoto Y, Wong GX, Melling L, Aeries EB, Kiew F, Lo KS, Musin KK, Waili JW, Ishii Y
    Ecosystems 22 8 1852 - 1868 2019年12月 [査読有り][通常論文]
  • Sun L, Hirano T, Yazaki T, Teramoto M, Liang N
    Plant and Soil 446 1-2 471 - 486 2019年11月 [査読有り][通常論文]
  • Wu L, Kato T, Sato H, Hirano T, Yazaki T
    Forest Ecology and Management 451 117529 - 117529 2019年11月 [査読有り][通常論文]
  • Masato Hayashi, Takahiro Abe, Takashi Hirano, Ryuichi Hirata, Tomohiro Shiraishi, Lulie Melling
    IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium 2019年07月
  • Surface conductance for evapotranspiration of tropical forests: calculations, variations, and controls
    Zheng-Hong Tan, JUNFU ZHAO, Guanze Wang, Meng-Ping Chen, Lianyan Yang, Chunsheng He, Natalia Restrepo-Coupe, Shushi Peng, Xueyan Liu, Humberto R da Rocha, Yoshiko Kosugi, Takashi Hirano, Scott Saleska, Michael Goulden, Jiye Zeng, Fangjun Ding, Fu Gao, Liang Song
    Agricultural and Forest Meteorology 275 317 - 328 2019年 [査読有り][通常論文]
  • FLUXNET-CH4 Synthesis Activity: Objectives, Observations, and Future Directions
    Sara H. Knox, Robert Jackson, Benjamin Poulter, Gavin McNicol, Etienne Fluet-Chouinard, Zhen Zhang, Gustaf Hugelius, Philippe Bousquet, Josep G. Canadell, Marielle Saunois, Dario Papale, Housen Chu, Trevor F. Keenan, DenniS Baldocchi, Margaret S. Torn, Ivan Mammarella, Carlo Trotta, Mika Aurela, Gil Bohrer, David I. Campbell, Alessandro Cescatti, Samuel Chamberlain, Jiquan Chen, Weinan Chen, Sigrid Dengel, Ankur R. Desai, Eugenie Euskirchen, Thomas Friborg, Daniele Gasbarra, Ignacio Goded, Mathias Goeckede, Martin Heimann, Manuel Helbig, Takashi Hirano, David Y. Hollinger, Hiroki Iwata, Minseok Kang, Janina Klatt, Ken W. Krauss, Lars Kutzbach, Annalea Lohila, Bhaskar Mitra, Timothy H. Morin, Mats B. Nilsson, Shuli Niu, Asko Noormets, Walter C. Oechel, Matthias Peichl, Olli Peltola, Michele L. Reba, Andrew D. Richardson, Benjamin R, K. Runkle, Youngryel Ryu, Torsten Sachs, Karina V, R. Schäfer, Hans Peter Schmid, Narasinha Shurpali, Oliver Sonnentag, Angela C. I. Tang, Masahito Ueyama, Rodrigo Vargas, Timo Vesala, Eric J. Ward, Lisamarie Windham-Myers, Georg Wohlfahrt, Donatella Zona
    Bulletin of the American Meteorological Society 100 12 2607 - 2632 2019年 [査読有り][通常論文]
  • Guan Xhuan Wong, Ryuichi Hirata, Takashi Hirano, Frankie Kiew, Edward Baran Aeries, Kevin Kemudang Musin, Joseph Wenceslaus Waili, Kim San Lo, Lulie Melling
    Agricultural and Forest Meteorology 256-257 353 - 361 2018年06月15日 [査読有り][通常論文]
     
    Tropical peat swamp forest is a unique ecosystem, in which both swamp forest and peat soil have coexisted over millennia and accumulated a significant amount of soil carbon as peat. Owing to the huge soil carbon stock and high groundwater level (GWL), tropical peatlands potentially represent a significant source of methane (CH4) to the atmosphere. However, a few studies of CH4 flux by the soil chamber technique have reported that annual CH4 emissions from tropical peat swamp forest were very low as compared to mid- and high-latitude peatlands. Recently, it has been reported that some tree species growing in peat swamp forest emit CH4 from their stems. It is impossible to continuously measure ecosystem-scale CH4 flux including both soil and plant-mediated CH4 emissions by the chamber technique. Thus, we have measured net ecosystem CH4 exchange (FCH4) above a tropical peat swamp forest in Sarawak, Malaysia using the eddy covariance technique from February 2014 to July 2015 (18 months). The mean (±1 standard deviation) of half-hourly measured FCH4 was 24.0 ± 42.2 nmol m–2 s–1. Monthly mean FCH4 was always positive during the 18 months, even in the driest month with mean GWL of –30 cm. FCH4 was positively associated with GWL or soil moisture in a quadratic form. Annual FCH4 from March 2014 through February 2015 was 7.5–10.8 g C m–2 yr–1. The annual FCH4 was much higher than annual soil CH4 emissions from tropical peatlands, because the FCH4 included aboveground CH4 emissions mainly from tree stems. However, the annual FCH4 was relatively low in comparison with those measured by the eddy covariance technique in mid- and high-latitude peatlands.
  • Kiwamu Ishikura, Takashi Hirano, Yosuke Okimoto, Ryuichi Hirata, Frankie Kiew, Lulie Melling, Edward Baran Aeries, Kim San Lo, Kevin Kemudang Musin, Joseph Wenceslaus Waili, Guan Xhuan Wong, Yoshiyuki Ishii
    Agriculture, Ecosystems and Environment 254 202 - 212 2018年02月15日 [査読有り][通常論文]
     
    Soil carbon dioxide (CO2) efflux was measured continuously for two years using an automated chamber system in an oil palm plantation on tropical peat. This study investigated the factors controlling the CO2 efflux and quantified the annual cumulative CO2 emissions through soil respiration and heterotrophic respiration, which is equivalent to oxidative peat decomposition. Soil respiration was measured in close-to-tree (< 2.5 m, CT) and far-from-tree (> 3 m, FT) plots, and heterotrophic respiration was measured in root-cut (RC) plots by a trenching method. The daily mean CO2 efflux values (mean ± 1 standard deviation) were 2.80 ± 2.18, 1.59 ± 1.18, and 1.94 ± 1.58 μmol m−2 s−1 in the CT, FT, and RC plots, respectively. Daily mean CO2 efflux increased exponentially as the groundwater level or water-filled pore space decreased, indicating that oxidative peat decomposition and gas diffusion in the soil increased due to enhanced aeration resulting from lower groundwater levels. Mean annual gap-filled CO2 emissions were 1.03 ± 0.53, 0.59 ± 0.26, and 0.69 ± 0.21 kg C m−2 yr−1 in the CT, FT, and RC plots, respectively. Soil CO2 emissions were significantly higher in the CT plots (P < 0.05), but did not differ significantly between the FT and RC plots. This implies that root respiration was negligible in the FT plots. Heterotrophic respiration accounted for 66% of soil respiration. Annual CO2 emissions through both soil and heterotrophic respiration were smaller than those of other oil palm plantations on tropical peat, possibly due to the higher groundwater levels, land compaction, and continuous measurement of soil CO2 efflux in this study. Mean annual total subsidence was 1.55 to 1.62 cm yr−1, of which oxidative peat decomposition accounted for 72 to 74%. In conclusion, water management to raise groundwater levels would mitigate soil CO2 emissions from oil palm plantations on tropical peatland.
  • Fu Z, Gerken T, Bromley G, Araújo A, Bonal D, Burban B, Ficklin D, Fuentes J, Goulden M, Hirano T, Kosugi Y, Liddell M, Nicolini G, Niu S, Roupsard O, Stefani P, Mi, C, Tofte Z, Xiao J, Valentini R, Wolf S, Stoy P
    Agricultural and Forest Meteorology 263 292 - 307 2018年 [査読有り][通常論文]
  • Sakabe A, Itoh M, Hirano T, Kitso K
    Global Change Biology 24 11 5123 - 5136 2018年 [査読有り][通常論文]
     
    Data on ecosystem-scale methane (CH4 ) fluxes in tropical peatlands are currently lacking in the global CH4 budget. Although the waterlogged Indonesian peatlands contain the largest share of peat carbon in South-East Asia, ecosystem-scale CH4 budgets have not yet been reported, although these peatlands have the potential to emit CH4 . We observed 1-year variations in the ecosystem-scale CH4 flux in an undrained secondary peat swamp forest in central Kalimantan, Indonesia, using the eddy covariance method. We found that the peat swamp forest switched from being a CH4 sink during the dry season (as low as -8.9 mg C m-2  day-1 ) to a source of CH4 during the wet season (up to 10.7 mg C m-2  day-1 ), and this was dependent on changes in the groundwater level (GWL). The high GWL during the wet season enhanced the anaerobic CH4 production in the surface layer that had more labile organic matter. However, the CH4 emission also increased when the GWL dropped during dry spells in the wet season. The annual CH4 budget in the studied tropical peat swamp forest (0.09-0.17 g C m-2  year-1 ) was much lower than that in northern, temperate, and subtropical wetlands. We found that CH4 fluxes had almost no effect on the global warming gas budget of the peat swamp forest, and values were only a few percent less than the CO2 fluxes at the same site. In addition, we conducted anaerobic soil incubation experiments to examine the effect of land-use change on CH4 production. The results indicated much higher CH4 production potential in undrained forest soil than in drained or drained and burned ex-forest soils. However, although CH4 production decreased in drained soils relative to undrained soils, conserving pristine peat swamp forests with high GWLs is important to suppress global warming because CO2 emissions increase in drained peatlands.
  • Frankie Kiew, Ryuichi Hirata, Takashi Hirano, Guan Xhuan Wong, Edward Baran Aeries, Kevin Kemudang Musin, Joseph Wenceslaus Waili, Kim San Lo, Mariko Shimizu, Lulie Melling
    AGRICULTURAL AND FOREST METEOROLOGY 248 494 - 501 2018年01月 [査読有り][通常論文]
     
    Tropical peat swamp forest (PSF) has accumulated a huge amount of carbon as peat over millennia, though the carbon rich ecosystem is now threatened with disturbances due to land-use change to industrial plantations of oil palm and pulp woods. Through the land conversion, peat carbon has become vulnerable and potentially changes to a great carbon dioxide (CO2) source to the atmosphere. It is essential to quantify the CO2 balance of the ecosystem and understand how the CO2 balance responds to environmental changes to predict the role of PSF in global carbon cycles. However, filed studies based on the ecosystem-scale monitoring of CO2 flux are quite limited. Thus, we began CO2 flux monitoring over a secondary PSF in Sarawak, Malaysia, by the eddy covariance technique in 2010. Daily NEE and RE were significantly different between the dry and wet periods (p < 0.01), respectively, whereas no significant difference was found in daily GPP. As a result, the seasonal difference in NEE between the two periods (0.52 g C m(-2) d(-1)) was due to that in RE (0.57 g C m(-2) d(-1)). Daily RE was significantly greater in the dry period mainly because of lower groundwater level (GWL). Lower GWL enhances peat aeration and potentially increases oxidative peat decomposition, which results in higher soil CO2 efflux. Annual NEE was -136 +/- 51 g C m(-2) yr(-1) (mean +/- 1 standard deviation) during the four years until 2014. The negative annual NEE was equivalent to those of some tropical rain forests on mineral soil, but was more negative than 174 g C m(-2) yr(-1) for an almost undrained PSF in Central Kalimantan, Indonesia (Hirano et al., 2012). The difference in annual NEE between the two sites is attributable to higher leaf area index and less distinct seasonality in precipitation in this site.
  • Masayuki Itoh, Yosuke Okimoto, Takashi Hirano, Kitso Kusin
    SCIENCE OF THE TOTAL ENVIRONMENT 609 906 - 915 2017年12月 [査読有り][通常論文]
     
    The increasing frequency of fire due to drainage of tropical peatland has become a major environmental problemin Southeast Asia. To clarify the effects of changes in land use on carbon dioxide emissions, wemeasured oxidative peat decomposition (PD) at different stages of disturbance at three sites in Central Kalimantan, Indonesia: an undrained peat swamp forest (UF), a heavily drained peat swamp forest (DF), and a drained and burned ex-forest (DB). PD exhibited seasonality, being less in the wet season and greater in the dry season. From February 2014 to December 2015, mean PD (+/-SE) were 1.90 +/- 0.19, 2.30 +/- 0.33, and 1.97 +/- 0.25 mu mol m(-2) s(-1) at UF, DF, and DB, respectively. The groundwater level (GWL) was a major controlling factor of PD at all sites. At UF and DF, PD and GWL showed significant quadratic relationships. At DB, PD and GWL showed significant positive and negative relationships during the dry and wet seasons, respectively. Using these relationships, we estimated annual PD from GWL data for 2014 and 2015 as 698 and 745 g C m(-2) yr(-1) at UF (mean GWL: -0.23 and -0.39 m), 775 and 825 g C m(-2) yr(-1) at DF (-0.55 and -0.59 m), and 646 and 748 g C m(-2) yr(-1) at DB (-0.22 and -0.62 m), respectively. The annual PD was significantly higher in DF than in UF or DB, in both years. Despite the very dry conditions, the annual PD values at these sites were much lower than those reported for tropical peat at plantations (e.g., oil palm, rubber, and acacia). The differences in the relationship between PD and GWL indicate that separate estimations are required for each type of land. Moreover, our results suggest that PD can be enhanced by drainage both in forests and at burned sites. (C) 2017 Elsevier B.V. All rights reserved.
  • Zhiyuan Zhang, Renduo Zhang, Alessandro Cescatti, Georg Wohlfahrt, Nina Buchmann, Juan Zhu, Guanhong Chen, Fernando Moyano, Jukka Pumpanen, Takashi Hirano, Kentaro Takagi, Lutz Merbold
    SCIENTIFIC REPORTS 7 3108  2017年06月 [査読有り][通常論文]
     
    The net ecosystem CO2 exchange is the result of the imbalance between the assimilation process (gross primary production, GPP) and ecosystem respiration (RE). The aim of this study was to investigate temperature sensitivities of these processes and the effect of climate warming on the annual terrestrial net ecosystem CO2 exchange globally in the boreal and temperate regions. A database of 403 site-years of ecosystem flux data at 101 sites in the world was collected and analyzed. Temperature sensitivities of rates of RE and GPP were quantified with Q(10), defined as the increase of RE (or GPP) rates with a temperature rise of 10 degrees C. Results showed that on the annual time scale, the intrinsic temperature sensitivity of GPP (Q(10sG)) was higher than or equivalent to the intrinsic temperature sensitivity of RE (Q(10sR)). Q(10sG) was negatively correlated to the mean annual temperature (MAT), whereas Q(10sR) was independent of MAT. The analysis of the current temperature sensitivities and net ecosystem production suggested that temperature rise might enhance the CO2 sink of terrestrial ecosystems both in the boreal and temperate regions. In addition, ecosystems in these regions with different plant functional types should sequester more CO2 with climate warming.
  • Zheng-Hong Tan, Jiye Zeng, Yong-Jiang Zhang, Martijn Slot, Minoru Gamo, Takashi Hirano, Yoshiko Kosugi, Humberto R. da Rocha, Scott R. Saleska, Michael L. Goulden, Steven C. Wofsy, Scott D. Miller, Antonio O. Manzi, Antonio D. Nobre, Plinio B. de Camargo, Natalia Restrepo-Coupe
    ENVIRONMENTAL RESEARCH LETTERS 12 5 054022  2017年05月 [査読有り][通常論文]
  • Kazuhito Ichii, Masahito Ueyama, Masayuki Kondo, Nobuko Saigusa, Joon Kim, Ma. Carmelita Alberto, Jonas Ardoe, Eugenie S. Euskirchen, Minseok Kang, Takashi Hirano, Joanna Joiner, Hideki Kobayashi, Luca Belelli Marchesini, Lutz Merbold, Akira Miyata, Taku M. Saitoh, Kentaro Takagi, Andrej Varlagin, M. Syndonia Bret-Harte, Kenzo Kitamura, Yoshiko Kosugi, Ayumi Kotani, Kireet Kumar, Sheng-Gong Li, Takashi Machimura, Yojiro Matsuura, Yasuko Mizoguchi, Takeshi Ohta, Sandipan Mukherjee, Yuji Yanagi, Yukio Yasuda, Yiping Zhang, Fenghua Zhao
    JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES 122 4 767 - 795 2017年04月 [査読有り][通常論文]
     
    The lack of a standardized database of eddy covariance observations has been an obstacle for data-driven estimation of terrestrial CO2 fluxes in Asia. In this study, we developed such a standardized database using 54 sites from various databases by applying consistent postprocessing for data-driven estimation of gross primary productivity (GPP) and net ecosystem CO2 exchange (NEE). Data-driven estimation was conducted by using a machine learning algorithm: support vector regression (SVR), with remote sensing data for 2000 to 2015 period. Site-level evaluation of the estimated CO2 fluxes shows that although performance varies in different vegetation and climate classifications, GPP and NEE at 8days are reproduced (e.g., r(2)=0.73 and 0.42 for 8day GPP and NEE). Evaluation of spatially estimated GPP with Global Ozone Monitoring Experiment 2 sensor-based Sun-induced chlorophyll fluorescence shows that monthly GPP variations at subcontinental scale were reproduced by SVR (r(2)=1.00, 0.94, 0.91, and 0.89 for Siberia, East Asia, South Asia, and Southeast Asia, respectively). Evaluation of spatially estimated NEE with net atmosphere-land CO2 fluxes of Greenhouse Gases Observing Satellite (GOSAT) Level 4A product shows that monthly variations of these data were consistent in Siberia and East Asia; meanwhile, inconsistency was found in South Asia and Southeast Asia. Furthermore, differences in the land CO2 fluxes from SVR-NEE and GOSAT Level 4A were partially explained by accounting for the differences in the definition of land CO2 fluxes. These data-driven estimates can provide a new opportunity to assess CO2 fluxes in Asia and evaluate and constrain terrestrial ecosystem models.
  • Lifei Sun, Munemasa Teramoto, Naishin Liang, Tomotsugu Yazaki, Takashi Hirano
    JOURNAL OF AGRICULTURAL METEOROLOGY 73 2 59 - 67 2017年04月 [査読有り][通常論文]
     
    Leaf litter decomposition strongly affects the global carbon cycle through carbon dioxide (CO2) emissions to the atmosphere. The litter bag method (LB) and chamber method with litter addition and removal treatments (C-LART) have been used to quantify the litter decomposition rate and its resultant CO2 flux. The C-LART method measures soil CO2 fluxes in control, litter addition, and litter removal plots, and thereby decomposition rates are calculated from differences of the fluxes. However, no report has described the applicability of C-LART in comparison with LB. This study measured the litter decomposition rate and its resultant CO2 flux using C-LART and LB in a temperate evergreen forest in central Japan to assess the applicability of the two methods. Annual soil respiration in the control plot was 1572 gC m(-2) yr(-1), which was approximately twice as high as the mean of temperate evergreen forests in the world. The litter decomposition rate was 0.42 g g(-1) yr(-1) in mass loss or 0.49 gC gC(-1) yr(-1) in carbon loss by LB, which are compatible with those reported from other temperature forests. In contrast, the decomposition rate of litter carbon ascertained using C-LART was greater than I (1.96-3.76 gC gC(-1) yr(-1)), meaning that carbon emissions increased more than applied, and that the carbon emissions were decreased more than those removed by litter treatments. The incredibly high decomposition was attributed to the enhanced or restricted microbial activities in the underlying mineral soil. Changes in microbial activity are probably caused by the alteration of material supply from the leaf litter layer to the soil by litter treatment (the priming effect). In conclusion, C-LART is not applicable to evaluate CO2 emissions through litter decomposition. Another approach must be used to compensate the priming effect for application of the chamber method.
  • Lahiru S. Wijedasa, Jyrki Jauhiainen, Mari Kononen, Maija Lampela, Harri Vasander, Marie-Claire Leblanc, Stephanie Evers, Thomas E. L. Smith, Catherine M. Yule, Helena Varkkey, Massimo Lupascu, Faizal Parish, Ian Singleton, Gopalasamy R. Clements, Sheema Abdul Aziz, Mark E. Harrison, Susan Cheyne, Gusti Z. Anshari, Erik Meijaard, Jenny E. Goldstein, Susan Waldron, Kristell Hergoualc'h, Rene Dommain, Steve Frolking, Christopher D. Evans, Mary Rose C. Posa, Paul H. Glaser, Nyoman Suryadiputra, Reza Lubis, Truly Santika, Rory Padfield, Sofyan Kurnianto, Panut Hadisiswoyo, Teck Wyn Lim, Susan E. Page, Vincent Gauci, Peter J. Van, der Meer, Helen Buckland, Fabien Garnier, Marshall K. Samuel, Liza Nuriati, Lim Kim Choo, Patrick O'Reilly, Matthew Warren, Surin Suksuwan, Elham Sumarga, Anuj Jain, William F. Laurance, John Couwenberg, Hans Joosten, Ronald Vernimmen, Aljosja Hooijer, Chris Malins, Mark A. Cochrane, Balu Perumal, Florian Siegert, Kelvin S. -H. Peh, Louis-Pierre Comeau, Louis Verchot, Charles F. Harvey, Alex Cobb, Zeehan Jaafar, Henk Wosten, Solichin Manuri, Moritz Muller, Wim Giesen, Jacob Phelps, Ding Li Yong, Marcel Silvius, Beatrice M. M. Wedeux, Alison Hoyt, Mitsuru Osaki, Takashi Hirano, Hidenori Takahashi, Takashi S. Kohyama, Akira Haraguchi, Nunung P. Nugroho, David A. Coomes, Le Phat Quoi, Alue Dohong, Haris Gunawan, David L. A. Gaveau, Andreas Langner, Felix K. S. Lim, David P. Edwards, Xingli Giam, Guido Van der Werf, Rachel Carmenta, Caspar C. Verwer, Luke Gibson, Laure Gandois, Laura Linda Bozena Graham, Jhanson Regalino, Serge A. Wich, Jack Rieley, Nicholas Kettridge, Chloe Brown, Romain Pirard, Sam Moore, B. Ripoll Capilla, Uwe Ballhorn, Hua Chew Ho, Agata Hoscilo, Sandra Lohberger, Theodore A. Evans, Nina Yulianti, Grace Blackham, Onrizal, Simon Husson, Daniel Murdiyarso, Sunita Pangala, Lydia E. S. Cole, Luca Tacconi, Hendrik Segah, Prayoto Tonoto, Janice S. H. Lee, Gerald Schmilewski, Stephan Wulffraat, Erianto Indra Putra, Megan E. Cattau, R. S. Clymo, Ross Morrison, Aazani Mujahid, Jukka Miettinen, Soo Chin Liew, Samu Valpola, David Wilson, Laura D'Arcy, Michiel Gerding, Siti Sundari, Sara A. Thornton, Barbara Kalisz, Stephen J. Chapman, Ahmad Suhaizi Mat Su, Imam Basuki, Masayuki Itoh, Carl Traeholt, Sean Sloan, Alexander K. Sayok, Roxane Andersen
    GLOBAL CHANGE BIOLOGY 23 3 977 - 982 2017年03月 [査読有り][通常論文]
  • Nur Wakhid, Takashi Hirano, Yosuke Okimoto, Siti Nurzakiah, Dedi Nursyamsi
    SCIENCE OF THE TOTAL ENVIRONMENT 581 857 - 865 2017年03月 [査読有り][通常論文]
     
    Land-use change in tropical peatland potentially results in a large amount of carbon dioxide (CO2) emissions owing to drainage, which lowers groundwater level (GWL) and consequently enhances oxidative peat decomposition. However, field information on carbon balance is lacking for rubber plantations, which are expanding into Indonesia's peatlands. To assess soil CO2 emissions from an eight-year-old rubber plantation established on peat after compaction, soil CO2 efflux was measured monthly using a closed chamber system from December 2014 to December 2015, in which a strong El Nino event occurred, and consequently GWL lowered deeply.Total soil respiration (SR) and oxidative peat decomposition (PD) were separately quantified by trenching. In addition, peat surface elevation was measured to determine annual subsidence along with GWL. With GWL, SR showed a negative logarithmic relationship (p < 0.01), whereas PD showed a strong negative linearity (p < 0.001). Using the significant relationships, annual SR and PD were calculated from hourly GWL data to be 3293 1039 and 1408 214 g C m(-2) yr(-1) (mean 1 standard deviation), respectively. PD accounted for 43% of SR on an annual basis. SR showed no significant difference between near and far positions from rubber trees (p > 0:05). Peat surface elevation varied seasonally in almost parallel with GWL. After correcting for GWL difference, annual total subsidence was determined at 5.64 3.20 and 5.96 0.43 cm yr(-1) outside and inside the trenching, respectively. Annual subsidence only through peat oxidation that was calculated from the annual PD, peat bulk density and peat carbon content was 1.50 cm yr(-1). As a result, oxidative peat decomposition accounted for 25% of total subsidence (5.96 cm yr(-1)) on average on an annual basis. The contribution of peat oxidation was lower than those of previous studies probably because of compaction through land preparation. (C) 2017 Elsevier B.V. All rights reserved.
  • Takashi Hirano, Keiji Suzuki, Ryuichi Hirata
    AGRICULTURAL AND FOREST METEOROLOGY 232 457 - 468 2017年01月 [査読有り][通常論文]
     
    Larch, a deciduous needle-leaf gymnosperm, is widely distributed in cool temperate and boreal forests of the Northern Hemisphere. Thus, evaluating evapotranspiration (ET) in larch forests is important to elucidate energy and water cycles on a global scale. In addition, severe forest disturbance is expected to change ET and energy balance through a drastic change in the canopy structure. However, knowledge related to the environmental functions of larch forests in cool temperate regions remains lacking compared with Siberian larch forests. Furthermore, few reports describe quantified changes in ET and energy balance before and after forest disturbance. Therefore, for more than a decade, we measured sensible and latent heat fluxes using the eddy covariance technique above a larch forest in northern Japan and its succeeding ex-forest after a stand-replacing disturbance caused by windthrow. In general, the larch forest's ET was not limited by water in contrast to that of a Siberian larch forest. Although the aboveground biomass decreased by 97% through the disturbance, both cumulative ET and latent heat flux normalized by incident solar radiation (IE/R-g) during the snow-free period of about seven months were decreased by only 24% in the second year after disturbance. The 24% decrease was caused by 17% decrease in the partition of incident solar radiation to net radiation (R-g/R-n) and 9% decrease in the partition of net radiation to ET (IE/R-n). The former resulted from increased albedo and decreased net longwave radiation, and the latter was mainly due to decrease in surface conductance. According to the vegetation recovery of shrubs and herbaceous plants, cumulative ET during the snow-free period increased gradually and almost reached pre-disturbance levels in six years. However, normalized ET by solar radiation (IE/Rg) decreased in the 11th and 12th years after reaching the pre-disturbance level. Positive relationship between cumulative ET and vegetation indices indicates that the ET recovery was due to vegetation recovery. (C) 2016 Elsevier B.V. All rights reserved.
  • Tomotsugu Yazaki, Takashi Hirano, Tomohito Sano
    FORESTS 7 11 doi:10.3390/f7110287  2016年11月 [査読有り][通常論文]
     
    Quantitative evaluations of biomass accumulation after disturbances in forests are crucially important for elucidating and predicting forest carbon dynamics in order to understand the carbon sink/source activities. During early secondary succession, understory vegetation often affects sapling growth. However, reports on biomass recovery in naturally-regenerating sites are limited in Japan. Therefore, we traced annual or biennial changes in plant species, biomass, and net primary production (NPP) in a naturally regenerating site in Japan after windthrow and salvage-logging plantation for nine years. The catastrophic disturbance depleted the aboveground biomass (AGB) from 90.6 to 2.7 Mg.ha(-1), changing understory dominant species from Dryopteris spp. to Rubus idaeus. The mean understory AGB recovered to 4.7 Mg.ha(-1) in seven years with the dominant species changing to invasive Solidago gigantea. Subsequently, patches of deciduous trees (mainly Betula spp.) recovered whereas the understory AGB decreased. Mean understory NPP increased to 272 g.C.m(-2).year(-1) within seven years after the disturbance, but decreased thereafter to 189 g.C.m(-2).year(-1). Total NPP stagnated despite increasing overstory NPP. The biomass accumulation is similar to that of naturally regenerating sites without increase of trees in boreal and temperate regions. Dense ground vegetation and low water and nutrient availability of the soil in the study site restrict the recovery of canopy-forming trees and eventually influence the biomass accumulation.
  • 吉川慶, 矢崎友嗣, 井手玲子, 栗原純一, 小熊宏之, 平野高司
    北海道の農業気象 68 68 11 - 20 2016年10月 [査読有り][通常論文]
  • Takashi Hirano, Hiroyuki Yamada, Masayuki Takada, Yoshiyasu Fujimura, Hiroko Fujita, Hidenori Takahashi
    AGRICULTURAL AND FOREST METEOROLOGY 220 90 - 100 2016年04月 [査読有り][通常論文]
     
    Plant succession triggered by drainage, which results in the expansion or invasion of vascular plants, has been reported from many peatlands. However, the effects of the vascular plant's expansion on evapotranspiration (ET), which is a key component of the water balance of ombrotophic bog, are still contradictory. To investigate the effects, ET was measured at a Sphagnum-dominated bog and an adjacent transition peatland dominated by Sasa, dwarf bamboo, in Hokkaido Island, northern Japan, using the eddy covariance technique during the four growing seasons from 2007 through 2010. Cumulative gap-filled ET during a snow-free period of 6.5 months was 362(2008) and 374 mm (2010) at the Sphagnum site and 300 (2008) and 372 mm (2010) at the Sasa site. In the mid-growing season (late June to mid-September) with the highest leaf area index (LAI) at the Sasa site, ET was 2.14 +/- 0.03 (mean 1 standard deviation of the four years) and 1.92 +/- 0.19 mm d(-1), respectively, at the Sphagnum and Sasa sites. ET was smaller at the Sasa site, except for 2010 with an unusual hot wet summer; mean air temperature and precipitation were higher than their 30-year normal values by 1.75 degrees C and 172 mm, respectively. At the Sphagnum site, ET was stable despite such interannual variation in meteorological conditions. However, ET increased significantly at the Sasa site in 2010 probably because of LAI increase due to the enhanced growth of Sasa plants. The ET increase at the Sasa site suggests that ET will increase at the Sasa-dominated area, if the future warming environment accompanies more precipitation. (C) 2016 Elsevier B.V. All rights reserved.
  • M. Mezbahuddin, R. F. Grant, T. Hirano
    JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES 120 11 2132 - 2157 2015年11月 [査読有り][通常論文]
     
    Soil carbon stocks in tropical peatlands have declined recently from water table depth (WTD) drawdown caused by increased frequency and intensity of climate extremes like El Nino and by artificial drainage. Restoration of these carbon stocks under these climatic and anthropogenic disturbances requires improved predictive capacity for hydrological feedbacks to ecological processes. Process-based modeling of tropical peatland ecohydrology could provide us with such capacity, but such modeling has thus far been limited. We aimed at using basic processes for water and O-2 transport and their effects on ecosystem water, carbon, and nitrogen cycling to model seasonal and interannual variations of WTD and surface energy exchange. We tested these processes in a process-based model ecosys in a drained tropical Indonesian peatland from an El Nino year 2002 to a wetter year 2005. WTD was modeled from hydraulically driven water transfers controlled vertically by precipitation versus evapotranspiration (ET) and laterally by discharge versus recharge to or from an external reference WTD. These transfers caused WTD drawdown and soil drying to be modeled during dry seasons, which reduced ET and increased Bowen ratio by lowering stomatal conductance. More pronounced dry seasons in drier years 2002-2004 versus wetter year 2005 caused deeper WTD, more intense peat drying, and greater plant water stress. These modeled trends were well corroborated by site measurements as apparent in regression statistics of modeled versus observed WTD (R-2 > 0.8), latent heat (R-2 > 0.8), and sensible heat (R-2 > 0.7) fluxes. Insights gained from this modeling would aid in predicting the fate of tropical peatlands under future drier climates.
  • Takashi Hirano, Kitso Kusin, Suwido Limin, Mitsuru Osaki
    GLOBAL CHANGE BIOLOGY 21 5 1914 - 1927 2015年05月 [査読有り][通常論文]
     
    In Southeast Asia, peatland is widely distributed and has accumulated a massive amount of soil carbon, coexisting with peat swamp forest (PSF). The peatland, however, has been rapidly degraded by deforestation, fires, and drainage for the last two decades. Such disturbances change hydrological conditions, typically groundwater level (GWL), and accelerate oxidative peat decomposition. Evapotranspiration (ET) is a major determinant of GWL, whereas information on the ET of PSF is limited. Therefore, we measured ET using the eddy covariance technique for 4-6years between 2002 and 2009, including El Nino and La Nina events, at three sites in Central Kalimantan, Indonesia. The sites were different in disturbance degree: a PSF with little drainage (UF), a heavily drained PSF (DF), and a drained burnt ex-PSF (DB); GWL was significantly lowered at DF, especially in the dry season. The ET showed a clear seasonal variation with a peak in the mid-dry season and a large decrease in the late dry season, mainly following seasonal variation in net radiation (R-n). The R-n drastically decreased with dense smoke from peat fires in the late dry season. Annual ET forced to close energy balance for 4years was 1636 +/- 53, 1553 +/- 117, and 1374 +/- 75mmyr(-1) (mean +/- 1 standard deviation), respectively, at UF, DF, and DB. The undrained PSF (UF) had high and rather stable annual ET, independently of El Nino and La Nina events, in comparison with other tropical rainforests. The minimum monthly-mean GWL explained 80% of interannual variation in ET for the forest sites (UF and DF); the positive relationship between ET and GWL indicates that drainage by a canal decreased ET at DF through lowering GWL. In addition, ET was decreased by 16% at DB in comparison with UF chiefly because of vegetation loss through fires.
  • Masato Hayashi, Nobuko Saigusa, Yoshiki Yamagata, Takashi Hirano
    CARBON MANAGEMENT 6 1-2 19 - 33 2015年03月 [査読有り][通常論文]
     
    Background: We aimed to clarify the potential of spaceborne light detection and ranging (LiDAR) to meet the increased demand for large-scale monitoring of forest resources.Results: We developed empirical models to estimate aboveground biomass (AGB) and canopy height in Borneo from Ice, Cloud, and land Elevation Satellite (ICESat)/Geoscience Laser Altimeter System (GLAS) data, and obtained root-mean-square errors of 38.7 Mg ha(-1) and 4.0 m, respectively. GLAS-estimated AGB averaged 191.8 Mg ha(-1). From 2004 to 2007, AGB decreased by an average of 33.1 Mg ha(-1), and the rate of forest loss was 2.4% year(-1). The total AGB in Borneo was estimated as 10.34 Gt.Conclusions: The results demonstrate the potential of spaceborne LiDAR for monitoring forest resources, and its potential to play an important role in REDD+ implementations.
  • Takashi Hirano, Siti Sundari, Hiroyuki Yamada
    Tropical Peatland Ecosystems 329 - 337 2015年01月01日 [査読有り][通常論文]
     
    We reanalyzed long-term field data of CO2 flux, including net ecosystem CO2 exchange (NEE), ecosystem respiration (RE), and soil CO2 efflux (RS) to examine their seasonal and interannual variations for three conditions of disturbance (almost undrained peat swamp forest (PSF), drained PSF, and drained burnt ex- PSF) in a tropical peat area in Central Kalimantan, Indonesia. In addition, we simulated the CO2 flux on a monthly basis using empirical equations shown by our previous studies under four scenarios of seasonal variations in groundwater levels (GWL). The GWL has a large interannual variation in October and November. The rainy season usually begins in October, but the onset is delayed until November in El Niño years, making the interannual variation in CO2 fluxes the largest in these 2 months owing to the large GWL variations. On an annual basis, minimum monthly-mean GWL explained 82 % of interannual variations in NEE for the two PSFs. The linearity suggests that 10-cm drawdown of minimum monthly-mean GWL increases NEE or net ecosystem CO2 emission by 48.5 gC m-2 year-1 from PSF, independently of drainage degree. It can be said that minimum monthly-mean GWL is a practical measure to assess annual NEE of PSF.
  • Kentaro Takagi, Ryuichi Hirata, Reiko Ide, Masahito Ueyama, Kazuhito Ichii, Nobuko Saigusa, Takashi Hirano, Jun Asanuma, Sheng-Gong Li, Takashi Machimura, Yuichiro Nakai, Takeshi Ohta, Yoshiyuki Takahashi
    SOIL SCIENCE AND PLANT NUTRITION 61 1 61 - 75 2015年01月 [査読有り][通常論文]
     
    Larch (Larix spp.) forests are predominantly distributed across high latitudes of Eurasia. They potentially have a strong influence on the terrestrial carbon and energy cycles, because of their vast area and the large carbon stocks in their peat soils in the permafrost. In this study, we elucidated intersite variation of ecosystem photosynthetic and respiratory parameters of eight larch forests in East Asia using the CarboEastAsia carbon flux and micrometeorology dataset. These parameters were determined using the empirical relationship between the carbon fluxes (photosynthesis and respiration) and micrometeorological variables (light and temperature). In addition, we examined leaf area index (LAI) determined by Moderate Resolution Imaging Spectroradiometer (MODIS) remote sensing data to explain the intersite variation. Linear or exponential relationships with annual mean temperature or seasonal maximum LAI at the study sites were found for the annual carbon fluxes (gross primary production [GPP] and total ecosystem respiration [RE]) as well as for four of the five seasonal maximum values of determined photosynthetic and respiratory parameters (maximum GPP at light saturation, initial slope of the light-response curve, daytime respiration, and RE at the reference temperature of 10 degrees C). Phenological indices, such as start day of the growing season, growing season length and growing season degree days explained much of the intersite variation of GPP and RE of the studied larch forests; however, the relationship between MODIS LAI and photosynthetic or respiratory parameters implies that the intersite variation in GPP and RE was caused not only by the temperature variation (abiotic factor), but also by the variation in the photosynthetic and respiration activity by vegetation (biotic factor) through the change in leaf (or whole vegetation) biomass. Our analysis shows that MODIS LAI serves as a good index to explain the variation of the ecosystem photosynthetic and respiratory characteristics of East Asian larch forests.
  • K. Mallick, A. Jarvis, G. Wohlfahrt, G. Kiely, T. Hirano, A. Miyata, S. Yamamoto, L. Hoffmann
    BIOGEOSCIENCES 12 2 433 - 451 2015年 [査読有り][通常論文]
     
    This paper introduces a relatively simple method for recovering global fields of monthly midday (13: 30 LT) near-surface net available energy (the sum of the sensible and latent heat flux or the difference between the net radiation and surface heat accumulation) using satellite visible and infrared products derived from the AIRS (Atmospheric Infrared Sounder) and MODIS (MODerate Resolution Imaging Spectroradiometer) platforms. The method focuses on first specifying net surface radiation by considering its various shortwave and longwave components. This was then used in a surface energy balance equation in conjunction with satellite day-night surface temperature difference to derive 12 h discrete time estimates of surface system heat capacity and heat accumulation, leading directly to retrieval for surface net available energy. Both net radiation and net available energy estimates were evaluated against ground truth data taken from 30 terrestrial tower sites affiliated with the FLUXNET network covering 7 different biome classes. This revealed a relatively good agreement between the satellite and tower data, with a pooled root-mean-square deviation of 98 and 72Wm(-2) for monthly 13: 30 LT net radiation and net available energy, respectively, although both quantities were underestimated by approximately 25 and 10 %, respectively, relative to the tower observation. Analysis of the individual shortwave and longwave components of the net radiation revealed the downwelling shortwave radiation to be main source of this systematic underestimation.
  • Fiolenta Marpaung, Takashi Hirano
    JOURNAL OF AGRICULTURAL METEOROLOGY 70 4 223 - 232 2014年12月 [査読有り][通常論文]
     
    Changes in cloud cover and atmospheric aerosol loading strongly affect the diffuse proportion of solar radiation (R-d/R-g). It has been reported that plant photosynthesis is more efficient under diffuse light conditions, but diffuse radiation (R-d) regimes in tropical peatland frequently subjected to large-scale fires are poorly described, and there are few or no site-based datasets to date. Therefore, we continuously measured R-d for more than three years at a burnt ex-forest on tropical peatland in Central Kalimantan, Indonesia. Daily R-d/R-g was significantly related to the clearness index (R-g/R-o) with a linear threshold model. The model parameters showed that R-d/R-g under a clear sky is larger in tropical peatland with a humid climate than in Australia. Using the model, long-term variation in R-d/R-g for more than 12 years was estimated from R-g measured above a nearby forest. As a result, R-d/R-g showed a seasonal variation with its minimum of 0.51 in June (the transition between the wet and dry seasons) and its maximum of 0.68 in October (the late dry season) on a monthly basis. The decreasing pattern from the late wet season to the early dry season corresponded to decreasing precipitation due to fewer clouds. In contrast, the increasing pattern through the latter half of the dry season was due to shading by smoke emitted through burning biomass and peat fires. In particular, during the El Nino droughts in 2002, 2006 and 2009, the monthly mean R-d/R-g rose above 0.72, because the ground was densely covered with smoke from large-scale fires.
  • Mi Zhang, Xuhui Lee, Guirui Yu, Shijie Han, Huimin Wang, Junhua Yan, Yiping Zhang, Yide Li, Takeshi Ohta, Takashi Hirano, Joon Kim, Natsuko Yoshifuji, Wei Wang
    ENVIRONMENTAL RESEARCH LETTERS 9 3 doi.10.1088/1748-9326/9/303400  2014年03月 [査読有り][通常論文]
     
    Climate models simulating continental scale deforestation suggest a warming effect of land clearing on the surface air temperature in the tropical zone and a cooling effect in the boreal zone due to different control of biogeochemical and biophysical processes. Ongoing land-use/cover changes mostly occur at local scales (hectares), and it is not clear whether the local-scale deforestation will generate temperature patterns consistent with the climate model results. Here we paired 40 and 12 flux sites with nearby weather stations in North and South America and in Eastern Asia, respectively, and quantified the temperature difference between these paired sites. Our goal was to investigate the response of the surface air temperature to local-scale (hectares) land clearing across latitudes using the surface weather stations as proxies for localized land clearing. The results show that north of 10 degrees N, the annual mean temperature difference (open land minus forest) decreases with increasing latitude, but the temperature difference shrinks with latitude at a faster rate in the Americas [-0.079 (+/- 0.010) degrees C per degree] than in Asia [-0.046 (+/- 0.011) degrees C per degree]. Regression of the combined data suggests a transitional latitude of about 35.5 degrees N that demarks deforestation warming to the south and cooling to the north. The warming in latitudes south of 35 degrees N is associated with increase in the daily maximum temperature, with little change in the daily minimum temperature while the reverse is true in the boreal latitudes.
  • Junbang Wang, Jingwei Dong, Jiyuan Liu, Mei Huang, Guicai Li, Steven W. Running, W. Kolby Smith, Warwick Harris, Nobuko Saigusa, Hiroaki Kondo, Yunfen Liu, Takashi Hirano, Xiangming Xiao
    REMOTE SENSING 6 3 2108 - 2133 2014年03月 [査読有り][通常論文]
     
    Gross primary production (GPP) plays an important role in the net ecosystem exchange of CO2 between the atmosphere and terrestrial ecosystems. It is particularly important to monitor GPP in Southeast Asia because of increasing rates of tropical forest degradation and deforestation in the region in recent decades. The newly available, improved, third generation Normalized Difference Vegetation Index (NDVI3g) from the Global Inventory Modelling and Mapping Studies (GIMMS) group provides a long temporal dataset, from July 1981 to December 2011, for terrestrial carbon cycle and climate response research. However, GIMMS NDVI3g-based GPP estimates are not yet available. We applied the GLOPEM-CEVSA model, which integrates an ecosystem process model and a production efficiency model, to estimate GPP in Southeast Asia based on three independent results of the fraction of photosynthetically active radiation absorbed by vegetation (FPAR) from GIMMS NDVI3g (GPP(NDVI3g)), GIMMS NDVI1g (GPP(NDVI1g)), and the Moderate Resolution Imaging Spectroradiometer (MODIS) MOD15A2 FPAR product (GPP(MOD15)). The GPP results were validated using ground data from eddy flux towers located in different forest biomes, and comparisons were made among the three GPPs as well as the MOD17A2 GPP products (GPP(MOD17)). Based on validation with flux tower derived GPP estimates the results show that GPP(NDVI3g) is more accurate than GPP(NDVI1g) and is comparable in accuracy with GPP(MOD15). In addition, GPP(NDVI3g) and GPP(MOD15) have good spatial-temporal consistency. Our results indicate that GIMMS NDVI3g is an effective dataset for regional GPP simulation in Southeast Asia, capable of accurately tracking the variation and trends in long-term terrestrial ecosystem GPP dynamics.
  • Ayaka Sakabe, Masahito Ueyama, Yoshiko Kosugi, Ken Hamotani, Takashi Hirano, Ryuichi Hirata
    JOURNAL OF ATMOSPHERIC CHEMISTRY 71 1 79 - 94 2014年03月 [査読有り][通常論文]
     
    The relaxed eddy accumulation (REA) method is an attractive alternative to the eddy covariance method to measure trace-gas flux, because it allows the use of analyzers with an optimal integration time to reduce the noise. However, the use of an empirical coefficient b results in uncertainties in the REA method. The consistency of b for temperature was investigated using a 1 year dataset obtained at three forest sites in East Asia: a temperate evergreen coniferous forest, a tropical evergreen broadleaf forest, and a cool-temperate deciduous coniferous forest. The observational b ranged from 0.54 to 0.57 under unstable conditions. Although the values for observational b were within narrow ranges among the sites, there were slight site-specific differences. We introduced new expression of b, similarity b, based on scalar similarity using the integral turbulence characteristics to investigate the nature of b. Both the observational and similarity b increased with increasing atmospheric stability under stable conditions, when lower values for the standard deviation of the vertical wind velocity resulted in higher values for b. The variations in b under stable conditions differed among sites. There were no seasonal variations in the observational b at all sites. Consequently, the present study recommends determining the coefficient b for unstable conditions for each site and considering changes in b associated with atmospheric stability in order to minimize errors in the REA method.
  • Takashi Hirano, Kitso Kusin, Suwido Limin, Mitsuru Osaki
    GLOBAL CHANGE BIOLOGY 20 2 555 - 565 2014年02月 [査読有り][通常論文]
     
    In Southeast Asia, a huge amount of peat has accumulated under swamp forests over millennia. Fires have been widely used for land clearing after timber extraction, thus land conversion and land management with logging and drainage are strongly associated with fire activity. During recent El Nino years, tropical peatlands have been severely fire-affected and peatland fires enlarged. To investigate the impact of peat fires on the regional and global carbon balances, it is crucial to assess not only direct carbon emissions through peat combustion but also oxidative peat decomposition after fires. However, there is little information on the carbon dynamics of tropical peat damaged by fires. Therefore, we continuously measured soil CO2 efflux [peat respiration (RP)] through oxidative peat decomposition using six automated chambers on a burnt peat area, from which about 0.7m of the upper peat had been lost during two fires, in Central Kalimantan, Indonesia. The RP showed a clear seasonal variation with higher values in the dry season. The RP increased logarithmically as groundwater level (GWL) lowered. Temperature sensitivity or Q(10) of RP decreased as GWL lowered, mainly because the vertical distribution of RP would shift downward with the expansion of an unsaturated soil zone. Although soil temperature at the burnt open area was higher than that in a near peat swamp forest, model simulation suggests that the effect of temperature rise on RP is small. Annual gap-filled RP was 382 +/- 82 (the mean +/- 1 SD of six chambers) and 362 +/- 74gCm(-2)yr(-1) during 2004-2005 and during 2005-2006years, respectively. Simulated RP showed a significant negative relationship with GWL on an annual basis, which suggests that every GWL lowering by 0.1m causes additional RP of 89gCm(-2)yr(-1). The RP accounted for 21-24% of ecosystem respiration on an annual basis.
  • M. Mezbahuddin, R. F. Grant, T. Hirano
    BIOGEOSCIENCES 11 3 577 - 599 2014年 [査読有り][通常論文]
     
    Seasonal variation in water table depth (WTD) determines the balance between aggradation and degradation of tropical peatlands. Longer dry seasons together with human interventions (e. g. drainage) can cause WTD drawdowns making tropical peatland C storage highly vulnerable. Better predictive capacity for effects of WTD on net CO2 exchange is thus essential to guide conservation of tropical peat deposits. Mathematical modelling of basic eco-hydrological processes under site- specific conditions can provide such predictive capacity. We hereby deploy a process- based mathematical model ecosys to study effects of seasonal variation in WTD on net ecosystem productivity (NEP) of a drainage affected tropical peat swamp forest at Palangkaraya, Indonesia. Simulated NEP suggested that the peatland was a C source (NEP similar to -2 gCm(-2) d(-1), where a negative sign represents a C source and a positive sign a C sink) during rainy seasons with shallow WTD, C neutral or a small sink (NEP similar to + 1 gCm(-2) d(-1)) during early dry seasons with intermediate WTD and a substantial C source (NEP similar to - 4 gCm(-2) d(-1)) during late dry seasons with deep WTD from 2002 to 2005. These values were corroborated by regressions (P < 0.0001) of hourly modelled vs. eddy covariance (EC) net ecosystem CO2 fluxes which yielded R-2 > 0.8, intercepts approaching 0 and slopes approaching 1. We also simulated a gradual increase in annual NEP from 2002 (-609 gCm(-2)) to 2005 (-373 gCm(-2)) with decreasing WTD which was attributed to declines in duration and intensity of dry seasons following the El Nino event of 2002. This increase in modelled NEP was corroborated by ECgap filled annual NEP estimates. Our modelling hypotheses suggested that (1) poor aeration in wet soils during shallow WTD caused slow nutrient (predominantly phosphorus) min-eralization and consequent slow plant nutrient uptake that suppressed gross primary productivity (GPP) and hence NEP (2) better soil aeration during intermediate WTD enhanced nutrient mineralization and hence plant nutrient uptake, GPP and NEP and (3) deep WTD suppressed NEP through a combination of reduced GPP due to plant water stress and increased ecosystem respiration (R-e) from enhanced deeper peat aeration. These WTD effects on NEP were modelled from basic eco-hydrological processes including microbial and root oxidation- reduction reactions driven by soil and root O-2 transport and uptake which in turn drove soil and plant carbon, nitrogen and phosphorus transformations within a soil- plant- atmosphere water transfer scheme driven by water potential gradients. Including these processes in ecosystem models should therefore provide an improved predictive capacity for WTD management programs intended to reduce tropical peat degradation.
  • K. Mallick, A. Jarvis, G. Wohlfahrt, G. Kiely, T. Hirano, A. Miyata, S. Yamamoto, L. Hoffmann
    BIOGEOSCIENCES 11 24 7369 - 7382 2014年 [査読有り][通常論文]
     
    This paper introduces a relatively simple method for recovering global fields of latent heat flux. The method focuses on specifying Bowen ratio estimates through exploiting air temperature and vapour pressure measurements obtained from infrared soundings of the AIRS (Atmospheric Infrared Sounder) sensor onboard NASA's Aqua platform. Through combining these Bowen ratio retrievals with satellite surface net available energy data, we have specified estimates of global noontime surface latent heat flux at the 1 degrees x 1 degrees scale. These estimates were provisionally evaluated against data from 30 terrestrial tower flux sites covering a broad spectrum of biomes. Taking monthly average 13: 30 data for 2003, this revealed promising agreement between the satellite and tower measurements of latent heat flux, with a pooled root-mean-square deviation of 79Wm(-2), and no significant bias. However, this success partly arose as a product of the underspecification of the AIRS Bowen ratio compensating for the underspecification of the AIRS net available energy, suggesting further refinement of the approach is required. The error analysis suggested that the landscape level variability in enhanced vegetation index (EVI) and land surface temperature contributed significantly to the statistical metric of the predicted latent heat fluxes.
  • R. Hirata, K. Takagi, A. Ito, T. Hirano, N. Saigusa
    BIOGEOSCIENCES 11 18 5139 - 5154 2014年 [査読有り][通常論文]
     
    We evaluated the long-term (52-year) effect of climate, disturbance, and subsequent recovery on the carbon balance of cool temperate forests by using the process-based ecosystem model VISIT. The study sites were artificial larch forests planted after clear-cutting of mixed forest in Hokkaido, Japan. The model was validated, scenarios were computed, and a sensitivity analysis was performed. First, we performed a baseline simulation of carbon dynamics and compared these values with those observed across a wide range of stand ages (old mixed forest and young and middle-aged larch forests). Second, we ran scenarios to investigate how disturbance and several climate factors affect long-term carbon fluxes. Third, we analyzed the sensitivity of carbon balance to the amount of disturbance-generated tree biomass residues. By taking into account seasonal variation in the understory leaf area index, which played an important role, especially in the initial stage of recovery, the simulated net ecosystem production (NEP), gross primary production, ecosystem respiration, and biomass for the three types of forest were consistent with observed values (mean +/- SD of R-2 of monthly NEP, GPP and RE for the three types of forest were 0.63 +/- 0.26, 0.93 +/- 0.07, 0.94 +/- 0.2, respectively). The effect of disturbances such as clear-cutting, land-use conversion, and thinning on the long-term trend of NEP was larger than that of climate variation, even 50 years after clear-cutting. In contrast, interannual variation in the carbon balance was primarily driven by climate variation. These findings indicate that disturbance controlled the long-term trend of the carbon balance, whereas climate factors controlled yearly variation in the carbon balance. Among the meteorological factors considered, temperature and precipitation were the main ones that affected NEP and its interannual variation. The carbon balance in the initial post-disturbance period, which is strongly affected by the amount of residues, influenced the subsequent long-term carbon budget, implying the importance of residue management. Consequently, carbon release just after disturbance and the length of the recovery period required to balance the carbon budget are controlled by the amount of residues.
  • Zhi Chen, Guirui Yu, Jianping Ge, Xiaomin Sun, Takashi Hirano, Nobuko Saigusa, Qiufeng Wang, Xianjin Zhu, Yiping Zhang, Junhui Zhang, Junhua Yan, Huimin Wang, Liang Zhao, Yanfen Wang, Peili Shi, Fenghua Zhao
    AGRICULTURAL AND FOREST METEOROLOGY 182 266 - 276 2013年12月 [査読有り][通常論文]
     
    Carbon exchange between terrestrial ecosystems and the atmosphere is one of the most important processes in the global carbon cycle. Understanding the spatial variation and controlling factors of carbon exchange fluxes is helpful for accurately predicting and evaluating the global carbon budget. In this study, we quantified the carbon exchange fluxes of different terrestrial ecosystems in the Asian region, and analyzed their spatial variation and controlling factors based on long-term observation data from ChinaFLUX (19 sites) and published data from AsiaFlux (37 sites) and 32 other sites in Asia. The results indicated that the majority of Asian terrestrial ecosystems are currently large carbon sinks. The average net ecosystem production (NEP) values were 325+/-187, 274+/-207, 236+/-260, 89+/-134g C m(-2) yr(-1) in cropland, forest, wetland and grassland ecosystems, respectively. The spatial variation of gross primary production (GPP) and ecosystem respiration (Re) were mainly controlled by the mean annual temperature (MAT) and the mean annual precipitation (MAP) in the Asian region. There was a clear linear relationship between GPP and MAT, and a strong sigmoid relationship between GPP and MAP. Re was exponentially related to MAT and linearly related to MAP. Interestingly, those response modes were consistent across different ecosystem types. The different responses of GPP and Re to MAT and MAP determined the spatial variation of NEP. The combined effects of MAT and MAP contributed 85%, 81% and 36% to the spatial variations of GPP, Re and NEP, respectively. Our findings confirmed that the spatial variation of carbon exchange fluxes was mainly controlled by climatic factors, which further strongly supports the use of the climate-driven theory in the Asian region. (C) 2013 Elsevier B.V. All rights reserved.
  • カラマツ林の蒸発散とエネルギー収支
    鈴木啓司, 平田竜一, 平野高司
    北海道の農業気象 65 32 - 41 2013年10月 [査読有り][通常論文]
  • 植生遷移が進む森林跡地のCO2フラックスに与える環境要因の影響
    東健太, 平野高司, 寺本宗正, 梁乃申
    北海道の農業気象 65 23 - 31 2013年10月 [査読有り][通常論文]
  • Ma Carmelita R. Alberto, Roland J. Buresh, Takashi Hirano, Akira Miyata, Reiner Wassmann, James R. Quilty, Teodoro Q. Correa, Joseph Sandro
    FIELD CROPS RESEARCH 146 51 - 65 2013年05月 [査読有り][通常論文]
     
    A growing scarcity of irrigation water could progressively lead to changes in rice production to systems using less irrigation water for rice or more crop diversification. A shift from current production of rice on flooded soils to production of rice on non-flooded soil with water-saving irrigation or to production of more water-efficient crops will have profound effects on carbon, water, and energy exchanges. This study used the eddy covariance technique to examine C uptake and water use efficiencies for water-saving, dry-seeded rice production and production of hybrid maize under overhead sprinkler irrigation as an alternative to flooded rice during two growing seasons. Maize with its C-4 physiology has greater photosynthetic capacity than rice. In 2011, maize had 1.4 times higher net C uptake than rice and twice as much grain yield as rice (10.4 vs 5.3 Mg ha(-1)). In 2012, lower solar radiation due to increased cloudiness and heavy rainfall during critical growth stages (late vegetative to early reproductive) decreased LAI and resulted to about 20% less net C uptake and maize yield (8.2 Mg ha(-1)), but the rice yield was unchanged (5.3 Mg ha(-1)) presumably because of improved crop management which included effective crop establishment at lower seed rate and efficient N application using fertigation. Canopy light use efficiency, crop water productivity (WPET), and photosynthetic water use efficiency were 1.8, 1.9, and 1.6 times higher for maize than rice, respectively, despite sensitivity of maize to excess water. Net C uptake, evapotranspiration, and WPET of dry-seeded rice under overhead sprinkler irrigation were comparable to those reported elsewhere for flooded rice. Average total water input (irrigation + rainfall) for rice was only 908 mm, as compared to 1300-1500 mm reported in literature for typical puddled transplanted rice. (C) 2013 Elsevier B.V. All rights reserved.
  • Nobuko Saigusa, Sheng-Gong Li, Hyojung Kwon, Kentaro Takagi, Lei-Ming Zhang, Reiko Ide, Masahito Ueyama, Jun Asanuma, Young-Jean Choi, Jung Hwa Chun, Shi-Jie Han, Takashi Hirano, Ryuichi Hirata, Minseok Kang, Tomomichi Kato, Joon Kim, Ying-Nian Li, Takahisa Maeda, Akira Miyata, Yasuko Mizoguchi, Shohei Murayama, Yuichiro Nakai, Takeshi Ohta, Taku M. Saitoh, Hui-Ming Wang, Gui-Rui Yu, Yi-Ping Zhang, Feng-Hua Zhao
    JOURNAL OF FOREST RESEARCH 18 1 41 - 48 2013年02月 [査読有り][通常論文]
     
    The datasets of net ecosystem CO2 exchange (NEE) were acquired from 21 forests, 3 grasslands, and 3 croplands in the eastern part of Asia based on the eddy covariance measurements of the international joint program, CarboEastAsia. The program was conducted by three networks in Asia, ChinaFLUX, JapanFlux, and KoFlux, to quantify, synthesize, and understand the carbon budget of the eastern part of Asia. An intercomparison was conducted for NEE estimated by three gap-filling procedures adopted by ChinaFLUX, JapanFlux, and KoFlux to test the range of uncertainty in the estimation of NEE. The overall comparison indicated good agreement among the procedures in the seasonal patterns of NEE, although a bias was observed in dormant seasons depending on the different criteria of data screening. Based on the gap-filled datasets, the magnitude and seasonality of the carbon budget were compared among various biome types, phenology, and stress conditions throughout Asia. The annual values of gross primary production and ecosystem respiration were almost proportional to the annual air temperature. Forest management, including clear-cutting, plantation, and artificial drainage, was significant and obviously affected the annual carbon uptake within the forests. Agricultural management resulted in notable seasonal patterns in the crop sites. The dataset obtained from a variety of biome types would be an essential source of knowledge for ecosystem science as well as a valuable validation dataset for modeling and remote sensing to upscale the carbon budget estimations in Asia.
  • Kazuhito Ichii, Masayuki Kondo, Young-Hee Lee, Shao-Qiang Wang, Joon Kim, Masahito Ueyama, Hee-Jeong Lim, Hao Shi, Takashi Suzuki, Akihiko Ito, Hyojung Kwon, Weimin Ju, Mei Huang, Takahiro Sasai, Jun Asanuma, Shijie Han, Takashi Hirano, Ryuichi Hirata, Tomomichi Kato, Sheng-Gong Li, Ying-Nian Li, Takahisa Maeda, Akira Miyata, Yojiro Matsuura, Shohei Murayama, Yuichiro Nakai, Takeshi Ohta, Taku M. Saitoh, Nobuko Saigusa, Kentaro Takagi, Yan-Hong Tang, Hui-Min Wang, Gui-Rui Yu, Yi-Ping Zhang, Feng-Hua Zhao
    JOURNAL OF FOREST RESEARCH 18 1 13 - 20 2013年02月 [査読有り][通常論文]
     
    Based on the model-data comparison at the eddy-covariance observation sites from CarboEastAsia datasets, we report the current status of the terrestrial carbon cycle modeling in monsoon Asia. In order to assess the modeling performance and discuss future requirements for both modeling and observation efforts in Asia, we ran eight terrestrial biosphere models at 24 sites from 1901 to 2010. By analyzing the modeled carbon fluxes against the CarboEastAsia datasets, the strengths and weaknesses of terrestrial biosphere modeling over Asia were evaluated. In terms of pattern and magnitude, the carbon fluxes (i.e., gross primary productivity, ecosystem respiration, and net ecosystem exchange) at the temperate and boreal forest sites were simulated best, whereas the simulation results from the tropical forest, cropland, and disturbed sites were poor. The multi-model ensemble mean values showed lower root mean square errors and higher correlations, suggesting that composition of multiple terrestrial biosphere models would be preferable for terrestrial carbon budget assessments in Asia. These results indicate that the current model-based estimation of terrestrial carbon budget has large uncertainties, and future research should further refine the models to permit re-evaluation of the terrestrial carbon budget.
  • Jing Chen, Baozhang Chen, T. Andrew Black, John L. Innes, Guangyu Wang, Gerard Kiely, Takashi Hirano, Georg Wohlfahrt
    Journal of Geophysical Research: Biogeosciences 118 4 1715 - 1731 2013年 [査読有り][通常論文]
     
    The mass transfer (MT) equation and the Penman-Monteith (PM) equation are two common approaches used in various land surface models for simulating evapotranspiration (ET). Yet assessments are rarely conducted to determine how well these structurally differing equations simulate ET across various biomes and climatic environments with different canopy upscaling strategies. We evaluated the capacity of models to estimate ET using the MT equation with the one-leaf strategy in the Community Land Model version 4 and the PM equation in the Dynamic Land Model using the one-leaf and two-leaf upscaling approaches for 22 selected eddy covariance flux towers representing 10 typical plant functional types. Overall, across half-hourly, daily, monthly, and seasonal scales, the MT equation performed less robust than the PM equation in forests. The former had 8-15% higher root-mean-square error and 1-4% lower index of agreement and a large uncertainty in warm and wet seasons for several sites. It leaves a doubt about its application of estimating ET across regional to global scales. Considering the net radiation available on the surface of leaf/soil and adopting the two-leaf approach made the PM equation closer to the EC measurements on average but still could not capture the variation during the cold season. We suggest that further improvements in simulation of ET require seasonal variation of some key parameters and quantification of spatial heterogeneity. Key Points The MT equation performs less robust than the PM equation in LSMs ET estimated by the MT equation has a large uncertainty in warm and wet seasons ET estimated by the PM equation is closer to the EC measurements on average ©2013. American Geophysical Union. All Rights Reserved.
  • Takashi Hirano, Hendrik Segah, Kitso Kusin, Suwido Limin, Hidenori Takahashi, Mitsuru Osaki
    GLOBAL CHANGE BIOLOGY 18 11 3410 - 3422 2012年11月 [査読有り][通常論文]
     
    Tropical peatlands have accumulated huge soil carbon over millennia. However, the carbon pool is presently disturbed on a large scale by land development and management, and consequently has become vulnerable. Peat degradation occurs most rapidly and massively in Indonesia, because of fires, drainage, and deforestation of swamp forests coexisting with tropical peat. Peat burning releases carbon dioxide (CO2) intensively but occasionally, whereas drainage increases CO2 emission steadily through the acceleration of aerobic peat decomposition. Therefore, tropical peatlands present the threat of switching from a carbon sink to a carbon source to the atmosphere. However, the ecosystem-scale carbon exchange is still not known in tropical peatlands. A long-term field experiment in Central Kalimantan, Indonesia showed that tropical peat ecosystems, including a relatively intact peat swamp forest with little drainage (UF), a drained swamp forest (DF), and a drained burnt swamp forest (DB), functioned as net carbon sources. Mean annual net ecosystem CO2 exchange (NEE) (+/- a standard deviation) for 4 similar to years from July 2004 to July 2008 was 174 +/- 203, 328 +/- 204 and 499 +/- 72 similar to gC similar to m-2 similar to yr-1, respectively, for the UF, DF, and DB sites. The carbon emissions increased according to disturbance degrees. We found that the carbon balance of each ecosystem was chiefly controlled by groundwater level (GWL). The NEE showed a linear relationship with GWL on an annual basis. The relationships suggest that annual CO2 emissions increase by 79-238 C-g m(-2) every 0.1m of GWL lowering probably because of the enhancement of oxidative peat decomposition. In addition, CO2 uptake by vegetation photosynthesis was reduced by shading due to dense smoke from peat fires ignited accidentally or for agricultural practices. Our results may indicate that tropical peatland ecosystems are no longer a carbon sink under the pressure of human activities.
  • Tomohito Sano, Takashi Hirano, Tomomi Takeda, Yasumi Fujinuma
    Journal of Agricultural Meteorology 68 1 35 - 43 2012年09月01日 [査読有り][通常論文]
     
    Leaf area index (LAI) is an important parameter used to characterize the canopy structure of forest ecosystems. Disturbances such as thinning change the canopy structure and influence various ecosystem functions. A larch plantation in Hokkaido, Japan was thinned during the winter of 2003-2004, decreasing its basal area density by 23% from 29.7 to 22.8 m2 ha-1. To evaluate the LAI change caused by the thinning, we measured LAI in 2003 and 2004 using a direct method with litter collection (LC) and two indirect methods using a plant canopy analyzer (PCA) and a ground-based laser scanner (LS), although a September 2004 typhoon disaster halted LC measurements. In 2003, the annual maximum LAI measured via the LC (LAILC) was 5.6 m2 m-2, of which the LAILC of broadleaf trees accounted for about half. Using rings 1-5 of five sky sectors, the annual maximum LAI indicated by the PCA (LAIPCA) was 3.4 m2 m-2, demonstrating that the PCA underestimated LAI. However, using rings 1-4 and 1-3, LAIPCA increased to 4.4 and 4.8 m2 m-2,respectively. This result shows that eliminating the outer rings of the PCA improves LAI underestimation because some scattering light reflected by leaves engenders underestimation of LAIPCA when the zenith angle is large. The maximum LAI by the LS (LAILS) was equal to LAILC. However, the LS greatly overestimated LAI in the leaf-fall and leafless seasons. The laser beam is thought to have increased in diameter with distance and consequently underestimated the gap fraction. Maximum LAIPCA and LAILS after thinning were each half of that before thinning. The rates of decrease were greater than the basal area density, which is linearly related with LAI, because canopy inhomogeneity is expected to cause LAI underestimation after thinning. LAI probably decreased to about 4.6 m2 m-2, assuming that the ratio of LAI to basal area remained constant despite thinning. © 2012, The Society of Agricultural Meteorology of Japan. All rights reserved.
  • Siti Sundari, Takashi Hirano, Hiroyuki Yamada, Kitso Kusin, Suwido Limin
    Journal of Agricultural Meteorology 68 2 121 - 134 2012年09月01日 [査読有り][通常論文]
     
    Tropical peatlands store soil carbon constituting up to 15-19% of global peat carbon. That huge carbon pool is presently being disturbed on a large scale by land development and management, and has consequently become vulnerable. Peat degradation occurs most rapidly and massively in Indonesia fs peatlands because of fires, drainage and deforestation of swamp forests. Peat burning releases carbon dioxide (CO2) intensively but occasionally, whereas drainage increases CO2 emissions steadily through accelerated aerobic peat decomposition. Under such circumstances, tropical peatlands might become a huge source of carbon emissions to the atmosphere. Nevertheless, the effects of drainage on the carbon balance of tropical peatland ecosystems are not well understood more field data must be accumulated. Therefore, we measured soil respiration (RS), which is a major source of CO2 efflux, continuously for more than one year using automated chamber systems, with consideration of microtopography, at two sites in Central Kalimantan, Indonesia: undrained and drained peat swamp forests. The RS was determined mainly by local hydrology. In the undrained forest, RS decreased sharply under flooded conditions because of anoxia. In contrast, in the drained forest, with its lower groundwater level (GWL), RS showed a quadratic relationship with GWL and gradually increased as GWL decreased when GWL was lower than about -0.8 m, which was caused chiefly by the enhancement of peat decomposition. These relationships indicate that lowering GWL by drainage increased RS, whereas annual RS was larger in the undrained forest (1347 gC m-2 y-1) than in the drained forest (1225 gC m-2 y-1) in 2005. The difference in annual RS was probably attributable to higher forest productivity in the undrained forest. © 2012, The Society of Agricultural Meteorology of Japan. All rights reserved.
  • Ma Carmelita R. Alberto, Takashi Hirano, Akira Miyata, Reiner Wassmann, Arvind Kumar, Agnes Padre, Modesto Amante
    FIELD CROPS RESEARCH 134 80 - 94 2012年08月 [査読有り][通常論文]
     
    Seasonal rainfall in the Philippines is known to be modulated by ENSO phenomenon, with El Nino frequently contributing to reduced rainfall and drought while La Nina resulting in excessive rainfalls, floods and more intense typhoons. The alterations in rainfall patterns can have considerable feedback on solar radiation, air temperature, and soil moisture which can affect the ecosystem CO2 exchange. In this paper, we assessed the effects of the ENSO events (2008-mid 2010) on the seasonal climate conditions and determined how it affected the gross primary production (GPP), ecosystem respiration (Re), and net ecosystem production (NEP) of two contrasting rice environments: flooded and non-flooded. The 2008 dry season (DS) was under a La Nina event while the 2008 wet season (WS) was a neutral one with strong tropical cyclones associated during the wet season. The 2009DS was also La Nina while the 2009WS was El Nino; however, the northern part of the Philippines experienced strong tropical cyclones. The 2010DS was under an El Nino event. The La Nina in 2008DS resulted in about 15% lower solar radiation (SR), 0.3 degrees C lower air temperature (T-a) and 60% higher precipitation compared to the 28-year climate normal patterns. Both flooded and non-flooded rice fields had lower NEP in 2008 DS (164 and 14 gC m(-2), respectively) than in 2008 WS (295 and 82 gC m(-2), respectively) because the climate anomaly resulted in SR - driven decrease in GPP. The La Nina in 2009DS even resulted in 0.2 degrees C lower air temperature and 40% more precipitation than the 2008DS La Nina. This cooler temperature resulted in lower Re in flooded rice fields while the higher precipitation resulted in higher GPP in non-flooded fields since the climate was favorable for the growth of the aerobic rice, the ratoon crops and the weeds. This climate anomaly benefitted both flooded and non-flooded rice fields by increasing NEP (351 and 218 gC m(-2), respectively). However, NEP decreased in 2009WS in both flooded and non-flooded rice fields (225 and 39 gC m(-2), respectively) due to the devastating effects of the strong tropical cyclones that hit the northern part of the Philippines. On the other hand, the El Nino event during 2010DS resulted in about 6% higher solar radiation, 0.4 degrees C higher air temperature and 67% lower precipitation than the 28-year climate normal pattern. The NEP of flooded and non-flooded rice fields were closely similar at 187 and 174 gC m(-2), respectively. This climate anomaly resulted in T-a - driven increase in Re, as well as vapor pressure deficit (VPD) - driven decrease in GPP in flooded rice fields. The GPP and Re in non-flooded rice fields were less sensitive to higher VPD and higher T-a, respectively. It appears that the net ecosystem CO2 exchange in non-flooded rice field was less sensitive to an El Nino event. (C) 2012 Elsevier B.V. All rights reserved.
  • Shuli Niu, Yiqi Luo, Shenfeng Fei, Wenping Yuan, David Schimel, Beverly E. Law, Christof Ammann, M. Altaf Arain, Almut Arneth, Marc Aubinet, Alan Barr, Jason Beringer, Christian Bernhofer, T. Andrew Black, Nina Buchmann, Alessandro Cescatti, Jiquan Chen, Kenneth J. Davis, Ebba Dellwik, Ankur R. Desai, Sophia Etzold, Louis Francois, Damiano Gianelle, Bert Gielen, Allen Goldstein, Margriet Groenendijk, Lianhong Gu, Niall Hanan, Carole Helfter, Takashi Hirano, David Y. Hollinger, Mike B. Jones, Gerard Kiely, Thomas E. Kolb, Werner L. Kutsch, Peter Lafleur, David M. Lawrence, Linghao Li, Anders Lindroth, Marcy Litvak, Denis Loustau, Magnus Lund, Michal Marek, Timothy A. Martin, Giorgio Matteucci, Mirco Migliavacca, Leonardo Montagnani, Eddy Moors, J. William Munger, Asko Noormets, Walter Oechel, Janusz Olejnik, Kyaw Tha Paw U, Kim Pilegaard, Serge Rambal, Antonio Raschi, Russell L. Scott, Guenther Seufert, Donatella Spano, Paul Stoy, Mark A. Sutton, Andrej Varlagin, Timo Vesala, Ensheng Weng, Georg Wohlfahrt, Bai Yang, Zhongda Zhang, Xuhui Zhou
    NEW PHYTOLOGIST 194 3 775 - 783 2012年05月 [査読有り][通常論文]
     
    It is well established that individual organisms can acclimate and adapt to temperature to optimize their functioning. However, thermal optimization of ecosystems, as an assemblage of organisms, has not been examined at broad spatial and temporal scales. Here, we compiled data from 169 globally distributed sites of eddy covariance and quantified the temperature response functions of net ecosystem exchange (NEE), an ecosystem-level property, to determine whether NEE shows thermal optimality and to explore the underlying mechanisms. We found that the temperature response of NEE followed a peak curve, with the optimum temperature (corresponding to the maximum magnitude of NEE) being positively correlated with annual mean temperature over years and across sites. Shifts of the optimum temperature of NEE were mostly a result of temperature acclimation of gross primary productivity (upward shift of optimum temperature) rather than changes in the temperature sensitivity of ecosystem respiration. Ecosystem-level thermal optimality is a newly revealed ecosystem property, presumably reflecting associated evolutionary adaptation of organisms within ecosystems, and has the potential to significantly regulate ecosystemclimate change feedbacks. The thermal optimality of NEE has implications for understanding fundamental properties of ecosystems in changing environments and benchmarking global models.
  • Masahito Ueyama, Ryuichi Hirata, Masayoshi Mano, Ken Hamotani, Yoshinobu Harazono, Takashi Hirano, Akira Miyata, Kentaro Takagi, Yoshiyuki Takahashi
    TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY 64 http://dx.doi.org/10.3402/tell  2012年 [査読有り][通常論文]
     
    Synthesis studies using multiple-site datasets for eddy covariance potentially contain uncertainties originating from the use of different flux calculation options, because the choice of the process for calculating half-hourly fluxes from raw time series data is left to individual researchers. In this study, we quantified the uncertainties associated with different flux calculation methods at seven sites. The differences in the half-hourly fluxes were small, generally of the order less than a few percentiles, but they were substantial for the annual fluxes. After the standardisation under current recommendations in the FLUXNET communities, we estimated the uncertainties in the annual fluxes associated with the flux calculations to be 2.6 +/- 2.7 W m(-2) (the mean 90% +/- confidence interval) for the sensible heat flux, 72 +/- 37 g C m(-2) yr(-1) for net ecosystem exchange (NEE), 12 +/- 6% for evapotranspiration, 12 +/- 6% for gross primary productivity and 16 +/- 10% for ecosystem respiration. The self-heating correction strongly influenced the annual carbon balance (143 +/- 93 g C m(-2) yr(-1)), not only for cold sites but also for warm sites, but did not fully account for differences between the open- and closed-path systems (413 +/- 189 g C m(-2) yr(-1)).
  • Geographical assessment of factors for Sasa expansion in the Sarobetsu Mire, Japan
    Takada M, Inoue T, Mishima Y, Fujita H, Hirano T, Fujimura Y
    Journal of Landscape Ecology 5 58 - 71 2012年 [査読有り][通常論文]
  • 木塚 俊和, 山田 浩之, 平野 高司
    応用生態工学 15 1 45 - 59 応用生態工学会 2012年 [査読有り][通常論文]
     
    Water chemistry deterioration has become increasingly evident at mire pools with agricultural development occurring in pool catchment areas. Improvement of hydrochemical conditions is urgently necessary for the conservation of such mire pools' ecosystems. We investigated the hydrological and chemical budgets of Lake Miyajima-numa, a Ramsar Convention wetland, which is surrounded by paddy fields in Ishikari Peatland, northern Japan, during its ice-free period in 2007-2008. Surface water inflow and outflow via ditches dominate its hydrological budget, respectively constituting 88% of total input and 78% of total output. Similarly, chemical budgets including Ca2+, total nitrogen, and total phosphorus were dominated by ditch inflow and outflow Chemical constituents of the ditch inflow were derived from mineral-rich and nutrient-rich river water supplied to paddy fields as irrigation water. Therefore, the input fluxes of Ca2+, total nitrogen, and total phosphorus were much greater than those of a pristine mire pool. Increased input fluxes of chemical constituents induced by irrigation changed the hydrological and chemical budgets of mire pools, which degraded the water chemistry through eutrophication and other processes.
  • Akira Tani, Daisuke Tozaki, Motonori Okumura, Susumu Nozoe, Takashi Hirano
    ATMOSPHERIC ENVIRONMENT 45 34 6261 - 6266 2011年11月 [査読有り][通常論文]
     
    Effect of drought on isoprene emission from 2 major Quercus species native to East Asia is investigated. Three individuals of Quercus serrata and 2 individuals of Quercus crispula continued to emit isoprene under moderate and severe drought conditions, although the emission rates were lower than under normal conditions. Diurnal variation in the isoprene emission rates was monitored in real-time when temperature and light intensity were changed stepwise to imitate natural conditions. Under normal and moderate drought conditions, isoprene emission showed hysteresis with regard to the environmental parameters, but generally followed the common G93 model. Under severe drought conditions, isoprene emission rates were not explained using given coefficients in the G93 model, probably due to a depletion of isoprene substrate. (C) 2011 Elsevier Ltd. All rights reserved.
  • Ma Carmelita R. Alberto, Reiner Wassmann, Takashi Hirano, Akira Miyata, Ryusuke Hatano, Arvind Kumar, Agnes Padre, Modesto Amante
    AGRICULTURAL WATER MANAGEMENT 98 9 1417 - 1430 2011年07月 [査読有り][通常論文]
     
    The seasonal and annual variability of sensible heat flux (H), latent heat flux (LE), evapotranspiration (ET), crop coefficient (K-c) and crop water productivity (WPET) were investigated under two different rice environments, flooded and aerobic soil conditions, using the eddy covariance (EC) technique during 2008-2009 cropping periods. Since we had only one EC system for monitoring two rice environments, we had to move the system from one location to the other every week. In total, we had to gap-fill an average of 50-60% of the missing weekly data as well as those values rejected by the quality control tests in each rice field in all four cropping seasons. Although the EC method provides a direct measurement of LE, which is the energy used for ET, we needed to correct the values of H and LE to close the energy balance using the Bowen ratio closure method before we used LE to estimate ET. On average, the energy balance closure before correction was 0.72 +/- 0.06 and it increased to 0.99 +/- 0.01 after correction. The Gin both flooded and aerobic fields was very low. Likewise, the energy involved in miscellaneous processes such as photosynthesis, respiration and heat storage in the rice canopy was not taken into consideration. Average for four cropping seasons, flooded rice fields had 19% more LE than aerobic fields whereas aerobic rice fields had 45% more H than flooded fields. This resulted in a lower Bowen ratio in flooded fields (0.14 +/- 0.03) than in aerobic fields (0.24 +/- 0.01). For our study sites, evapotranspiration was primarily controlled by net radiation. The aerobic rice fields had lower growing season ET rates (3.81 +/- 0.21 mm d(-1)) than the flooded rice fields (4.29 +/- 0.23 mm d(-1)), most probably due to the absence of ponded water and lower leaf area index of aerobic rice. Likewise, the crop coefficient, K-c, of aerobic rice was significantly lower than that of flooded rice. For aerobic rice, K-c values were 0.95 +/- 0.01 for the vegetative stage, 1.00 +/- 0.01 for the reproductive stage, 0.97 +/- 0.04 for the ripening stage and 0.88 +/- 0.03 for the fallow period, whereas, for flooded rice, K-c values were 1.04 +/- 0.04 for the vegetative stage, 1.11 +/- 0.05 for the reproductive stage, 1.04 +/- 0.05 for the ripening stage and 0.93 +/- 0.06 for the fallow period. The average annual ET was 1301 mm for aerobic rice and 1440 mm for flooded rice. This corresponds to about 11% lower total evapotranspiration in aerobic fields than in flooded fields. However, the crop water productivity (WPET) of aerobic rice (0.42 +/- 0.03 g grain kg(-1) water) was significantly lower than that of flooded rice (1.26 +/- 0.26 g grain kg(-1) water) because the grain yields of aerobic rice were very low since they were subjected to water stress. The results of this investigation showed significant differences in energy balance and evapotranspiration between flooded and aerobic rice ecosystems. Aerobic rice is one of the promising water-saving technologies being developed to lower the water requirements of the rice crop to address the issues of water scarcity. This information should be taken into consideration in evaluating alternative water-saving technologies for environmentally sustainable rice production systems. (C) 2011 Elsevier B.V. All rights reserved.
  • Toshikazu Kizuka, Hiroyuki Yamada, Takashi Hirano
    JOURNAL OF HYDROLOGY 401 1-2 106 - 116 2011年04月 [査読有り][通常論文]
     
    Mire pools - permanently water-filled depressions on peatlands - provide important habitats for myriad organisms. Recently, water balance change and eutrophication resulting from agricultural development are increasingly evident in mire pools of alluvial lowlands. Conservation of mire pool hydrochemistry is necessary. We investigated the hydrological and chemical budgets of a pristine mire pool, Akanuma Pool (95,280 m(2) area; 1.8 m mean depth), located in Kushiro Mire in Hokkaido, northern Japan, during its ice-free period (April-November) in 2007-2008. Thereby we elucidated the hydrochemical characteristics of mire pools formed on alluvial lowlands. Surface water inflow and surface water outflow dominated the hydrological budget, respectively representing 18.3 and 20.2 mm day(-1). Groundwater seepage through the pool bottom and surface water inflow mainly supplied the lake water with total nitrogen and Ca(2+). Total phosphorus was supplied mostly by groundwater seepage through the bottom. These chemical constituents were run off from the pool mostly by surface water outflow. The input and output fluxes of water were 16-20 times greater than those of North American mire pools because of Hokkaido's higher values of precipitation minus evapotranspiration (P-En. Moreover, the Ca(2+) input into the Akanuma Pool was several times greater than those reported from North American studies. Alluvial mineral soil under the peat layer supplied large amounts of nutrients and mineral ions including Ca(2+). These results demonstrate that Hokkaido mire pools' hydrochemical characteristics differ greatly from those of pools in North America. Furthermore, each hydrological budget component maintained a constant fraction throughout the two year study period, although the absolute flow rate varied concomitantly with the precipitation level. Maintaining this budget stability is important for the conservation of mire pool hydrochemistry. (C) 2011 Elsevier B.V. All rights reserved.
  • Khatun R, Ohta T, Kotani A, Asanuma J, Gamo M, Han S, Hirano T, Nakai Y, Saigusa N, Takagi K, Wang H, Yoshifuji N
    Hydrological Research Letters 5 88 - 92 THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES 2011年 [査読有り][通常論文]
     
    Evapotranspiration over forest surfaces is mainly constrained by environmental and forest structural components through their influence on surface conductance (Gs) and aerodynamic conductance (Ga). Tower based eddy covariance data from 16 forest sites in East Asia (2°S to 64°N) were used to examine the sensitivity of Matsumoto and Nakai models for predicting Gs and Ga, respectively. Daytime dry-canopy data for the growing season were used in this study. Comparisons between model predictions and observed Gs and Ga showed good agreement, suggesting that the models were suitable for predicting Gs and Ga with reasonable accuracy. However, the model for Gs was unable to predict Gs accurately when soil water content was low (∼10%). In this circumstance, effective soil water content and a more comprehensive method for modelling the soil water content function must be used. Gs in East Asia was largely depended on vapour pressure deficit and secondarily on soil water content. Ga was largely affected by leaf area index compared with stand density.
  • Khatun R, Ohta T, Kotani A, Asanuma J, Gamo M, Han S, Hirano T, Nakai Y, Saigusa N, Takagi K, Wang H, Yoshifuji N
    Hydrological Research Letters 5 83 - 87 THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES 2011年 [査読有り][通常論文]
     
    Evapotranspiration (ET) is not only a vital component of water budget, but also plays an important role in the energy budget of the earth-atmospheric system, ultimately driving many regional and global scale climatological processes. This paper describes the ET characteristics and factors controlling ET across the 17 forest sites in East Asia (2°S to 64°N latitude). ET was measured using the eddy covariance technique at each site. Daytime dry-canopy data for the growing season were used in this study. Growing season mean ET gradually decreased as latitude increased, with a range of 4.4 to 1.2 mm d−1. The growing season mean decoupling coefficient (Ω) ranged from 0.42 to 0.11 across the studied sites. At low-latitude forest sites, Ω was close to 0.50, indicating that the bulk surface was partially decoupled from the atmosphere and ET was strongly controlled by net radiation and vapour pressure deficit. At high-latitude forest sites, Ω was low (∼0.12), indicating that the bulk surface was well coupled to the atmosphere and ET was mainly controlled by surface conductance. The value of Ω was determined mainly by the ratio of aerodynamic conductance to surface conductance across the studied forests of East Asia.
  • Tomohito Sano, Takashi Hirano, Naishen Liang, Ryuichi Hirata, Yasumi Fujinuma
    FOREST ECOLOGY AND MANAGEMENT 260 12 2214 - 2223 2010年12月 [査読有り][通常論文]
     
    A typhoon event catastrophically destroyed a 45-year-old Japanese larch plantation in southern Hokkaido, northern Japan in September 2004, and about 90% of trees were blown down. Vegetation was measured to investigate its regeneration process and CO2 flux, or net ecosystem production (NEP), was measured in 2006-2008 using an automated chamber system to investigate the effects of typhoon disturbance on the ecosystem carbon balance. Annual maximum aboveground biomass (AGB) increased from 2.7 Mg ha(-1) in 2006 to 4.0 Mg ha(-1) in 2007, whereas no change occurred in annual maximum leaf area index (LAI), which was 3.7 m(2) m(-2) in 2006 and 3.9 m(2) m(-2) in 2007. Red raspberry (Rubus idaeus) had become dominant within 2 years after the typhoon disturbance, and came to account for about 60% and 50% of AGB and LAI, respectively. In comparison with CO2 fluxes measured by the eddy covariance technique in 2001-2003, for 4.5 months during the growing season, the sum of gross primary production (GPP) decreased on average by 739 gC m(-2) (64%) after the disturbance, whereas ecosystem respiration (RE) decreased by 501 gC m(-2) (51%). As a result, NEP decreased from 159 +/- 57 gC m(-2) to -80 +/- 30 gC m(-2), which shows that the ecosystem shifted from a carbon sink to a source. Seasonal variation in RE was strongly correlated to soil temperature. The interannual variation in the seasonal trend of RE was small. Light-saturated GPP (P-max) decreased from 30-45 mu mol m(-2) s(-1) to 8-12 mu mol m(-2) s(-1) during the summer season through the disturbance because of large reduction in LAI. (C) 2010 Elsevier B.V. All rights reserved.
  • Rodrigo Vargas, Dennis D. Baldocchi, Michael F. Allen, Michael Bahn, T. Andrew Black, Scott L. Collins, Jorge Curiel Yuste, Takashi Hirano, Rachhpal S. Jassal, Jukka Pumpanen, Jianwu Tang
    ECOLOGICAL APPLICATIONS 20 6 1569 - 1582 2010年09月 [査読有り][通常論文]
     
    We seek to understand how biophysical factors such as soil temperature (T-s), soil moisture (theta), and gross primary production (GPP) influence CO2 fluxes across terrestrial ecosystems. Recent advancements in automated measurements and remote-sensing approaches have provided time series in which lags and relationships among variables can be explored. The purpose of this study is to present new applications of continuous measurements of soil CO2 efflux (F-0) and soil CO2 concentrations measurements. Here we explore how variation in T-s, theta, and GPP (derived from NASA's moderate-resolution imaging spectroradiometer [MODIS]) influence F-0 and soil CO2 production (P-s). We focused on seasonal variation and used continuous measurements at a daily timescale across four vegetation types at 13 study sites to quantify: (1) differences in seasonal lags between soil CO2 fluxes and T-s, theta, and GPP and (2) interactions and relationships between CO2 fluxes with T-s, theta, and GPP. Mean annual T-s did not explain annual F-0 and P-s among vegetation types, but GPP explained 73% and 30% of the variation, respectively. We found evidence that lags between soil CO2 fluxes and T-s or GPP provide insights into the role of plant phenology and information relevant about possible timing of controls of autotrophic and heterotrophic processes. The influences of biophysical factors that regulate daily F-0 and P-s are different among vegetation types, but GPP is a dominant variable for explaining soil CO2 fluxes. The emergence of long-term automated soil CO2 flux measurement networks provides a unique opportunity for extended investigations into F-0 and P-s processes in the near future.
  • Ueyama M., Ichii K., Hirata R., Takagi K., Asanuma J., Machimura T., Nakai Y., Ohta T., Saigusa N., Takahashi Y., Hirano T.
    Biogeosciences 7 3 959 - 977 Copernicus Publications 2010年03月10日 [査読有り][通常論文]
     
    Larch forests are widely distributed across many cool-temperate and boreal regions, and they are expected to play an important role in global carbon and water cycles. Model parameterizations for larch forests still contain large uncertainties owing to a lack of validation. In this study, a process-based terrestrial biosphere model, BIOME-BGC, was tested for larch forests at six AsiaFlux sites and used to identify important environmental factors that affect the carbon and water cycles at both temporal and spatial scales. The model simulation performed with the default deciduous conifer parameters produced results that had large differences from the observed net ecosystem exchange (NEE), gross primary productivity (GPP), ecosystem respiration (RE), and evapotranspiration (ET). Therefore, we adjusted several model parameters in order to reproduce the observed rates of carbon and water cycle processes. This model calibration, performed using the AsiaFlux data, substantially improved the model performance. The simulated annual GPP, RE, NEE, and ET from the calibrated model were highly consistent with observed values. The observed and simulated GPP and RE across the six sites were positively correlated with the annual mean air temperature and annual total precipitation. On the other hand, the simulated carbon budget was partly explained by the stand disturbance history in addition to the climate. The sensitivity study indicated that spring warming enhanced the carbon sink, whereas summer warming decreased it across the larch forests. The summer radiation was the most important factor that controlled the carbon fluxes in the temperate site, but the VPD and water conditions were the limiting factors in the boreal sites. One model parameter, the allocation ratio of carbon between belowground and aboveground, was site-specific, and it was negatively correlated with the annual climate of annual mean air temperature and total precipitation. Although this study substantially improved the model performance, the uncertainties that remained in terms of the sensitivity to water conditions should be examined in ongoing and long-term observations.
  • Hendrik Segah, Hiroshi Tani, Takashi Hirano
    INTERNATIONAL JOURNAL OF REMOTE SENSING 31 20 5297 - 5314 2010年 [査読有り][通常論文]
     
    Multitemporal Principal Component Analysis (MPCA) was used for processing Landsat Thematic Mapper (TM)/Enhanced Thematic Mapper plus (ETM+) satellite images. MPCA was able to merge spectral data corresponding to TM-1996 (pre-fire in 1997), ETM-2000 (post-fire 1997 and pre-fire 2002) and ETM-2003 (post-fire in 2002), which was crucial for detecting the fire impact and vegetation recovery. Results indicate that the burnt areas of 1997 and 2002 were 89,086 ha (16.5%) and 31,859 ha (5.9%), respectively, within the study area of 540,000 ha. Satellite Pour 1'Observation de la Terre (SPOT)-VEGETATION 10-day Maximum Value Composite (MVC) data were also used and compared with Normalized Difference Vegetation Index (NDVI) from ground-based NDVI. Our research demonstrates the strong relationship between Landsat- TM/ETM+, SPOT-VEGETATION data and ground-based NDVI in identifying land-cover changes and vegetation recovery over the tropical peat swamp forest area in Central Kalimantan, Indonesia that is affected by forest fires that occurred in 1997 and 2002.
  • N. Liang, T. Hirano, Z. -M. Zheng, J. Tang, Y. Fujinuma
    BIOGEOSCIENCES 7 11 3447 - 3457 2010年 [査読有り][通常論文]
     
    We had continuously measured soil CO2 efflux (R-s) in a larch forest in northern Japan at hourly intervals for the snow-free period in 2003 with an automated chamber system and partitioned R-s into heterotrophic respiration (R-h) and autotrophic respiration (R-r) by using the trench method. In addition, we applied the soil CO2 concentration gradients method to continuously measure soil CO2 profiles under snowpack in the snowy period and to partition R-s into topsoil (O-a and A horizons) CO2 efflux (F-t) with a depth of 0.13 m and sub-soil (C horizon) CO2 efflux (F-c). We found that soil CO2 effluxes were strongly affected by the seasonal variation of soil temperature but weakly correlated with soil moisture, probably because the volumetric soil moisture (30-40% at 95% confidence interval) was within a plateau region for root and microbial activities. The soil CO2 effluxes changed seasonally in parallel with soil temperature in topsoil with the peak in late summer. On the other hand, the contribution of R-r to R-s was the largest at about 50% in early summer, when canopy photosynthesis and plant growth were more active. The temperature sensitivity (Q(10)) of R-r peaked in June. Under snowpack, R-s was stable until mid-March and then gradually increased with snow melting. R-s summed up to 79 gC m(-2) during the snowy season for 4 months. The annual R-s was determined at 934 gC m(-2) y(-1) in 2003, which accounted for 63% of ecosystem respiration. The annual contributions of R-h and R-r to R-s were 57% and 43%, respectively. Based on the gradient approach, R-s was partitioned vertically into litter (O-i and O-e horizons) with a depth of 0.01-0.02 m, topsoil and sub-soil respirations with proportions of 6, 72 and 22%, respectively, on an annual basis. The vertical distribution of CO2 efflux was consistent with those of soil carbon and root biomass.
  • Joshua B. Fisher, Yadvinder Malhi, Damien Bonal, Humberto R. Da Rocha, Alessandro C. De Araujo, Minoru Gamo, Michael L. Goulden, Takashi Hirano, Alfredo R. Huete, Hiroaki Kondo, Tomo'Omi Kumagai, Henry W. Loescher, Scott Miller, Antonio D. Nobre, Yann Nouvellon, Steven F. Oberbauer, Samreong Panuthai, Olivier Roupsard, Scott Saleska, Katsunori Tanaka, Nobuaki Tanaka, Kevin P. Tu, Celso Von Randow
    GLOBAL CHANGE BIOLOGY 15 11 2694 - 2714 2009年11月 [査読有り][通常論文]
     
    Tropical vegetation is a major source of global land surface evapotranspiration, and can thus play a major role in global hydrological cycles and global atmospheric circulation. Accurate prediction of tropical evapotranspiration is critical to our understanding of these processes under changing climate. We examined the controls on evapotranspiration in tropical vegetation at 21 pan-tropical eddy covariance sites, conducted a comprehensive and systematic evaluation of 13 evapotranspiration models at these sites, and assessed the ability to scale up model estimates of evapotranspiration for the test region of Amazonia. Net radiation was the strongest determinant of evapotranspiration (mean evaporative fraction was 0.72) and explained 87% of the variance in monthly evapotranspiration across the sites. Vapor pressure deficit was the strongest residual predictor (14%), followed by normalized difference vegetation index (9%), precipitation (6%) and wind speed (4%). The radiation-based evapotranspiration models performed best overall for three reasons: (1) the vegetation was largely decoupled from atmospheric turbulent transfer (calculated from X decoupling factor), especially at the wetter sites; (2) the resistance-based models were hindered by difficulty in consistently characterizing canopy (and stomatal) resistance in the highly diverse vegetation; (3) the temperature-based models inadequately captured the variability in tropical evapotranspiration. We evaluated the potential to predict regional evapotranspiration for one test region: Amazonia. We estimated an Amazonia-wide evapotranspiration of 1370 mm yr(-1), but this value is dependent on assumptions about energy balance closure for the tropical eddy covariance sites; a lower value (1096 mm yr(-1)) is considered in discussion on the use of flux data to validate and interpolate models.
  • Ma. Carmelita R. Alberto, Reiner Wassmann, Takashi Hirano, Akira Miyata, Arvind Kumar, Agnes Padre, Modesto Amante
    AGRICULTURAL AND FOREST METEOROLOGY 149 10 1737 - 1750 2009年10月 [査読有り][通常論文]
     
    The seasonal fluxes of heat, moisture and CO2 were investigated under two different rice environments: flooded and aerobic soil conditions, using the eddy covariance technique during 2008 dry season. The fluxes were correlated with the microclimate prevalent in each location. This study was intended to monitor the environmental impact, in terms of C budget and heat exchange, of shifting from lowland rice production to aerobic rice cultivation as an alternative to maintain crop productivity under water scarcity. The aerobic rice fields had higher sensible heat flux (H) and lower latent heat flux (LE) compared to flooded fields. On seasonal average, aerobic rice fields had 48% more sensible heat flux while flooded rice fields had 20% more latent heat flux. Consequently, the aerobic rice fields had significantly higher Bowen ratio (0.25) than flooded fields (0.14), indicating that a larger proportion of the available net radiation was used for sensible heat transfer or for warming the surrounding air. The total C budget integrated over the cropping period showed that the net ecosystem exchange (NEE) in flooded rice fields was about three times higher than in aerobic fields while gross primary production (GPP) and ecosystem respiration (R-e) were 1.5 and 1.2 times higher, respectively. The high GPP of flooded rice ecosystem was evident because the photosynthetic capacity of lowland rice is naturally large. The R, of flooded rice fields was also relatively high because it was enhanced by the high photosynthetic activities of lowland rice as manifested by larger above-ground plant biomass. The NEE, GPP, and R, values for flooded rice fields were -258, 778, and 521 g C m(-2), respectively. For aerobic rice fields, values were -85, 515, and 430 g C m(-2) for NEE, GPR and R-e respectively. The ratio of R-e/GPP in flooded fields was 0.67 while it was 0.83 for aerobic rice fields. This short-term data showed significant differences in C budget and heat exchange between flooded and aerobic rice ecosystems. Further investigation is needed to clarify seasonal and inter-annual variations in microclimate, carbon and water budget of different rice production systems. (C) 2009 Elsevier B.V. All rights reserved.
  • Takashi Hirano, Jyrki Jauhiainen, Takashi Inoue, Hidenori Takahashi
    ECOSYSTEMS 12 6 873 - 887 2009年09月 [査読有り][通常論文]
     
    The carbon balance of tropical peatlands was investigated using measurements of gaseous fluxes of carbon dioxide (CO(2)) and methane (CH(4)) at several land-use types, including nondrained forest (NDF), drained forest (DF), drained regenerating forest (DRF) after clear cutting and agricultural land (AL) in Central Kalimantan, Indonesia. Soil greenhouse gas fluxes depended on land-use, water level (WL), microtopography, temperature and vegetation physiology, among which WL was the strongest driver. All sites were CH(4) sources on an annual basis and the emissions were higher in sites providing fresh litter deposition and water logged conditions. Soil CO(2) flux increased exponentially with soil temperature (T(s)) even within an amplitude of 4-5 degrees C. In the NDF soil CO(2) flux sharply decreased when WLs rose above -0.2 and 0.1 m for hollows and hummocks, respectively. The sharp decrease suggests that the contribution of surface soil respiration (RS) to total soil CO(2) flux is large. In the DF soil CO(2) flux increased as WL decreased below -0.7 m probably because the fast aerobic decomposition continued in lower peat. Such an increase in CO(2) flux at low WLs was also found at the stand level of the DF. Soil CO(2) flux showed diurnal variation with a peak in the daytime, which would be caused by the circadian rhythm of root respiration. Among the land-use types, annual soil CO(2) flux was the largest in the DRF and the smallest in the AL. Overall, the global warming potential (GWP) of CO(2) emissions in these land-use types was much larger than that of CH(4) fluxes.
  • Nobuko Saigusa, Susumu Yamamoto, Ryuichi Hirata, Yoshikazu Ohtani, Reiko Ide, Jun Asanuma, Minoru Gamo, Takashi Hirano, Hiroaki Kondo, Yoshiko Kosugi, Sheng-Gong Li, Yuichiro Nakai, Kentaro Takagi, Makoto Tani, Huimin Wang
    AGRICULTURAL AND FOREST METEOROLOGY 148 5 700 - 713 2008年05月 [査読有り][通常論文]
     
    Measurements of net ecosystem production (NEP) over forest stands were conducted from 11 flux towers in sub-arctic, temperate, and tropical regions in East Asia between 2000 and 2005. The sites extend over a wide latitude, ranging from 3 to 64 degrees N, and include sub-arctic and temperate needle-leaf deciduous forests (larch) (central Siberia, Mongolia, China, and northern Japan), temperate mixed, broadleaf deciduous, needle-leaf evergreen forests (northern and central japan), and seasonal and tropical rain forests (Thailand and Malaysia). The sub-arctic larch forests had short growing periods of 3-4 months. The temperate deciduous forests showed the greatest positive NEP after leaf expansion in early summer. Among the 11 sites, the maximum gross primary production (GPP) was observed in a temperate larch forest during the early stages of the growing period due to the high productivity of the larch species. The temperate evergreen sites displayed positive NEP earlier in the spring than the deciduous sites and had long growing periods (>10 months). The tropical seasonal forests showed negative NEP during the dry period from February to April, and turned positive after the rainy season started. The tropical rain forest showed a small flux (<30 g C m(-2) month(-1)) throughout the year without a clear seasonal change. In 2002 and 2003, several significant weather anomalies were observed, such as increased temperature in the temperate sites and less precipitation than average in the tropical sites in the beginning of 2002, and decreased solar radiation in the temperate sites in the 2003 summer. The seasonal patterns of NEP were sensitive to the anomalies, and the variations were caused by: (1) high spring air temperature, which induced an early start of the growing period in the temperate forests, (2) summer solar radiation, which controlled the summer GPP in the temperate forests with a slight variation among sites due to different responses of GPP to the temperature and water vapor pressure deficit (VPD) conditions, and (3) a long dry season, which significantly reduced GPP in a tropical seasonal forest. The dataset, which was obtained from a wide variety of forest ecosystems in East Asia over several years, is essential to validate ecosystem models and to generate technological developments of satellite remote sensing in the distribution of the terrestrial carbon budget in Asia. (C) 2007 Elsevier B.V. All rights reserved.
  • Ryuichi Hirata, Nobuko Saigusa, Susumu Yamamoto, Yoshikazu Ohtani, Reiko Ide, Jun Asanuma, Minoru Gamo, Takashi Hirano, Hiroaki Kondo, Yoshiko Kosugi, Sheng-Gong Li, Yuichiro Nakai, Kentaro Takagi, Makoto Tani, Huimin Wang
    AGRICULTURAL AND FOREST METEOROLOGY 148 5 761 - 775 2008年05月 [査読有り][通常論文]
     
    The objective of this paper is to clarify what kind of environmental factors that regulate net ecosystem production (NEP), gross primary production (GPP), and ecosystem respiration (RE) in forest ecosystems across East Asia. Study sites were widely distributed and included diverse ecosystems, such as evergreen and deciduous, coniferous and broadleaf, planted and natural forests, from subarctic to tropical zones. We measured NEP using the eddy covariance technique at 13 forest sites in East Asia. Annual values of GPP and RE are simply regulated by annual mean air temperature across East Asia. There is a clear linear relationship between annual GPP and annual mean air temperature because the air temperature influences both growing period length and the seasonal variation of the maximum photosynthetic capacity, which, together, regulate the annual GPP. On the other hand, there is a strong exponential relationship between annual RE and annual mean air temperature on an East Asia scale, which is quite similar to the relation obtained on a canopy scale. The dependency of annual RE on air temperature on the East Asia scale was similar to that of monthly RE on air temperature on an individual site scale excepting for temperate larch and mixed forests in northern Japan. The reason why the relation is simple is that severe stress, which affects GPP or RE, is small in East Asia. The present study suggests that RE is sensitive to non-climate environmental factors when compared to GPP, thus the annual RE-air temperature relationship is more scattered than the annual GPP-air temperature relationship. The NEP is small at high latitude, relatively large at mid-latitude, and scattered at low latitude. As a whole, the NEP is more influenced by RE than GPP in East Asia. Compared to North America and Europe, the increase in the ratio of GPP to air temperature is slightly higher in East Asia. One of the possible reasons for this is that GPP in East Asia is not exposed to severe environmental stresses, such as summer drought. (C) 2007 Elsevier B.V. All rights reserved.
  • 木塚俊和, 山田浩之, 平野高司
    環境情報科学論文集 22 22 493 - 498 環境情報科学センター 2008年 [査読有り][通常論文]
  • Ryuichi Hirata, Takashi Hirano, Nobuko Saigusa, Yasumi Fujinuma, Koh Inukai, Yasuyuki Kitamori, Yoshiyuki Takahashi, Susumu Yamamoto
    AGRICULTURAL AND FOREST METEOROLOGY 147 3-4 110 - 124 2007年12月 [査読有り][通常論文]
     
    This paper reports 3-year measurements (2001-2003) of the net ecosystem CO, exchange (NEE) over a northern Japan larch plantation forest, using an eddy covariance technique with both open- and closed-path systems. The study evaluates interannual variations in the seasonal patterns of NEE, the annual NEE, clarifying the factors controlling the carbon balance. NEE for both open- and closed-path systems look equivalent from the half-hourly mean values; however, there is a small systematic bias in the annual cumulative totals. In this study, we used closed-path data because open-path data during winter are doubtful and the annual NEE from closed-path data was closer to the biometric NEP than that from open-path data. The 3-year averages of annual NEE, gross primary production (GPP), and ecosystem respiration (RE) were -212 +/- 43 (standard deviation), -1673 +/- 59, and 1462 +/- 42 gC m(-2) y(-1), respectively. The larch plantation forest absorbed large amounts of CO2 during just 1 month, June. During that period, photosynthetic photon flux density (PPFD) was large while the temperature was not high. These meteorological conditions were suitable for CO, absorption before the leaf area index (LAI) reached its peak. Maximum GPP at light saturation (P-max) was also large. During the 3-year measurement period, PPFD in summer, and temperatures in spring and summer engendered remarkable interannual differences of GPP, RE, and NEE. In spring, snowmelt and larch foliation occurred about 2 weeks earlier in 2002 than in either 2001 or 2003 because of higher temperatures; consequently, the ecosystem began to photosynthesize earlier. In July, NEE was more negative in 2003 than in other years. The GPP became larger because of higher PPFD, larger P-max; while the RE became smaller because of lower temperatures. Compared with similar forests, the amounts of GPP and RE measured here were large, but NEE was similar. The reason is that the photosynthetic capacity of larch is naturally large: the ample PPFD, and the lack of environmental stresses from dry air or soil, consequently allows high photosynthesis rates to be maintained. Moreover, it can be inferred that RE values are enhanced by the high photosynthetic activity of larch forest during the growing season. (c) 2007 Elsevier B.V. All rights reserved.
  • N. Kobayashi, T. Hiyama, Y. Fukushima, M. L. Lopez, T. Hirano, Y. Fujinuma
    WATER RESOURCES RESEARCH 43 3 W03407, doi:10.1029/2006WR005556  2007年03月 [査読有り][通常論文]
     
    Nighttime transpiration in a larch forest in northern Japan was investigated using concurrent measurements of the energy budget below and above the canopy and sap flow velocities. Upward latent heat flux ( lE) above the canopy was observed on similar to 20% of nights during the growing season. Nighttime lE was similar to 7% of daily totals during the dry season (September-October) and averaged similar to 3% over the entire growing season. A relatively low contribution of the understory to lE (<30%) and strong synchronicity between larch sap flow rates and lE on two warm windy nights indicated nighttime lE, occurring when warm dry air intruded from above, was largely due to transpiration from the larch overstory. High canopy conductance on some nights relative to reported maximum cuticular conductance and a strong correlation between canopy conductance and air humidity on these nights indicate the stomata of the larch trees did not close tightly at night.
  • Takashi Hirano, Hendrik Segah, Tsuyoshi Harada, Suwido Limin, Tania June, Ryuichi Hirata, Mitsuru Osaki
    GLOBAL CHANGE BIOLOGY 13 2 412 - 425 2007年02月 [査読有り][通常論文]
     
    Tropical peatlands, which coexist with swamp forests, have accumulated vast amounts of carbon as soil organic matter. Since the 1970s, however, deforestation and drainage have progressed on an enormous scale. In addition, El Nino and Southern Oscillation (ENSO) drought and large-scale fires, which grow larger under the drought condition, are accelerating peatland devastation. That devastation enhances decomposition of soil organic matter and increases the carbon release to the atmosphere as CO2. This phenomenon suggests that tropical peatlands have already become a large CO2 source, but related quantitative information is limited. Therefore, we evaluated the CO2 balance of a tropical peat swamp forest in Central Kalimantan, Indonesia, using 3 years of CO2 fluxes measured using the eddy covariance technique from 2002 through 2004. The forest was disturbed by drainage; consequently, groundwater level (GL) was reduced. The net ecosystem CO2 production (NEP) measurements showed seasonal variation, which was slightly positive or almost zero in the early dry season, and most-negative late in the dry season or early the rainy season. This seasonality is attributable to the seasonal pattern of climate, tree phenology and fires. Slightly positive NEP resulted from smaller ecosystem respiration (RE) and larger gross primary production (GPP) under conditions of high photosynthetic photon flux density (PPFD) and large leaf area index (LAI). The most-negative NEP resulted from smaller GPP and larger RE. The smaller GPP was related to high vapor pressure deficit (VPD), small LAI and low PPFD because of smoke from fires. The larger RE was related to low GL. Annual NEP values were estimated respectively as -602, -382 and -313 g C m(-2) yr(-1) for 2002, 2003 and 2004. These negative NEP values show that the tropical peat swamp forest, disturbed by drainage, functioned as a CO2 source. That source intensity was highest in 2002, an ENSO year, mainly because of low PPFD caused by dense smoke emitted from large fires.
  • Makoto Ooba, Takashi Hirano, Jun-Ichi Mogami, Ryuichi Hirata, Yasumi Fujinuma
    ECOLOGICAL MODELLING 198 3-4 473 - 486 2006年10月 [査読有り][通常論文]
     
    In many cases of field measurements, missing data of net ecosystem CO2 exchange (NEE) constitute a quarter to almost half of all data. Those omissions result from accidents of instruments, unfavorable weather, and quality-control screening. Accurate gap-filling methods are needed for interpolating these missing data. This study evaluated the performance of interpolation methods for gap-filling of NEE data: a conventional method with empirical equations of bioreaction whose parameters were estimated using nonlinear regression (NR) methods, an artificial neural network (ANN) method, and an automated ANN method (genetic neural network, GNN). In the GNN method, parameters of an ANN model, such as initial weight matrixes and input-data-selections, were determined automatically using a genetic algorithm (GA). A tested dataset was observed in a Japanese larch plantation in northern Japan for 5 months from May to September 2002. The available dataset was divided into two subsets to train and validate the models. Averaged coefficients of determination (r(2)) of ANN models between observed and estimated values of NEE were almost identical to that of the NR method (r(2) = 0.86). The performance of the GNN method (r(2) = 0.88, averaged value) was somewhat better than those of the two methods. Using the GNN method, the mean daily NEE was estimated at -0.29 mol m(-1) d(-1) for the S-month period using ANNs, thereby showing better performance. The mean daily NEE, which was reported previously, was compatible with that from the NR method (-0.23 mol m(-2) d(-1)). From those results, it was concluded that the proposed GNN method offers better performance for gap-filling and high availability because of the obviated need for specialization of ecological or physiological mechanisms. (c) 2006 Elsevier B.V. All rights reserved.
  • Wenjie Wang, Yuangang Zu, Song Cui, Takashi Hirano, Yoko Watanabe, Takayoshi Koike
    TREE PHYSIOLOGY 26 10 1363 - 1368 2006年10月 [査読有り][通常論文]
     
    Larch (Larix gmelinii (Rupr.) Rupr.) cone scales are green, but little is known of their photosynthetic role in cone development or about how they differ in gas exchange characteristics from needle leaves. In contrast to leaf photosynthesis (P-leaf), we found that stomatal regulation of cone photosynthetic rate (P-cone) was marginal because the photosynthetic carbon came from internal recycling of respiratory carbon dioxide (CO2). Photosynthetic recycling of respired CO2 was confirmed by the finding that the intercellular CO2 concentration (C-i) in cone scales was much higher than ambient [CO2]; also, there was a positive correlation between P-cone and C-i, whereas P-leaf was almost constant as C-i varied. Low chlorophyll (Chl) concentration was a limiting factor for P-leaf but not for P-leaf, as indicated by the correlation between P-cone, and chlorophyll concentration. Moreover, chlorophyll utilization efficiency (P-sat/Chl a+b) for cone scales was lower than that for leaves. In both cones and leaves, nitrogen (N) was positively correlated with photosynthetic capacity (P), but the P/N value was much lower for cones than for leaves. For both organs, the ratio of respiration to N was broadly similar. Although mature cones have no photosynthetic capacity, P-cone, of young cones was as high as 5.3 mu mol m(-2) s(-1), about 1.26 times the value of P-leaf, and accounted for the refixation of 30-40% of the respiratory CO2 produced by cones, equivalent to the photosynthetic capacity of a bundle of short shoots near each cone. Thus, P-cone may be an important additional source of photosynthate for cones, given the weak assimilating capacity of leaves that are not fully expanded during cone development.
  • Teruyo Ieda, Yasuyuki Kitamori, Michihiro Mochida, Ryuichi Hirata, Takashi Hirano, Kou Inukai, Yasumi Fujinuma, Kimitaka Kawamura
    TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY 58 3 177 - 186 2006年07月 [査読有り][通常論文]
     
    Volatile and semi-volatile organic compounds (VOCs and SVOCs) in the atmosphere control oxidative capacity of the air and formation of organic aerosols. To investigate sources, variations and fluxes of VOCs and SVOCs in the forest atmosphere, samples were collected in a larch forest at different heights in Tomakomai, Japan, from 3 to 5 September 2003 and were analyzed for VOCs (isoprene and a-pinene) and SVOCs (n-nonanal, n-decanal, glycolaldehyde, hydroxyacetone. glyoxal and methylglyoxal) using GC-FID and GC-MS. Isoprene (8-851 pptv) showed a diurnal variation with a maximum in daytime, whereas diurnal pattern was indistinct for a-pinene (6-145 pptv). SVOCs showed diurnal variations similar to isoprene, suggesting their origin to be biogenic. Denuder samplings of SVOCs demonstrated that up to 60% of SVOCs were present in aerosol particles. n-Nonanal and n-decanal were more abundant at lower altitude, suggesting their primary emissions from vegetations. In contrast, other four SVOCs showed an opposite or no trend and are considered as oxidation products of biogenic precursors such as isoprene. The averaged upward fluxes of isoprene and a-pinene were obtained to be 34.8 and 9.8 ng m(-2) s(-1), respectively. Magnitudes of SVOC fluxes were comparable to those of a-pinene, indicating that SVOCs affect budgets of organic gases/aerosols over the forest.
  • Oxana V. Masyagina, Takashi Hirano, Dong Hun Ji, Dong Su Choi, Laiye Qu, Yasumi Fujinuma, Kaichiro Sasa, Yojiro Matsuura, Stanislav G. Prokushkin, Takayoshi Koike
    Forest Science and Technology 2 2 80 - 91 2006年 [査読有り][通常論文]
     
    Harvesting of trees or the loss of trees due to strong winds may lead to large variations at the ground surface that, in turn, causes spatial and temporal variability of soil respiration. We performed thinning (partial harvest) on a mature larch plantation (ca. 50 yr-old) in Tomakomai National Forest (Japan) with the purpose of studying the effects of thinning on soil respiration (Rs). We conducted field measurements to determine how soil temperature (Ts), mineral soil water content (MSWC), litter water content (LWC), fine root density, litter density, and carbon to nitrogen ratio (C/N) individually influence soil respiration. Soil respiration values did not differ significantly at the disturbed site. Soil temperature was significantly greater at the disturbed site than at the control site (t-test= -12.7, P< 0.05), and the MSWC and LWC did not differ between sites. Despite these observations we found no proof that Ts or MSWC influences Rs. At the disturbed site, LWC appeared to be a primary microclimatic factor driving spatial variations in Rs (r= -0.41, P< 0.05). Thinning led to large variations in Rs, Ts, fine root density, and litter density. Root and litter densities were 18% (insignificant value) and 15% (t-test=2.86, P< 0.05) lower in the disturbed site, respectively. In fact, variations in soil respiration can be explained on the basis of litter density and C/N. © 2006, Taylor & Francis Group, LLC.
  • WJ Wang, YG Zu, HM Wang, XY Li, T Hirano, T Koike
    PHOTOSYNTHETICA 44 1 147 - 150 2006年 [査読有り][通常論文]
     
    A stem-girdling experiment was carried out on an evergreen conifer, the Korean pine (Pinus koraiensis Sieb. et Zucc.), in mid summer in Northeast China. A 50 % higher respiration rate at the upper part of the stem was observed 3 d after stem girdling, and a stable higher rate (1.2-2.8 times) one week later. However, no higher soluble sugar or starch contents were found in the upper bark of the girdled stems in measurements over three weeks. These findings indicate that most of the newly-formed photosynthates were consumed by the high respiratory activity; this is also implied by the strong correlation between the photosynthetic photon flux over the canopy (PPF) and respiration at the upper parts of girdled stems. Moreover, the maximum PPF and cumulative PPF one day before measurement (PPFmax-Y and CPPF-Y, respectively) were closely correlated with the respiratory difference between the upper and the lower parts, but no such correlation was found with the instantaneous PPF (PPF-I) and Cumulative PPF on the current day from sunrise to measured time point (CPPF-C). This shows that photosynthates newly formed by canopy needles need at least one day for transportation in order to increase the stem respiration at tree breast height.
  • Changes in CO2 exchanges during the development of larch (Larix gmelinii) cones
    Wang W, Zu Y, Cui S, Hirano T, Watanabe Y, Koike T
    Tree Physiology 26 1363 - 1368 2006年 [査読有り][通常論文]
  • T Hirano
    GLOBAL BIOGEOCHEMICAL CYCLES 19 2 GB2011, doi:10.1029/2004GB002259  2005年04月 [査読有り][通常論文]
     
    We measured soil CO2 concentration at half-hour intervals with infrared gas analyzers buried in soil at four depths throughout the snow cover season extending from early December to early April in a deciduous temperate forest. We evaluated soil CO2 efflux or total soil respiration, topsoil (the A-horizon) respiration, and subsoil (the C-horizon) respiration using a modified flux gradient method. Thereby, we investigated seasonal and diurnal variations in these soil respirations under snowpack. Soil CO2 concentration and soil respiration changed dynamically under the condition of constant soil temperature. Topsoil respiration decreased rapidly in late autumn and relatively constant until mid-winter, whereas it increased in late winter when snowmelt progressed. On the other hand, subsoil respiration decreased gradually until mid-winter and increased slightly in late winter. Both topsoil and subsoil respirations showed similar diurnal variations with a peak in early or mid-afternoon, respectively, independently of soil temperature. These seasonal and diurnal variations in soil respiration were inferred to result from the supply of labile carbon compounds, which were respiratory substrates for microorganisms, into soil from litter with meltwater. The seasonal sum of topsoil, subsoil, and total respirations for the snow cover period of 4 months were 21.4, 48.0, and 69.4 gC m(-2), respectively; these accounted for 3.0, 27.3, and 7.7% of the annual sum, respectively. The ratio of topsoil respiration to total soil respiration was 0.31 on average during the snow period, which was considerably lower than that in the summer season.
  • WJ Wang, YG Zu, HM Wang, T Hirano, K Takagi, K Sasa, T Koike
    JOURNAL OF FOREST RESEARCH 10 1 57 - 60 2005年02月 [査読有り][通常論文]
     
    Little information is available on the effect of root cutting by the collar pre-insertion technique on soil respiration. In this study, we found that soil respiration rates decreased with increasing depth of collar insertion in both the "with live roots intact" and "with live roots severed" treatments, but the rate of decrease was substantially higher in the former. The cutting of roots, especially fine roots, may be responsible for this result.
  • Yamamoto S, Saigusa N, Gamo M, Fujinuma Y, Inoue G, Hirano T
    Journal of Geographical Sciences 15 2 142 - 148 2005年 [査読有り][通常論文]
  • 生物複雑系に適応するモデルとその背景
    大場 真, 平野高司
    北海道の農業気象 57 49 - 63 2005年 [査読有り][通常論文]
  • Hirano T, Urano S, Yazaki T, Yabe K, Kawauchi K, Okada K, Hinzman L, Ishikawa N
    Journal of Agricultural Meteorology 60 5 737 - 740 日本農業気象学会 2005年 [査読有り][通常論文]
  • Hirata R, Hirano T, Okada K, Fujinuma Y, Inukai K, Saigusa N, Yamamoto S
    Journal of Agricultural Meteorology 60 5 741 - 744 日本農業気象学会 2005年 [査読有り][通常論文]
  • Machimura T, Kobayashi Y, Iwahana G, Hirano T, Lopez L, Fukuda M, Fedorov A
    Journal of Agricultural Meteorology 60 5 653 - 656 日本農業気象学会 2005年 [査読有り][通常論文]
  • H. Kim, T. Hirano, T. Koike, S. Urano
    PHYTON-ANNALES REI BOTANICAE 45 4 385 - 388 2005年 [査読有り][通常論文]
     
    CO2 efflux from a forest floor is produced in subsoil, topsoil and litter layers. We evaluated topsoil respiration (R-t), subsoil respiration (R-s) and litter CO2 production (R-L) seperately in a deciduous broadleaf forest and a larch forest in northern Japan from April through November to investigate the contribution of R-L to total soil respiration (R-all: R-L + R-t + R-s). In the broadleaf forest, R-L peaked at 0.97 gC m(-2) d(-1) in late May. The R-L contribution to R-all (R-L / R-all) was large at 0.15-0.40 in spring, whereas it was less than 0.07 in summer. In the larch forest, only larch litter was examined. R-L of larch litter decreased gradually from 0.32 to 0.08 gC m(-2) d(-1) between April and November. R-L /R-all decreased rapidly during April and May from 0.19 to 0.04 and was almost constant in summer at 0.01-0.03. Seasonal sums of R-L, R-s and R-t were 85, 683 and 145 gC m(-2) for the broadleaf forest and 34, 700 and 253 gC m(-2) for the larch forest, respectively, for 8 months; R-L accounted for 9.3 and 3.4% of R-all for the broadleaf and larch forests, respectively.
  • Mogami J, Hirano T, Hirata R, Kitaoka S, Koike T, Fujinuma Y
    Journal of Agricultural Meteorology 60 6 1161 - 1163 日本農業気象学会 2005年 [査読有り][通常論文]
  • Urano S, Okada K, Ide K, Sano T, Kimura M, Hirano T, Funakoshi H, Takenoshita Y, Dohkoshi J
    Journal of Agricultural Meteorology 60 5 801 - 804 日本農業気象学会 2005年 [査読有り][通常論文]
  • T. Hirano, H. Segah, S. Limin, T. June, S. J. Tuah, K. Kusin, R. Hirata, M. Osaki
    PHYTON-ANNALES REI BOTANICAE 45 4 67 - 71 2005年 [査読有り][通常論文]
     
    Tropical peat swamp forests grow over tropical peatlands, which are widely distributed in flat lowlands in Southeast Asia. Recently, however, deforestation and drainage are in progress on a large scale because of growing demands for timber and farmland. In addition, the El Nino drought and its consequent fires are accelerating the forest devastation. The forest devastation alters energy balance and will influence regional climate. Thus, we have measured eddy energy fluxes above a tropical peat swamp forest left in a devastated peatland in Central Kalimantan, Indonesia since November 2001. Both in the rainy and dry seasons, latent heat flux (lE) considerably exceeded sensible heat flux (H). Net radiation (R-n) was mainly used by evapotranspiration (ET). The El Nino event occurred in 2002, and the consequent drought caused large-scale peatland fires in Central Kalimantan. A large amount of smoke emitted from the fires decreased Rn from mid-August through October. Bowen ratio (H/lE) decreased gradually from January through July in the range of 0.20-0.35. Although Bowen ratio decreased to a minimum of 0.15 in late September, it continued to increase during the late fire period and was high at 0.35-0.45 after the fires. ET accounted for 67% of precipitation (1856 mm) on an annual basis in 2002. Annual mean daily ET was 3.4 mm d(-1).
  • H. Wang, N. Saigusa, Y. Zu, S. Yamamoto, H. Kondo, F. Yang, W. Wang, T. Hirano, Y. Fujinuma
    PHYTON-ANNALES REI BOTANICAE 45 4 339 - 346 2005年 [査読有り][通常論文]
     
    The relationships between CO2 fluxes in larch forest ecosystems and environmental variables were investigated. The results indicate that the ecosystem CO2 uptake tended to decrease with an increasing vapor pressure deficit (VPD) when the VPD exceeded 15 hPa at both the Laoshan site (LS) in Northeast China and at the Tomakomai site (TFS) in northern Japan. The similarity of the VPD threshold value indicates that the larch forests at these two sites have a similar response to a dry environment. The carbon uptake rate of the larch forest was significantly lower on cloudy days (3.62 mu mol m(-2) s(-1) at LS and 3.76 mu mol m(-2) s(-1) at TFS) than on clear days (6.18 mu mol m(-2) s(-1) at LS and 6.53 mu mol m(-2) s(-1) at TFS) due to the significantly reduced incident radiation on cloudy days. However, the light-use efficiency of larch forests was much higher on cloudy than on clear days. This was due not only to the more diffused radiation on the cloudy days but also to a low VPD. Beyond our expectation, the air temperature showed almost no effect on the light-use efficiency of the larch forests.
  • Honghyun Kim, Takashi Hirano, Shin-Ichi Urano
    Journal of Agricultural Meteorology 61 2 95 - 104 2005年 [査読有り][通常論文]
     
    We collected leaf litter from a deciduous broadleaf forest and a larch forest in Hokkaido, Japan naturally without using litter traps or litter bags. The litter collection was conducted every month from October 2001 through October 2002 except in the snowy season. We measured the CO2 production rate of the litter samples through microbial respiration using the chamber method in a laboratory under different temperature and moisture conditions to investigate the seasonal pattern and temperature and moisture responses of CO2 production at the early stage of litter decomposition. Seasonal variation was found in the CO2 production rate per unit of litter dry weight (Pdw), or the litter decomposition rate, for both broadleaf and larch litters. Although seasonal patterns differed somewhat according to temperatures and species, Pdw reached the minimum in June. The moisture sensitivity of Pdw decreased with time and reached the minimum in summer for both broadleaf and larch litters, whereas the seasonal pattern of the temperature sensitivity (Q10) was not clear. The seasonal pattern of Pdw was explained by its C: N ratio for broadleaf litter. For larch litter, however, the relationship between Pdw and the C:N ratio was complicated because of fresh litterfall supplied gradually before defoliation. The temperature and moisture sensitivities of Pdw changed in parallel with the C:N ratio for both broadleaf and larch litters, respectively. These facts suggest the importance of litter chemical quality in the early decomposition process of fresh litter and the validity of the C:N ratio as an index of litter quality. © 2005, The Society of Agricultural Meteorology of Japan. All rights reserved.
  • カラマツ林におけるLAIの季節変化が林内気象に与える影響
    福田達也, 平野高司, 佐野智人, 平田竜一, 犬飼 孔, 藤沼康実
    北海道の農業気象 57 29 - 38 2005年 [査読有り][通常論文]
  • Segah H, Tani H, Hirano T, Kasahara T, Limin S
    Journal of Agricultural Meteorology 60 5 415 - 420 2005年 [査読有り][通常論文]
  • R. Hirata, T. Hirano, J. Mogami, Y. Fujinuma, K. Inukai, N. Saigusa, S. Yamamoto
    PHYTON-ANNALES REI BOTANICAE 45 4 347 - 351 2005年 [査読有り][通常論文]
     
    In the northern part of Japan, snow covers the land for several months in winter. It is necessary to estimate the CO2 flux during the snow-cover season to evaluate annual net CO2 exchange between the atmosphere and ecosystems (NEE); CO2 flux is probably small because of snow accumulation and low temperature. This paper reports NEE, as measured using an open-path system (NEEO) over a larch forest during the snow-cover season. NEEO ranged from -2 to -6 mu mol m(-2) s(-1) under sunshine conditions, whereas NEE measured with a closed-path system was always slightly positive. Such negative NEEO was unexpected because the forest canopy had no leaves and floor vegetation was under snowpack. One reason for negative NEEO under sunshine conditions is that the CO2 resolution of the open-path analyzer was low when CO2 fluctuation was small. During the snow-cover season, eddy energy flux accounted for 70% of available energy. Therefore, incomplete WPL correction of CO2 flux resulting from underestimated sensible heat flux would partly explain the unexpected negative NEEO.
  • HM Wang, N Saigusa, S Yamamoto, H Kondo, T Hirano, A Toriyama, Y Fujinuma
    ATMOSPHERIC ENVIRONMENT 38 40 7021 - 7032 2004年12月 [査読有り][通常論文]
     
    Larch forests are distributed extensively in the cast Eurasian continent and are expected to play a significant role in the terrestrial ecosystem carbon cycling process. In view of the fact that studies on carbon exchange for this important biome have been very limited, we have initiated a long-term flux observation in a larch forest ecosystem in Hokkaido in northern Japan since 2000. The net ecosystem CO2 exchange (NEE) showed large seasonal and diurnal variation. Generally, the larch forest ecosystem released CO2 in nighttime and assimilated CO2 in daytime during the growing season from May to October. The ecosystem started to become a net carbon sink in May, reaching a maximum carbon uptake as high as 186 g C m(-2) month(-1) in June. With the yellowing, senescing and leaf fall, the ecosystem turned into a carbon source in November. During the non-growing season, the larch forest ecosystem became a net source Of CO2, releasing an average of 16.7 g C m(-2) month(-1). Overall, the ecosystem sequestered 141-240 g C m(-2) yr(-1) in 2001. The NEE was significantly influenced by environmental factors. Respiration of the ecosystem, for example, was exponentially dependent on air temperature, while photosynthesis was related to the incident PAR in a manner consistent with the Michaelis-Menten model. Although the vapor pressure deficit (VPD) was scarcely higher than 15 hPa, the CO2 uptake rate was also depressed when VPD surpassed 10 hPa. (C) 2004 Elsevier Ltd. All rights reserved.
  • NS Liang, T Nakadai, T Hirano, LY Qu, T Koike, Y Fujinuma, G Inoue
    AGRICULTURAL AND FOREST METEOROLOGY 123 1-2 97 - 117 2004年05月 [査読有り][通常論文]
     
    Soil surface CO2 efflux (F-c) in a 45-year-old northern larch forest was continuously measured, using a multichannel automated chamber system, between June and October, 2001. The results were compared with periodic measurements obtained at the same site with an LI-6400 chamber system and an open-top chamber system, and also with continuous measurements obtained at the same site with a soil CO2 gradient system. The diurnal and seasonal changes in F-c measured by the automated chamber and Soil CO2 gradient approaches followed the soil temperature patterns. We found only a weak correlation between F-c and soil moisture, probably because the volumetric soil moisture (30-40% at 95% confidence interval) in this larch forest favors microbial and root activities. Among the four approaches, the LI-6400 chamber yielded a substantially higher F-c value than the other three approaches. The open-top chamber gave higher values of F-c than the automated chamber at efflux rates below 3.0 mumol m(-2) s(-1) and lower values above this level; however, the results of both these approaches were closely correlated (R-2 = 0.87, n = 105). Although F-c measured with the Soil CO2 gradient approach was, on average, 45% higher than the results of the automated chamber approach, the correlation between the two techniques was good (R-2 = 0.77, n = 2945). The annual soil CO2 efflux estimated by the automated chamber (665 g C m(-2)) and open-top chamber (720 g C m(-2)) matched the total annual ecosystem respiration, as estimated by the above-canopy eddy covariance method. However, the LI-6400 chamber and soil CO2 gradient approaches gave higher values for annual Soil CO2 efflux than the eddy covariance method. (C) 2003 Elsevier B.V. All rights reserved.
  • T Hirano, H Kim, Y Tanaka
    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 108 D20 doi:10.1029/2003JD003766  2003年10月 [査読有り][通常論文]
     
    [1] We conducted a field experiment in a cool-temperate deciduous forest to investigate the dynamic behavior of soil CO2 and the vertical distribution of soil respiration. Soil CO2 concentration (C) was measured half-hourly at four depths for 6 months in 2000 with infrared gas analyzers installed below ground. Using C profiles, soil surface CO2 efflux (F-0), CO2 production rates of the topsoil (P-A), and CO2 flux from the subsoil to topsoil (F-CA) were evaluated half-hourly by applying Fick's first law. Some remarkable short-term and long-term variations were found in C, F-0, P-A, F-CA, and the contribution of topsoil respiration to total soil respiration (P-A/F-0), which include (1) rapid increase in C and decrease in F-0 and P-A due to rainwater infiltration, (2) diurnal variation in C coupled with that of the atmosphere, (3) diurnal variation in F-0 and P-A similar to that of topsoil temperature, (4) decrease in C, F-0, and P-A following soil drying in August, (5) linearly increasing F-CA between late May and mid-September, and (6) decrease in P-A/F-0 from around 0.9 during summer to 0.3 in November. The variation of P-A was mainly controlled by soil temperature at -0.07 m between 7degrees and 17degreesC, although P-A did not respond well to soil temperature above and below this temperature range. Above 17degreesC, P-A increased linearly with soil moisture, and moisture variation accounted for the P-A decrease in August. Neither temperature nor moisture explained the P-A behavior below 7degreesC. Subsoil respiration (F-CA) showed an exponential relationship with soil temperature at -1 m.
  • T Hirano, R Hirata, Y Fujinuma, N Saigusa, S Yamamoto, Y Harazono, M Takada, K Inukai, G Inoue
    TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY 55 2 244 - 257 2003年04月 [査読有り][通常論文]
     
    In the northern part of East Asia, forests dominated by larch are extensively distributed and probably play an important role in the global carbon cycle. However, a knowledge of the CO2 balance of larch forests based on long-term flux measurements is very restricted in East Asia. Thus, a long-term flux measurement has been started in 2000 at a larch plantation on a flat terrain in Hokkaido, Japan to obtain more information on the CO2 and energy balances of larch forests. From September 2000 to August 2001 the net ecosystem CO2 exchange (NEE) changed seasonally in accordance with the annual cycles of phenology and climate. NEE was negative for six months of the growing season, May-September; the larch ecosystem was a carbon sink with a peak intensity of -0.38 mol m(-2) d(-1) for this period. In the leafless season from November to April the forest ecosystem was a carbon source with an intensity ranging between 0 and 0.05 mol m(-2) d(-1). Annual NEE from September 2000 to August 2001 was -24.4 to -32.4 mol m(-2) yr(-1) (= -293 to -389 gC m(-2) yr(-1)); this value is compatible with those reported from other temperate forests. Annual evapotranspiration for the same period was 367 turn, which was only 29% of annual precipitation.
  • 平井 源一, 稲村 達也, 奥村 俊勝, 芦田 馨, 田中 修, 中條 博良, 平野 高司
    日本作物學會紀事 72 2 196 - 202 日本作物学会 2003年 [査読無し][通常論文]
     
    本研究は水稲と陸稲の栄養生長期の生育に及ぼす大気湿度の影響を相対湿度60%と90%で比較したものである.その結果,低湿度条件は高湿度条件に比較して,水稲の乾物生産を有意に減少させたが,陸稲では乾物生産の減少は認められなかった.低湿度下の水稲では,単位葉面積当たり気孔密度が増大し,気孔装置面積も大となり葉面積に占める気孔装置面積の割合が高湿度に比較して有意に大きかった.また,水稲は低湿度で,気乱闘度の低下が少なく,単位葉面積当たり蒸散量が顕著に大きくなり,葉身の本部水ポテンシャルが大きく低下することが認められた.一方,陸稲では水稲に比し低湿度によって,気孔密度,気孔装置面積が変化せず,葉面積の中で気孔装置面積の占める割合に湿度間で有意差がなかった.また,陸稲では,低湿度によって気乱闘度が低下し,蒸散量を抑制するため,葉身の本部水ポテンシャルが低下しなかった.さらに,低湿度による葉身の本部水ポテンシャルの低下した水稲では,葉面積の相対生長率(LA-RGR)が,高湿度に比して有意に低下した.なお,純同化率(NAR)は低湿度によって低下したが,高湿度との間に有意差は認められなかった.したがって,水稲では低湿度で有意なNARの低下をまねく以前に葉面積の低下を引きおこし,乾物生産は抑制されたが,陸稲では湿度間で葉面積の生長速度に差を生じなかった.この点が水稲と,陸稲の生育,乾物生産におい...
  • 森林でのフラックス観測における欠測値補間法の比較
    最上純一, 平田竜一, 平野高司, 三浦昌孝, 藤沼康実, 犬飼孔
    北海道の農業気象 55 9 - 16 2003年 [査読有り][通常論文]
  • 中井太郎, 浦野慎一, 佐藤隆光, 平野高司
    農業気象 59 2 155 - 164 2003年 [査読有り][通常論文]
     
    Sensible heat advection from a 3-m-tall cornfield to a short grassland with a height of 0.3m was evaluated by wind speed and turbulent diffusivity, which were numerically calculated with a standard k-ε model including the effect of plant-atmosphere interaction, together with measured air temperature. The calculated wind speed agreed with the measurements. Air temperature was interpolated at each grid point by a bicubic spline method the grid dataset of air temperature was used as a boundary condition to solve the advection-diffusion equation. At noon on a sunny day in late summer, air temperature showed a horizontally-decreasing distribution from the cornfield to the grassland and a vertical lapse over the grassland. Horizontal wind accelerated between the cornfield and grassland, and downward wind existed over the grassland. Under these conditions, the horizontal advection increased the vertical gradient of sensible heat flux ∂H/∂z, while the vertical advection decreased it. Since the horizontal advection was predominant, ∂H/∂z was generally positive. The effect of the vertical advection was significant near the leading edge. However, the effect decreased with downwind distance from the edge and was negligible near the grassland surface. © 2003, The Society of Agricultural Meteorology of Japan. All rights reserved.
  • Yoshinobu Harazono, Takashi Hirano, Nobuko Saigusa, Yoshikazu Ohtani, Akira Miyata, Eiji Ohtaki, Nobutaka Monji
    農業気象 59 1 69 - 80 2003年 [査読有り][通常論文]
     
    Continuous long term micrometeorological CO2 flux observation has become an essential component to accurate determine CO2 uptake in terrestrial ecosystems after COP3. Because the intergovernmental agreement on CO2 emission control (Kyoto protocol) allows each country to subtract the annual accumulation of CO2 uptake by their ecosystems from the total anthropogenic CO2 emission. Hence, the demands to determine the CO2 uptake more accurately at the ecosystem level, and to make the long term CO2 flux observation a major research within multidisciplinary study fields such as ecology, biology, meteorology and agriculture have been increased significantly. Several flux observation sites have been operating in ecosystems of North America and Europe since 90's. These sites were initially independent research projects, but were later organized into networks such as AmeriFlux and EUROFLUX. FLUXNET was also established to enhance the understanding of ecosystem CO2 exchange including data exchange and to promote the measurement methodology among the networks. AsiaFlux was established in fall of 1999 as part of a flux observation research network in Japan and some Asian countries. The Study Group for Flux Measurement and Evaluation (S-FluME), the Society of Agricultural Meteorology of Japan (SAMJ) was organized to enhance the research activities of flux observations, and has been contributing to the activities of AsiaFlux. This paper reviews the development of theoretical and practical methodology of flux observation and discusses topics that arose from previous long term flux observations. Some suggestions and comments to improve the flux determination are also shown. © 2003, The Society of Agricultural Meteorology of Japan. All rights reserved.
  • Analysis of stomatal and non-stomatal regulation of the diurnal pattern of photosynthesis in Sasa saneanensis grown under a balanced nutrient regime
    Wang W, Osaki M, Hirano T, Hiura T, Koike T
    Bamboo Journal 20 19 - 32 2003年 [査読有り][通常論文]
  • 三浦昌孝, 平野高司, 平田竜一, 最上純一, 犬飼孔, 藤沼康実
    農業気象 59 3 245 - 250 2003年 [査読有り][通常論文]
     
    Sum of sensible and latent heat fluxes measured by the eddy covariance technique is systematically smaller than available energy in many terrestrial ecosystems, which includes forests. This energy imbalance is an essential issue for the flux measurement. In this study, we evaluated heat storage flux and investigated its effect on energy balance in a larch plantation developing on a flat terrain. Above-ground biomass was the largest component producing the heat storage flux of the forest ecosystem about 70-80% of the heat storage flux was generated in above-ground biomass for summer and fall. Moreover, the heat storage flux of topsoil over heat plates had a considerable bearing on the evaluation of soil heat flux. Adding these heat storage fluxes improved energy balance by 6-10% it increased the slope of the ordinary least square between eddy energy fluxes and available energy, which was used as an index of energy balance closure, from 0.83 to 0.88 in summer and from 0.93 to 1.03 in fall. This suggests that we have to measure and consider heat storage flux when we investigate the energy balance of forest ecosystems. © 2003, The Society of Agricultural Meteorology of Japan. All rights reserved.
  • 平井源一, 稲村俊勝, 芦田肇, 田中修, 中條博良, 平野高司
    日本作物学会紀事 72 2 196 - 202 2003年 [査読有り][通常論文]
     
    The effects of atmospheric humidity on vegetative growth of paddy and upland rice were compared. A low atmospheric humidity (60%RH) significantly decreased the dry-matter production in paddy rice but not in upland rice. In paddy rice, exposure to low atmospheric humidity significantly increased the stomatal density in leaves, stomatal aperture and the ratio of stomatal apparatus to leaf area. Thus, stomatal opening was only slightly decreased by the low humidity, resulting in a striking increase in transpiration rate per unit leaf area and marked reduction in water potential of leaf blade. On the other hand, in upland rice, stomatal density and stomatal apparatus area were not influenced by exposure to a low humidity and the ratio of stomatal apparatus area to leaf area was not influenced by atmospheric humidity up to 60%RH. In paddy rice, the relative leaf expansion rate was significantly reduced by exposure to a low humidity, but in upland rice, it was not. Thus, in the present study the low atmospheric humidity reduced the leaf expansion rate without reducing the net assimilation rate in paddy rice, but not in upland rice. This may be why the effect of atmospheric humidity on growth and dry-matter production differed between paddy and upland rice.
  • Nobutaka Monji, Ken Hamotani, Ryuichi Tosa, Toshifumi Fukagawa, Kazutoshi Yabuki, Takashi Hirano, Vipak Jintana, Somsak Piriyayota, Akifumi Nishimiya, Masahiro Iwasaki
    Journal of Agricultural Meteorology 58 2 63 - 69 2002年09月01日 [査読有り][通常論文]
     
    Two types of the modified gradient method for CO2 and water vapor flux estimation, in which the eddy correlation is applied only to the sensible heat flux, are presented. One type uses the eddy diffusivity for the sensible heat flux, and the other establishes the flux-gradient relation in the form of the product Φm Φh as a function of the gradient Richardson number. The latter method can be used even in heavy rains. In order to confirm the applicability of these methods, the dimensionless profile relations for momentum, sensible heat, latent heat and CO2 are estimated over a mangrove forest. Although these dimensionless profiles indicate smaller values than the Businger-Dyer representation under stable conditions, they indicate similar tendency with each other. The two modified gradient methods agree with each other although the scatter in the individual comparison is large. © 2002, The Society of Agricultural Meteorology of Japan. All rights reserved.
  • G Hirai, T Okumura, K Ashida, T Inamura, O Tanaka, H Chujo, T Hirano
    PLANT PRODUCTION SCIENCE 5 2 101 - 109 2002年06月 [査読有り][通常論文]
     
    High atmospheric humidity promotes vegetative growth and dry-matter production in japonica rice. In this study, the varietal differences in the response to atmospheric humidity were examined using three japonica varieties (Nipponbare, Kinmaze, Yamadanishiki), one indica variety IR24 and japonica X indica variety (Milyang 23). The indica and japonica X indica varieties are referred to as indica varieties hereafter. The growth of the japonica varieties was greatly promoted by high humidity (90%) and greatly reduced by low humidity (60%), but that of the indica varieties was less sensitive to humidity and the growth was hardly affected by low humidity. We compared the responses of the above varieties to low humidity (water stress) using the plants under high humidity as a control. Under low humidity, as compared to the indica varieties, the japonica varieties had a higher stomatal density, longer stomata and larger stomatal aperture, resulting in a lower water potential in leaf blades and lower water -use efficiency. Under high humidity, the japonica and indica varieties showed a similar transpiration rate (per unit area), stomatal aperture and water-use efficiency, but the japonica varieties had a higher water content than the indica varieties. This may be why the japonica varieties show greatly suppressed growth and dry matter production under low humidity. These differences between the japonica and indica varieties in morphophysiological characters under low humidity might cause the varietal differences in the plant growth and dry matter production in rice.
  • Y Kitaya, K Yabuki, M Kiyota, A Tani, T Hirano, Aiga, I
    TREES-STRUCTURE AND FUNCTION 16 2-3 155 - 158 2002年03月 [査読有り][通常論文]
     
    We conducted in situ measurements of gas exchange and O-2 concentration in pneumatophores of Sonneratia alba, Avicennia marina and Bruguiera gymnorrhiza and prop roots of Rhizophora stylosa. The mean rates of photosynthesis were 0.6 and 0.2 mumol CO2 m(-2)s(-1) in the raised pneumatophores of S. alba and A. marina, respectively, at a photosynthetic photon flux density of 100 mumol m(-2)s(-1). Photosynthetic activity was also detected in the prop roots of R. stylosa but the photosynthetic rate was lower than in A. marina. B. gymnorrhiza had no photosynthetic activity in knee pneumatophores. O-2 concentrations in the pneumatophores of these four species decreased by 4-8% when the pneumatophores were submerged under water. The O-2 concentrations in submerged pneumatophores of S. alba and A. marina were higher with higher solar radiation. Such photosynthetically generated O-2 could diffuse down through the pneumatophores into the roots, particularly when sunlit pneumatophores were submerged by high tide. This may contribute to the success of S. alba and A. marina in zones where tidal inundation is common.
  • 中井裕一郎, 三枝信子, 平野高司, ロバート エバンス, 大谷義一, 平田竜一, 鳥山敦, 北村兼三, 鈴木覚, 山本晋
    水文・水資源学会誌 15 6 665 - 672 THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES 2002年 [査読有り][通常論文]
  • 風蓮川湿原におけるミズゴケハンモックとホローの地中熱環境
    矢崎友嗣, 浦野慎一, 矢部和夫, 河内邦夫, 高橋宣之, 隈部篤興, 犬飼孔, 平野高司
    北海道の農業気象 54 45 - 52 2002年 [査読有り][通常論文]
  • 平田竜一, 杉本和之, 平野高司, 小池孝良, 北岡哲, 油津雄夫, 藤田玲, 藤沼康実, 高田雅之, 犬飼孔
    北海道の農業気象 54 54 53 - 62 2002年 [査読有り][通常論文]
  • 夏期における水稲個体群の葉温と大阪府立大学農学部附属農場の水稲収量
    平井源一, 稲野藤一郎, 簗瀬雅則, 中條博良, 平野高司, 田中修, 奥村俊勝
    近畿作物育種研究 47 13 - 17 2002年 [査読有り][通常論文]
  • Monji N, Hamotani K, Hamada Y, Agata Y, Hirano T, Yabuki K, Jintana V, Piriyayota S, Nishimiya A, Iwasaki M
    Journal of Agricultural Meteorology 58 2 71 - 77 養賢堂 2002年 [査読有り][通常論文]
     
    タイ南部のマングローブ林でC02と熱の交換の特性を雨季と乾季について調べた。林上のC02と熱フラックスの測定には2種類の改良傾度法(Monji et al.,2002)を用いた。1つは顕熱フラックスを渦相関法で求めて傾度との関係から拡散係数を求め、それをC02と水蒸気フラックスに適用する方法で、もう一つはこの森林の特定高度についてフラックスと傾度の関係、ここではΦm、Φh、とリチャードソン数の関係を求めておき、傾度法を適用する方法である。後者はかなり雨が激しいときに顕熱フラックスが渦相関法で求まらないときに用いた。熱フラックスについては雨季と乾季では大きな違いが見られた。雨天日には大きな上方向の潜熱フラックスがあり、これを補うように顕熱は大きく下方に運ばれていた。また、雨天日にはC02フラックスは日中でもわずかに上方向であった。全天日射量とC02フラックスの関係は雨季と乾季では大きな相違を示さなかった。 マングローブ林内の微気象を調べるために、プローブを上下させて測定を行った。林内に進入する汽水は熱環境やC02分布に影響を与えることがわかった。また、林内のCO2、は夜間に貯留され朝の日射の開始と共にそれが消費される様子が認められた。貯留の割合は風が強いときは林上のC02フラックスに比べると小さいが、弱風時には10％を超え、無視できない量であることがわかった。
  • 武田知己, 平野高司, 浦野慎一, 堀口郁夫
    農業気象 57 3 145 - 153 2001年09月01日 [査読有り][通常論文]
     
    Canopy structure of crops is an important factor determining the radiation environment of the canopy. Although many researchers have dealt with foliage distribution by using a probability density function, studies that reproduce a spatial destribution and spatial form of foliage in 3 dimensional (3D) space have only recently been reported. In this study, we developed a geometric model by using L-system to reproduce the form of sunflower plants in 3D space. The model consisits of frame and leaf models. In order to obtain functions to illustrate the frame model, positions of nodes, leaf bases, and leaf tips were measured from photographs of sunflower plants taken at five different stages in a growing season, and lengths of internode, petiole and leaf were determined. Moreover, lengths of five lateral veins, and divergence angle between midrib and fifth lateral vein were measured. Growth curve of internode and petiole could be expressed as a logistic function of step number in L-system. Leaves elongated as a function of petiole length. Zenith angle of petiole decreased with step number from 1 to 7, and then stabilized at about 35°. Leaf zenith angle was related to petiole zenith angle. Divergence angles between successive leaves differed in different phyllotaxis. In distichous phyllotaxis, divergence angle was 180° between the leaves at the same node, and 90° between the leaves at successive nodes. On the other hand, in alternate phyllotaxis, divergence angle was about 135°. Leaf expansion could be related to increase in leaf length. In conclusion, the geometric model using L-system successfully reproduced the growth of sunflower plants with increase in node number. © 2001, The Society of Agricultural Meteorology of Japan. All rights reserved.
  • 重久眞至, 平野高司, 清田信
    環境情報科学論文集 14 249 - 254 環境情報科学センター 2000年 [査読有り][通常論文]
  • T Hirano, K Morimoto
    ENVIRONMENTAL POLLUTION 106 1 5 - 12 1999年 [査読有り][通常論文]
     
    Changes of tree-ring widths of Japanese black pine (Pinus thunbergii Par1.) trees growing in air-polluted and unpolluted areas were analyzed. In the stand close to an industrial complex, a large reduction in the series of tree-ring index (TRI), which were computed by removing endogenous effects from the measured series, appeared from the 1960s to 1970s. This reduction in radial tree growth was not explained by the climatic response model calibrated for a pre-pollution period. TRI changes corresponding with changes in concentrations of sulfur dioxide (SO2), and a significant negative correlation between the TRI and SO2 concentration were found in the polluted area. Reduction in tree-ring growth was not seen in the unpolluted area. These results indicate that the past reduction in the growth of Japanese black pine trees growing in an industrial area was mainly caused by SO2. (C) 1999 Elsevier Science Ltd. All rights reserved.
  • Sung I, Kiyota M, Hirano T
    Life Support & Biosphere Science 5 137 - 142 1998年 [査読有り][通常論文]
  • 大阪府下における通称フェニックスの植栽分布と寒さによる葉の被害程度
    平井源一郎, 平野高司, 西田実
    南紀生物 40 79 - 81 1998年 [査読有り][通常論文]
  • 成日慶, 清田信, 平野高司
    生物環境調節 36 2 85 - 90 Japanese Society of Agricultural, Biological and Environmental Engineers and Scientists 1998年 [査読有り][通常論文]
     
    Cucumber (Cucumis sativus L. cv. Naoyosi) plants were grown hydroponically at air temperatures of 28/24°C (D/N) and 300μmol m-2 s-1 PPF, in a walk-in type growth cabinet equipped with 3-band fluorescent lamps. For 0, 5, 30 or 120 min, blue-lighting at 30 μmol m-2 s-1 in PPF was applied daily just before the 14 h photoperiod (morning twilight) . Growth parameters were measured after 12 and 24 d of treatment. After 13 d of treatment, the stomatal conductance, transpiration rate and net photosynthetic rate were measured under 3-band fluorescent lamps at a PPF of 200 μmol m-2 s-1. At 17-19 d of treatment, changes in net photosynthetic rate affected by blue-light were measured continuously for 30 min. Fresh and dry weight, leaf area, plant height and stem diameter of plants were the greatest with bluelighting for 5 min. The stomatal conductance, transpiration rate and net photosynthetic rate after 13 d of treatment were greatest in the plants grown with supplemental blue-light for 5 min. The net photosynthetic rate for 5 min treatment increased by 60% as compared with that of control plants grown without lighting. Continuous measurements showed net photosynthetic rate to rise and the high level was maintained with 5 min blue-lighting treatment. These results indicate that the promotion of plant growth by blue-lighting during morning twilight is dependent on the lighting time. For cucumber seedlings, blue-lighting for 5 min was more effective for growth than for 30 and 120 min.
  • 富田統子, 平野高司, 清田信
    生物環境調節 36 3 177 - 181 Japanese Society of Agricultural, Biological and Environmental Engineers and Scientists 1998年 [査読有り][通常論文]
     
    In order to know the effect of supplemental UV-A irradiation on the growth of lettuce (Lactuca sativa L. cv. Okayama) and radish (Raphanus sativus L, cv. Comet), these plants were grown under artificial irradiation with 3-band fluorescent lamps and additional UV-A lamps. The UV-A irradiation promoted shoot growth of both plants, and reduced the bitter taste intensity of mature lettuce leaves. However, the UV-A effects varied with stage of vegetative development. Moreover, there was no significant effect of the UV-A on the hypocotyl growth of radish plants.
  • 樹木によるガス状大気汚染物質の時期別収着速度
    重久眞至, 平野高司, 清田信
    環境情報科学論文集 12 35 - 42 1998年 [査読有り][通常論文]
  • Monji N, Hamotani K, Hirano T, Yabuki K, Jintana V
    Journal of Agricultural Meteorology 52 489 - 492 1997年 [査読有り][通常論文]
  • フィールドチャンバーを用いた樹木のガス状大気汚染物質収着速度の測定法
    重久眞至, 平野高司, 清田信
    環境情報科学論文集 11 1 - 6 1997年 [査読有り][通常論文]
  • 成日慶, 清田信, 平野高司
    植物工場学会誌 9 4 271 - 277 JAPANESE SOCIETY OF AGRICULTURAL, BIOLOGICAL AND ENVIRONMENTAL ENGINEERS AND SCIENTISTS 1997年 [査読有り][通常論文]
     
    Cucumber (Cucumis sativus L. cv. Naoyosi) plants were grown hydroponically at air temperatures of 28/24°C (D/N) and 300 μmol m-2 s-1 PPFD, in a walk-in type growth cabinet equipped with 3-band fluorescent lamps. At 10, 30, 100, 200 μmol m-2 s-1 PPFD, supplemental blue-lighting was applied daily for 5min just before the 14h photoperiod (morning twilight).
    Growth parameters were measured after 7 and 14 days of treatment. After 13 days of treatment, the stomatal conductance, transpiration rate and photosynthetic rate were measured under 3-band fluorescent lamps at a PPFD of 300 μmol m-2 s-1. At 12-14 days of treatment, changes in photosynthetic rate were measured continuously for 30 minutes, after the end of supplemental blue-lighting.
    Dry weight, leaf area, stem diameter of plants were the greatest with blue-lighting at 30 μmol m-2 s-1 PPFD. The stomatal conductance, transpiration rate and photosynthetic rate after 13days of treatment were greatest in the plants grown with supplemental blue light at 30 and 100 μmol m-2 s-1 PPFD. The photosynthetic rate at 30 μmol m-2 s-1 PPFD increased by 23% as compared with that of control plants grown without supplemental lighting. Continuous measurements showed photosynthetic rate to rise, and the high level was maintained with 30 μmol m-2 s-1 PPFD blue-lighting treatment.
    These results indicate that the promotion of plant growth by supplemental blue-lighting at morning twilight is dependent on the lighting intensity.
  • T. Hirano, N. Tomita, I. Aiga
    Journal of Agricultural Meteorology 52 5 863 - 866 1997年 [査読有り][通常論文]
     
    Radish plants were grown in chambers (PPFD 300 μmol m2s-1, day length 14 h, 21°C, 70 %RH) for 10 days, under UV-B irradiation (UV-BBE 0, 6.5 (low) and 8.6 (high) kJ m-2d-1) for 12ha day the plants were exposed to acid mist (pH 3.0 and 5.6) every 2 days. At the end of the treatments, leaf area, dry weights of shoot and hypocotyl, total chlorophyll content, water loss rate and water droplet contact angle (DCA), which is a measure of wettability, on adaxial and abaxial leaf surfaces were determined in each of 9 combinations of treatments, 3 (UV-B)×3 (mist, including no mist). UV-B radiation significantly decreased leaf area and dry weights of shoot and hypocotyl, and increased total chlorophyll content per unit leaf area. Similarly, acid mist of pH 3.0 significantly decreased leaf area and hypocotyl dry weight. However, no combined effect of UV-B and mist on these growth parameters and chlorophyll content was found. On the other hand, there were significant combined effects on DCA on both adaxial and abaxial surfaces at the high UV-B level, DCA on adaxial surfaces of treated leaves with mist decreased, although that of untreated leaves increased. © 1997, The Society of Agricultural Meteorology of Japan. All rights reserved.
  • Nobutaka Monji, Ken Hamotani, Takashl Hirano, Kazutoshl Yabuki, Vlpak Jintana
    Journal of Agricultural Meteorology 52 2 149 - 154 1996年09月01日 [査読有り][通常論文]
     
    An experiment was conducted to find out the characteristics of CO2 flux in a mangrove forest of Thailand during the rainy season. The relaxed eddy accumulation method was applied to the measurement of the CO2 flux over the forest. The CO2 flux increased with solar radiation, and the daytime downward CO2 flux was -0.5~-1.0 mg m-2 s-1 for the global radiation 400~800 Wm-2, which is about the same magnitude as the typical values obtained in other tropical or temperate forests. The soil respiration was an order of magnitude smaller in the mangrove forest compared to other forests. © 1996, The Society of Agricultural Meteorology of Japan. All rights reserved.
  • Vegetation in Sakai city, Osaka as a sink of air pollutants
    Hirano T, Kiyota M, Aiga I
    Bulletin of Osaka Prefecture University, Series B 48 55 - 64 1996年 [査読有り][通常論文]
  • Hirano T, Monji N, Hamotani K, Jintana V, Yabuki K
    Environment Control in Biology 34 4 285 - 293 Japanese Society of Agricultural, Biological and Environmental Engineers and Scientists 1996年 [査読有り][通常論文]
     
    マングローブの蒸散の季節変化を調べるために, タイ南部においてBruguiera cylindricaの茎内流量を茎熱収支法を用いて雨季と乾季に野外測定した.その結果, B.cylindricaの葉面積当たりの蒸散速度は, 雨季と乾季でそれぞれ0.50, 1.04kgm-2d-1と評価された.この季節間差は, 主に日射量や大気湿度の違いによるものと考えられた.また, 蒸散特性の種間差を調べるために, 雨季に4種類のマングローブ (Rhizophora apiculata, Ceriops decandra, Xylocarpus moluccensis, B. cylindrica) の気孔コンダクタンス (gs) をポロメータ法により測定した.gsは, 4樹種ともに200～400μmolm-2s-1以上のPPFDでほぼ一定 (光飽和) となった.そのときのR.apiculataのgsは150～250mmolm-2s-1であり, 日本の常緑樹での平均値とほぼ同程度であった.一方, 残りの3樹種のgsは, かなり低いレベルであった.
  • Hirano T, Aiga I, Monji N, Hamotani K, Jintana V, Ishikawa T, Yabuki K
    Environment Control in Biology 34 1 87 - 90 Japanese Society of Agricultural, Biological and Environmental Engineers and Scientists 1996年 [査読有り][通常論文]
     
    潮間帯に生息するマングローブのAvicennia属やSonneratia属の直立気根には, 表皮の直下に葉緑素を含む層状の組織が存在する.この組織では光合成が行われ, 生成される酸素が地中根の呼吸に利用されることが知られている.本研究では, 直立気根の水没時における光合成を評価するために, 色素の光退色を利用した簡易積算日射フィルムを用いて, 水中での水平面および鉛直面における積算日射量をタイのマングローブ林において測定した.その結果, かなり濁った水中においても, 30cm程度までの水深では, 鉛直面での日平均日射量は光合成の光補償点以上であった.このことは, 水没時においても直立気根が光合成によって地中根へ酸素を供給することを示唆している.
  • 平野 高司
    関西自然保護機構会報 17 2 137 - 143 関西自然保護機構 1995年 [査読有り][通常論文]
  • 清田信, 谷晃, 村上克介, 平野高司, 相賀一郎
    CELSS Journal 7 2 27 - 34 1995年 [査読有り][通常論文]
  • 平野高司, 関和雄, 相賀一郎, 河瀬憲次
    生物環境調節 33 2 113 - 122 日本生物環境調節学会 1995年 [査読有り][通常論文]
  • T HIRANO, M KIYOTA, AIGA, I
    ENVIRONMENTAL POLLUTION 89 3 255 - 261 1995年 [査読有り][通常論文]
     
    The physical effects of dust accumulating on leaf surfaces, on leaf physiology, such as photosynthesis, transpiration, stomatal conductance and leaf temperature of cucumber and kidney bean plants were investigated by the use of chemically inert dust. It was found that dust decreased stomatal conductance in the light, and increased it in the dark by plugging the stomata, when the stomata were open during dusting. When dust of smaller particles was applied the effect was greater. However, the effect was negligible when the stomata were closed during dusting. The dust decreased the photosynthetic rate by shading the leaf surface. The dust of smaller particles had a greater shading effect. Moreover, it was found that the additional absorption of incident radiation by the dust increased the leaf temperature, and consequently changed the photosynthetic rate in accordance with its response curve to leaf temperature. The increase in leaf temperature also increased the transpiration rare.
  • 平野高司, 内田晶夫, 清田信, 榎, 相賀一郎
    大気環境学会誌 30 5 327 - 336 Japan Society for Atmospheric Environment 1995年 [査読有り][通常論文]
     
    0.1 ppmと0.2 ppmのO3, NO2, SO2を, スギの3年生クローン苗 (品種: シバハラ) に25℃, 70%RHで3時間, 単独および複合暴露し, 純光合成速度と葉面拡散コンダクタンス (LDC) に与える影響を調べた。さらにO3とNO2については, 0.1 ppmの混合ガスがスギ苗の純光合成速度とLDCに与える影響の品種 (シバハラ, ナカゲン) および暴露中の温湿度条件 (15, 25, 35℃;50, 70%RH) による違いについても調べた。25℃, 70%RHにおいて, 0.1 ppmのO3, NO2, SO2が単独でシバハラの純光合成速度を低下させることはなかったが, それら3種類のガスが同時に存在する場合には純光合成速度とLDCは有意に低下した。葉肉コンダクタンスの低下から, 純光合成速度の低下には気孔の閉鎖だけでなく葉緑体の光合成活性の低下も関与していると考えられた。
    0.1 ppmのO3とNO2の混合ガスがスギ苗の純光合成速度を有意に低下させることはなかった。しかし, LDCに与える影響は品種および温湿度条件により異なった。シバハラのLDCは50%RHでは変化しなかったが, 70%RHの15, 35℃において有意に低下した。一方, ナカゲンではすべての温湿度条件においてガス暴露によりLDCが有意に低下することはなかった。
  • 平野高司, 相賀一郎
    環境技術 123 12 728 - 732 環境技術学会 1994年 [査読有り][通常論文]
  • 相賀一郎, 清田信, 平野高司, 村上克介, 谷晃
    生物環境調節 32 2 71 - 78 Japanese Society of Agricultural, Biological and Environmental Engineers and Scientists 1994年 [査読有り][通常論文]
  • 平野高司, 関和雄, 清田信, 相賀一郎
    農業気象 49 4 273 - 277 1994年 [査読有り][通常論文]
     
    Cucumber plants were grown in the pots cantaining the soil covered with volcanic ash from Mt. Unzen-Fugendake, and the concentration of CO2 and O2 in the soil was measured during the cucumber growth. Diffusion of O2 was also measured in the volcanic ashes from Mt. Unzen-Fugendake and Mt. Sakurajima, and in the soil. The O2 diffusion coefficients were much smaller in the volcanic ashes than in the soil. In the rhizosphere, the concentration of CO2 increased and that of O2 decreased under the soil cover with the volcanic ash. This was attributed to the slower exchanges of CO2 and O2 between the atmosphere and the soil through the volcanic ash layer. The cucumber growth in the pots with the soil cover was slower than in the control pots. The increased CO2 concentration in the rhizosphere may be the cause of the growth reduction. © 1994, The Society of Agricultural Meteorology of Japan. All rights reserved.
  • 平井源一郎, 中條博良, 田中修, 奥村俊勝, 竹内史郎, 平野高司, 大森雅代
    日本作物学会紀事 62 3 395 - 400 1993年 [査読有り][通常論文]
     
    The effect of relative humidity (RH) on the dry matter production and nitrogen absorption of rice seedlings (age in leaf mumber of 5) was investigated. Plants were grown for 4 days under 60 or 90% RH at 12 -hr day/12-hr night temperatures of 24/20, 28/24, 32/28 and 36/32°C. 1. Dry matter increase of leaves and roots in the plants grown at 90% RH was higher at 24/20 and 28/24°C, but lower at 32/28 and 36/32°C than that of the plants grown in 60% RH. 2. Nitrogen absorption and content of heavy nitrogen of leaves and roots in the plants grown at 90% RH were also higher at 24/20 and 28/24°C, but lower at 32/28 and 36/32°C than those of the plants grown in 60% RH. These results indicate that dry matter increase and nitrogen absorption of rice seedlings are affected by humidity and temperature, with highly significant correlations. © 1993, CROP SCIENCE SOCIETY OF JAPAN. All rights reserved.
  • 植物による都市の熱環境緩和
    清田信, 平野高司, 相賀一郎
    環境情報科学 22 96 - 100 1993年 [査読有り][通常論文]
  • 洞口公俊, 森田, 平野高司, 清田信, 相賀一郎
    National Technical Report 38 1 114 - 122 松下電器産業技術総務センター技術情報部 1992年 [査読有り][通常論文]
  • 平井源一郎, 中條博良, 田中修, 平野高司, 大森雅代
    日本作物学会紀事 61 3 364 - 368 1992年 [査読有り][通常論文]
     
    The effect of relative humidity (RH) on the growth and dry matter production of rice seedlings was investigated at the early vegetative stage. Plants were grown for 10 days under 60 or 90% RH at 12-hr day/12-hr night temperatures of 22/18 (low), 28/24 (moderate) and 34/30 (high) °C. Dry matter production of the plants grown at 90% RH was higher at low and moderate temperatures, but much lower at high temperature than that of the plant grown in 60% R.H. The increase of root dry weight was more influenced by RH than that of the top dry weight. Thus, the relative value of top weight to root weight (T-R ratio) of the plant grown under 90% RH decreased at the low temperature, but increased at the high temperature, as compared with that of the plant grown under 60% R.H. At the moderate temperature, T-R ratio of the plant grown in 90% RH was almost the same as that of the plant grown in 60% R.H. These results indicate that the effect of humidity on growth and dry matter production must be considered in association with the temperature. © 1992, CROP SCIENCE SOCIETY OF JAPAN. All rights reserved.
  • 平野高司, 清田信, 関和雄, 相賀一郎
    農業気象 48 2 139 - 145 養賢堂 1992年 [査読有り][通常論文]
     
    This study was conducted to infer the effects of volcanic ash accumulating on a leaf surface on its photosynthesis. Particle size distribution and shading ratio were measured on 2 kinds of ash from Mt. Sakurajima (white and black) and 4 kinds from Mt. Unzen-Fugendake. Reflected spectral radiant flux density, temperature and stomatal conductance of cucumber leaves covered with those ashes were also measured. Particle size distribution of ashes were different each other. Particle (< 3 μm) contents of them were 6 to 13%. Shading ratios were 8 to 20% at 5 g m-2 of ash load. The ash with smaller particle size had bigger shading ratio. Integrated radiant flux density (280-2500 nm) of reflection from leaves covered with ashes from Mt. Sakurajima (black and white) and Mt. Unzen-Fugendake at 50 gm-2 were 65, 53 and 106% to control leaves, respectively. Temperature of leaves covered with these ashes at 50 g m-2 increased by 2.4, 2.6 and 1.2°C, respectively, at a solar radiation of 876 Wm-2. The ash from Mt. Unzen-Fugendake, with the smallest particle size, decrease stomatal conductance significantly even after it was washed out from the leaf surface. These results suggest that the volcanic ash with dark color and small particle size reduces photosynthesis through shading, increasing temperature and plugging stomata. © 1992, The Society of Agricultural Meteorology of Japan. All rights reserved.
  • 観葉植物のガス交換と室内ガス環境の改善
    清田信, 平野高司, 石黒武, 三輪, 相賀一郎
    環境情報科学 21 107 - 111 1992年 [査読有り][通常論文]
  • 堺市におけるサンゴジュの葉内重金属含有量の20年間の変化
    矢吹万寿, 平野高司, 清田信, 青木正敏, 今村太, 相賀一郎
    環境情報科学 21 102 - 106 1992年 [査読有り][通常論文]
  • 平井源一, 中山登, 中條博良, 稲野藤一郎, 平野高司, 下田, 田中修
    日本作物学会紀事 61 1 41 - 48 1992年 [査読有り][通常論文]
     
    The horizontal distribution of leaf temperature in a rice population of 40 X 40 meters was investigated with an infrared scanning thermometer under a high temperature and high solar radiation during the period from late-July to late-August. The results obtained are summarized as follows: 1. Either the west wind blowing from a paved road toward the rice population or the east wind blowing across the field was the predominant wind direction in the examined rice population. These winds formed some belt-like low-temperature areas (rice plant waving) on the surface of the rice population. The leaf temperature in the cross section of the rice plant waving was the lowest at the middle of the rice plant waving and increased with distance from the middle. The temperature at the middle of the rice plant waving decreased gradually from windward to lee side in the case of the west wind, but did not vary in the case of the east wind. 2. In the case of the west wind, leaf temperature increased from the border to inside of the population at the wind speed of less than 1 m/sec, but it decreased with the distance from the bordering area at the wind speed of more than 1 m/sec. In the case of the east wind, the leaf temperature varied little in the rice population irrespective of the wind. speed. © 1992, CROP SCIENCE SOCIETY OF JAPAN. All rights reserved.
  • 平野高司, 清田信, 相賀一郎
    大気汚染学会誌 26 5 352 - 358 Japan Society for Atmospheric Environment 1991年 [査読有り][通常論文]
     
    樹木葉面に付着した粉じんは, 主に遮光作用により光合成に影響を与えると考えられる。そこで, 粉じん発生量が多い工事用道路周辺の樹木 (温州ミカン) 葉面に付着した粉じんについて, 主に遮光率 (100%一透過率) という指標を用いて調査し, 粉じんが光合成に与える影響評価を試みた。粉じんの遮光率は, 透明粘着テープで採取した粉じんの, 分光光度計を用いて測定した400～700nmの平均透過率から求めた。粉じんが光合成に与える影響は, 粉じんの遮光率と日射量から光-光合成曲線を用いて評価した。
    粉じんの遮光率と粉じん付着量との関係 (r=0.91) から, 遮光率によって付着量を表すことができることがわかった。葉の下面の粉じん付着量は, 葉の上面に比べかなり小さかった。遮光率は道路からの距離とともに急激に減衰した。道路の近くの樹では, 車両通行量 (粉じん発生量) や降水量の影響を受け, 遮光率は大きく変化した。なお, 樹冠内部の葉面の粉じん付着量は, 表層部に比べ変化が小さいことがわかった。1989年8月に遮光率の最大値 (30%) を示した樹について, 粉じんが遮光作用によって光合成に与える影響を試算した結果, 光合成量の減少は16%となった。
  • 水稲における葉温と光合成速度の関係
    平井源一, 中山登, 中條博良, 田中修, 平野高司
    近畿作物育種研究 36 91 - 93 1991年 [査読有り][通常論文]
  • 平野高司, 清田信, 相賀一郎
    農業気象 46 4 215 - 222 1991年 [査読有り][通常論文]
     
    The physical effects of dust on gaseous exchange through stomata were investigated by measuring stomatal conductance of dusted and clean leaves. The effects of dust by increasing leaf temperature on net photosynthetic rate and transpiration rate were investigated. Four classes of dust (JIS Z 8901: three classes of Kanto-loam powder and carbon-black), which were different in particle size and were chemically inert to plants, were made to adhere to upper surface of leaves of cucumber plants. In order to except the shading effect of dust, stomatal conductance, net photosynthetic rate and transpiration rate were measured under the condition of fairly high light intensity. The stomatal conductance of upper surface of dusted leaves whose stomata had been open in exposure of dust to leaves decreased in light peoriod and increased in dark peoriod. As particle size of dust became smaller, the changes of stomatal conductance increased both in light peoriod and dark peoriod. There was no change of stomatal conductance of leaves which had been exposed to dust when stomata had been closed. It seemed that dust caused these changes of stomatal conductance by covering and plugging stomata. Temperature of leaves covered with carbon-black were higher than clean leaves by 1.7-3.7°C in 15-40°C of air temperature. The net photosynthetic rates of leaves which had been exposed to carbon-black when stomata had been closed were higher than the rates of clean leaves below 25°C of air temperature, and were lower above 30°C. The transpiration rates of the same dusted leaves were higher than the rates of clean leaves by 0.4-0.6 g • dm-2 • hr-1 in 15-40°C of air temperature. The results suggest that dust affects net photosynthetic rate by covering and plugging stomata, and by increasing leaf temperature. © 1991, The Society of Agricultural Meteorology of Japan. All rights reserved.
  • 平野高司, 清田信, 北宅善昭, 相賀一郎
    農業気象 46 1 1 - 7 1990年 [査読有り][通常論文]
     
    Dust cover on leaves is considered to affect photosynthesis directly, mainly by shading leaf surface, increasing leaf temperature and plugging stomata. This study was carried out to make clear these physical effects of dust on photosynthesis. Four classes of JIS Z 8901 dust (Carbon-Black and Kanto-loam powder Coarse, Fine, Ultrafine), which were different in particle size and had pH values around neutrality, were applied to upper surfaces of leaves of kidney bean and cucumber plants at various densities. These two species were different in stomatal density. Both net photosynthetic rates and leaf temperatures of dusted leaves and clean leaves were measured at the same time, over a range of light intensities. The following results were obtained both in kidney bean and cucumber plants. (1) Photosynthetic rate was reduced by dust. As dust density on leaf surface increased, it was reduced further. (2) When carbon-black was applied, leaf temperature increased by 3°C at the maximum, but none of three classes of kanto-loam powder increased leaf temperature. (3) Regardless of dust characteristics or dust density, the reduction in photosynthetic rate was nearly equal to the reduction in PPFD incoming to upper surface of leaf by dust accumulation, in all measurments in this study. Therefore it seemed that the shading leaf surface was the most important of the injurious physical effects of dust on photosynthesis. © 1990, The Society of Agricultural Meteorology of Japan. All rights reserved.
  • 堀口 郁夫, 平野 高司
    農業気象 43 4 295 - 303 養賢堂 1988年 [査読有り][通常論文]
     
    Following the previous studies (Horiguchi I., et al, 1983, 1985), a study on fog formation in greenhouses and the characteristics of plastic films was made with regard to the following objectives. 1) Comparison of fog formation or density in the tunnels when using films with different duration of use (Table 1). In addition to fog formation, temperature, humidity and the amount of water flowed down on the film were also measured. 2) Investigation of fog formation or density with regard to the different contents of surface active agent contained in films (Tables 2 & 3). The surface active agent used was a sorbitan group (named Surfactant S). 3) Investigation of fog formation or density through changing the quality of the surface active agents contained in the films (Tables 3 & 4). In this case, two kinds of experiments were conducted as follow: a) adding surfactant F (fluorine group surface active agent) to surfactant S, b) adding surfactant Sb plus surfactant F to surfactant Sa. 4) Investigation of fog formation or density for different types of plastic films. Six different kinds of films, i.e., polyolefin, EVA, PE, none-dropping-type PVC, none-fog formation-type PVC, and dropping-type PVC, were used. Major results of the experiments can be summarized as follows: 1) The less fog formation or density, the larger amount of water flowed down on the film, was observed. 2) Fog formation or density was not related to both the minimum temperature and humidity. 3) With both none-dropping-type and dropping-type PVC films, fog formation or density was reduced with the age of films. 4) In case of none-fog formation-type PVC film, the amount of fog formed increased with duration of use of the films until a certain point, and then was reduced. 5) In both cases of films containing no surface active agents (dropping-type PVC) and films containing only a small amount of surface active agents, fog formation or density was less. 6) Up to around 1.5 phr, work of adhesion increased in proportion to the amount of surface active agents contained in the films. 7) Beyond about 1.5 phr, work of adhesion slightly decreased. However, the relationship between work of adhesion and the amount of active surface agents was not clear. 8) Addition of surfactant F to films containing surfactant Sa and Sb, greatly reduced fog formation and density. 9) Among the samples of six different plastic films which are on the market, the lowest fog formation or density was observed with dropping-type PVC without surface active agents. From these results, it can be concluded that fog formation, density and quality of films are closely related to the easy flow of water adhered to the film and the ease with which vapor adheres to the film. Although these two characteristics are contrary to each other, it is considered that a feature combining allowance of water flowing down and ease of vapor adhesion is developed by adding surfactants F to S. © 1988, The Society of Agricultural Meteorology of Japan. All rights reserved.
  • 海洋性冷気流の農業地帯への影響に関する研究―勇払・石狩平野における気温変化―
    平野高司, 堀口郁夫, 谷宏, 松岡延浩
    北海道の農業気象 37 18 - 20 1985年 [査読有り][通常論文]

MISC

書籍等出版物

  • 平野高司 (担当:共著範囲:異常気象と気候変動，光合成と気象環境)
    文永堂出版 2021年01月 (ISBN: 9784830041419) xvi, 301p
  • 持続可能な社会への道 : 環境科学から目指すゴール
    平野高司 (担当:共著範囲:熱帯における土地利用変化と物質循環)
    日本学術協力財団 2020年10月 (ISBN: 9784990997236) 263p
  • 平野高司 (担当:共編者(共編著者)範囲:地表近くを吹く風，熱と物質の流れ，植物群落の熱・物質収支の測定法)
    朝倉書店 2020年04月 (ISBN: 9784254440300) ix, 199p, 図版 [2] 枚
  • 平野高司 (担当:共著範囲:熱帯林への気候変動および人間活動の影響)
    共立出版 2019年12月 (ISBN: 9784320058224) xii, 216p, 図版 [12] p
  • 図説 日本の湿地
    平野 高司 (担当:分担執筆範囲:二酸化炭素の吸収と蓄積)
    朝倉書店 2017年06月
  • 湿地の科学と暮らし 北のウエットランド大全
    平野 高司 (担当:分担執筆範囲:湿地の炭素固定機能)
    北海道大学出版会 2017年04月
  • Tropical Peatland Ecosystems
    平野 高司 (担当:共著範囲:Estimation model of graound water table at peatland in Central Kalimantan, Indonesia)
    Springer 2016年
  • サロベツ湿原と稚咲内砂丘林帯湖沼群
    平野 高司 (担当:共著範囲:地表のエネルギー収支と蒸発散)
    北海道大学出版会 2014年
  • 北海道の気象と農業（日本農業気象学会北海道支部）
    平野 高司 (担当:編者(編著者)範囲:はじめに，森林と大気の関係)
    北海道新聞社 2012年11月
  • Agricultural Sciences for Human Sustainability
    平野高司 (担当:分担執筆範囲:Carbon dioxide exchange between the atmosphere and terrestrial ecosystems)
    海青社 2012年06月
  • The Biodiveristy Observation Network in the Asia-Pacific Region, Ecological Research Monographs; Part 5
    Osaki M, Hirano T, Inoue G, Honma T, Takahashi H, Takeuchi W, Kobayashi N, Evri M, Kohyama T, Ito A, Setiadi B, Sekine H, Hirose K (担当:分担執筆範囲:Sensing/monitoring networks on carbon balance and biodiversity in tropical peatland)
    Springer 2012年
  • 浦野 慎一, 山川 修治, 文字 信貴, 小林 哲夫, 大槻 恭一, 平野 高司, 町村 尚, 上村 賢治, 鈴木 晴雄, 谷 宏, 蔵田 憲次, 干場 信司, 蓑輪 雅好 (担当:分担執筆範囲:光合成による生物生産，異常気象と気候変動)
    文永堂出版 2009年 (ISBN: 9784830041167)
  • 続・環境負荷を予測する（日本土壌肥料学会監修）
    平野高司, 児玉裕二, 梁 乃申 (担当:分担執筆範囲:土壌呼吸の自動測定)
    博友社 2005年09月
  • 森林の科学（中村太士，小池孝良編著）
    平野 高司 (担当:分担執筆範囲:北方林と気候との相互作用)
    朝倉書店 2005年09月
  • 新農業情報工学（農業情報学会編）
    平野 高司 (担当:分担執筆範囲:気象予測)
    養賢堂 2004年08月
  • 陸域生態系における二酸化炭素等のフラックス観測の実際（AsiaFlux運営委員会編）
    平野高司, 三枝信子 (担当:分担執筆範囲:渦相関法によるフラックス測定の実際)
    国立環境研究所地球環境研究センター 2004年
  • 地球温暖化－世界の動向から対策技術まで－
    藤沼康実, 三枝信子, 平野高司 (担当:分担執筆範囲:温室効果ガスのモニタリングと森林フラックスの測定)
    裳華房 2003年11月
  • 地表面フラックス測定法（気象研究ノート199）
    平野 高司 (担当:分担執筆範囲:土壌呼吸量)
    日本気象協会 2001年03月
  • 文字信貴, 平野高司, 高見晋一, 堀江武, 桜谷哲夫, 文字 信貴, 高見 晋一, 桜谷 哲夫, 平野 高司, 堀江 武 (担当:共編者(共編著者)範囲:植物の放射環境，地表に接した大気の特徴，熱と物質の流れ，環境汚染と植物)
    丸善 1997年08月 (ISBN: 462104351X) 199
  • 新版 生物環境調節ハンドブック（日本生物環境調節学会編）
    平野 高司 (担当:分担執筆範囲:環境に対する生物の反応（エアロゾル，粉じん）)
    養賢堂 1995年04月

講演・口頭発表等

  • Networking flux researches to assess the carbon balance of tropical peatland ecosystems in SE Asia  [招待講演]
    平野高司
    9th AsiaFlux Workshop 2011年11月 口頭発表（招待・特別）
  • Evapotranspiration of peatlands with different vegetation types  [招待講演]
    平野高司
    Yangling International Agri-Science Forum 2011 2011年11月 公開講演，セミナー，チュートリアル，講習，講義等
  • Increasing vulnerability of tropical peat carbon  [招待講演]
    平野高司
    3rd ASIAHOECs Joint Symposium 2011年10月 口頭発表（招待・特別）
  • Carbon Flux in Tropical Peat  [通常講演]
    平野高司
    5th Technical Roundtable on MRV "Key Workshop on MRV and REDD+" 2010年10月 口頭発表（招待・特別）
  • 熱帯泥炭林の現状と炭素収支  [招待講演]
    平野高司
    SELIS-GCOE合同セミナー 2010年10月 公開講演，セミナー，チュートリアル，講習，講義等
  • Effect of drainage on soil respiration in tropical peat swamp forest  [通常講演]
    平野高司
    International Workshop on "Wild fire and carbon management in Peat-Forest in Indonesia" 2010年09月 口頭発表（基調）
  • 熱帯泥炭林の炭素収支  [招待講演]
    平野高司
    統合的陸域圏研究連絡会 2009年05月 公開講演，セミナー，チュートリアル，講習，講義等
  • Fire, degradation and carbon flux: monitoring and field experiment in East Asia  [通常講演]
    平野高司
    IGBPシンポジウム 2009年04月 口頭発表（招待・特別）
  • 陸上植物はどれだけ二酸化炭素を吸収しているのか？  [招待講演]
    平野高司
    北海道芝草研究会講演会 2009年01月 公開講演，セミナー，チュートリアル，講習，講義等
  • タワー観測ネットワーク（JapanFlux）の現状  [招待講演]
    平野高司
    地球観測連携拠点国内ワークショップ 2008年12月 公開講演，セミナー，チュートリアル，講習，講義等
  • 微気象学的方法による陸域生態系の炭素吸収量の推定 －わかることとわからないこと－  [招待講演]
    平野高司
    日本農業気象北海道支部・東北支部合同シンポジウム 2008年11月 口頭発表（招待・特別）
  • フラックス研究の現状と将来像  [招待講演]
    平野高司
    日本農業気象学会シンポジウム 2008年11月 口頭発表（招待・特別）
  • Carbon dioxide balance of tropical and temperate forests  [招待講演]
    平野 高司
    G8関連シンポジウム 2008年07月 口頭発表（招待・特別）
  • 泥炭と地球環境  [招待講演]
    平野高司
    北海道土質試験協同組合技術懇談会 2008年05月 公開講演，セミナー，チュートリアル，講習，講義等
  • 熱帯泥炭の炭素収支  [通常講演]
    平野高司
    「熱帯泥炭のCDM化」ワークショップ 2007年08月 公開講演，セミナー，チュートリアル，講習，講義等
  • Field manipulative experiments for evaluating disturbance effects on ecosystem carbon exchange  [招待講演]
    平野高司
    International Symposium on monitoring and predicting the change in the terrestrial human-environment systems 2006年02月 公開講演，セミナー，チュートリアル，講習，講義等
  • 空気質と植物生産  [招待講演]
    平野高司
    植物工場学会北海道支部講演会 2005年11月 公開講演，セミナー，チュートリアル，講習，講義等
  • Three years of flux measurement at Tomakomai FRS  [招待講演]
    平野高司
    APGC-Post Flux Meeting 2004年10月 公開講演，セミナー，チュートリアル，講習，講義等
  • 苫小牧カラマツ林におけるCO2フラックスモニタリング  [招待講演]
    平野高司
    IGBP国内シンポジウム 2001年03月 公開講演，セミナー，チュートリアル，講習，講義等
  • 植物のガス交換計測  [招待講演]
    平野高司
    日本農業気象学会北海道支部講演会 2000年12月 公開講演，セミナー，チュートリアル，講習，講義等
  • 都市の大気汚染と植物  [招待講演]
    平野高司
    日本農業気象近畿支部50周年記念シンポジウム 1996年11月 口頭発表（招待・特別）
  • 作物の成長に与える紫外線（UV-B）の影響  [招待講演]
    平野高司
    照明学会1996年全国大会 1996年06月 公開講演，セミナー，チュートリアル，講習，講義等

担当経験のある科目（授業）

  • 農業気象学北海道大学農学部
  • 生物環境物理学特論北海道大学大学院
  • 生存基盤環境学北海道大学大学院
  • 生物環境管理学北海道大学大学院
  • 温暖化影響論北海道大学大学院
  • フィールド環境情報学演習北海道大学大学院
  • フィールド環境情報学北海道大学大学院
  • フィールド環境計測論北海道大学大学院
  • 地域環境学演習北海道大学大学院
  • 地域環境学北海道大学大学院
  • 農業工学演習北海道大学
  • 情報解析学演習北海道大学
  • 情報解析学北海道大学
  • 環境情報学北海道大学
  • 湿原の科学北海道大学
  • 食料生産と環境保全北海道大学
  • 環境を食べ続ける人類北海道大学
  • 農業工学実験北海道大学
  • Environmental Science of Biological Resources北海道大学
  • 生物環境気象学北海道大学
  • 農業災害学北海道大学
  • 農村計画学北海道大学
  • 計測学北海道大学
  • 農業工学基礎実験北海道大学
  • 地学概論北海道大学
  • 測量学北海道大学
  • 植物情報工学大阪府立大学
  • 環境測定法大阪府立大学

所属学協会

  • 日本生態学会   日本地球惑星科学連合   日本気象学会   日本生物環境工学会   AsiaFlux   日本農業気象学会   JapanFlux   

共同研究・競争的資金等の研究課題

  • 日本学術振興会：科学研究費助成事業 学術変革領域研究(A)
    研究期間 : 2022年06月 -2024年03月 
    代表者 : 平野 高司
  • 文部科学省：科学研究費補助金（基盤研究S）
    研究期間 : 2019年07月 -2024年03月 
    代表者 : 平野 高司
  • メタン吸収能を含めたアジア域の森林における土壌炭素動態の統括的観測に基づいた気候変動影響の将来予測
    独立行政法人環境再生保全機構：環境省環境研究総合推進費
    研究期間 : 2020年04月 -2023年03月 
    代表者 : 梁乃申, 高橋善幸, 高木健太郎, 平野高司, 石田祐宣, 髙木正博, 市井和仁, 近藤俊明, 小嵐淳, 安藤麻里子, 寺本宗正
  • 総合地球環境学研究所：実践プロジェクト
    研究期間 : 2013年04月 -2022年03月
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2018年04月 -2021年03月 
    代表者 : 伊藤 雅之, 平田 竜一, 平野 高司, 常田 岳志, 坂部 綾香
     
    インドネシア・中カリマンタン州のサイトにおいては、フラックス観測タワーを用いた生態系スケールのメタンフラックス観測を継続して行っており、気象の年々変動を受けてどのように変動するかについてのデータが蓄積されつつある。新型コロナウィルスの拡大により現地でのデータ回収等が行えなくなったため、カウンターパートとオンライン会議システムを用いることで観測データの回収を継続している。 入荷が遅れていたレーザーメタン計を用いた現地でのチャンバー法によるメタンフラックス観測の準備を整えた。しかしながら新型コロナウィルスの感染症の拡大により海外渡航し現地調査できない状況となっている。そのため過去に採取した様々な土地利用条件下の熱帯泥炭地の地下水中溶存有機態炭素の量と質の分析及びデータ解析を進めた。インドネシア・スマトラ島のリアウ州（未火災の泥炭地二次林・複数回の火災を受けた焼け跡や後に小規模オイルパーム農園化した泥炭地・アカシアプランテーションから流出する排水路の水・天然泥炭湿地林など）とカリマンタン島の中カリマンタン州（未排水の泥炭湿地然林・排水泥炭林・複数回火災を受けた焼け跡）を含む約250個の試料について、燃焼式吸光光度法によるDOC濃度測定、EEMSによるDOMの蛍光特性分析を行った。クラスター解析及び主成分分析を行ったところ、土地利用ごとに個別のクラスターとして分類され、現在、既に得られている水質データと合わせてデータを検討している。これまでの結果から、火災を受けた泥炭地下水のDOCの性質は未火災の泥炭地のものとは異なることなどが示唆された。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2017年04月 -2021年03月 
    代表者 : 熊谷 朝臣, 溝上 展也, 中静 透, 彦坂 幸毅, 平野 高司, 佐藤 保, 村岡 裕由, 檜山 哲哉, 佐藤 永, 市榮 智明, 小杉 緑子
     
    当初、東南アジア熱帯林全域に多数の観測点からなる森林簿ネットワークを構築し、森林炭素収支の統合解析を行おうとした。しかし、今般の新型コロナウィルス感染拡大により、ほとんどの観測点の構築が頓挫した。そのような環境下で、（１）ベトナムの高地針広混交林サイトの設定に成功した。（２）ミャンマーの森林炭素収支において、違法伐採の影響は大きく、その評価の成否が極めて重要であることが明らかになった。（３）日本の総森林炭素蓄積の再評価を行い、これまでの推定の２倍以上の蓄積を明らかにした。（４）全球スケールに適用可能な革新的な個体ベース森林動態シミュレータの開発を進めることができた。
  • 日本学術振興会：二国間交流事業 オープンパートナーシップ共同研究
    研究期間 : 2018年04月 -2020年03月 
    代表者 : 平野 高司
  • 文部科学省：科学研究費補助金（萌芽）
    研究期間 : 2017年07月 -2020年03月 
    代表者 : 平野 高司
  • 環境省：環境研究総合推進費
    研究期間 : 2015年06月 -2018年03月 
    代表者 : 平野 高司
  • 旭硝子財団：環境研究 近藤次郎グラント
    研究期間 : 2015年04月 -2018年03月 
    代表者 : 平野 高司
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2014年04月 -2017年03月 
    代表者 : 高木 健太郎, 平野 高司, 梁 乃申, 井手 玲子, 平山 宏次郎
     
    北海道北部の冷温帯林において，2004年と2014年の2回の航空機レーザ観測結果を利用して，10年間の森林炭素貯留量の変化を広域（225 km2）・高分解能（1 ha）で推定した。10年間の正味の森林炭素貯留変化量の平均値は4.18±6.64(SD) MgC/haであり，フラックス観測研究より得られた森林の正味CO2交換量と同等の範囲にあった。高標高，急傾斜，北向き斜面，大きな樹高のばらつき，針葉樹林の場合に有意に正味の炭素貯留変化量が少なくなり，南向き斜面，広葉樹林，二次林で有意に多くなった。森林の成長量と２つの植生指標(NDVI， GR)との間には線形の関係が見られた。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2013年04月 -2016年03月 
    代表者 : 市井 和仁, 小林 秀樹, 佐藤 永, 加藤 知道, 植山 雅仁, 佐々井 崇博, 近藤 雅征, 渡邊 明, 伊藤 昭彦, 三枝 信子, 平野 高司
     
    AsiaFluxに代表される地上観測データと様々な衛星データと複数の陸域生態系モデルを用いて、モデル・データ相互比較実験を行うことで、アジア域における陸域炭素収支の変動を定量化し、その変動要因を解析した。まず、AsiaFluxデータ等のデータと衛星データを利用した経験モデルを構築し、アジア域のCO2フラックスを2000-2015年の期間で推定した。更に共通の実験設定下で複数の陸域炭素循環モデルを動作させ、様々なデータと比較した。シベリア域では経験モデルとのCO2収支推定結果と一貫性が高いことを示した。一方で、熱帯域についてはモデル間の違いや経験モデルとの違いが大きく、今後の課題として残された。
  • 文部科学省：科学研究費補助金（基盤研究（A））
    研究期間 : 2013年 -2016年 
    代表者 : 平野 高司
  • 文部科学省：科学研究費補助金（基盤研究（A））
    研究期間 : 2013年 -2016年 
    代表者 : 平野 高司
  • 土地利用変化が熱帯泥炭の分解にともなう二酸化炭素排出に与える影響の評価
    住友財団：環境研究助成
    研究期間 : 2014年11月 -2015年11月 
    代表者 : 平野 高司
  • 東アジア陸域生態系における炭素動態の定量化のための日中韓研究ネットワークの構築
    日本学術振興会：日中韓フォーサイト事業
    研究期間 : 2007年08月 -2012年07月 
    代表者 : 平野 高司
  • 文部科学省：科学研究費補助金(基盤研究(A))
    研究期間 : 2008年 -2012年 
    代表者 : 野口 伸, 平野 高司, 波多野 隆介, 山田 浩之, 石井 一暢, 海津 裕
     
    本研究は空間情報を高度に活用して湖沼群の水環境形成機構を解明し,数理工学的手法に基づいて回復策を提案できる方法論の提案を目的とした。リモートセンシングのグランドトゥルースとなる分光放射・水環境データを自動収集できる自律移動観測ボートシステムの開発,水・物質収支のモニタリングと解析,ニューラルネットワークによる非線形物質収支モデルの構築,低空・衛星リモートセンシングによる広域評価,そして遺伝的アルゴリズム(GA)を利用した物質収支モデル逆解析による環境回復策の提案を行う。次の4課題を設定して進める。
  • 文部科学省：科学研究費補助金(基盤研究(A))
    研究期間 : 2009年 -2011年 
    代表者 : 平野 高司, 前田 高尚, 小杉 緑子, 高梨 聡, 田中 延亮, 熊谷 朝臣
     
    1.平成21年度に試作した「樹冠定点映像記録装置」試作機の野外試運転を開始し,長期運転に必要な改良を行うとともに,並行して装置の量産を開始した。2.フラックスの変動解析のために,単純な時間平均でなく,晴天日(最大日射量の多寡で分類),曇天日,降雨日で分けてアンサンブル平均をとる手法を検討した。3.半島マレーシア熱帯雨林およびタイ北部熱帯落葉季節林,常緑季節林等においてタワーフラックス観測を行うとともに,東南アジア8サイトにおける比較解析を行うためのデータベース構築作業を行った。4.不均一な気孔開閉を含む気孔開閉による蒸散・光合成の制御の仕組みを明らかにし,炭素・酸素安定同位体比を利用した新たなガス交換特性の解析を行うために,気孔開閉の不均一性が炭素安定同位体分別に与える影響について解析した。モデルを利用した解析の結果,気孔開閉の不均一性はガス交換特性を大きく変化させるが,同位体分別はおおむねそのガス交換特性を反映した物となることが示された。5.タイ北部にある常緑性の熱帯季節林と落葉性の熱帯季節林において,顕熱・潜熱フラックスとCO_2フラックスのデータセットを整備した。ここで整備したデータセットは,東南アジアの多様な森林サイト間のフラックスの諸特性の横断的解析に貢献する。6.カンボジア国の低地常緑林を対象に,decoupling coefficient(Ω)の特性を解析した。...
  • 文部科学省：科学研究費補助金(基盤研究(A))
    研究期間 : 2008年 -2010年 
    代表者 : 平野 高司, 波多野 隆介, 井上 京, 冨士田 裕子, 山田 浩之, 高田 雅之
     
    微気象学的方法(渦相関法)を用いて,ミズゴケ区とササ区においてCO_2フラックスの連続観測を継続した。その結果,生態系呼吸(RE),光合成(GPP)ともにササ区の方が大きいが,正味CO_2吸収速度(NEP)に両区で大きな差が認められなかった。チャンバー法による結果は昨年度とほぼ同様であり,メタン(CH_4)放出速度がミズゴケ区でかなり大きかった。その量は,他の湿原に比べても大きいものであった。生態学的手法により,ミズゴケの伸長成長が1生育期間で25mm程度であること,ササは8月下旬に,群落全体では9月下旬にバイオマスのピークが存在し,地下部のバイオマスは地上部の約25倍であることがわかった。水文学的アプローチとして,ミズゴケ区とササ区において,溶存態有機炭素(DOC)を含む水質調査,動水勾配観測,透水試験を行ない,DOC流出量がミズゴケ域よりもササ域で多いことが明らかとなった。また,平坦な泥炭湿地の小集水域における流出を観測し,降雨の約70%は中間流(泥炭表層での浅い地下水流)として流出することを明らかにした。さらに,高含水比で未分解の泥炭を不撹乱で採取できるピートサンプラーの試作を行った。これまで採取した13地点の泥炭堆積構造,および8地点での最深部の炭素年代測定から,大きくサロベツ湿原の南北で泥炭の履歴が異なることなど,地点間の共通性と異質性を明らかにした。これらと地形情...
  • 文部科学省：科学研究費補助金(基盤研究(A))
    研究期間 : 2007年 -2010年 
    代表者 : 井上 京, 大崎 満, 橋床 泰之, 俵谷 圭太郎, 原口 昭, 波多野 隆介, 平野 高司, 谷 宏, 斎藤 秀之, 玉井 裕, 大崎 満, 秦 寛, 橋床 泰之, 浦木 康光, 俵谷 圭太郎, 原口 昭, 安部 竜一郎
     
    巨大なカーボン・シンクであり,かつ生物多様性に富みつつも脆弱な生態系である熱帯泥炭地を対象に、カーボンフロー・コントロールに立脚した土地利用・管理の最適化方策を確立することを目的に,泥炭火災の抑止と荒廃した土地の再生をすすめ、熱帯泥炭地における持続的生物生産活動を確立しつつ環境負荷を軽減するための種々の方策について検討した。
  • 文部科学省：科学研究費補助金(基盤研究(B))
    研究期間 : 2006年 -2008年 
    代表者 : 平野 高司, 谷 宏, 井上 京, 島田 沢彦, 山田 浩之
     
    東南アジアの低平地に分布する熱帯泥炭地は膨大な量の土壌炭素を貯留しているが, 開発による地下水位の低下などにより, 大量のCO_2を大気に放出する危険性が高まっている。そのため, CO_2排出量を抑制するために, 排水路を堰上げする簡易ダムによる環境修復が実施されている。本研究では, 生態系と大気との間のCO_2交換量をモニタリングし, ダムによる環境修復が熱帯泥炭の好気的分解を抑制し, CO_2排出量を低減させることを実証した。また, 衛星リモートセンシングを利用した地下水位の広域評価の可能性を示した。
  • 文部科学省：科学研究費補助金(基盤研究(B))
    研究期間 : 2005年 -2007年 
    代表者 : 平野 高司, 藤沼 康実, 小熊 宏之, 梁 乃申, 犬飼 孔
     
    北海道苫小牧市のカラマツ人工林(樹齢約45年の植林地)は,2004年9月の台風18号により風倒壊被害を受けた。台風による大規模攪乱は,林内環境や植生に大きな変化を与え,森林の炭素循環および炭素蓄積を変化させる。本研究では,植生が回復過程にあるカラマツ林跡地において現地調査を行い,台風による大規模環境撹乱がカラマツ林生態系の炭素動態に与える影響を明らかにすることを目的とした。微気象学的方法(渦相関法)および大型の自動開閉チャンバーを用いて連続測定したCO_2フラックスを基に,生態系呼吸量(RE),生態系光合成量(GPP)および生態系正味CO_2吸収量(NEP=GPP-RE)の季節変化,経年変化および環境応答特性を評価した。成長期間(6月13日〜11月12日の5ヶ月間)のRE,GPP,NEPの積算値は,倒壊前の森林(2001〜2003年の平均)でそれぞれ1125, 1370, 245 gCm^<-2>,倒壊2年後(2006年)にそれぞれ711, 607, -104gCm^<-2>,倒壊3年後(2007年)にそれぞれ664,622,-42gCm^<-2>となった。したがって,2004年の台風被害により,カラマツ林はCO_2の吸収源から放出源に変化し,エゾイチゴなどの潅木や草本を中心とした植生の回復にともない,徐々に吸収源に戻りつつあることがわかった。なお,2007年のREのうち,土...
  • 文部科学省：科学研究費補助金(基盤研究(B))
    研究期間 : 2004年 -2006年 
    代表者 : 谷 晃, 高山 真策, 平野 高司, 小池 真
     
    陽子移動反応質量分析計(PTR-MS)を用いて,植物の有害VOC吸収能力を評価するため,以下の実験をした.1.PTR-MSによるVOCガス種ごとの測定法の確立,特に湿度の影響の評価2.植物へのVOC沈着を吸収と吸着に分別して測定する方法の開発3.各植物種のVOC除去能力の評価4.光強度や暴露濃度とVOC沈着量の関係の検討5.群落へのVOC沈着フラックス測定方法の開発6.日本の代表植生であるコナラ林による主要VOC除去量の測定1に関しては,暴露対象物質である,低級アルデヒド類(〜C5),ケトン類(〜C5),アルコール類(〜C5),芳香族炭化水素(〜C7)の陽子移動反応後のフラグメントイオンを同定し,これらのイオン量におよぼす湿度の影響を調べた.2に関しては,ヘンリー定数から葉に可溶なVOC量を算出し,暴露中に吸収されたVOC量と比較した結果,植物によって吸収されたVOCが何らかの代謝系で消費されていることを明らかにした.3に関しては,観葉植物や樹木苗を用い,ケトン類,アルデヒド類および芳香族炭化水素を暴露した.アルコール類およびケトン類は全ての植物に吸収されたが,芳香族炭化水素のベンゼンとトルエンでは吸収は認められなかった.4では,光強度を変えた実験から,VOCは気孔から吸収されることが裏付けられた.また,植物はこれら有機ガスを速やかに気孔から吸収し,葉内で代謝できることわかつ...
  • 文部科学省：科学研究費補助金(基盤研究(S))
    研究期間 : 2002年 -2006年 
    代表者 : 福田 正己, 平野 高司, 町村 尚
     
    現地観測の結果東シベリアヤクーツクのタイガ内に攪乱と不攪乱個所のキャノピーを超える観測タワーを設置し、水・熱・二酸化炭素収支の連続モニタリングを行った。そのための機器(CO2/H2Oアナライザー、超音波風速計、土壌水分計)を用いた。毎年4月末に現地入りし、2本のタワーを設置して10月までの連続観測を実施した。更にオープントップチャンバー法により土壌呼吸の連続観測を行った。永久凍土融解過程をモニタリングするために、対象サイトでボーリング調査を毎年実施した。伐採前にはNEPとして86mg/m2・dayの二酸化炭素が森林に吸収されていた。しかし伐採後には日射の増加で地中温度が上昇し、土壌中の有機物分解が促進されて大気側への二酸化炭素の放出に転じた。更に撹乱で地表面での熱収支バランスが乱れ、永久凍土の上部での融解が進行した。その結果地中への伝達熱が増加し永久凍土は約10%より深くまで融解した。こうした融解では上部に含まれるメタンガスの放出を促す。攪乱による温暖化の促進タイガの攪乱のおもな原因は森林火災である。本研究では森林火災の代わりに全面伐採による影響評価実験を行い、タワー観測・土壌呼吸観測・永久凍土融解観測を行った。それらの結果から地球温暖化へ多大の影響を与えることが明確になった。(1)火災時の直接的な二酸化炭素放出(2)火災後の土壌呼吸増加による二酸化炭素の放出(火災後数十年間...
  • 文部科学省：科学研究費補助金(基盤研究(A))
    研究期間 : 2003年 -2005年 
    代表者 : 平野 高司, 高橋 英紀, 大崎 満, 谷 宏, 井上 京, 岡田 啓嗣, 兒玉 裕二
     
    インドネシア中央カリマンタン州の熱帯泥炭地を調査対象とし,a)未撹乱の熱帯泥炭林(SFサイト),b)排水路により地下水位の低下した熱帯泥炭林(KFサイト),c)熱帯泥炭林の火災跡地(KBサイト),において,主に微気象学的方法(渦相関法)によりCO_2収支とエネルギー収支を長期(3年間)連続観測した。KFサイトで信,2001年から観測を継続している。また,SFサイトとKBサイトでは,タワー建設が送れたため,当初の予定より1年遅れの2004年に観測を開始した。この地域は,平均して5〜10月の6ヶ月間が乾季に相当する。乾季には地下水位が大きく低下し,土壌水分も低下した。ENSOが発生した2002年には,森林周辺で大規模な泥炭火災が発生し,大量の煙で覆われたため,乾季の後半に光合成有効放射(PPFD)が大きく低下した。正味生態系CO_2交換量(NEE)は,乾季の後半に上昇し,雨季から乾季の前半にかけて低下するという季節変化を示したが,負の値(正味のCO_2吸収)となる月は無かった。乾季の後半における上昇は,生態系呼吸量(RE)の増加によるもので,これは地下水位の低下にともなって泥炭の分解が促進された結果であると考えられる。これらの結果から,年間のNEEは300〜700gCm^<-2>y^<-1>となり,この熱帯泥炭林がすでにCO_2ソースとなっていることがわかった。乾季の降水量が少な...
  • 文部科学省：科学研究費補助金(基盤研究(B))
    研究期間 : 2003年 -2004年 
    代表者 : 谷 宏, 平野 高司, 王 秀峰, 矢沢 正士, 鮫島 良次
     
    静止気象衛星データから推定した日射量や地上気象観測データを入力することにより,コンピュータ上に広域にわたる作物生育の状況を再現する広域農業生産モデルの構築を目標として研究を行った。本研究は,新規に打上げられるMTSAT衛星の観測データを使用することを重点項目としたが,打上げ失敗等の影響で観測データが得られなかったため多少の方針転換を余儀なくされ,次の項目について研究した。(1)衛星データから求めた日射量とアメダス気象データの時別値メッシュデータを利用し,気象関係値推定モデルと作物生育モデルの結合によって,成育シミュレーションを行うことによる通常の技術水準における生育状況のマップ作成,(2)気象衛星データによる推定を外国へ適用するための基礎研究,(3)地上気象観測において観測点密度を高くすることによる農業生産に関する環境情報のモニタリングの精度向上,である。各項目の成果は以下のとおりである。(1)衛星データによる日射量の推定については,GMS可視データによる陸域用の日射量推定モデルに改良を加え,日積算値のRMS誤差を低減できた。アメダスの気象値を1kmメッシュに拡張し,気温・風速・日照時間の空間分布を求め,作物生育モデルの入力値として用いることにより作物生育の状況を再現し,誤差は10a当り65kgとなった。(2)渇水が農業生産を圧迫している中国の黄河中下流域において,水消費に強...
  • 文部科学省：科学研究費補助金(基盤研究(B))
    研究期間 : 2001年 -2004年 
    代表者 : 平野 高司, 町村 尚, 鱧谷 憲, 文字 信貴, 岡田 啓嗣, 高木 健太郎
     
    北海道苫小牧市のカラマツ林を対象とし,現地での連続観測およびデータの解析を行なった。2001〜2003年の3年間の結果をまとめた結果,CO_2交換量の年積算値の平均(±標準偏差)は,純生態系生産量(NEP),総生態系生産量(GEP),生態系呼吸量(RE)でそれぞれ499±26,1595±65,1095±52gCm^<-2>y^<-1>と推定された。また,REがGEPに占める割合は67〜70%であった。このように,CO_2交換量の年積算値における年次差は比較的小さかったが,季節変化には大きな違いが認められた。特徴的なのは,2002年のGEPであった。この年は冬から春にかけて気温が高かったため,融雪と開葉が他の年より2週間ほど早く,光合成も早く始まった。しかし,2002年の夏期はP_が小さく,PPFDも低かったため,GEPが他の年より小さくなった。結果として,成長期間が長いにもかかわらず,2002年のGEPは他の年より小さくなった。2002年におけるP_低下の原因として,多雨による光合成酵素(Rubisco)の損失や早期の開葉による窒素利用効率の低下が考えられた。なお,2003年7月の気温は他の年より2〜3℃低かったが,GEPが減少することはなかった。低温は大気飽差を低下させ,結果としてGEPを増大させた。成長期間の土壌水分は0.2〜0.4m^3m^<-3>で...
  • 文部科学省：科学研究費補助金(基盤研究(A))
    研究期間 : 2001年 -2004年 
    代表者 : 大崎 満, 蒲生 稔, 平野 高司, 井上 京, 甲山 隆司, 松原 健司
     
    インドネシアカリマンタンには熱帯泥炭が存在し、膨大な量の炭素を貯蔵しているが、近年急速な開発と不法伐採により、頻繁に火災が発生し、地球大気にはっきりと影響を与えるようになりつつある。そこで、この放棄地、焼け跡地を中心に、森林植生の回復と泥炭の保全のシステムを構築することを目指して調査研究を進め、以下の成果を得た。(1)環境評価システム1)化学物質の動態とリグニン分解の評価土壌試料、河川や湖沼の水試料を採取し、化学物質の動態を解明した。泥炭土壌からは、多数の白色腐朽菌が得られ、この白色腐朽菌の代謝機能を評価し、リグニン分解、PCB、ダイオキシンといった毒性化合物の分解に応用出来るものを見いだした。2)熱帯泥炭林における微気象およびフラックス観測カリマンタン・パランカラヤ近郊の1)カランパンガンの天然林(運河掘削により乾燥化が進んでいる)、2)カランパンガンの焼失地(運河掘削により乾燥化が進んでいる)、3)セテアラムのナチュラルラボ(自然条件下の天然林)にて熱帯泥炭林における微気象およびフラックスの連続観測を実施した。運河掘削により、火災が無くとも微生物分解と森林の光合成能力の低下で、膨大な炭素が放出されていることを、世界で初めて解明した。(2)地域社会支援システム1)森林修復活動Shorea balangeranが生残率、成長量が大きく、撹乱跡地における泥炭林修復に適当な樹種で...
  • 冬期積雪条件における森林土壌からのCO2発生量の評価
    住友財団：環境研究助成
    研究期間 : 2003年 -2003年 
    代表者 : 平野 高司
  • 文部科学省：科学研究費補助金(基盤研究(C))
    研究期間 : 2002年 -2003年 
    代表者 : 鱧谷 憲, 文字 信貴, 平野 高司
     
    REA法による森林メタンフラックスの長期連続測定装置を開発し,森林での試験観測を行った。この装置はマイクロコンピュータを使って装置を稼動させ,自動的にフラックスの測定を行うものである。これらサンプリング装置や複数のコンピュータシステムのハードウエアー,ソフトウエアーは測定条件や測定上の具体的な問題点にあわせて作成した。ガス分析計には検出器がFIDのものを用いた。この分析計の測定精度は±50ppbであった。しかし,REA法では2つのサンプリング空気の濃度差が測定量になるので,このときの濃度差の測定精度は数ppbとなり僅かなフラックスの測定も可能となった。観測前にこの装置と同じ構造のものを用いてCO_2フラックスについて渦相関法とREA法による測定を同時に行い比較検討した。この結果,両測定値は驚くほど良く一致した。長期間の測定では測定機器の検定や装置の思いもかけないトラブルなどがあり,1〜2週間に1回程度の保守作業が必要であった。しかし,装置は比較的順調に稼動し,森林のメタンフラックスの長期的な変化が次第に明らかになってきた。9月のメタンフラックスの測定では日中の輸送方向は下向(吸収)に、夜間にはほぼゼロになり,深さ1cmの地温とフラックスを較べると気温12℃まではゼロで,それより気温が高くなるとメタンの輸送方向が下向になった。しかし11月には地温が12℃以上になってもフラックス...
  • 文部科学省：科学研究費補助金(基盤研究(B))
    研究期間 : 2001年 -2003年 
    代表者 : 石川 信敬, 平野 高司, 石井 吉之, 兒玉 裕二, 知北 和久, 浦野 慎一
     
    平成13-15年度にアラスカ中央部の実験流域において「土壌の凍結融解にともなう熱、水蒸気、炭酸ガスの交換特性や水循環の微物理過程の特性」を把握する観測を実施した。流域の熱収支、水収支、流出機構は短期集中観測により、また気候値や長期変動を知るためには通年連続観測を実施し、永久凍土地帯の水循環、物質交換特性に関する多くの知見を得た。観測項目は微気象要素(気温、風速、湿度、乱流、放射)や水文要素(土壌水分量、地温、水温、河川流量、地下水位、降水量)、水の含有化学成分、CO_2交換量である。また流域内の凍土分布は地下電気探査により求め掘削による検証も行った。その結果(1)狭い流域内でも地表面状態によって熱収支が異なる、特に植生面の蒸発が生じるのに対して水面では夏でも凝結が生じており、凍結土壌の融解による河川水温の低温化の影響が現れている。(2)表面近傍の土壌水分は斜面の方位と植生に大きく依存する。また地下水位は活動層の中では降水や蒸発の影響を受けて変動するのに対して、凍土層の下ではほとんど変動がない。(3)CO_2は植生上面と下面でフラックス量と伝達の向きが異なり、土壌呼吸量は融解層の厚さに関係する。(4)河川の降雨流出応答は流域を構成する斜面の向きによって異なる、すなわち夏期でも永久凍土が存在する北斜面では降雨に応じた顕著な増水を示すが、凍土が融解した南斜面では目立った流出が見られ...
  • 文部科学省：科学研究費補助金(基盤研究(C))
    研究期間 : 2000年 -2002年 
    代表者 : 矢部 和夫, 平野 高司, 倉持 寛太, 浦野 慎一, 植村 滋
     
    北海道内のミズゴケハンモックの形状に地域的差異が生じる原因を解明するため,ハンモックの高さが異なる4湿原(風蓮川:円筒形で高い,サロベツ・歌才:扁平で低い,ウトナイ:山形で中程度)においてミズゴケ3種のシュートの成長量を測定した.さらに,冬期の雪圧と他の植物の有無が成長に与える影響も検討した.年間成長量は日本海側で太平洋を上回った.他の植物の除去によってミズゴケの成長が抑制された.これは被陰による蒸発抑制効果が失われたためと考えられる.雪圧を除去した場合,多雪地帯で成長が抑制されたのは,冬期の雪圧によってハンモックが沈降せず,相対的に水位が低くなったためと推察された.サロベツでイボミズゴケの成長が6月に抑制されたのは,余剰降水量の低下による乾燥が原因と考えられる.風蓮川湿原のハンモックの水収支を調査し,ハンモック内の水移動を検討した.晴天日は日中に蒸発散によって失われたのと同量の水が下層から供給されていた.降雨中は,ハンモック表面から供給された雨水が表層で貯留されず浸透し,深層では一部が貯留された.表層の未分解泥炭は緻密な構造をしており,毛管水の保持・吸収能力が高い.そのため,蒸発散によって表層の水が失われても深層から吸引できたと考えられる.一方,深層の分解泥炭は構造が崩壊し透水性が低いため,降雨時には水移動量が表層より小さくなり,水が深層に貯留されたと考えられる.このように...
  • 文部科学省：科学研究費補助金(基盤研究(B))
    研究期間 : 1999年 -2002年 
    代表者 : 石川 信敬, 兒玉 裕二, 田中 夕美子, 石井 吉之, 平野 高司, 高橋 英紀, 兒玉 裕二, 田中 夕美子
     
    平成11-14年度に「積雪寒冷森林地域の水循環及び物質循環におよぼす森林と積雪の影響」について現地観測を実施した。観測項目は林内の乱流構造と蒸発散量、積雪と林内における炭酸ガス濃度、土壌呼吸量、大気熱収支に及ぼす積雪と森林の熱的効果、河川水や地下水及び積雪内の塩化物イオンと酸性度である。その結果、1)樹冠上では蒸発散量に明瞭な季節変化を認めたが夏期の蒸発散量は放射収支量の30-40%に過ぎずこれまでの報告に比べて小さかった。また林内の炭酸ガス濃度は測定器の送風量によって値が大きく変動し、さらに場所による変動が大きいため多点での測定が不可欠であることを指摘した。2)落葉広葉樹林の炭素吸収量は2680-2200(kgC/ha/yr)であり、経年変動は別に推定した樹木の成長量の年変動と定性的に一致した。一方、土壌呼吸速度(土壌からの炭酸ガス放出速度)は4100-3900(kgC/ha/yr)であり、その日変化や季節変化は地温の変化に対応した。また降雨後に大きく変動することを見出した。3)積雪最下層部の炭酸ガス濃度は大気に比べてはるかに大きな値(1200ppm以上)を示したが、これは冬期間でも深い積雪下では微生物活動があり充分な土壌呼吸量があったものと推察された。なおこの高濃度の炭酸ガスはしばしば短時間で400ppm以下に低下し積雪を通して大気中に抜けている事が分かった。なお積雪面上...
  • 熱帯泥炭林の消失にともなう環境劣化機構に関する研究
    昭和シェル石油：環境研究助成
    研究期間 : 2001年 -2001年 
    代表者 : 平野 高司
  • 北方森林土壌におけるCO2の動態と発生量に関する研究
    アサヒビール学術振興財団：研究助成
    研究期間 : 2001年 -2001年 
    代表者 : 平野 高司
  • 文部科学省：科学研究費補助金(萌芽的研究)
    研究期間 : 2000年 -2001年 
    代表者 : 平野 高司
     
    土壌のCO_2濃度,土壌表面からのCO_2放出速度(土壌呼吸速度),および土壌の層別CO_2発生速度を長期・連続測定(モニタリング)する手法を開発し,森林において実証試験を行った(現在も継続中)。開発した手法は,小型の赤外線CO_2分析計を土壌の数深度に埋め込み,土壌CO_2濃度を連続測定し,得られたCO_2の濃度勾配,土壌のCO_2拡散係数,および土壌層でのCO_2貯留変化量を用いて,土壌中のCO_2の輸送速度(フラックス),土壌呼吸速度,CO_2発生速度を連続的に定量評価するものである。現地実験は,北海道大学苫小牧研究林の落葉広葉樹林において,1999年5月から,また隣接する苫小牧国有林のカラマツ林において2001年6月から連続して行っており,現在も継続中である。現地実験の結果,本研究で考案したシステムにより,土壌CO_2濃度および土壌呼吸速度を長期にわたり連続測定できることが実証された。土壌のCO_2濃度を,このような長期にわたって連続測定した例は過去にない。なお,2年間以上にわたる現地実験を通して得られた主要な結果は,1)土壌のCO_2濃度は,基本的には地温の変化にともなって日変化および季節変化するが,降雨にともなう土壌水分の変化にも影響を受ける,2)土壌呼吸速度は,地温の上昇にともなって指数関数的に増大し,7〜9月に最大となった,3)2000年6〜11月の無積雪期の...
  • 文部科学省：科学研究費補助金(基盤研究(B))
    研究期間 : 1997年 -2000年 
    代表者 : 清田 信, 平野 高司, 北宅 善昭, 渋谷 俊夫
     
    本研究では、高CO_2濃度下での木本植物のガス交換について検討し、得た結果を次のようにまとめた。(1)木本植物の光合成・蒸散速度におよぼすCO_2濃度の影響(2)二酸化炭素濃度上昇による樹木のガス交換特性の変化と水ストレス緩和(3)二酸化炭素濃度の上昇が樹木苗群落の熱収支におよぼす影響(4)フィールドチャンバーを用いた樹木のガス状大気汚染物質吸着速度の測定法(5)樹木によるガス状大気汚染物質の時期別吸着速度(6)短期のCO_2濃度上昇がキョウチクトウおよびヒノキのガス状大気汚染物質吸着速度におよぼす影響樹種によってそのガス交換速度は多いに異なる。植林用樹種として注目されているユーカリやアカシアは、CO_2濃度が上昇するとCO_2吸収量は増加するが、蒸散速度はかなり減少する。これらは、水利用効率が高まることによって水不足の地域での成長の可能性が高まるが、蒸散の減少が熱環境にも影響を生じる。
  • 文部科学省：科学研究費補助金(基盤研究(B))
    研究期間 : 1997年 -1999年 
    代表者 : 浦野 慎一, 堀口 郁夫, 山梨 光訓, 町村 尚, 上田 宏, 高橋 英紀, 平野 高司
     
    陸地水体と生物生産の相互関係を明らかにするため、北海道の洞爺湖とその周辺を対象に水温、気温、風向風速等を観測し、貯熱量と湖効果を検討した。またアフリカのザンベジ河氾濫原で水文気象観測を実施し、氾濫原の特性と水田開発の関係を検討した。さらに基礎的研究として、様々な植生における蒸発散量を観測し、比較した。以上のことを13編の論文にまとめ、報告書(158ページ)にまとめた。得られた結果の概要は以下のとおりである。洞爺湖では、水体の貯熱量が大きいため、陸地と湖水面における有効エネルギーの季節変化に約半年の位相のズレが確認され、この位相のズレが湖効果の原因になっていることがわかった。また洞爺湖の湖効果は相対的に冬期より夏期に強く出現すること、地域的には夏期の一般風の主風向が南よりであるため北側の湖岸で強く出現することがわかった。以上のことから、夏期の生物生産最盛期に湖効果が出現する地域では、気温を考慮してその地域に適切な作目を選ぶ必要があると考えられた。ザンベジ河氾濫原では、蒸発散量は雨季終了後および冷涼乾期に大きな減少が見られなかった。これは周辺台地から供給される地下水の流れによるものと推察され、水田開発を行うにはこのような地下水流を考慮に入れる必要があると考えられた。また、基礎的研究として森林、トーモロコシ畑、牧草地の蒸発散量を比較した結果、牧草地ではデカップリングファクターが最も...
  • 文部科学省：科学研究費補助金(一般研究(C))
    研究期間 : 1994年 -1995年 
    代表者 : 平野 高司, 清田 信
     
    大阪府立大学の実験圃場に造成した芝生地(コウライシバ)と裸地において,1994年10〜12月および1995年7月〜10月に熱収支(顕熱,潜熱フラックス),窒素酸化物(NOとNO_2),CO_2および水蒸気のフラックスを傾度法を用いて同時測定し,それらの季節変化を調べるとともに,植物の有無がフラックスに与える影響を調べた。その結果,顕熱フラックスは芝生地<裸地,潜熱フラックスは逆に芝生地>裸地となり,芝生(植生)が温度上昇を抑える効果のあることが確認された。一方,NOフラックスは芝生地,裸地ともに多くの場合上向きであり,土壌から大気中に放出されていること,および裸地における放出量が芝生地よりも多いことが確認された。また,季節変化がみられ,10月にはフラックスの絶対値が減少したが,これは地温の低下にともなう微生物活性の低下が原因だと考えられる。NO_2フラックスは,芝生地ではほぼ下向きであったが,裸地では向きが一定ではなく,上向きの場合もあった。芝生地でのNO_2フラックスは,NO_2濃度との間に負の相関が認められ,濃度が高いほど芝生による収着(吸収+吸着)が多いことが確認された。NO_2の沈着速度は,芝生地では裸地に比べてかなり大きかったが,7〜8月に比べて10月には低下した。芝生地におけるこの季節変化は,風速や気孔開度の変化によるものと考えられた。なお,NO_X(NO+NO_...
  • 文部科学省：科学研究費補助金(試験研究(B))
    研究期間 : 1993年 -1995年 
    代表者 : 相賀 一郎, 洞口 公俊, 谷 晃, 村上 克介, 平野 高司, 清田 信
     
    本研究は、著者らにより以前に開発された遠赤色光(FR)付加照射による植物の伸長成長制御法ならびにFR分光特性を持つ4波長域発光形蛍光ランプを基本として、(1)4波長域発光形蛍光ランプの分光特性の改善による効率的な植物成長制御法(2)4波長域発光形蛍光ランプの設計法を自然光に応用し、分光特性の調節により植物の成長制御をおこなう温室用被覆材の開発(3)付帯技術であるが光放射に関連する実験を行なうのに特に重要な植物栽培光環境の高速計測技術、を中心に実施した。人工光源の開発においては、遠赤色光の分光特性を持たせた4波長域発光形蛍光ランプについて、色温度を高くする(光を相対的に減少させる)ことにより効率的に赤色光遠赤色光光量子束比(R/FR比)を変化できることを見いだし、栽培実験にてその有効性を実証した。これらの結果に基づき、平成8年度より、本ランプの市販を松下電器産業にて開始した。また自然光のR域、FR域を特異的に遮断する色素によりR/FR比を変化させる植物成長制御用樹脂被覆材を開発し、それらを用いたグロースキャビネットや温室内において、多くの作物の成長制御が可能であることを見いだした。また、植物栽培光環境の高速計測技術は、上記人工光源もしくは被覆材の開発ならびに実証実験に重要であるため、今回とくにマルチチャンネル形分光測定装置を改良し、入射特性、測定誤差補正法などに改善を加えて分光...
  • 文部科学省：科学研究費補助金(一般研究(C))
    研究期間 : 1994年 -1994年 
    代表者 : 文字 信貴, 鱧谷 憲, 平野 高司
     
    増え続ける温室効果気体が地球の気候環境を変えることが懸念されているが,大気の微量気体がどの程度の量,どの様なメカニズムで,さまざまな地表から出ているか,あるいは植生などによって吸収されているが明確にされていないことは気候変化の予測を困難にする一因となっている.これは,微量気体の動態の測定技術が未開発であることが原因である.微量気体の交換過程は大気乱流の混合がその役割を果たす.したがって,微量気体濃度の乱流変動をさまざまな植被上などではかる必要があるが,現在の技術では分析器の応答性,安定性に限界がある.この点を解決する方法として提案されたのが渦集積法である.渦集積法は気流が上向きの成分と下向きの成分を持つ場合にわけてそれぞれ空気を別々にその成分の大きさに比例して容器に収集し,それぞれの濃度を計測する方法である.しかし,誤差が大きいため,条件を緩和して空気の収納を定速で行う簡易渦集積法が提案されている.本研究ではその方法を実用化するためにサンプリング装置を開発し,森林で試験観測を実施した.観測は滋賀県南部の針葉樹林で行った.この簡易渦集積法では係数を実験によって決定しなければならない.そのために,すでに乱流変動の測定が可能な赤外線の二酸化炭素変動計をもちいて直接的な渦相関法により二酸化炭素のフラックスを求め,その一方でサンプルした二つの容器の二酸化炭素濃度は購入した赤外線分析計を...
  • 文部科学省：科学研究費補助金(奨励研究(A))
    研究期間 : 1993年 -1993年 
    代表者 : 平野 高司
     
    本研究では、緑化樹の大気浄化(NO_2吸収)機能と温湿度環境緩和機能を評価するための基礎的な実験データを得ることを目的として、いくつかの条件で植物のNO_2吸収速度、蒸散速度、光合成速度および葉温を同時測定し、それらの相互関係を調べた。実験は現有の人工光型グロースチャンバー内に設置した開放系のガス交換測定システム(同化箱法)を用いて行い、ガス濃度差などの出力データは設備備品として購入したパソコンを用いてガス交換速度に変換した。システムへのNO_2の吸着ができるだけ少なくなるように、配管にはステンレス、あるいはテフロン製のものを用い、また同化箱の壁面をテフロンシートで被覆したが、吸着量は温度条件などにより変化した。そのため、まず植物を入れる前の段階でシステムへのNO_2吸着量に与える測定条件の影響を調べ、測定値を補正する方法を検討した。植物材料には鉢植えのポプラのクローン苗(系統:I-214)を用いた。土壌水分が十分、大気の飽差が一定の条件で気温とひかり強度を変化させて実験を行った結果、NO_2吸収速度、蒸散速度、光合成速度は同様に変化し、気温15〜35℃で光強度500mumolm^<-2>s^<-1>(PPFD)以下では、それぞれのガス交換速度間の関係はほぼ直線となった。これらの関係は、気孔コンダクタンスによって説明できることが認められた。現在、大気湿度を変化させて同様の実験...
  • 文部科学省：科学研究費補助金(一般研究(C))
    研究期間 : 1991年 -1993年 
    代表者 : 清田 信, 平野 高司
     
    熱帯産果実の多くは、呼吸量が多く、蒸散量も多いため、収穫後の鮮度の低下は著しく、損耗、腐敗による損失が多い。果実周辺のガス組成を調節することによって、鮮度を保持するための簡易法について検討した。供試した熱帯産果実は、パパイヤ、アボカド、バナナ、マンゴ-などであった。貯蔵中のガス組成としては、常温でも酸素濃度を1〜3%に下げることによって鮮度保持効果は認められ、果実表皮の色の変化、軟化を抑制できた。一方、二酸化炭素濃度は、5〜10%ではそれが果実に与える影響は少なかった。このようなガス組成を維持するために、プラスチックフィルムによるMAP(Modified Atmosphere Packaging)による簡易鮮度保持法について検討した。ガス収支よりフィルムのガス透過性、フィルム面積、果実重量と、包装内ガス濃度を求め、果実の鮮度保持について実験を行い、簡易鮮度保持の可能性を確認した。問題として、エチレンガス、湿度の上昇を抑えることも必要となるが、吸着剤との併用によるガス濃度の調節は可能である。湿度が高くなると空気を流動させることによって、果実近くの微細環境を制御することも有効であり、これらの方法を合わせることで、簡易貯蔵庫、輸送コンテナなどの内部環境の調節法に有用な知見も得た。また、電子冷却装置や空気流動のための循環扇に、太陽電池を利用することで無電源地域での小型貯蔵庫が開発可能...
  • Monitaring of environmental functions of terrestrial ecosystems

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