基本情報

所属

• 地球環境科学研究院　統合環境科学部門　自然環境保全分野

職名

• 准教授

学位

• Ph.D. (Geography)（National University of Singapore）

ホームページURL

https://kaken.nii.ac.jp/d/r/90423029.ja.html

J-Global ID

• 201501041678793586

研究キーワード

• 底生動物   氾濫原   湧水   生息環境   河床低下   生態系保全   保全   水生生物   生態系管理   底性動物   流域管理   河川   生物多様性   流域保全   森林渓流生態系   生物濃縮   鳥類   放射性セシウム   農地生態系   森林農地生態系   放射性物質の移行   撹乱   有機物動態   森林生態系   放射性核種   食物網解析   渓流生態系   淡水魚類   河川生態系   河川流出   

研究分野

• 環境・農学 / 生物資源保全学
• ライフサイエンス / 森林科学
• 環境・農学 / ランドスケープ科学
• 環境・農学 / 環境農学

担当教育組織

•  修士課程　環境科学院
•  博士課程　環境科学院

職歴

• 2011年 - 現在 北海道大学 地球環境科学研究科(研究院) 准教授

研究活動情報

論文

• Tributary mitigates river discontinuity by dam depending on the distance from dam to the tributary confluence

  Izumi Katano, Hideyuki Doi, Junjiro N. Negishi, Tomoko Minagawa, Yuichi Kayaba

  River Research and Applications 1 - 14 2023年11月 [査読有り]
  
• Habitat aging and degradation in terrestrialized floodplains: a need to rejuvenate processes for sustaining freshwater mussel populations

  Shigeya Nagayama, Morihiro Harada, Junjiro N. Negishi, Jyun-ichi Kitamura, Terutaka Mori, Seiichi Mori

  Restoration Ecology 2023年10月25日 [査読有り]
  
• Recruitment status and host-fish-limitation threats to endangered freshwater pearl mussel (Margaritifera laevis) in eastern Hokkaido, northern Japan

  Kazuki Miura, Nobuo Ishiyama, Junjiro N. Negishi, Keita Kawajiri, Hokuto Izumi, Daisetsu Ito, Futoshi Nakamura

  2023年05月22日 

  Abstract Recruitment failure is a major threat to freshwater mussel (Order Unionoida) populations worldwide. Assessments of the recruitment status and determining the bottleneck factors of mussel recruitment are crucial for preventing future declines in mussel populations. In this study, we investigated the recruitment status (i.e., size structure and the proportion of juveniles within a population) of the endangered freshwater pearl musselMargaritifera laevisin 22 rivers in eastern Hokkaido, northern Japan. We also quantified the density of the host fishOncorhynchus masou masouand examined the relationship between the proportion of juveniles and host-fish density to assess host-limitation threats toM. laevisrecruitment. Our assessments showed that 13 (59.1%) rivers had no signs of recent recruitment within 10 years, with a low mean proportion of juveniles (mean:0.02 [range:0.00–0.09] fraction), indicating that these populations are threatened by sustained recruitment failure. The proportion of juveniles was positively associated with host-fish density, suggesting that host-fish limitation could be a bottleneck factor forM. laevisrecruitment. These results highlight the urgent need for prompt conservation measures, including the enhancement of host-fish availability, to sustainM. laevispopulations in the study region.
• Geology‐Climate Interactions are Key Determinants of Climate‐Change Refugia in Japanese Mountain Streams

  Nobuo Ishiyama, Masanao Sueyoshi, Jorge García Molinos, Kenta Iwasaki, Junjiro N. Negishi, Itsuro Koizumi, Shigeya Nagayama, Akiko Nagasaka, Yu Nagasaka, Futoshi Nakamura

  The Bulletin of the Ecological Society of America 2023年03月15日
• Underlying geology and climate interactively shape climate change refugia in mountain streams

  Nobuo Ishiyama, Masanao Sueyoshi, Jorge García Molinos, Kenta Iwasaki, Junjiro N. Negishi, Itsuro Koizumi, Shigeya Nagayama, Akiko Nagasaka, Yu Nagasaka, Futoshi Nakamura

  Ecological Monographs 93 2 2023年02月16日
• Contrasting seasonality of 137Cs concentrations in two stream animals that share a trophic niche

  Masaru Sakai, Yumiko Ishii, Hideki Tsuji, Asuka Tanaka, Jaeick Jo, Junjiro N. Negishi, Seiji Hayashi

  Environmental Pollution 315 120474 - 120474 2022年12月
• Three years in the dark: life history and trophic traits of the hyporheic stonefly, Alloperla ishikariana Kohno, 1953 (Plecoptera, Chloroperlidae)

  J. N. Negishi, M. K. Alam, M. A. T. M. T. Rahman, R. Kawanishi, H. Uno, G. Yoshinari, K. Tojo

  Hydrobiologia 849 19 4203 - 4219 2022年11月
• Catchment geology preconditions spatio-temporal heterogeneity of ecosystem functioning in forested headwater streams

  Janine Rodulfo Tolod, Junjiro N. Negishi, Nobuo Ishiyama, Md. Khorshed Alam, Mirza A. T. M. Tanvir Rahman, Pongpet Pongsivapai, Yiyang Gao, Masanao Sueyoshi, Futoshi Nakamura

  Hydrobiologia 2022年09月07日
• Disturbance legacy of a 100-year flood event: large wood accelerates plant diversity resilience on gravel-bed rivers

  Kei Uchida, Azumi Okazaki, Takumi Akasaka, Junjiro N. Negishi, Futoshi Nakamura

  Journal of Environmental Management 317 115467 - 115467 2022年09月
• Effects of sediment replenishment on riverbed environments and macroinvertebrate assemblages downstream of a dam

  Izumi Katano, Junjiro N. Negishi, Tomoko Minagawa, Hideyuki Doi, Yôichi Kawaguchi, Yuichi Kayaba

  Scientific Reports 11 1 7525 - 7525 2021年12月 [査読有り]
   

  Riverbeds downstream of dams are starved of sediment, impacting habitat structure and ecological function. Despite the implementation of sediment management techniques, there has been no evaluation of their conservational effectiveness; the impacts on high trophic level organisms remain unknown. This study examined the effects of sediment replenishment on riverbeds and macroinvertebrates in a dammed river before and after sediment replenishment. We evaluated the particle sizes of replenished sediments and the case material of a case-bearing caddisfly. We observed significant changes in macroinvertebrate assemblages before and after sediment replenishment, and between the upstream and tributary references and downstream of the dam. The percentages of Ephemeroptera, Plecoptera, and Trichoptera, and the number of inorganic case-bearing caddisflies downstream of the dam following sediment replenishment, were significantly higher than the upstream and tributary reference sites. The particle size of case materials used by case-bearing caddisfly corresponded to the size of the replenished sediment. Dissimilarity results after replenishment showed that assemblages downstream of the dam differed from upstream sites, although they were similar to the tributary sites. The dissimilarity between the tributary and downstream of the dam was the same as that between the upstream and tributary. Sediment replenishment was observed to reduce the harmful effects of the dam, and partly restore benefits such as increasing species diversity and altering community assemblages, similar to the effects of tributary inflows.
• Impacts of detritivore diversity loss on instream decomposition are greatest in the tropics

  Luz Boyero, Naiara López-Rojo, Alan M. Tonin, Javier Pérez, Francisco Correa-Araneda, Richard G. Pearson, Jaime Bosch, Ricardo J. Albariño, Sankarappan Anbalagan, Leon A. Barmuta, Ana Basaguren, Francis J. Burdon, Adriano Caliman, Marcos Callisto, Adolfo R. Calor, Ian C. Campbell, Bradley J. Cardinale, J. Jesús Casas, Ana M. Chará-Serna, Eric Chauvet, Szymon Ciapała, Checo Colón-Gaud, Aydeé Cornejo, Aaron M. Davis, Monika Degebrodt, Emerson S. Dias, María E. Díaz, Michael M. Douglas, Andrea C. Encalada, Ricardo Figueroa, Alexander S. Flecker, Tadeusz Fleituch, Erica A. García, Gabriela García, Pavel E. García, Mark O. Gessner, Jesús E. Gómez, Sergio Gómez, Jose F. Gonçalves, Manuel A.S. Graça, Daniel C. Gwinn, Robert O. Hall, Neusa Hamada, Cang Hui, Daichi Imazawa, Tomoya Iwata, Samuel K. Kariuki, Andrea Landeira-Dabarca, Kelsey Laymon, María Leal, Richard Marchant, Renato T. Martins, Frank O. Masese, Megan Maul, Brendan G. McKie, Adriana O. Medeiros, Charles M.M’ Erimba, Jen A. Middleton, Silvia Monroy, Timo Muotka, Junjiro N. Negishi, Alonso Ramírez, John S. Richardson, José Rincón, Juan Rubio-Ríos, Gisele M. dos Santos, Romain Sarremejane, Fran Sheldon, Augustine Sitati, Nathalie S.D. Tenkiano, Scott D. Tiegs, Janine R. Tolod, Michael Venarsky, Anne Watson, Catherine M. Yule

  Nature Communications 12 1 3700 - 3700 2021年12月 [査読有り]
   

  The relationship between detritivore diversity and decomposition can provide information on how biogeochemical cycles are affected by ongoing rates of extinction, but such evidence has come mostly from local studies and microcosm experiments. We conducted a globally distributed experiment (38 streams across 23 countries in 6 continents) using standardised methods to test the hypothesis that detritivore diversity enhances litter decomposition in streams, to establish the role of other characteristics of detritivore assemblages (abundance, biomass and body size), and to determine how patterns vary across realms, biomes and climates. We observed a positive relationship between diversity and decomposition, strongest in tropical areas, and a key role of abundance and biomass at higher latitudes. Our results suggest that litter decomposition might be altered by detritivore extinctions, particularly in tropical areas, where detritivore diversity is already relatively low and some environmental stressors particularly prevalent.
• Exceptional color preferences for flying adult aquatic insects

  Junjiro N. Negishi, Tomohiro Nakagawa, Futoshi Nakamura

  Aquatic Ecology 56 1 325 - 330 2021年10月13日 [査読有り]
   

  This study tested the hypothesis that color affects the behavior of Ephemeroptera, Plecoptera, and Trichoptera (EPT) adults in the riparian zone of a gravel-bed river in northern Japan. EPT abundance was measured using plot scale surveys and a color-choice experiment that utilized non-shiny sticky traps in two contrasting colors, yellow and blue. Chloroperlidae and Hydrobiosidae were caught more abundantly in yellow and blue traps, respectively, whereas other taxa exhibited little or no color-affected responses. We proposed that Chloroperlidae responses were driven by relatively strong diurnal activity compared with those of other taxa. Hydrobiosidae's preference of blue remained unknown. Understanding the evolutionary background of color preferences in relation to other possibly interfering factors, such as reflection-polarization characteristics, at the species level will help advance the visual sensory ecology of aquatic insects.
• The effects of endangered freshwater pearl mussels on channel morphology and flow in a low-gradient sandy river

  Kazuki Miura, Nozomi Watanabe, Yuuka Takagi, Nobuo Ishiyama, Junjiro N. Negishi

  Hydrobiologia 2021年10月05日 [査読有り]
  
• Multiple stressors and recruitment failure of long-lived endangered freshwater mussels with a complex life cycle

  Kazuki Miura, Nobuo Ishiyama, Junjiro N. Negishi, Daisetsu Ito, Keita Kawajiri, Hokuto Izumi, Takahiro Inoue, Masahiro Nakaoka, Futoshi Nakamura

  2021年09月23日 

  Multiple stressors can interactively affect the population of organisms; however, the process by which they affect recruitment efficiency remains unclear for empirical populations. Recruitment efficiency can be regulated at multiple stages of life, particularly in organisms with complex life cycles. Understanding the interactive effects of multiple stressors on recruitment efficiency and determining the bottleneck life stages is imperative for species conservation. The proportion of <20-year-old juveniles of the endangered freshwater pearl mussel Margaritifera togakushiensis, which has an obligate parasitic larval stage, was investigated in 24 rivers from eastern Hokkaido, northern Japan to reveal the influence of nutrients, fine sediment, and their combined effects on juvenile recruitment efficiency. The following indices for recruitment at adult, parasitic, and post-parasitic juvenile stages were obtained from 11 of these rivers: gravid female density, glochidia density (the number of glochidia infections per stream area), and juvenile survival rate. This study explored the bottleneck stages of recruitment efficiency and the interactive effects of the two stressors on these stages. Twenty-four population status assessments determined that the proportion of juveniles ranged from 0.00 to 0.53, and juveniles were absent from four rivers. The results showed that the parasitic and post-parasitic juvenile stages were bottlenecks for recruitment efficiency. Juvenile survival rates had a more significant positive effect on recruitment efficiency in rivers with a high glochidia density. Juvenile survival rate was decreased by the synergistic interaction of nutrients and fine sediment, although factors limiting glochidia density were not found. The nutrient concentration of rivers in the study region was well explained by the proportion of agricultural land cover and urban areas in the watersheds, but no relationship was detected between fine sediment abundance and land use. This study suggests that nutrient management at a catchment scale can be effective for re-establishing the recruitment of M. togakushiensis, particularly in rivers with a high content of fine sediments. The results also emphasise the importance of considering both parasitic and post-parasitic juvenile stages of mussels to maximise the positive effects of stressor mitigation.
• Testing local adaptations of affiliate freshwater pearl mussel, Margaritifera laevis, to its host fish, Oncorhynchus masou masou

  Hitoshi Kitaichi, Junjiro N. Negishi, Daisetsu Ito, Kazuki Miura, Hirokazu Urabe

  Ecological Research 36 5 803 - 814 2021年09月 [査読有り]
   

  Understanding the limiting factors of the reproduction process in host–affiliate relationships is a high priority. We examined the effects of habitat location on the reproductive process of freshwater pearl mussels Margaritifera laevis (Bivalvia, Unionida) as a parasite using sympatric and allopatric Oncorhynchus masou masou (Actinopterygii, Salmoniformes) as a host fish. Initial infection rates of parasitic larvae (glochidia) and transformation rates to cysts (encysted glochidia) were examined for all parasite-host combinations from three habitat locations (a total of nine combinations) to test the hypothesis that sympatric pairs of mussels and fish result in the highest success rates of glochidia infection and encystment. Measurements of glochidia-infected fish reared in flow-through experimental indoor tanks were taken at the initial infection point as well as at encystment, 2 weeks after the infection. Results disagreed with our hypothesis. Instead, an unexpected heterogeneity in a pathological deformity in gills explained a greater amount of variance in these processes. This deformity was responsible for reducing the initial infection rate and increasing the metamorphosis rates of initially attached glochidia to cysts. The field-measured prevalence of the gill deformity was low in all habitat locations, indicating that the deformity occurred during the acclimation period before infection for relatively small-sized host fish more susceptible to infection. Our results did not show the local adaptation of parasitic freshwater mussels to host fish but shed light on one of the least studied factors, providing an empirical underpinning of the importance of pathologically diversified host conditions in the reproductive processes of unionid mussels.
• Seasonal variations of Cs-137 concentration in freshwater charr through uptake and metabolism in 1-2 years after the Fukushima accident

  Kengo Okada, Masaru Sakai, Takashi Gomi, Aimu Iwamoto, Junjiro N. Negishi, Masanori Nunokawa

  ECOLOGICAL RESEARCH 2021年09月 [査読有り]
   

  Understanding the factors influencing Cs-137 concentrations in freshwater salmonids is crucial for reviving inland fisheries in polluted regions. We studied seasonal variations of Cs-137 concentration in charr (Salvelinus leucomaenis) through uptake and metabolism in forested headwaters at Fukushima and Gunma sites. Charr consumed both terrestrial and aquatic animals, and terrestrial prey was predated more in summer at both sites. The Cs-137 concentrations in litter, which is a dominant basal food resource of both forest and stream ecosystems, differed between forest and stream due to Cs-137 leaching effect on litter submerged in streams. The concentration difference in both litter and prey was greater at Fukushima site than at Gunma site. The estimated prey Cs-137 concentration at Fukushima site peaked in summer when terrestrial preys are most available, whereas it remained relatively constant at Gunma site because of the small difference of Cs-137 concentrations in between terrestrial and aquatic preys. The specific metabolic rate of charr was commonly changed with stream water temperature, greatest in summer, and lowest in winter at both sites. Because both prey Cs-137 concentrations and specific metabolic rates peaked in summer, the combination of uptake and metabolism at Fukushima site largely negated seasonal Cs-137 fluctuations in charr, whereas specific metabolic rate fluctuations could be the major determinant of charr Cs-137 concentrations at Gunma site. Our results suggested that Cs-137 concentrations in prey items, whose seasonality are varied due to initial Cs-137 fallout volume, were expected to be an important determinant for Cs-137 concentrations in charr.
• Lateral and longitudinal flight dispersals of a stonefly, Alloperla ishikariana (Plecoptera, Chloroperlidae), from the hyporheic zone in a gravel-bed river in Japan

  Mirza A. T. M. Tanvir Rahman, Junjiro N. Negishi, Md. Khorshed Alam, Gao Yiyang, Janine Rodulfo Tolod, Pongpet Pongsivapai

  LIMNOLOGICA 89 2021年07月 [査読有り]
   

  The life-history traits of amphibitic insects are not well understood. These insects inhabit saturated interstitial areas below the riverbed (hyporheic zone) at the larval stage, mate in terrestrial habitats, and return to rivers for oviposition, but there is no knowledge concerning their dispersal characteristics. We sought to address this by examining how far amphibitic insects disperse away from the channel (laterally) and along upstream or downstream (longitudinally) in a gravel-bed river. Alloperla ishikariana was selected as the focal species because it numerically dominates other amphibites in an 18-km study segment of a 4th-order gravel-bed river in Hokkaido, Northern Japan. Malaise traps were set at various distances from the channel towards the riparian forest to estimate lateral dispersal distances. An elevated stable nitrogen isotope ratio in downstream larvae, caused by the influence of effluent from a wastewater treatment plant, was used to assess longitudinal dispersal by identifying and tracking adult movements. Laterally, 50th and 90th percentile dispersal distances were 11.66 and 35.09 m for female A. ishikariana and 20.59 and 59.20 m for male, respectively; this overlapped with distances previously estimated for other aquatic benthic taxa. Longitudinally, 50th and 90th percentile dispersal distances were 0.74 and 1.43 km for female and 3.11 and 7.87 km for male, respectively. Alloperla ishikariana had one of the longest upstream traveling distances compared with other aquatic insects, and the longest among Plecoptera taxa known thus far where male exhibited a greater dispersal distance. A higher number of adults demonstrated upstream movement, suggesting an upstream bias in the longitudinal dispersal of A. ishikariana. Overall, amphibitic stoneflies did not exhibit distinct dispersal characteristics compared with the results of previous reports on presumably benthic taxa. Our findings support an improved visualization of a multi-dimensionally connected river ecosystem in terms of material flow, including vertical connectivity.
• Additive effects of sediment and nutrient on leaf litter decomposition and macroinvertebrates in hyporheic zone

  Md Khorshed Alam, Junjiro N. Negishi, Pongpet Pongsivapai, Shohei Yamashita, Tomohiro Nakagawa

  Water (Switzerland) 13 10 2021年05月02日 [査読有り]
   

  Despite the fact that leaf decomposition constitutes an important function in rivers, how multiple environmental stressors simultaneously affect it remains largely unknown. This study investigated the interactive effects of fine sediments (particle size: <2 mm; experimentally manipulated) and a specific nutrient (i.e., nitrate) on subsurface (hyporheic) leaf litter decomposition rate and macroinvertebrates in a gravel-bed river and its tributary in eastern Hokkaido, Japan. The experiment was conducted by measuring leaf litter decomposition of dried Alnus japonica leaves (3 ± 0.05 g) in benthic and hyporheic zones with and without sediment treatments at four sites that had a gradient of nitrate concentration. The decomposition rate was comparable between the two zones but was slowed down by sediment addition in the hyporheic zone. The functional responses were highly predictable for the individual stressors. Detritivore invertebrates were the main driving component of decomposition in the decreased leaf litter decomposition rate under a higher fine sediment condition, whereas higher nitrate accelerated the leaf litter decomposition rate by stimulated microbe-driven decomposition as well as detritivore feeding. Overall, the negative effect of fine sediment could be offset in the presence of nitrate while considering gross functional responses. We demonstrated the additive effects of fine sediment and nitrate on leaf litter decomposition in the hyporheic zone.
• Estimates of resource transfer via winged adult insects from the hyporheic zone in a gravel-bed river

  Mirza A. T. M. Tanvir Rahman, Junjiro N. Negishi, Takumi Akasaka, Futoshi Nakamura

  ECOLOGY AND EVOLUTION 11 9 4656 - 4669 2021年05月 [査読有り]
   

  Hyporheic zone (HZ) locates below the riverbed providing habitat for macroinvertebrates from where the winged adult insects (i.e., hyporheic insects, HIs) emerge and bring out aquatic resources to the riparian zone. This study estimated mean daily flux as dry biomass (BM), carbon (C), and nitrogen (N) deriving from the dominant HI species Alloperla ishikariana (Plecoptera, Chloroperlidae) for a 4th-order gravel-bed river during the early-summer to summer periods. We hypothesized that HIs were an important contributor in total aquatic resources to the riparian zone. In 2017 and 2018, we set parallelly (May to August) and perpendicularly (June to October) oriented Malaise traps to catch the lateral and longitudinal directional dispersing winged adults of A. ishikariana, and other Ephemeroptera, Plecoptera, Trichoptera, and Diptera from the river and estimated the directional fluxes of them. We further split the directional fluxes as moving away or back to the channel (for lateral) and from down- to upstream or up- to downstream (for longitudinal). Alloperla ishikariana was similar to other Plecoptera species and differed clearly from Ephemeroptera and Trichoptera in directional characteristics of resources flux, suggesting that the extent and directions of HZ-derived resource transfer depend on taxon-specific flight behaviors of HIs. Contributions of A. ishikariana to the riparian zone in total aquatic C and N transfer seasonally varied and were lower in May (5%-6%) and August (2%-4%) and the highest in July (52%-70%). These conservative estimates largely increased (9% in May) after the supplementary inclusion of Diptera (Chironomidae and Tipulidae), part of which were considered HIs. We demonstrated that HZ could seasonally contribute a significant portion of aquatic resources to the riparian zone and highlighted the potential importance of HZ in nutrient balance in the river-riparian ecosystem.
• Latitude dictates plant diversity effects on instream decomposition

  Luz Boyero, Javier Pérez, Naiara López-Rojo, Alan M. Tonin, Francisco Correa-Araneda, Richard G. Pearson, Jaime Bosch, Ricardo J. Albariño, Sankarappan Anbalagan, Leon A. Barmuta, Leah Beesley, Francis J. Burdon, Adriano Caliman, Marcos Callisto, Ian C. Campbell, Bradley J. Cardinale, J. Jesús Casas, Ana M. Chará-Serna, Szymon Ciapała, Eric Chauvet, Checo Colón-Gaud, Aydeé Cornejo, Aaron M. Davis, Monika Degebrodt, Emerson S. Dias, María E. Díaz, Michael M. Douglas, Arturo Elosegi, Andrea C. Encalada, Elvira De Eyto, Ricardo Figueroa, Alexander S. Flecker, Tadeusz Fleituch, André Frainer, Juliana S. França, Erica A. García, Gabriela García, Pavel García, Mark O. Gessner, Paul S. Giller, Jesús E. Gómez, Sergio Gómez, Jose F. Gonçalves, Manuel A.S. Graça, Robert O. Hall, Neusa Hamada, Luiz U. Hepp, Cang Hui, Daichi Imazawa, Tomoya Iwata, Edson S.A. Junior, Samuel Kariuki, Andrea Landeira-Dabarca, María Leal, Kaisa Lehosmaa, Charles M’Erimba, Richard Marchant, Renato T. Martins, Frank O. Masese, Megan Camden, Brendan G. McKie, Adriana O. Medeiros, Jen A. Middleton, Timo Muotka, Junjiro N. Negishi, Jesús Pozo, Alonso Ramírez, Renan S. Rezende, John S. Richardson, José Rincón, Juan Rubio-Ríos, Claudia Serrano, Angela R. Shaffer, Fran Sheldon, Christopher M. Swan, Nathalie S.D. Tenkiano, Scott D. Tiegs, Janine R. Tolod, Michael Vernasky, Anne Watson, Mourine J. Yegon, Catherine M. Yule

  Science Advances 7 13 2021年03月 [査読有り]
   

  Running waters contribute substantially to global carbon fluxes through decomposition of terrestrial plant litter by aquatic microorganisms and detritivores. Diversity of this litter may influence instream decomposition globally in ways that are not yet understood. We investigated latitudinal differences in decomposition of litter mixtures of low and high functional diversity in 40 streams on 6 continents and spanning 113° of latitude. Despite important variability in our dataset, we found latitudinal differences in the effect of litter functional diversity on decomposition, which we explained as evolutionary adaptations of litter-consuming detritivores to resource availability. Specifically, a balanced diet effect appears to operate at lower latitudes versus a resource concentration effect at higher latitudes. The latitudinal pattern indicates that loss of plant functional diversity will have different consequences on carbon fluxes across the globe, with greater repercussions likely at low latitudes.
• Morphometry-Driven Divergence in Decadal Changes of Sediment Property in Floodplain Water Bodies

  Pongpet Pongsivapai, Junjiro N. Negishi, Hokuto Izumi, Paolo A. Garrido, Kanta Kuramochi

  WATER 13 4 2021年02月 [査読有り]
   

  Sediments are potentially the internal source that supply nutrients to water in lentic to semi-lentic ecosystems. The understanding of factors that cause temporal changes in sediment properties is critical for the internal source management. This study investigated the spatial variations and temporal changes in sediment properties in relation to their controlling factors in water bodies of the Ishikari River, Northern Japan. Sediment data in 29 water bodies were measured twice (around 2005 and 2019) to study the temporal changes in sediment properties, and were compared using Generalized Linear Mixed Models (GLMMs). The controlling factors of sediment properties including catchment and morphometry were examined by partial least square (PLS) regression. Our results showed that the temporal change in sediment properties over decades was largely driven by morphometry, while land use in the catchment played a relatively minor role in those changes. The rate of change in organic matter (OM) differed among water bodies depending on their morphometry. The small and shallow water bodies provided suitable habitat for macrophytes that led to OM deposits, resulting to an increase in OM and OM to total nitrogen (TN) ratio over time. The consequences of these changes are important for internal source management and biodiversity conservation.
• Stable isotope ratios of emergent adult aquatic insects can be used as indicators of water pollution in the hyporheic food web

  Md Khorshed Alam, Junjiro N. Negishi, Mirza A.T.M.Tanvir Rahman, Janine Rodulfo Tolod

  Ecological Indicators 118 2020年11月 

  Bio-assessment protocols for the subsurface domain of river channels (i.e. hyporheic zone) are scarce despite of the known importance of its ecological function in river ecosystems. The larvae of the Alloperla ishikariana Plecoptera species inhabit the hyporheic zone. Therefore, we examined whether emergent adult A. ishikariana could serve as proxy indicators of the effects of pollution in the hyporheic food web. The study site comprised a 15-km stretch of a gravel bed river in Hokkaido, Japan, from which all invertebrates were collected from the riverbed at a depth of 30–50 cm, and emergent A. ishikariana adults were sampled in riparian zones. Water quality changed gradually along the river owing to the effects of a wastewater treatment plant and surrounding land uses. Nitrogen and carbon stable isotope ratios (SIRs) of epilithic biofilms, hyporheic particulate organic matter (POM), benthic POM, and invertebrates were used to determine the major basal carbon sources, the effects of water pollution on the hyporheic zone, and the trophic positions of dominant invertebrates. Generalized linear (mixed) models were used for statistical testing and modeling. Amphipoda and the larvae of A. ishikariana were considered as top predators and secondary consumers in the hyporheic food web, respectively. The observed similarity in water quality between the hyporheic and surface water suggested a large degree of hydrological exchange between the two zones, and resulted in positive increases in the nitrogen SIRs of hyporheic invertebrates, including A. ishikariana larvae, in proportion to nitrate levels in the surface water. The nitrogen SIRs of A. ishikariana adults were significantly correlated with the nitrogen SIRs of their larvae within the same location (adjusted R2 = 0.78), indicating that emerged adults can provide information on the longitudinal variability of the effects of synthetic nitrogen. In contrast, the carbon SIRs of adults did not predict those of their larvae, possibly reflecting the diverse feeding habitats of larvae. Overall, we demonstrated that adult aquatic insects emerging from the hyporheic zone can be used as indirect indicators of pollution-associated nutrient assimilation as well as the spatial heterogeneity of dietary carbon resources in hyporheic food web.
• Restoration of the shifting mosaic of floodplain forests under a flow regime altered by a dam

  Futoshi Nakamura, Yasuharu Watanabe, Junjiro Negishi, Takumi Akasaka, Yuki Yabuhara, Akira Terui, Satoshi Yamanaka, Miwa Konno

  Ecological Engineering 157 2020年10月01日 [査読有り]
   

  A braided gravel-bed river provides essential habitats for various plants and animals. However, human regulation of rivers, such as dams, channelization, and other engineering works, alter flow and sediment regimes, which generally cause the degradation of river and riparian ecosystems. One of the prominent changes prevailing in Japanese rivers is forest expansion over gravel bars, and many native plants and animals that depend on gravel-bar habitat are now endangered. The Satsunai River is typical of rivers experiencing forest expansion, so the Japanese government launched a restoration project in 2012 to partially restore its riparian ecosystems. This is a large-scale experiment developed jointly by an interdisciplinary science team and river managers, who conduct monitoring and evaluation under an adaptive management scheme. The main measure to restore gravel bed habitat was an artificial flood regime, releasing a maximum water volume of 120 m3/s, which was a 2-year return period flood before dam construction. A unique feature of the project is that we considered the role of high-magnitude floods with recurrence intervals greater than 20 years after dam construction. We hypothesize that the artificial floods can be timed seasonally to create sites for regeneration and nesting of riparian species, and the high-magnitude floods contribute to maintaining a shifting mosaic structure of floodplain forest and unvegetated gravel-bar patches. We also used critical non-dimensional shear stress analysis to define “flood-disturbance areas” that can be disturbed under the artificial flow regime created by a dam. Artificial floods have been initiated once a year since 2012 at the end of June, synchronized with the seed dispersal period of Salix arbutifolia, which is endangered and a high conservation priority in the project. Thus far, the idea of setting floodplain-disturbance areas and the strategy of using both artificial and high-magnitude floods to restore a shifting mosaic of floodplain habitat patches is appropriate, as we found successful regeneration of S. arbutifolia and an exponential decay curve of the age distribution of floodplain forest patches. However, the sediment regime regulated by the dam was not addressed in this research, so future monitoring should track changes in river morphology associated with reduced sediment supply caused by the dam.
• 石狩川氾濫原水域におけるイシガイ目二枚貝の生息分布と生活史特性

  泉北斗, 根岸淳二郎, 三浦一輝, 伊藤大雪, PONGSIVAPAI Pongpet

  応用生態工学 23 1 1 - 20 2020年09月28日 [査読有り]
   

  Despite of the importance of floodplain waterbodies for biodiversity and ecosystem services, human activities have degraded their quality as habitat for biological communities. Detailed understanding of life-history traits and population dynamics of organisms is crucial to the development and realization of effective management practices for the conservation of biodiversity. This study examined the distribution, reproductive traits, and host-fish utilizations of Unionoid mussels in floodplain waterbodies of the Ishikari River, northern Japan, and highlighted challenges in ecosystem management. Three target species exhibited the differences in habitat preferences, with Anemina arcaeformis Heude, 1877 being disproportionately most abundant in marsh-type waterbodies. Two species, Sinanodonta lauta Martens, 1877 and Unio douglasiae nipponensis Martens, 1877, were gravid in summer July and August while A. arcaeformis was more gravid in fall and winter October and November The low abundances of immature small individuals and the absence of parasitic attachments of mussel larvae to field-collected fish suggested the reduced levels of recent recruitments. The proliferations of invasive fish species such as Rhodeus ocellatus ocellatus, which comprised 30-70% of the total abundances of fish and were not suitable as host for the parasitic larvae of mussels, might be a possible cause of poor recruitment rates. Recognition of the diversity of waterbody types as a driver of species diversity, continued monitoring of population sizes and further elucidations of habitat quality as well as other aspects of life-history processes will contribute to improved ecosystem-based management of floodplain waterbodies in the Ishikari River.
• Contribution of small isolated habitats in creating refuges from biological invasions along a geomorphological gradient of floodplain waterbodies

  Nobuo Ishiyama, Kazuki Miura, Satoshi Yamanaka, Junjiro N. Negishi, Futoshi Nakamura

  Journal of Applied Ecology 57 3 548 - 558 2020年03月01日 [査読有り]
   

  Habitat fragmentation, which involves habitat size reduction and isolation, is a major cause of biodiversity decline. However, interest in small isolated habitats has increased among ecosystem managers because these fragments can serve as remnant refuges for unique and/or endangered species in human-altered landscapes. In a fragmented floodplain of northern Japan, we demonstrate how habitat fragmentation and habitat quality shape the refuges for a unique endangered minnow Rhynchocypris percnurus sachalinensis from biological invasions. We focused on two invasive minnows, topmouth gudgeon Pseudorasbora parva and rosy bitterling Rhodeus ocellatus ocellatus, which are the dominant invasive species. By using a graph theoretical approach and structural equation modelling, we elucidated the relationships among habitat fragmentation, habitat quality and the abundance of invasive minnows with the endangered swamp minnow. We found that the invasion of topmouth gudgeon, which has a high mobility and environmental tolerance, negatively affected swamp minnow populations. The invasive species may outcompete the native species in their overlapping trophic niche. Analyses indicated that habitat fragmentation (decreasing habitat size and connectivity) indirectly and positively affected the population abundance of swamp minnow by reducing the potential for invasion by topmouth gudgeon. We further found an interaction between the indirect effects of habitat fragmentation and local habitat quality: the indirect effects became more apparent in the relatively deeper habitats that were of better quality for natives. This result was likely attributed to the strong control effect of the abiotic stressor. Interspecific competition between the two minnows would be masked in shallow ponds because the native populations are primarily restricted by the abiotic factor, and its abundance is inherently limited regardless of pressure by invaders. Synthesis and applications. In fragmented landscapes, evenly conserving all small fragments within a limited budget is difficult. The change in importance of small isolated ponds across a pond-depth gradient suggests that conservation priorities for small fragments should be established by considering local habitat quality. Our findings do not justify habitat fragmentation but suggest that both landscape-scale and local-scale perspectives synergistically aid in the management of biological invasions in modified habitat networks.
• Estimating native and invasive crayfish distributions in relation to culvert barriers with environmental DNA

  Kousuke Ikeda, Hideyuki Doi, Shigeharu Terui, Atsuko Kato, Takashi Mitsuzuka, Tadashi Kawai, Junjiro N. Negishi

  Freshwater Science 38 3 629 - 641 2019年09月01日 [査読有り]
   

  The signal crayfish, Pacifastacus leniusculus, is non-native to Japan, and its invasion may have contributed to the habitat loss of the endemic Japanese crayfish, Cambaroides japonicus. We assessed the distribution of the signal crayfish and the Japanese crayfish in small streams that flow into Lake Akan (Hokkaido, Japan), which the signal crayfish inhabits. We conducted this survey with 2 methods: analysis of environmental DNA (eDNA) and hand capture. Of the 17 streams we surveyed, we detected signal crayfish DNA in 16 streams and Japanese crayfish DNA in 9 streams. In contrast, with our hand-capture survey of the same 17 streams, we found signal crayfish in 9 streams and Japanese crayfish in 4 streams. These results suggest that the signal crayfish may have invaded almost all the small streams with culverts around Lake Akan. The presence of signal crayfish was also confirmed on the upstream side of a 69-cm-high road-crossing culvert. There were only 2 culverts above which the absence of signal crayfish was supported by eDNA analysis, suggesting that culverts have limited effectiveness against signal crayfish invasion in our study site. Active species-specific removal projects may be an effective management option to minimize the negative impacts of signal crayfish where they are already present. eDNA has great potential as a cost-effective tool to monitor crayfish range expansion.
• Simple nonlethal identification criteria for two endangered freshwater pearl mussels, Margaritifera laevis and Margaritifera togakushiensis, in Hokkaido, northern Japan

  Kazuki Miura, Nobuo Ishiyama, Keita Kawajiri, Keisuke Atsumi, Michikusa Tachibana, Yu Nagasaka, Yoshiyasu Machida, Gao Yiyang, Junjiro N. Negishi, Itsuro Koizumi, Futoshi Nakamura

  Ecological Research 34 5 667 - 677 2019年09月01日 [査読有り]
   

  Species identification is a fundamental process for ecological studies and conservation practices, and simple nonlethal identification criteria are important for endangered species. This study developed species identification criteria for two endangered freshwater pearl mussels (Margaritifera laevis and Margaritifera togakushiensis) based on linear discriminant functions (LDFs) that were established considering intraspecific regional morphological differences from sites at Hokkaido, northern Japan. We collected a total of 1,110 mussels from 52 rivers across 32 watersheds in two geographical regions (east and west). Shell morphologies (length, height, and width) of the collected mussels were measured, followed by species identification with gel electrophoresis banding patterns of 16S rRNA polymerase chain reaction products. LDFs were constructed for two size classes (≥40 mm and < 40 mm) using forward stepwise procedures to determine key morphological differences between the two species and consideration of whether regional morphological differences improved identification accuracies. The LDFs revealed that the morphologies of the two species were clearly distinguished by the relationship between height and length for both size classes. Region-specific LDFs produced better identification accuracies. Regardless of region, the maximum length of M. laevis exceeded 100 mm, whereas all M. togakushiensis were < 100 mm in length. Identification accuracies of the established LDFs were high for each of the five length classes (0–20 mm, 20–40 mm, 40–60 mm, 60–80 mm, and 80–100 mm) with 85–96% (mean: 92%) accuracy in the east and 67–96% (mean: 80%) in the west. These criteria for species identification will progress future ecological studies and conservation practices for freshwater mussels.
• Coupled benthic-hyporheic responses of macroinvertebrates to surface water pollution in a gravel-bed river

  Junjiro N. Negishi, Aiko Hibino, Kazuki Miura, Ryota Kawanishi, Nozomi Watanabe, Kazuhiro Toyoda

  FRESHWATER SCIENCE 38 3 591 - 604 2019年09月 [査読有り]
   

  Interactions between the hyporheic and benthic zones play a vital role in maintaining the integrity of river ecosystems, but simultaneous assessments of hyporheic and benthic macroinvertebrate responses to surface water pollution are limited. We examined how hyporheic (50 cm below surface) and benthic (surface) invertebrates responded to water pollution that originated from a point source (wastewater treatment plant) in a gravel-bed river in Hokkaido, Japan. Dissolved nutrient levels and algal biomass were significantly higher at sample sites down- than upstream of the point source. Furthermore, nitrate concentrations increased gradually from up- to downstream sites, which suggest the presence of diffuse pollution sources in the surrounding areas. Closely synchronized fluctuations of water temperature and similar water quality in the surface and hyporheic zones indicated that the hyporheic zone was highly hydrologically interactive with the surface water. Chloroperlidae (mostly Alloperla ishikariana) had a disproportionately high abundance in the hyporheic zone relative to the benthic zone, regardless of the surface water quality. Numerically dominant invertebrate taxa increased in abundance below the point source of pollution in both the benthic and hyporheic habitats. High N stable isotope ratios (SIR) of the invertebrates in both habitat types indicated that invertebrates assimilated anthropogenic N via the ingestion of pollution-contaminated food resources. End-member mixing analyses based on C SIR demonstrated that assimilation of anthropogenic N occurred because of the increase in available food resources originating from the biofilm. The trophic structure of invertebrates changed less markedly in the hyporheic zone than in the benthic zone, suggesting that the hyporheic assemblage was less sensitive than the benthic assemblage to the changes in surface water quality. Overall, our findings showed that the numeric responses of the invertebrate assemblage to anthropogenic changes in surface water quality were similar and coupled between the benthic and hyporheic zones.
• High resilience of aquatic community to a 100-year flood in a gravel-bed river

  Junjiro N. Negishi, Akira Terui, Badrun Nessa, Kazuki Miura, Takeaki Oiso, Keizo Sumitomo, Tomoko Kyuka, Mitsuaki Yonemoto, Futoshi Nakamura

  LANDSCAPE AND ECOLOGICAL ENGINEERING 15 2 143 - 154 2019年04月 [査読有り]
   

  Our understanding of ecosystem responses to exceedingly large rare flood events is currently limited. We report the resilience of aquatic community to a 100-year record-high flood, and how it varies depending on levels of water pollution, in a fourth-order gravel-bed river in northern Japan. We used data on riparian landscape structure, channel morphology, and community structure of aquatic fauna, which were collected in sites with and without effluent before (1 month-3 years) and after (10 months) the flood. Carbon and nitrogen stable isotope ratios of consumers and basal resources were measured only before (1 year) the flood. We observed aquatic food web with introduced rainbow trout (Oncorhynchus mykiss) as the top predator, with variable relative contributions of basal resources and their pathways to the rainbow trout, under the effects of water pollution. Biofilm-originating dietary carbon became the more dominant resource, with a slightly shorter food-chain length in the polluted sites. The flood led to a loss of riparian forest and a substantial increase in the proportion of exposed gravel bars (5-24%). While the average river-bed elevation changed a little, the localized scours of river bed down to > 2 m were observed with lateral shifts of channel thalweg. Despite the landscape-level physical and structural changes of ecosystem, aquatic community showed a remarkably high resilience exhibiting negligible changes in abundance, except in the polluted site where only fish abundance showed a slight decrease. This study suggests that the abundance of aquatic organisms in gravel-bed rivers is resilient to a flood of unprecedented magnitude in recent history.
• Ecological resilience of ecosystems to human impacts: resilience of plants and animals

  Junko Morimoto, Junjiro Negishi

  Landscape and Ecological Engineering 15 2 131 - 132 2019年04月 [査読有り][通常論文]
  
• Research priorities for freshwater mussel conservation assessment

  Noé Ferreira-Rodríguez, Yoshihiro B. Akiyama, Olga V. Aksenova, Rafael Araujo, M. Christopher Barnhart, Yulia V. Bespalaya, Arthur E. Bogan, Ivan N. Bolotov, Prem B. Budha, Cristhian Clavijo, Susan J. Clearwater, Gustavo Darrigran, Van Tu Do, Karel Douda, Elsa Froufe, Clemens Gumpinger, Lennart Henrikson, Chris L. Humphrey, Nathan A. Johnson, Olga Klishko, Michael W. Klunzinger, Satit Kovitvadhi, Uthaiwan Kovitvadhi, Jasna Lajtner, Manuel Lopes-Lima, Evelyn A. Moorkens, Shigeya Nagayama, Karl-Otto Nagel, Mitsunori Nakano, Junjiro N. Negishi, Paz Ondina, Panu Oulasvirta, Vincent Prié, Nicoletta Riccardi, Mudīte Rudzīte, Fran Sheldon, Ronaldo Sousa, David L. Strayer, Motoi Takeuchi, Jouni Taskinen, Amilcar Teixeira, Jeremy S. Tiemann, Maria Urbańska, Simone Varandas, Maxim V. Vinarski, Barry J. Wicklow, Tadeusz Zając, Caryn C. Vaughn

  Biological Conservation 231 77 - 87 2019年03月 [査読有り]
  
• 北海道における希少淡水二枚貝カワシンジュガイ属2 種（Margaritifera laevis, Margaritifera togakushiensis）の河川区間での生息の重複

  三浦 一輝, 石山 信雄, 川尻 啓太, 渥美 圭佑, 長坂 有, 折戸 聖, 町田 善康, 臼井 平, Gao Yiyang, 能瀬 晴菜, 根岸 淳二郎, 中村 太士

  保全生態学研究 24 1 39 - 48 2019年02月 [査読有り]
  
• Global patterns and drivers of ecosystem functioning in rivers and riparian zones

  Scott D. Tiegs, David M. Costello, Mark W. Isken, Guy Woodward, Peter B. McIntyre, Mark O. Gessner, Eric Chauvet, Natalie A. Griffiths, Alex S. Flecker, Vicenc Acuna, Ricardo Albarino, Daniel C. Allen, Cecilia Alonso, Patricio Andino, Clay Arango, Jukka Aroviita, Marcus V. M. Barbosa, Leon A. Barmuta, Colden V. Baxter, Thomas D. C. Bell, Brent Bellinger, Luz Boyero, Lee E. Brown, Andreas Bruder, Denise A. Bruesewitz, Francis J. Burdon, Marcos Callisto, Cristina Canhoto, Krista A. Capps, Maria M. Castillo, Joanne Clapcott, Fanny Colas, Checo Colon-Gaud, Julien Cornut, Veronica Crespo-Perez, Wyatt F. Cross, Joseph M. Culp, Michael Danger, Olivier Dangles, Elvira de Eyto, Alison M. Derry, Veronica Diaz Villanueva, Michael M. Douglas, Arturo Elosegi, Andrea C. Encalada, Sally Entrekin, Rodrigo Espinosa, Diana Ethaiya, Veronica Ferreira, Carmen Ferriol, Kyla M. Flanagan, Tadeusz Fleituch, Jennifer J. Follstad Shah, Andre Frainer, Nikolai Friberg, Paul C. Frost, Erica A. Garcia, Liliana Garcia Lago, Pavel Ernesto Garcia Soto, Sudeep Ghate, Darren P. Giling, Alan Gilmer, Jose Francisco Goncalves, Rosario Karina Gonzales, Manuel A. S. Graca, Mike Grace, Hans-Peter Grossart, Francois Guerold, Vlad Gulis, Luiz U. Hepp, Scott Higgins, Takuo Hishi, Joseph Huddart, John Hudson, Samantha Imberger, Carlos Iniguez-Armijos, Tomoya Iwata, David J. Janetski, Eleanor Jennings, Andrea E. Kirkwood, Aaron A. Koning, Sarian Kosten, Kevin A. Kuehn, Hjalmar Laudon, Peter R. Leavitt, Aurea L. Lemes da Silva, Shawn J. Leroux, Carri J. Leroy, Peter J. Lisi, Richard MacKenzie, Amy M. Marcarelli, Frank O. Masese, Brendan G. Mckie, Adriana Oliveira Medeiros, Kristian Meissner, Marko Milisa, Shailendra Mishra, Yo Miyake, Ashley Moerke, Shorok Mombrikotb, Rob Mooney, Tim Moulton, Timo Muotka, Junjiro N. Negishi, Vinicius Neres-Lima, Mika L. Nieminen, Jorge Nimptsch, Jakub Ondruch, Riku Paavola, Isabel Pardo, Christopher J. Patrick, Edwin T. H. M. Peeters, Jesus Pozo, Catherine Pringle, Aaron Prussian, Estefania Quenta, Antonio Quesada, Brian Reid, John S. Richardson, Anna Rigosi, Jose Rincon, Geta Risnoveanu, Christopher T. Robinson, Lorena Rodriguez-Gallego, Todd V. Royer, James A. Rusak, Anna C. Santamans, Geza B. Selmeczy, Gelas Simiyu, Agnija Skuja, Jerzy Smykla, Kandikere R. Sridhar, Ryan Sponseller, Aaron Stoler, Christopher M. Swan, David Szlag, Franco Teixeira-de Mello, Jonathan D. Tonkin, Sari Uusheimo, Allison M. Veach, Sirje Vilbaste, Lena B. M. Vought, Chiao-Ping Wang, Jackson R. Webster, Paul B. Wilson, Stefan Woelfl, Marguerite A. Xenopoulos, Adam G. Yates, Chihiro Yoshimura, Catherine M. Yule, Yixin X. Zhang, Jacob A. Zwart

  SCIENCE ADVANCES 5 1 eaav0486  2019年01月 [査読有り]
   

  River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth's biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented "next-generation biomonitoring" by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.
• Chestnut goby, Gymnogobius castaneus (O’Shaughnessy 1875), as a suitable host of Anemina arcaeformis (Heude 1877) in floodplain water bodies, Hokkaido, Northern Japan

  Junjiro N. Negishi, Kazuki Miura, Hokuto Izumi, Yutaka Negishi

  Limnology 19 3 343 - 354 2018年08月 [査読有り]
  
• タンクモデルを参考にした小学校高学年向けの地下水学習の教材開発

  岩井尚人, 山中康裕, 根岸淳二郎, 山田朋人

  水利科学 364 5 59 - 80 2018年08月 [査読有り][通常論文]
   

  地下水の持続可能な利用は，その保全にとって必要である。地下水を保全す る態度を育むために，小学校教育の中で地下水について学ぶ機会を作ることは，重要なことである。本研究では，小学校高学年生が地下水涵養に関する森 林の機能などの地下水に関する基本的知識を学べる教材を，タンクモデルを参 考にして開発した。教材は，3 段タンクで構成され，森林領域の下にある帯水 層に設置したスポンジが水を貯留し，その水は装置外へゆっくりと流出するよ うになっている。教材で表現したのは，森林は主要な地下水の涵養域であるこ と，地下水は地表水に比べて滞留時間が長いことの 2 つである。教材を用いた 散水実験では，3 段のタンクそれぞれからの流出ピークのタイムラグや滞留時 間の違いなど，上記 2 点を定量的に確認した。小学校等の教員13名を対象に実 施した教材の実演と，彼らに対する聞き取り調査では，多くの教員は，小学校 児童にとって，上記 2 点が分かりやすいと判断した。
• Ecohydrological disturbances associated with roads: Current knowledge, research needs, and management concerns with reference to the tropics

  Beverley C. Wemple, Trevor Browning, Alan D. Ziegler, Jorge Celi, Kwok Pan Sun Chun, Fernando Jaramillo, Nei K. Leite, Sorain J. Ramchunder, Junjiro N. Negishi, Ximena Palomeque, Derek Sawyer

  Ecohydrology 11 3 2018年04月01日 [査読有り][通常論文]
   

  Roads are a pervasive form of disturbance with potential to negatively affect ecohydrological processes. Some of the most rapid growth in road networks is occurring in developing countries, particularly in the tropics, where political agendas are often focused on strengthening the economy, improving infrastructure, bolstering national security, achieving self-sufficiency, and increasing citizen well-being, often at the expense of the environment. We review what is known about road impacts on ecohydrological processes, focusing on aquatic systems, both temperate and tropical. We present seven cases that represent the broader trends of road development and impacts in tropical settings. Many of these process dynamics and impacts are not different from those experienced in temperate settings, although the magnitude of impacts in the tropics may be amplified with intense rainfall and lack of best management practices applied to road construction/maintenance. Impacts of roads in tropical settings may also be unique because of particular organisms or ecosystems affected. We outline a set of best practices to improve road network management and provide recommendations for adopting an agenda of research and road management in tropical settings. Importantly, we call for incorporation of transdisciplinary approaches to further study the effects of roads on ecohydrological processes in the tropics. Specific emphasis should also be placed on collaboration with governments and developers that are championing road development to help identify the drivers of road expansion and thresholds of negative impact, as well as methods of sustainable road construction and maintenance.
• Seasonal variation in food web-based transfer factors of radiocesium in white-spotted char (Salvelinus leucomaenis) from headwater streams

  M. E. Haque, T. Gomi, M. Sakai, J. N. Negishi

  Landscape and Ecological Engineering 14 1 45 - 53 2018年01月 [査読有り]
  
• Assessment of a unionid freshwater mussel (Pronodularia japanensis) population in an agricultural channel during the 4 years following reintroduction

  Kazuki Miura, Hokuto Izumi, Yuya Saito, Kaito Asato, Junjiro N. Negishi, Kazuo Ito, Akio Oomori

  Landscape and Ecological Engineering 14 1 157 - 164 2018年01月 [査読有り]
  
• Throughfall at an Abandoned Skid Trail in a Tropical Rain Forest in Peninsular Malaysia

  Shoji Noguchi, Junjiro N. Negishi, Zulkifli Yusop, Yoshiko Kosugi, Siti Aisah Shamsuddin, Makoto Tani

  JARQ-JAPAN AGRICULTURAL RESEARCH QUARTERLY 52 1 63 - 75 2018年 [査読有り]
   

  Knowledge of throughfall at abandoned skid trails in tropical forests is extremely scarce. Thus, throughfall was measured using 120 storage rain gauges set on a skid trail left abandoned 41 years after forest harvesting in the Bukit Tarek Experimental Watershed (BTEW) in Peninsular Malaysia. All trees of >= 1 m height in the plot were identified to the species level, and their diameter at breast height (DBH) and height were measured. Vegetation along the skid trail comprises trees with smaller DBH (0.2-31.0 cm, with a mean of 2.0 cm) and shorter height (1.0-20.0 m, with a mean of 2.8 m) than those in the regenerated secondary forests of BTEW. The diversity (i.e. 43 families, 131 species) at the skid trail was similar to that in an old tropical forest at BTEW. The ratio of throughfall to gross rainfall (Th/Rg) for 84 rain events ranged from 27.4% to 204.7% with a mean and standard deviation of 98.1% and 33.2%, respectively. We found that a considerable amount of rainwater dropped under bertam (i.e. Eugeissona tristis) and rattan (i.e. Daemonorops callicarpa, Calamus insignis) vegetation. The Th/Rg ratio weakly correlated with canopy openness. The mean Th/Rg ratio is the largest mean ratio ever reported for forests in Malaysia.
• Cesium-137 contamination of river food webs in a gradient of initial fallout deposition in Fukushima, Japan

  J. N. Negishi, M. Sakai, K. Okada, A. Iwamoto, T. Gomi, K. Miura, M. Nunokawa, M. Ohhira

  Landscape and Ecological Engineering 14 1 55 - 66 2018年01月01日 [査読有り][通常論文]
   

  We examined the cesium-137 (137Cs) contamination of river food webs in a gradient of initial fallout deposition (net density estimates 2.5–3.5 months after the Fukushima Daiichi Nuclear Power Plant accident in March 2011), in Fukushima Prefecture, Japan. Litter, aquatic insects, and salmonid fish were collected in five headwater stream reaches (watershed-average fallout density, 368.1–1398.4 kBq/m2) for the measurement of 137Cs concentration and stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in June 2014. The stable isotope ratios suggested that the detrital food chain was a dominant energy pathway in rivers originating from a basal resource (litter) to primary (aquatic insects) and secondary (fish) consumers. The 137Cs concentration decreased with an increase in the trophic level, with the highest value for litter (10930 ± 5381 Bq/kg, mean ± SD), the lowest for fish (2825 ± 2451 Bq/kg), and the intermediate one for dominant (numerically and biomass-wise) detritivorous insect, Ephemera japonica McLachlan (4605 ± 1970 Bq/kg). 137Cs concentrations of three trophic levels were linearly predicted by the initial fallout amount of 137Cs. The evacuation of the gut contents of E. japonica during field experiments led to a reduction in their 137Cs concentration by approximately 50% within 1–2 day(s) without loss of body weight. This suggested that a substantial portion of 137Cs contamination of E. japonica was derived from highly contaminated fine solids deposited in depositional habitats at a disproportionately high density. Overall, the initial fallout amount of 137Cs was helpful in roughly predicting the contamination levels of headwater river-riparian ecosystems with the detrital food chain as a dominant energy pathway. Long-term monitoring of the dynamics and fates of 137Cs associated with fine organic and inorganic particulates appears important for better prediction of 137Cs contamination of food webs in forested headwater streams.
• Stream Resource Gradients Drive Consumption Rates of Supplemental Prey in the Adjacent Riparian Zone

  根岸淳二郎

  Ecosystems 21 4 772 - 781 2017年09月 [査読有り][通常論文]
   

  Decades of research have revealed the crucial roles of cross-system energy flows (spatial subsidies) in mediating trophic interactions in recipient systems. Food web theory predicts that the responses of subsidized consumers are a key to understanding the net impacts of spatial subsidies on in situ prey/resources of recipient systems. However, less is known about the factors triggering the cascading biotic interactions across coupled ecosystems. Here, we quantify how riverine productivity (donor system) mediates terrestrial food web interactions through spatial subsidies to simplified gravel bar communities. Our comparative study in Japan indicated that higher algal biomass in aquatic systems led to increased supplies of emerging aquatic insects, which were associated with greater densities of terrestrial consumers (Carabid beetles) and enhanced consumption rates of supplemental in situ prey on gravel bars. Our results highlight the potential of donor productivity to drive cascading biotic interactions across coupled ecosystems. Because cross-system energy flows should originate, at least in part, from primary producers of donor systems, our fundamental finding may form the basis of future studies exploring the driving factors of cross-system trophic interactions.
• Developing a food web-based transfer factor of radiocesium for fish, whitespotted char (Salvelinus leucomaenis) in headwater streams.

  Md Enamul Haque, Takashi Gomi, Masaru Sakai, Junjiro N Negishi

  Journal of environmental radioactivity 172 191 - 200 2017年06月 [査読有り]
   

  We developed a food web-based transfer factor (TFweb) to study contaminant movements from multiple prey items to a predator based on the dietary contributions of prey items with their respective contamination levels. TFweb was used to evaluate the transfer of 137Cs into whitespotted char (Salvelinus leucomaenis) from the trophic structure of a stream-riparian ecosystem in headwater streams draining a Japanese cedar forest. We also examined the applicability of this method by comparing sites with different contamination levels but similar surrounding environments in Fukushima and Gunma. All samples were collected from August 2012 to May 2013. The dietary contributions from both aquatic and terrestrial prey items to whitespotted char were analyzed using stable carbon and nitrogen isotope ratios. 137Cs activity concentrations in char ranged from 704 to 6082 Bq kg-1-dry in Fukushima and from 193 to 618 Bq kg-1-dry in Gunma. Dominant prey taxa such as mayflies (Ephemera japonica), spider crickets (Rhaphidosphoridae gen. spp.), and freshwater crabs (Geothelphusa dehaani), each of them accounted for 3-12% of the fish diet, based on lower and upper estimates, respectively. TFweb ranged from 1.12 to 3.79 in Fukushima and from 1.30 to 4.30 in Gunma, which suggested bioaccumulation from prey items to predator. Widely used ecological parameters TFs by media-char and TTF by single prey-char showed high variability with both dilution and accumulation. TFweb is applicable for 137Cs transfer in predator-prey systems with complex food web structures of stream-riparian ecosystems.
• Leaf litter patches in stream create overwintering habitats for Ezo brown frog (Rana pirica)

  Miura Kazuki, Watanabe Nozomi, Negishi Junjiro N.

  Limnology 18 1 9 - 16 Springer Japan 2017年01月 [査読有り]
  
• Species-specific use of allochthonous resources by ground beetles (Carabidae) at a river-land interface

  Akira Terui, Takumi Akasaka, Junjiro N. Negishi, Fumihiko Uemura, Futoshi Nakamura

  ECOLOGICAL RESEARCH 32 1 27 - 35 2017年01月 [査読有り]
   

  A variety of organisms mediate river-terrestrial linkages through spatial subsidies. However, most empirical studies have classified organisms rather broadly (e.g., by functional group or taxonomic family) and have dismissed species-level linkages at the interface of ecosystems. Here, we show how allochthonous resource use varies among taxonomically similar species of ground beetles (family Carabidae) across seasons (June-September). We investigated seasonal shifts in the distribution of five beetle species and their dietary responses to spatial subsidies (emerging aquatic insects) in a Japanese braided river. Despite their taxonomic closeness, the ground beetles showed species-specific responses to spatial subsidies, and beetle distribution patterns tended to coincide with their diets. Overall, 1-56% of ground beetle diets were derived from aquatic prey. One genus (Bembidion spp.) mainly consumed aquatic prey, while three species fed primarily on terrestrial prey across all seasons. However, one species (Lithochlaenius noguchii) showed shifts in its diet from aquatic to terrestrial prey according to subsidy availability. The observed variation in allochthonous resource use was likely related to species-specific foraging modes, physiological tolerance to dry conditions, and interspecific competition. Our findings suggest that considering species-specific interactions is necessary to fully understand cross-system interactions and recipient food-web dynamics.
• Fallout volume and litter type affect Cs-137 concentration difference in litter between forest and stream environments

  Masaru Sakai, Takashi Gomi, Junjiro N. Negishi

  JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 164 169 - 173 2016年11月 [査読有り]
   

  It is important to understand the changes in the Cs-137 concentration in litter through leaching when considering that Cs-137 is transferred from basal food resources to animals in forested streams. We found that the difference of Cs-137 activity concentration in litter between forest and stream was associated with both litter type and Cs-137 fallout volume around Fukushima, Japan. The Cs-137 activity concentrations in the litter of evergreen conifers tended to be greater than those in the litter of broad-leaved deciduous trees because of the absence of deciduous leaves during the fallout period in March 2011. Moreover, Cs-137 activity concentrations in forest litter were greater with respect to the Cs-137 fallout volume. The Cs-137 activity concentrations in stream litter were much lower than those in forest litter when those in forest litter were higher. The Cs-137 leaching patterns indicated that the differences in Cs-137 activity concentration between forest and stream litter could change with changes in both fallout volume and litter type. Because litter is an important basal food resource in the food webs of both forests and streams, the Cs-137 concentration gradient reflects to possible Cs-137 transfer from lower to higher trophic animals. Our findings will improve our understanding of the spatial heterogeneity and variability of Cs-137 concentrations in animals resident to the contaminated landscape. (C) 2016 Elsevier Ltd. All rights reserved.
• Using environmental DNA to detect an endangered crayfish Cambaroides japonicus in streams

  Kousuke Ikeda, Hideyuki Doi, Kazunori Tanaka, Tadashi Kawai, Junjiro N. Negishi

  Conservation Genetics Resources 8 3 231 - 234 2016年09月 [査読有り]
  
• Different cesium-137 transfers to forest and stream ecosystems

  Masaru Sakai, Takashi Gomi, Junjiro N. Negishi, Aimu Iwamoto, Kengo Okada

  ENVIRONMENTAL POLLUTION 209 46 - 52 2016年02月 [査読有り]
   

  Understanding the mechanisms of Cs-137 movement across different ecosystems is crucial for projecting the environmental impact and management of nuclear contamination events. Here, we report differential movement of Cs-137 in adjacent forest and stream ecosystems. The food webs of the forest and stream ecosystems in our study were similar, in that they were both dominated by detrital -based food webs and the basal energy source was terrestrial litter. However, the concentration of Cs-137 in stream litter was significantly lower than in forest litter, the result of Cs-137 leaching from litter in stream water. The difference in Cs-137 concentrations between the two types of litter was reflected in the Cs-137 concentrations in the animal community. While the importance of Cs-137 fallout and the associated transfer to food webs has been well studied, research has been primarily limited to cases in a single ecosystem. Our results indicate that there are differences in the flow of Cs-137 through terrestrial and aquatic ecosystems, and that Cs-137 concentrations are reduced in both basal food resources and higher trophic animals in aquatic systems, where primary production is subsidized by a neighboring terrestrial ecosystem. (C) 2015 Elsevier Ltd. All rights reserved.
• Radiocesium leaching from contaminated litter in forest streams.

  Masaru Sakai, Takashi Gomi, Risa S Naito, Junjiro N Negishi, Michiko Sasaki, Hiroto Toda, Masanori Nunokawa, Kaori Murase

  Journal of environmental radioactivity 144 15 - 20 2015年06月 [査読有り]
   

  In Japanese forests suffering from the Fukushima Daiichi Nuclear Power Plant accident, litter fall provides a large amount of radiocesium from forests to streams. Submerged litter is processed to become a vital food resource for various stream organisms through initial leaching and subsequent decomposition. Although leaching from litter can detach radiocesium similarly to potassium, radiocesium leaching and its migration are poorly understood. We examined both radiocesium and potassium leaching to the water column and radiocesium allocation to minerals (glass beads, silica sand, and vermiculite) in the laboratory using soaked litter with and without minerals on a water column. The mineral types did not affect radiocesium leaching from litter, but soaking in water for 1, 7, and 30 days decreased the radiocesium concentration in litter by ×0.71, ×0.66, and ×0.56, respectively. Meanwhile, the 1-, 7-, and 30-day experiments decreased potassium concentration in litter by ×0.17, ×0.11, and ×0.09, respectively. Leached radiocesium remained in a dissolved form when there was no mineral phases present in the water, whereas there was sorption onto the minerals when they were present. In particular, vermiculite adsorbed radiocesium by two to three orders of magnitude more effectively than the other minerals. Because radiocesium forms (such as that dissolved or adsorbed to organic matter or minerals) can further mobilize to ecosystems, our findings will increase our understanding regarding the dynamics of radiocesium in stream ecosystems.
• Imperiled freshwater mussels in drainage channels associated with rare agricultural landscape and diverse fish communities (Special Feature : Freshwater biodiversity in human-dominated landscapes)

  Negishi J. N., Tamaoki H., Watanabe N., Nagayama S., Kume M., Kayaba Y., Kawase M.

  Limnology 15 3 237 - 247 Springer 2014年08月 [査読有り]
   

  Identification of landscape structures that predict the distribution of aquatic organisms has the potential to provide a practical management tool for species conservation in agricultural drainage channels. We tested the hypothesis that sites with imperiled freshwater mussels have distinct rural landscape structures and are characterized by the presence of diverse fish communities. In central Japan, the proportion of developed land use in surrounding areas was compared among sites with mussel populations (mussel sites) and randomly chosen sites (random sites) across multiple spatial scales (with a radius ranging from 100 to 3,000 m). Mussel sites were characterized by a much lower proportion of developed land (mean 5-18 %) compared with random sites (mean 32-35 %) at a scale of a parts per thousand currency sign300 m. The areas that met the landscape criteria for mussel sites across multiple scales constituted only 0.23 % of the area that was presumed to have suitable slope and elevation as a mussel habitat. Landscape metrics derived from mussel sites to locate unknown populations had a low predictability (16.7 %). Sites with mussels were located close to each other and had fish communities with higher taxonomic diversity than in sites without mussels. In addition, mussel taxonomic richness was a good predictor of fish community diversity. The quantitative measures of landscape structure may serve as a useful tool when prioritizing or identifying areas for conservation of mussels and fish if spatially autocorrelated distribution of habitat and other critical environmental factors such as habitat connectivity are also considered.
• Freshwater biodiversity in human-dominated landscapes: introduction

  Nisikawa Usio, Junjiro N. Negishi

  LIMNOLOGY 15 3 199 - 200 2014年08月 [査読有り]
  
• The Significance of Meander Restoration for the Hydrogeomorphology and Recovery of Wetland Organisms in the Kushiro River, a Lowland River in Japan

  Futoshi Nakamura, Nobuo Ishiyama, Masanao Sueyoshi, Junjiro N. Negishi, Takumi Akasaka

  Restoration Ecology 22 4 544 - 554 2014年07月 [査読有り]
   

  The meanders and floodplains of the Kushiro River were restored in March 2011. A 1.6-km stretch of the straightened main channel was remeandered by reconnecting the cutoff former channel and backfilling the straightened reach, and a 2.4-km meander channel was restored. Additionally, flood levees were removed to promote river-floodplain interactions. There were four objectives of this restoration project: to restore the in-stream habitat for native fish and invertebrates; to restore floodplain vegetation by increasing flooding frequency and raising the groundwater table; to reduce sediment and nutrient loads in the core wetland areas; to restore a river-floodplain landscape typical to naturally meandering rivers. In this project, not only the natural landscape of a meandering river but also its function was successfully restored. The monitoring results indicated that these goals were likely achieved in the short term after the restoration. The abundance and species richness of fish and invertebrate species increased, most likely because the lentic species that formerly inhabited the cutoff channel remained in the backwater and deep pools created in the restored reach. In addition, lotic species immigrated from neighboring reaches. The removal of flood levees and backfilling of the formerly straightened reach were very effective in increasing the frequency of flooding over the floodplains and raising the water table. The wetland vegetation recovered rapidly 1 year after the completion of the meander restoration. Sediment-laden floodwater spread over the floodplain, and approximately 80-90% of the fine sediment carried by the water was filtered out by the wetland vegetation. © 2014 Society for Ecological Restoration.
• Terrestrialization alters organic matter dynamics and habitat quality for freshwater mussels (Unionoida) in floodplain backwaters

  Junjiro N. Negishi, Kotaro Katsuki, Manabu Kume, Shigeya Nagayama, Yuichi Kayaba

  Freshwater Biology 59 5 1026 - 1038 2014年05月 [査読有り]
  
• Geomorphic legacy controls macrophyte distribution within and across disconnected floodplain lakes

  Junjiro N. Negishi, Masashi Soga, Nobuo Ishiyama, Noriyasu Suzuki, Teruaki Yuta, Masanao Sueyoshi, Chitose Yamazaki, Itsuro Koizumi, Shigeru Mizugaki, Kazufumi Hayashida, Masanori Nunokawa, Nobuhiko Yoshimura

  Freshwater Biology 59 5 942 - 954 2014年05月 [査読有り]
   

  Degradation of floodplains continues with an increasing number of floodplain lakes disconnected from the fluvial dynamics of rivers. Limited understanding is available as to how historical geomorphic formation processes (i.e. geomorphic legacy) determine contemporary ecosystem structure and function. We tested the hypothesis that geomorphic legacy mediates morphometry and results in heterogeneity of macrophyte distributions in disconnected floodplain lakes.The distribution of macrophyte cover was examined in relation to environmental factors, including water nutrient level, morphometry of lakes and patch shelter level across and among three types of lakes along the Ishikari River, Japan. Artificial lakes (isolated by channelisation), natural oxbow lakes and marsh lakes have been disconnected for more than 40years from natural flood pulses because of dyke construction.The presence of macrophytes (in 5x5m areas) was predicted well by a combination of local water depth and bed slope. Lake average depth, higher values indicating lakes that are more deeply incised with a steeper-sloped littoral zone, had the strongest and most negative influence on total macrophyte cover across lakes. Cover was least in artificial lakes because of greater average depth.Predicted area of macrophyte cover was significantly less than occupied by actual cover in artificial lakes compared with other lake types. Macrophyte cover in artificial lakes was particularly vulnerable to external factors such as waves and wind.This study underscored the significance of geomorphic legacy in explaining a large proportion of heterogeneity of total macrophyte cover in the study lakes. Artificial lakes did not have the macrophyte habitat quality of natural lakes. When lake morphometry needs to be altered, local conditions as well as patch-scale properties should be carefully examined in the light of the geomorphic legacy left by dynamic river-floodplain interactions.
• Winter fish community structures across floodplain backwaters in a drought year

  Kume Manabu, Negishi Junjiro N., Sagawa Shiro

  Limnology 15 2 109 - 115 Springer Japan 2014年04月 [査読有り]
  
• イシガイ類を指標生物としたセグメント 2 における氾濫原環境の評価手法の開発：木曽川を事例として

  Shigeya NAGAYAMA, Morihiro HARADA, Yuichi KAYABA, Junjiro N. NEGISHI

  応用生態工学 17 1 29 - 40 2014年 [査読有り]
  
• Interaction between patch area and shape: lakes with different formation processes have contrasting area and shape effects on macrophyte diversity

  Masashi Soga, Nobuo Ishiyama, Masanao Sueyoshi, Yuichi Yamaura, Kazufumi Hayashida, Itsuro Koizumi, Junjiro N. Negishi

  LANDSCAPE AND ECOLOGICAL ENGINEERING 10 1 55 - 64 2014年01月 [査読有り]
   

  Although both patch area and shape are key factors driving biodiversity in fragmented terrestrial landscapes, researchers have had limited and mixed success in documenting the effects of these two factors on aquatic ecosystems. Here we examined the effects of lake area and shape on macrophyte species richness in a lowland floodplain by considering the differences in lake types (i.e. marsh, oxbow, man-made lakes). We surveyed species richness of native macrophytes in 35 lakes including 11 marshes, 11 oxbows and 13 man-made lakes with various complex shapes covering from 0.25 to 46.3 ha. Model selection clearly supported the existence of interaction between area and shape effects: large-circular and small-complex lakes supported a higher macrophyte species richness, while it was lower in large-complex and small-circular lakes. Among the three lake types, marsh lakes were more circular and man-made lakes had more complex shapes, while oxbow lakes were intermediate between these two. Also, marsh lakes had positive species-area relationships, while man-made lakes had negative relationships. Our results suggest the opposing shape complexity and species-area relationships of these two contrasting lake types are the result of the interactions between lake area and shape. These results indicate that different lake types result in variations in their conservation value for preserving macrophyte diversity. We suggest that small complex-shaped patches (especially oxbow lakes), which are often given the lowest conservation priority in terrestrial ecosystems, cannot be disregarded when conserving macrophyte biodiversity in aquatic ecosystems.
• Effects of biodiversity, habitat structure, and water quality on recreational use of rivers

  Hideyuki Doi, Izumi Katano, Junjiro N. Negishi, Seiji Sanada, Yuichi Kayaba

  Ecosphere 4 8 art102 - art102 2013年08月 [査読有り]
   

  Anthropogenic impacts on biodiversity and habitat conditions can lead to loss of ecosystem services. Cultural services of ecosystems are one of the major categories of ecosystem services, but the relationships between ecosystem conditions and human uses of their cultural services are still largely unknown. To estimate the effects of biodiversity, habitat structure, and environmental pollution on recreational uses of ecosystems, existing data sets for 109 rivers across Japan were used to analyze the relationships among recreational uses of these rivers (fishing, playing in the river, walking, and engaging in sports near the river) and their biodiversity, habitat structure, and water quality. Fish diversity, habitat structure, and water quality had significant effects on the number of people fishing and playing in the rivers. The number of people walking and engaging in sports, which typically takes place on floodplains and dikes, was significantly positively related to the size of the surrounding population rather than to biodiversity or habitat structure. However, water quality had significant effects on such uses of river ecosystems, even though these activities did not involve direct contact with river water. Overall, a decline in biodiversity and ecosystem health was related to a decrease in recreational use.
• Distribution of amphipods (Gammarus nipponensisUeno) among mountain headwater streams with different legacies of debris flow occurrence

  Sohei Kobayashi, Takashi Gomi, Roy C. Sidle, Junjiro N. Negishi

  Ecohydrology 6 1 117 - 124 2013年02月 [査読有り]
  
• Unionoid mussels as an indicator of fish communities : A conceptual framework and empirical evidence

  Negishi J. N., Nagayama S., Kume M., Sagawa S., Kayaba Y., Yamanaka Y.

  Ecological Indicators 24 127 - 137 Elsevier 2013年01月 [査読有り]
   

  We tested the hypothesis that globally imperiled freshwater mussels (Order: Unionoida) can be used as an indicator of fish communities in lowland aquatic systems for relatively small geographic areas (i.e., <100 km2). The survey was conducted in 13 reaches within a network of agricultural drainage channels and in 9 floodplain backwaters in Central Japan. In each site, the fish community was examined on four seasonal occasions (spring to early summer, mid-summer, fall to early winter, and winter) and related to the mussel community. Total abundance, taxon richness, and diversity index were used to characterize fish communities. Mussel community variables predicted some aspects of fish communities, but such patterns were seasonally limited. In both systems, mussel community variables had no predictive power for the total abundance of fishes. In drainage channels, taxon richness of mussels was a good predictor of all fish community variables except for total abundance in early summer. In winter, mussel abundance predicted well the taxon richness of the fish community, while taxon richness predicted the diversity index of the fish community. In backwaters, mussel abundance was a good predictor of fish community variables except total abundance in mid-summer. A relatively minor portion (<23%) of fish-mussel relationships was attributable to direct commensalism between mussels and bitterlings. A conceptual framework was provided to help identify the mechanisms behind fish-mussel relationships. Our findings validated the use of mussels as an indicator of high-quality summer rearing habitats in backwaters and wintering and reproduction habitats of fishes in drainage channels.
• Mussel responses to flood pulse frequency: the importance of local habitat

  JUNJIRO N. NEGISHI, SHIRO SAGAWA, YUICHI KAYABA, SEIJI SANADA, MANABU KUME, TETSUYA MIYASHITA

  Freshwater Biology 57 7 1500 - 1511 2012年07月 [査読有り]
  
• Using airborne scanning laser altimetry (LiDAR) to estimate surface connectivity of floodplain water bodies

  J. N. Negishi, S. Sagawa, S. Sanada, M. Kume, T. Ohmori, T. Miyashita, Y. Kayaba

  River Research and Applications 28 2 258 - 267 2012年02月 [査読有り]
  
• 応用生態工学的研究におけるプロセスベースアプローチ

  根岸 淳二郎

  応用生態工学 15 2 235 - 242 応用生態工学会 2012年 [査読有り]
  
• 木曽川氾濫原水域における特定外来生物ヌートリア (Myocastor coypus) によるイシガイ科二枚貝類の食害

  久米 学, 小野田 幸生, 根岸 淳二郎, 佐川 志朗, 永山 滋也, 萱場 祐一

  陸水生物学報 27 41 - 47 2012年 [査読有り][通常論文]
  
• 農業用の水路における季節と生活史段階に応じた魚類の生息場利用

  永山 滋也, 根岸 淳二郎, 久米 学, 佐川 志朗, 塚原 幸治, 三輪 芳明, 萱場 祐一

  応用生態工学 15 2 147 - 160 Ecology and Civil Engineering Society 2012年 [査読有り][通常論文]
   

  氾濫原に依存した生活史を持つ魚類にとって農業用の水路は代替の生息場として機能している．それゆえ，季節や生活史段階に応じた魚類の水路利用や生息場特性を把握しておくことは，保全上重要である．そこで，本研究では，岐阜県関市の 4 地域において，灌漑期 2 期 (6 月，8 月) と非灌漑期 2 期 (9 月，2 月) にわたり，水涸れしない農業用の水路を対象として調査を行った．全調査期にわたる総採捕個体数に占める割合が 5 ％以上であった魚類を優占種と定義したところ，6 種が該当した．これらの体長頻度分布および個体数の季節変化から，水路はアブラボテ，カワムツ属，ドジョウ，ヨシノボリ類の稚魚期における成育場，それ以外の生活史段階を含む冬季の生息場 (越冬場) として利用されていることが示唆された．また，生活史段階を特定できなかったが，シマドジョウ類の成育場および冬季の生息場として，さらに，当歳魚を含む小型個体 (39 mm 以下) のオイカワの成育場および冬季の生息場として水路が利用されていることが示唆された．水路底が土砂の水路 (土砂区間) では，コンクリートの水路 (コンクリート区間) よりも，8 月を除く 3 調査期において魚類の総生息密度は有意に高く，種多様度は冬季においてのみ有意に高かった．また，水深，砂割合，小礫割合も，全調査期において土砂区間の方が有意に高かった．魚類の生息密度に影響を与える物理環境として，温暖な時期 (6 月，8 月，9 月) ついては，優占 種 6 種中 4 種に対して水路底の土砂 (シルト割合，砂割合，小礫割合) が検出され，それぞれ生息密度と正の関係を示した．土砂は魚類の生息場や産卵場の基質，餌資源の生息場基質となることから，水路底に土砂を持つ土砂区間はコンクリート区間より適した生息場であったと考えられる．寒冷な冬季 (2 月) になると生息場のシフトが見られ，4 魚種についてカバー率，1 魚種について水深が重要な物理環境として選ばれ，それぞれ生息密度と正の関係を示した．カバー率は，土砂区間に含まれる素掘りの土羽水路の区間で高く (25. 4％) ，コンクリート区間 (1. 2％) や柵渠 (6. 0％) では低かった．また，水深も土砂区間の方が大きかった．このことから，カバーや大きな水深 158 応用生態工学15 (2) , 2012 が魚類の冬季生息場として適しており，それが担保された土砂区間で魚類の生息密度や多様度が高くなったと考えられる．加えて，アブラボテの生息量は産卵期以外も含む 3 調査期において二枚貝の生息量と密接な正の関係にあることが示された．以上のことから，灌漑期と非灌漑期を通した魚類生息場として農業用の水路を捉える場合，水路底の土砂やカバーがセットで水路に存在することが必要であると結論される．このような水路としては，素掘りの土羽水路が理想的ではあるが，少なくとも柵渠 (側岸だけコンクリートや板で固定) とすることが望ましい．柵渠においても水際部の植生やえぐれによるカバーを確保するためには，土砂の堆積や維持に関わる水理条件を整えると同時に，堆積を許容する設計が必要である．
• フロリダ州エバーグレイズ流域における流域再生プロジェクトと研究学習拠点

  山下 慎吾, 根岸 淳二郎, 河口 洋一, 赤坂 卓美, 中村 知美, 島谷 幸宏, 中村 太士

  流域圏学会誌 1 1 19 - 24 流域圏学会 2012年 [査読有り][招待有り]
  
• Seasonally tracking vertical and horizontal distribution of unionid mussels (Pronodularia japanensis): implications for agricultural drainage management

  Junjiro N. Negishi, Hideyuki Doi, Izumi Katano, Yuichi Kayaba

  Aquatic Conservation: Marine and Freshwater Ecosystems 21 1 49 - 56 2011年01月 [査読有り]
   

  1. The vertical and horizontal distribution of unionoid mussels (Pronodularia japanensis) were examined in spring, late summer and winter for different size classes, including juveniles (<20 mm) and large adults (>50 mm), in an agricultural drainage channel in Central Japan.2. A large number of small-sized juveniles were found at the surface (0-3 cm depth) in spring, whereas approximately half of the adults remained in the deep layer (3-8 cm depth). Most individuals were found in the surface layer irrespective of size classes in summer, and approximately 70% of all individuals descended to the deep layer in winter.3. Horizontal distribution did not substantially change across seasons and high density patches were consistently found in the areas where substrate appeared to be stable or hydraulically sheltered. Spatial distribution of small juveniles was relatively well predicted by the abundance of adults.4. The size-frequency distribution was multi-modal in three seasons and estimated numbers of newly recruited juveniles were highly variable in recent years, suggesting that juveniles were rarely found owing to irregular reproduction and/or recruitment not the overlooked habitat preferred by small-sized juveniles.5. As P. japanensis is characterized by the behaviour of burrowing down to a depth of similar to 10 cm, maintaining the processes of sediment deposition appears to be one of the critical criteria for the conservation of mussel habitats in agricultural drainage channel systems, which are commonly lined with smooth concrete materials. Copyright (C) 2010 John Wiley & Sons, Ltd.
• Short-term responses of macroinvertebrate drift following experimental sediment flushing in a Japanese headwater channel

  Takashi Gomi, Sohei Kobayashi, Junjiro N. Negishi, Fumitoshi Imaizumi

  Landscape and Ecological Engineering 6 2 257 - 270 2010年07月 [査読有り]
  
• Size-specific growth patterns and estimated longevity of the unionid mussel (Pronodularia japanensis)

  Negishi Junjiro N., Kayaba Yuichi

  Ecological research 25 2 403 - 411 Springer Japan 2010年03月 [査読有り]
  
• Effects of handling and density on the growth of the unionoid mussel Pronodularia japanensis

  Junjiro N. Negishi, Yuichi Kayaba

  Journal of the North American Benthological Society 28 4 821 - 831 2009年12月 [査読有り]
  
• Host mussel utilization of the Itasenpara bitterling (Acheilognathus longipinnis) in the Moo River in Himi, Japan

  Jyun-ichi Kitamura, Junjiro N. Negishi, Masaki Nishio, Shiro Sagawa, Jyun-ichi Akino, Shigeyuki Aoki

  Ichthyological Research 56 3 296 - 300 2009年07月 [査読有り]
  
• Changes in bedload transport rate associated with episodic sediment supply in a Japanese headwater channel

  Fumitoshi Imaizumi, Takashi Gomi, Sohei Kobayashi, Junjiro N. Negishi

  CATENA 77 3 207 - 215 2009年06月 [査読有り]
  
• Longitudinal macroinvertebrate organization over contrasting discontinuities: effects of a dam and a tributary

  Izumi Katano, Junjiro N. Negishi, Tomoko Minagawa, Hideyuki Doi, Yôichi Kawaguchi, Yuichi Kayaba

  Journal of the North American Benthological Society 28 2 331 - 351 2009年06月 [査読有り]
   

  Macroinvertebrate organization along a river was examined to relate biological responses to environmental changes observed across 2 discontinuities (a dam and a tributary). Benthic macroinvertebrates and a range of environmental variables were sampled from 4 study segments (above the dam, below the dam, below the tributary confluence, and in the tributary). Substrate was significantly coarser below than above the dam. In contrast, water-quality variables, such as water temperature and dissolved O-2, changed little below the dam. The most striking discontinuity was substrate coarseness at the tributary confluence. Substrate below the confluence was finer than substrate below the dam and similar to the substrate above the dam. Macroinvertebrate organization differed across the 2 discontinuities. Assemblage composition above the dam was more similar to composition below the confluence than to composition below the dam. The longitudinal organization of the macroinvertebrates could be explained largely by changes in substrate characteristics and habitat preferences of the indicator species. The densities of drifting zooplankton and phytoplankton were higher below than above the dam and were higher below the dam than below the confluence. However, the density of drifting plankton did not differ between the reach immediately above the confluence and the reaches below the confluence. This result suggests that the decrease of zooplankton and phytoplankton occurred above the tributary, probably because of biological entrapment or passive deposition rather than the contribution of the tributary inflow. The dam and tributary caused contrasting discontinuities in macroinvertebrate organization. The tributary generally reversed the dam-related changes to the main stem habitat and the macroinvertebrate community. A key management implication of our study is that efforts to restore dam-related environmental impacts would be facilitated by understanding the role of tributaries downstream of the dam.
• Throughfall in an evergreen-dominated forest stand in northern Thailand: Comparison of mobile and stationary methods

  Alan D. Ziegler, Thomas W. Giambelluca, Mike A. Nullet, Ross A. Sutherland, Chatchai Tantasarin, John B. Vogler, Junjiro N. Negishi

  AGRICULTURAL AND FOREST METEOROLOGY 149 2 373 - 384 2009年02月 [査読有り]
   

  Throughfall determined by stationary and mobile methods in a disturbed evergreen-dominated forest stand in northern Thailand was 82% of rainfall (1134 mm) during a 4-month study period in the monsoon rain season of 2002. Associated coefficients of variation and standard errors were <= 10% and 2%, respectively, for both methods. Agreement between four stationary trough collectors and 20 mobile standard gauge collectors was achieved only after 35 sampling occasions, having a total rainfall depth >700 mm, and included one storm event >100 mm. Several canopy trees contributed to points with throughfall > rainfall by channeling stemflow to common drip points on the trunk and large limbs. However, no significant correlation was observed between throughfall point measurements and corresponding canopy cover. Although 180-point measurements of throughfall provided a realistic representation of the spatial variability within the 500-m(2) forest stand, it is questionable that they duplicated the basin-scale variability, which would be affected both by tree gaps and variable topographically related rain shadow effects. (C) 2008 Elsevier B.V. All rights reserved.
• A new method to measure substrate coherent strength of Stenopsyche marmorata

  Masanori Nunokawa, Takashi Gomi, Junjiro N. Negishi, Osamu Nakahara

  LANDSCAPE AND ECOLOGICAL ENGINEERING 4 2 125 - 131 2008年11月 [査読有り]
   

  We developed a method for estimating the substrate coherent strength of a net-spinning caddis larva, Stenopsyche marmorata, in the field. Plastic experimental cages (prefabricated containers with 5-mm mesh; 0.1 m high, 0.12 m wide, 0.2 m long) that enclosed gravel substrate and an objective stone (5-6 cm in diameter) were prepared. We expected the caddisflies to build a retreat(s) between the objective stone and cage substrate when submerged in a riffle channel reach for 6 days. Ten final-instar larvae (4-5 cm long) were placed in the cage and allowed to form retreats. Two treatments (cages with and without larvae) with 15 replicates each were used in two experimental trials. The vertical lift-force of objective stones associated with a retreat (coherent strength) was measured using a spring weighing scale. In 87% of 30 cages of with-larvae treatment, retreats were formed between the objective stone and cage substrate. Coherent strength ranged from 0.0 to 1.6 kg. Our approach can be used under varying flow velocities, substrate conditions, and larval biomass, all of which are normally difficult to test in flume experiments. Findings based on our field method provide unique physical properties of the caddisfly retreats in stream ecosystems.
• イシガイ目二枚貝の生態学的研究 : 現状と今後の課題

  根岸 淳二郎, 萱場 祐一, 塚原 幸治, 三輪 芳明

  2008年10月 [査読有り]
  
• Contribution of intercepted subsurface flow to road runoff and sediment transport in a logging-disturbed tropical catchment

  NEGISHI J.N.

  Earth Surf. Process. Landforms 33 8 1174 - 1191 2008年07月 [査読有り]
  
• 指標・危急生物としてのイシガイ目二枚貝：生息環境の劣化プロセスと再生へのアプローチ

  Junjiro N. NEGISHI, Yuichi KAYABA, Koji TSUKAHARA, Yoshiaki MIWA

  応用生態工学 11 2 195 - 211 2008年 [査読有り]
  
• Persistence of road runoff generation in a logged catchment in Peninsular Malaysia

  Alan D. Ziegler, Junjiro N. Negishi, Roy C. Sidle, Takashi Gomi, Shoji Noguchi, Abdul Rahim Nik

  EARTH SURFACE PROCESSES AND LANDFORMS 32 13 1947 - 1970 2007年11月 [査読有り]
   

  Measurements of saturated hydraulic conductivity (K-s) and diagnostic model simulations show that all types of logging road/trail in the 14.4 ha Bukit Tarek Experimental Catchment 3 (BTEC3) generate substantial Horton overland flow (HOF) during most storms, regardless of design and level of trafficking. Near-surface K-s(0-0.05 m) on the main logging road, skid trails and newly constructed logging terraces was less than 1, 2 and 34 mm h(-1), respectively. Near-surface K-s on an abandoned skid trail in an adjacent basin was higher (62 nun h(-1)), owing to the development of a thin organic-rich layer on the running surface over the past 40 years. Saturated hydraulic conductivity measured at 0.25 m below the surface of all roads was not different (all <6 mm h(-1)) and corresponded to the K-s of the adjacent hillslope subsoil, as most roads were excavated into the regolith more than 0.5-1 m. After 40 years, only limited recovery in near-surface K-s occurred on the abandoned skid trail. This road generated HOF after the storage capacity of the upper near-surface layer was exceeded during events larger than about 20 mm. Thus, excavation into low-K-s substrate had a greater influence on the persistence of surface runoff production than did surface compaction by machinery during construction and subsequent use during logging operations. Overland flow on BTEC3 roads was also augmented by the interception of shallow subsurface flow traveling along the soilsaprolite/bedrock interface and return flow emerging from the cutbank through shallow biogenic pipes. The most feasible strategy for reducing long-term road-related impacts in BTEC3 is limiting the depth of excavation and designing a more efficient road network, including minimizing the length and connectivity of roads and skid trails. Copyright (c) 2007 John Wiley & Sons, Ltd.
• Stormflow generation involving pipe flow in a zero-order basin of Peninsular Malaysia

  J. N. Negishi, S. Noguchi, R. C. Sidle, A. D. Ziegler, Abdul Rahim Nik

  Hydrological Processes 21 6 789 - 806 2007年03月15日 [査読有り]
  
• Impacts of logging disturbance on hillslope saturated hydraulic conductivity in a tropical forest in Peninsular Malaysia

  Alan D. Ziegler, Junjiro N. Negishi, Roy C. Sidle, Shoji Noguchi, Abdul Rahim Nik

  CATENA 67 2 89 - 104 2006年10月 [査読有り]
   

  Using a constant-head permeameter we found an abrupt natural decrease in saturated hydraulic conductivity (K-s) within the upper 1.0-m soil profile of an Orthoxic Tropudult at the Bukit Tarek Experimental Catchments research area in tropical, Peninsular Malaysia. The depth at which low K-s could cause a perched water table in response to high-intensity rainfall, however, was too great to generate saturation overland flow on planar hillslopes in the study area. The effects of logging activity on K-s at five subsurface depths (0.1, 0.25, 0.5, 0.75, and 1.0 m) on the non-roaded portion of the harvest area were examined at the three following sites, which differed in the degree of disturbance and recovery since timber harvesting: (1) selective logging conducted in the 1960s; (2) mechanized selective tree removal conducted 4 years ago; and (3) high-impact clear-cutting just prior to measurement. This recent logging greatly disturbed the soil surface (via compaction, topsoil/subsoil mixing, burning) and produced comparatively high variability in near-surface K-s. Changes in K-s at or below 0.25-m, however, were not detected with certainty at any sites. In terms of hillslope hydrologic response, the connectivity of zones of low K-s in the harvest area with dense networks of skid trails and terraces was identified as one of the most important consequences of timber harvesting, although this phenomenon was not quantified. We estimate the recovery time for near-surface K-s on the non-roaded hillslope to be less than 40 years. (c) 2006 Elsevier B.V. All rights reserved.
• Potential influences of a net-spinning caddisfly (Trichoptera : Stenopsyche marmorata) on stream substratum stability in heterogeneous field environments

  Akira Takao, Junjiro N. Negishi, Masanori Nunokawa, Takashi Gomi, Osamu Nakahara

  JOURNAL OF THE NORTH AMERICAN BENTHOLOGICAL SOCIETY 25 3 545 - 555 2006年09月 [査読有り]
   

  The influence of the net-spinning caddisfly larva Stenopsyche marmorata on streambed substratum stability was examined in 14 riffles of 5 rivers in northern Hokkaido, Japan. In each riffle, 6 representative stones were measured and 7 variables were quantified for each stone: 1) ambient flow velocity, 2) ambient depth, 3) extent of embeddedness, 4) force required to initiate shifting of the stone parallel to the flow direction, 5) biomass of S. marmorata living on and under the stone, 6) wet mass of the stone, and 7) size of the stone. Regression analyses were used to examine which of the variables best predicted the coherent strength of a particle with the stream bed (F-C). Riffle-scale patterns derived from the means of 6 stones showed significant influences of biomass of S. marmoratalstone and embeddedness on F-C; however, the collinearity of these 2 variables hindered evaluation of their relative importance. At the stone scale, biomass of S. marmorata/stone was positively related to F-C when standardized for the degree of stone embeddedness. F-C of stones inhabited by S. marmorata at the maximum range of their biomass is predicted to be 50 to 260% greater than F-C of stones without S. marmorata. The effects of biological consolidation of substratum particles by S. marmorata probably are substantial, even in inherently heterogeneous natural environments.
• Sediment and wood accumulations in humid tropical headwater streams: Effects of logging and riparian buffers

  Takashi Gomi, Roy C. Sidle, Shoji Noguchi, Junjiro N. Negishi, Abdul Rahim Nik, Shozo Sasaki

  Forest Ecology and Management 224 1-2 166 - 175 2006年03月 [査読有り]
  
• Ecological roles of roadside fern (Dicranopteris curranii) on logging road recovery in Peninsular Malaysia: Preliminary results

  J.N. Negishi, R.C. Sidle, S. Noguchi, Abdul Rahim Nik, R. Stanforth

  Forest Ecology and Management 224 1-2 176 - 186 2006年03月 [査読有り]
  
• Erosion processes in steep terrain - Truths, myths, and uncertainties related to forest management in Southeast Asia

  RC Sidle, AD Ziegler, JN Negishi, AR Nik, R Siew, F Turkelboom

  FOREST ECOLOGY AND MANAGEMENT 224 1-2 199 - 225 2006年03月 [査読有り]
   

  To assess the effects of forest management on soil erosion in Southeast Asia, clear distinctions must be made between surface erosion and landslide processes. Although surface erosion is a natural process, it is exacerbated by surface disturbance and compaction that reduce the soil hydraulic conductivity and break down soil aggregates. Management practices and attributes such as roads and trails, agricultural cultivation, fire, land clearing, and recreation all accelerate surface erosion processes due to their disturbance, compaction, and connectivity along hillslopes. Agroforestry practices in Southeast Asia that incorporate cover crops with trees reduce surface erosion by more than an order of magnitude compared to monoculture plantations with no ground cover. Cleared fields tilled up and down steep slopes are highly erodible; passive conservation practices (e.g., contour tillage, strip cropping, reduced tillage; maintaining adequate ground cover) are effective in reducing surface erosion if properly implemented. Poorly designed and managed terraces are not effective in controlling surface erosion and may actually increase mass wasting if they concentrate water.In contrast to surface erosion, shallow, rapid landslides are episodic processes triggered by individual rainfall events or artificial inputs of water; slower, deep-seated landslides initiate or activate after a longer-term accumulation of water. Thus, landslide assessment must be based on long-term observations. Deep rooted trees and shrubs impart a significant cohesive strength into shallow soil mantles and facilitate preferential drainage, thereby reducing the probability of shallow landslides. Conversion of mountain forests to cropland or plantations permanently reduces rooting strength, thus increasing landslide potential, while timber harvesting with subsequent regeneration of secondary forests reduces rooting strength for up to two decades after initial cutting.Roads contribute the largest surface erosion and landslide losses (per unit area disturbed) compared to other land uses. Both landslide and surface erosion fluxes along roads are typically one to more than two orders of magnitude higher compared to undisturbed steepland forests. High storm runoff from roads is caused by the generation of infiltration-excess overland flow on compacted surfaces and the interception of subsurface flow at road cuts; these altered pathways increase surface erosion and accelerate the delivery of storm runoff to streams. Discharge nodes from roads facilitate the connectivity of water and sediment to headwater streams. Trails, although narrower than roads, can contribute significantly to soil loss and storm runoff and are important sediment conduits if directly linked to channels. Thus, the location of roads and paths with respect to the hydrologic network is a critical factor governing the spatial-temporal movement of sediment and water in the tropics. (c) 2005 Elsevier B.V. All rights reserved.
• Reduction of Stream Sediment Concentration by a Riparian Buffer: Filtering of Road Runoff in Disturbed Headwater Basins of Montane Mainland Southeast Asia

  Alan D. Ziegler, Junjiro Negishi, Roy C. Sidle, Pornchai Preechapanya, Ross A. Sutherland, Thomas W. Giambelluca, Sathaporn Jaiaree

  Journal of Environmental Quality 35 1 151 - 162 2006年01月 [査読有り]
  
• An experimental test of the effects of food resources and hydraulic refuge on patch colonization by stream macroinvertebrates during spates.

  Junjiro N Negishi, John S Richardson

  The Journal of animal ecology 75 1 118 - 29 2006年01月 [査読有り]
   

  1. The passive or active movement of organisms between habitat patches plays important roles in achieving ecosystem resilience to disturbance and long-term control of population levels. However, causal mechanisms of disturbance-induced movements of mobile biota across heterogeneous habitat patches at a relatively short time-scale are little understood. 2. We experimentally tested the effects of food resource values on macroinvertebrate colonization of hydraulic refugia from spates in a second-order creek. Experimental cages were colonized by macroinvertebrates with combinations of resource types (natural or polyester leaves), and extent of exposure to stream flow (exposed to or sheltered from current); one half of each set was collected before and after a spate. This experiment was repeated over three spates of varying magnitude and seasonal contexts. 3. Pre-spate colonization was consistently greater for the cages with natural leaves relative to artificial leaves regardless of the extent of flow exposure. Two autumn spates with relatively low and stable antecedent flow conditions caused large movements of organic matter and macroinvertebrates across the stream, showing community-level accumulations into hydraulically sheltered patches independent of food treatment. The smallest spate with high and variable antecedent flows during winter resulted in negligible responses, which we interpret to be a result of depletion of easily transportable organic matter and organisms. 4. Two detritivorous taxa, the mayfly Paraleptophlebia spp. and stonefly Despaxia augusta (Banks) were the most responsive to autumn spates, and had disproportionately higher colonization rates of cages when provided with natural leaves during the largest autumn spate. Preferential settlement in food-enriched hydraulic refugia was attributable to taxon-specific mobility related to efficient acquisition of detritus resource, whose availability varies spatially and temporally. 5. Our findings suggest (1) detritivorous macroinvertebrate colonization of hydraulic refugia can be influenced by hydraulic controls as well as food resource value, and (2) pre-spate environmental conditions in terms of resource distribution and availability may pre-condition organisms' susceptibility to spates and also affect refugium usage, at least in food-limited, detritus-based stream systems.
• Detritus processing, ecosystem engineering and benthic diversity: a test of predator-omnivore interference

  YX Zhang, JS Richardson, JN Negishi

  JOURNAL OF ANIMAL ECOLOGY 73 4 756 - 766 2004年07月 [査読有り]
   

  1. Interference between species from different functional groups may influence ecosystem functioning and biological diversity. This study tested whether interactions between predacious cutthroat trout and an omnivorous signal crayfish modified the crayfish's trophic and engineering effects within a detrital-based, stream benthic community.2. We show in a trough experiment that omnivorous crayfish through their trophic and engineering roles enhance detritus decomposition, reduce particulate organic matter (POM) accumulation, and diminish diversity in leaf packs.3. In crayfish troughs by day 30, leaf dry weight loss was 1.8-fold greater, whereas POM trapped in leaf packs was 80% less, than of those in controls, and the abundance, biomass and taxon richness of benthos in leaf packs were lower than those in controls. Predatory cutthroat trout did not affect those variables and did not interfere with the crayfish.4. Crayfish and cutthroat trout both decreased fine material sedimentation in the troughs.5. Thus, with no interference from cutthroat trout, the signal crayfish acted as ecosystem processors and engineers, and strongly influenced detrital processing, benthic diversity, and the accumulation of POM and fine sediments.
• Impacts of marine-derived nutrients on stream ecosystem functioning.

  Yixin Zhang, Junjiro N Negishi, John S Richardson, Renata Kolodziejczyk

  Proceedings. Biological sciences 270 1529 2117 - 23 2003年10月22日 [査読有り]
   

  Energy and nutrient subsidies transported across ecosystem boundaries are increasingly appreciated as key drivers of consumer-resource dynamics. As purveyors of pulsed marine-derived nutrients (MDN), spawning salmon are one such cross-ecosystem subsidy to freshwaters connected to the north Pacific. We examined how salmon carcasses influenced detrital processing in an oligotrophic stream. Experimental manipulations of MDN inputs revealed that salmon carcasses indirectly reduced detrital processing in streams through temporarily decoupling the detrital resource-consumer relationship, in which detrital consumers shifted their diet to the high-nutrient resource, i.e. salmon carcasses. The average decomposition rate of alder leaves with salmon carcass addition was significantly lower than that without the carcass, which was associated with lower abundance and biomass of detritivorous Trichoptera on the carcass-treated leaves. There were generally larger in size Trichopteran detritivores on the carcasses than on leaves. These results imply that cross-boundary MDN subsidies indirectly retard the ecosystem processing of leaf litter within the short term, but may enhance those food-limited detritivorous consumers. Because unproductive freshwaters in the Pacific northwest are highly dependent upon the organic matter inputs from surrounding forests, this novel finding has implications for determining conservation and management strategies of salmon-related aquatic ecosystems, in terms of salmon habitat protection and fisheries exploitation.
• Responses of organic matter and macroinvertebrates to placements of boulder clusters in a small stream of southwestern British Columbia, Canada

  Junjiro N Negishi, John S Richardson

  Canadian Journal of Fisheries and Aquatic Sciences 60 3 247 - 258 2003年03月01日 [査読有り]
   

  Diversity and productivity of stream food webs are related to habitat heterogeneity and efficiency of energy retention. We tested the hypothesis that experimental boulder placements in a second-order stream would increase diversity and abundance of macroinvertebrates by restoring detrital retention and habitat heterogeneity. Two relatively natural, upstream, reference reaches and a downstream treatment reach with a relatively straight channel and less woody debris were studied for 3 months before and 1.2 years after the placement of six boulder clusters in the treatment reach. Mean velocity and its coefficient of variation increased in the treatment reach (140 and 115%, respectively), whereas the reference reaches remained relatively unchanged after the placements. Enhanced particulate organic matter storage (550%) was accompanied by increased total macroinvertebrate abundance (280%) in the treatment reach, converging with those of the reference reaches almost 1 year after the treatment. Detritivorous taxa numerically dominated the macroinvertebrate community, the total densities of which were best predicted by the fine fraction of organic matter biomass at microhabitat scale. However, the effect of boulder clusters on taxonomic richness was negligible. Our findings suggest that boulder clusters can be used at least as a short-term means to restore macroinvertebrate productivity in detritus-based stream systems.
• Effects of channelisation on stream habitat in relation to a spate and flow refugia for macroinvertebrates in northern Japan

  NEGISHI JN

  Freshwat Biol 47 8 1515 - 1529 2002年08月 [査読有り]
  

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  永山滋也, 玉置弘幸, 根岸淳二郎, 久米学, 萱場祐一 日本魚類学会年会講演要旨 46th 2013年
• 異なる河川底質におけるカワシンジュガイの生態的機能

  高木優風花, 根岸淳二郎, 布川雅典, 久米学, 照井慧 応用生態工学会研究発表会講演集 17th 2013年
• 寒冷な地域特性を活かした産官学発展の取り組み : 星野リゾートトマム・占冠村・北海道大学の三者が発展する連携へ

  中村 一樹, 吉村 暢彦, 根岸 淳二郎 寒地技術論文・報告集 寒地技術シンポジウム 28 370 -375 2012年
• 水枯れしない農業用水路における魚類の生息環境と利用実態

  永山滋也, 根岸淳二郎, 久米学, 佐川志朗, 塚原幸治, 三輪芳明, 萱場祐一 応用生態工学会研究発表会講演集 15th 2011年
• 陸水環境保全のための指標種としてのイシガイ類の有用性

  根岸淳二郎, 大森徹治, 萱場祐一, 久米学, 佐川志朗, 真田誠至, 永山滋也, 宮下哲也 日本生態学会大会講演要旨集 57th 2010年
• 異なる冠水頻度をもつ氾濫原水域における四季および出水前後を通した魚類群集構造の変化

  永山滋也, 久米学, 根岸淳二郎, 佐川志朗, 宮下哲也, 萱場祐一 応用生態工学会研究発表会講演集 14th 2010年
• 産卵母貝の生きざまを理解する:イシガイ類の基礎から応用生態までの最新知見

  根岸淳二郎, 根岸淳二郎, 佐川志朗, 萱場祐一, 久米学, 永山滋也 日本魚類学会年会講演要旨 43rd 2010年
• 氾濫原の冠水パターンの変化とその生態的な影響--淡水性二枚貝の生息状況の観点から

  根岸 淳二郎, 萱場 祐一, 佐川 志朗 土木技術資料 50 (11) 38 -41 2008年11月 [査読無し][通常論文]
  
• ダム下流における支川の効果を考える：供給土砂量の異なる２河川間の比較

  片野 泉, 佐川 志朗, 真田 誠至, 土居 秀幸, 根岸 淳二郎, 皆川 朋子, 萱場 祐一 日本陸水学会 講演要旨集 73 (0) 84 -84 2008年 [査読無し][通常論文]
  
• 発電ダム廃止による自然流況の復活が本支流の生息魚類に与える影響

  佐川 志朗, 山下 慎吾, 秋野 淳一, 真田 誠至, 根岸 淳二郎, 片野 泉, 皆川 朋子, 萱場 祐一 日本陸水学会 講演要旨集 73 (0) 210 -210 2008年 [査読無し][通常論文]
  
• 支川流入がダム下流の河床環境と底生動物群集に与える影響：近畿8ダム河川間での比較

  片野 泉, 土居 秀幸, 根岸 淳二郎, 皆川 朋子, 萱場 祐一 日本陸水学会 講演要旨集 72 (0) 129 -129 2007年 [査読無し][通常論文]
  
• イシガイ類の生息場所環境解析

  根岸 淳二郎, 萱場 祐一, 皆川 朋子, 片野 泉, 田代 喬 日本陸水学会 講演要旨集 71 (0) 31 -31 2006年 [査読無し][通常論文]
  

共同研究・競争的資金等の研究課題

• 見えない自然を守る～DNAによる河川地下フロンティア領域の可視化

  日本学術振興会：科学研究費助成事業

  研究期間 : 2022年04月 -2025年03月 

  代表者 : 根岸 淳二郎, 三浦 彩, 早川 裕弌, 渡辺 幸三, 三宅 洋
• 防潮堤建設が及ぼす海浜性昆虫の種構成及び資源利用の変化

  日本学術振興会：科学研究費助成事業

  研究期間 : 2021年04月 -2024年03月 

  代表者 : 小林 憲生, 大原 昌宏, 根岸 淳二郎

   

  海浜性昆虫は、海浜という限られた環境にのみ生息する。特に飛翔力を欠く種が多く知られる海浜性甲虫は、海浜環境への適応を考える上で格好の材料である。さらに、この海浜性甲虫群集は、波打ち際（微環境a）、湿った砂（微環境b）、乾燥した砂（微環境c）と、僅か20-30mの範囲内で種構成が変化していく。その上、種によっては生息微環境と餌の場所が異なり、微環境a-bを行き来する種、微環境b-cを移動する種など、複数の微環境を利用する場合も有る。その結果、防潮堤建設によって、上記のいずれかの環境が消失する、或いはこれら微環境a-b-cが分断され、様々な海浜性生物の存否に影響を及ぼす可能性がある。その一方、消滅を免れた種においては、餌資源を変更するなどが生じている可能性もある。 本研究では、海浜性昆虫（主として甲虫類）の詳細な生息場所の調査、及び食性に関する実験等を行い、海浜性昆虫が生息可能な条件を探索すると共に、食物網（Food-Web）を拡張させた、生息場所から餌までの資源利用に関する多次元的な「資源利用-Web」を作成し、防潮堤がもたらすWeb構造の“変化”の解明を目的とする。 初年度は東北地方太平洋側の中でも宮城県中心（宮城県荒浜、蒲生、由比ガ浜、北浜、野蒜）に調査・採集を行い、海浜性昆虫の生息状況を確認した。 また、現在は、餌資源利用の実態を明らかにするため、ハマヒョウタンゴミムシダマシ、ヒョウタンゴミムシ等を用い、食性選好性、生息微環境の選好性に関する室内実験を行っている最中である。
• 海浜エコトーンの再生を目指した地域主体による「育てる防潮堤」の実証的提案

  日本学術振興会：科学研究費助成事業

  研究期間 : 2019年04月 -2023年03月 

  代表者 : 松島 肇, 島田 直明, 平吹 喜彦, 岡 浩平, 根岸 淳二郎

   

  本年度は初年度に設置した防潮堤への覆砂試験のモニタリング調査の継続、および防潮堤の海側・陸側における植生調査とともに、防潮堤の生態系への影響把握指標として徘徊性昆虫の食物網への影響に着目し調査をおこなった。また、宮城県や岩手県における学校カリキュラムと連動した海浜植物群落の保全・再生への取り組みを宮城県気仙沼市立大谷小学校、北海道石狩市立浜益小学校、浜益中学校でも実施し、合わせてアンケート調査による環境意識の変化の定量化をおこなった。 防潮堤への覆砂試験では、植物群落の定着が促進されている様子が確認されたものの、防潮堤の上部については、季節風の影響で砂の移動が顕著に確認され、特に内陸側の堤体法面では冬から春にかけて上部の砂が植生ごとなくなり、その後夏から秋にかけて再び砂と植生に覆われる様子が確認された。これが安定化するかについては引き続き継続した調査が求められる。防潮堤より海側の植生については大きな変化は見られないが、陸側ではニセアカシアなどの外来木本が顕著に侵入している様子が確認できた。徘徊性昆虫としてオオハサミムシに着目し、体の安定同位体比を計測して防潮堤の海側と陸側で比較した結果、汀線から陸に向かっていくについれて海由来の同位体の寄与率が低下していく様子が確認できた。しかし、防潮堤の影響で大きく変化する様子はみられなかった。小中学生との海浜植物群落の保全・再生活動は継続することで知識・関心が高まることが確認された。６年目となる仙台市立岡田小学校では、児童が家族とともに自主的に海浜植物の種子を採取するなど、大きな進展が見られた。植物種の判別だけでなく、多くの児童が種子からどの海浜植物種の種子かを同定できるようになっていり、自主的に図鑑を作成するなど、関心の高まりが伺えた。
• 河川と水辺環境保全のための地下生物指標による生態系健全度・回復力評価

  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 : 根岸 淳二郎, 東城 幸治, 宇野 裕美, 川西 亮太

   

  河川地下の飽和間隙水域（間隙域）が河川・河畔生態系の食物網にエネルギーを供給する機能を解明することを目的とし、次の主に4つの成果を得た．間隙性水生昆虫を特定し、その他無脊椎動物を含む間隙域食物網を可視化した．特定した間隙性昆虫の定量化によりその羽化成虫の移動を介して河畔消費者へ供給される物質量を推定した．間隙性生物の洪水および栄養塩付加への応答を明らかにした．間隙性水生昆虫を用いた河川健全性評価手法の提案を行った．総じて、相対的に容易に捕獲・計測が可能である羽化成虫に着目して、河川と水辺環境保全のための地下生物指標による生態系健全度・回復力評価の技術および概念基盤を示した．
• 資源利用変化と気候変動による水・土砂・森林レジーム変化と河川・水辺生態系の応答

  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 : 中村 太士, 萱場 祐一, 山浦 悠一, 根岸 淳二郎

   

  国土交通省が管理する109水系の管理区間を対象として樹林化の進行と河道内に形成された樹林地がどのような地被から転換されているかを分析した。具体的には、1㎞毎の地被状態を水面＋裸地、草地、樹林地、人工地に分類し、Ⅲ期（1990～1995年度）からⅤ期（2001年～2005年度）の2時期において1）河道面積が大きく変化せず、2）樹林地が5％以上増加した区間を抽出した。この結果、樹林化が進行した区間には、人工地の増大によって説明できる区間も多く、人為的な利用圧の低下（例、耕作放棄地）も樹林化に寄与していることが示唆された。 札内川中流域を対象に、水生昆虫羽化成虫による河畔域の森林植生利用と河川堤防に付随した多年草植生帯がその利用に及ぼす影響を定量化した。横断方向への飛翔距離や群集構造で評価した河畔域利用の程度は目レベルで明瞭に異なり、特に河床間隙域由来のカワゲラ目昆虫において森林植生の利用度が高かった。一方で、堤防の植生帯は、河川からの距離が水生昆虫の飛翔距離に対して十分に小さい場合に、生息場として利用されていた。河畔域の植生帯が、水生昆虫の成虫期の生息場として重要であることが示唆された。 火山性地質においては湧水成分が多くなり、非火山岩地質と比べると夏季においても低温が維持されることから、温暖化の影響を予測するために地質を加味した水温の分布を予測できるモデルを完成させた。 土地利用の変化が鳥類群集に与えた影響を北海道の石狩平野で推定した。各種資料から最近100年間の土地利用を再構築した。土地利用と鳥類各種の個体数の関係を統計モデルで記述し、過去の土地利用に当てはめた。その結果、この時期土地利用は森林が激減した一方で、畑は一時期増加したが水田に置き換わり減少していた。これに伴い、裸地性鳥類以外の湿地性、草地性、森林性鳥類は長期的に大きく個体数を減らしていたと推定された。
• 森林‐農地移行帯における放射性核種の移動・滞留と生態系濃縮の評価

  日本学術振興会：科学研究費助成事業

  研究期間 : 2012年05月 -2015年03月 

  代表者 : 五味 高志, 戸田 浩人, 木村 園子ドロテア, 渡邊 裕純, 浅野 友子, 水垣 滋, 布川 雅典, 根岸 淳二郎

   

  森林－渓流生態系の構成物質では、林床落葉の放射性セシウム濃度が最も高く、福島原発事故によって放出された放射性物質の多くは、陸域に現存していた。流域のCs-137空間分布は、林相、微地形、立地などに影響されていた。森林土壌では、農地土壌と比べて有機物に吸着したCs-137が多かった。森林から渓流に供給されたリターは、溶脱によって放射性セシウムが流出し、CS-137濃度は林床の２５％程度であった。これに応じて、同じ栄養段階の生物では、林床に生息するものより渓流に生息する動物でCs-137濃度が高くなっていた。本研究結果から、有機物に付着したCs-137の長期的な観測の重要性を示唆できた。
• 自然河川、農業用水路、および湧水に注目した流域スケールの生物多様性維持機構の解明

  日本学術振興会：科学研究費助成事業

  研究期間 : 2012年04月 -2015年03月 

  代表者 : 根岸 淳二郎

   

  第一に、絶滅危惧種であるイシガイ類二枚貝は下流河川との連続性が高い農業用水路に高い確率で生息し、同所的に豊かな魚類相の生息が確認された。また、そのような生息地は、開発地割合の低い景観構造を有する地域に存在した。第二に、河跡湖における水草種数は水草繁茂面積と正の相関を持ち、生息地の質は、人工的にショートカットされた水域で最も低かった。第三に、湧水河川には特徴的な水生昆虫相が確認され、流域スケールでの分類群多様性に貢献していた。これらより、地形や湧水に着目して景観スケールで流水環境をﾀｲﾌﾟ分けすることで効率的な水生生物多様性保全が行える可能性が示唆された。
• 生態系の連結性が生物多様性に与える影響とその再生手法に関する研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 2011年04月 -2015年03月 

  代表者 : 中村 太士, 鈴木 透, 山浦 悠一, 森本 淳子, 永山 滋也, 根岸 淳二郎, 赤坂 卓美, 石山 信雄, 末吉 正尚, 曽我 昌史, 松林 順, 藪原 佑樹, 山中 聡, 先崎 理之

   

  様々な生態系における「連結性」に注目し、その機能と再生方法を検討した。氾濫原や河川水域においては、水域間の連結性と魚類・水生昆虫の種および遺伝的多様性を検討した。その結果、連結性の高い水域において移動性の高い分類群の種数が高いこと、ならびに個体数および遺伝的多様性が影響を受ける距離が異なることが明らかになった。さらに、安定同位体を用いた食物網の解析から、明治以降の開発による景観の分断化が進み、ヒグマの食性が肉食から草食に大きく変化していることが明らかになった。蛇行復元による氾濫原の修復を試みた結果、水生動物の個体数、種多様性が増加したことが明らかになった。
• 流域保全に向けた河川中流域における河床露盤化の実態把握と影響評価

  日本学術振興会：科学研究費助成事業

  研究期間 : 2009年 -2011年 

  代表者 : 根岸 淳二郎

   

  木曽川中流域では河床低下の進行とともに本流域河床基質が砂礫から泥炭へ変化していた。水深20メートルを超える局所洗掘が見られ、泥炭基質が剥離すると下層に位置する浸食に対して脆弱な砂層が水平方向に大きく洗掘される可能性が示唆された。また、拡大しつつある泥炭基質はオオシロカゲロウ(Ephoron shigae)の主要な生息地であり、大量羽化を行う成熟個体の主要な発生起源として機能している可能性が示唆された。

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