研究者情報

マスター

アカウント（マスター）

• 氏名

  工藤　岳(クドウ　ガク), クドウ　ガク

所属（マスター）

• 地球環境科学研究院　環境生物科学部門　陸域生態学分野

所属（マスター）

• 地球環境科学研究院　環境生物科学部門　陸域生態学分野

独自項目

syllabus

• 2021, 植物生態学特論Ⅱ, Advanced Course in Plant Ecology II, 修士課程, 環境科学院, 繁殖生態学、進化生態学、適応、生活史、生物間相互作用、被食防衛系、送粉系、植物生態学 reproductive ecology, evolutionary ecology, adaptation, life-history, biological interaction, defensive system, pollination system, plant ecology
• 2021, 大学院共通授業科目（一般科目）：自然科学・応用科学, Inter-Graduate School Classes(General Subject):Natural and Applied Sciences, 修士課程, 大学院共通科目, 生態学、北方生態系、北海道、植物、動物、昆虫、魚類、森林、山岳、ツンドラ、沿岸、河川、湿原、相互作用、外来種、野生作物、気候変動 ecology, northern ecosystem, Hokkaido, plants, animals, insects, fishes, forest, mountain, tundra, seacoast, river, wetland, interaction, invasive species, field crop, climate change
• 2021, 北方生態系の生物多様性基礎論, Fundamental Course in Biodiversity of Northern Ecosystems, 修士課程, 環境科学院, 生態学、北方生態系、北海道、植物、動物、昆虫、魚類、森林、山岳、ツンドラ、沿岸、河川、湿原、相互作用、外来種、野生作物、気候変動 ecology, northern ecosystem, Hokkaido, plants, animals, insects, fishes, forest, mountain, tundra, seacoast, river, wetland, interaction, invasive species, field crop, climate change

researchmap

プロフィール情報

学位

• 博士（環境科学）（北海道大学）

プロフィール情報

• 姓

  工藤, クドウ

• 名

  岳, ガク

• ID各種

  200901066415106873

対象リソース

http://hosho.ees.hokudai.ac.jp/~gaku/index-j.html

業績リスト

研究キーワード

• 高山生態系   フェノロジー   気候変動生態学   繁殖生態学   植物生態学   Reproductive Ecology   Plant Ecology   

研究分野

• ライフサイエンス / 生態学、環境学

経歴

• 1994年 - 2000年 北海道大学大学院地球環境科学研究科助手 助手
• 1994年 - 2000年 Research Associate
• 2000年 - 北海道大学大学院地球環境科学研究科助教授 助教授
• 2000年 - Associate Professor

委員歴

• 2009年 - 2013年   日本生態学会   全国委員   日本生態学会
• 2007年   日本生態学会   英文誌編集員   日本生態学会

受賞

• 2020年03月 日本生態学会 日本生態学会賞
   

  受賞者: 工藤岳
• 1997年03月 日本生態学会 日本生態学会宮地賞
   

  受賞者: 工藤岳

論文

• General and specific effects of foundation species on the structure of alpine‐fellfield communities in the Taisetsu Mountains, northern Japan

  Zaal Kikvidze, Gaku Kudo, Maki Suzuki, Yoshiko Shimono, Mikio Sukeno

  Ecological Research 2024年06月19日 

  Abstract The great majority of studies on foundation species focused on a single dominant plant in a community, while more than one such species can often coexist and compete for space and limited resources. Morphologically different coexisting foundation species can create diverse niches occupied by different subsets of beneficiary species. To test this hypothesis, we sampled alpine plant communities at exposed fellfields in alpine zone, in the Taisetsu Mountains (Hokkaido, northern Japan), with coexisting putative foundation species Pinus pumila (evergreen shrub) and Diapensia lapponica (evergreen cushion‐forming shrub), and analyzed their spatial relationships with other plants. Preliminary vegetation survey indicated that fruticose lichens and Loiseleuria procumbens (evergreen mat‐forming shrub) might also act as a foundation species; thus, we included them in our analyses. The coexisting foundation species had both general as well as specific effects on plant community structure. Namely, almost all the members of the community aggregated spatially with lichens, while the other foundation species were spatially segregated from each other. These foundation plants associated with different members of the community, thus showing species‐specific effects on the community structure. Blooming species showed even stronger patterns of species‐specific spatial associations, suggesting that foundation species had beneficial effects on their associated species. We conclude that the focus on coexisting foundation species can reveal important details of community structure which would be hidden if we treated all species as equal members of the community. Studying the effects of coexisting foundation species could greatly advance our understanding of how species diversity functions in plant communities.
• Night and day: Contributions of diurnal and nocturnal visitors to pollen dispersal, paternity diversity and fruit set in an early‐blooming shrub, Daphne jezoensis

  Akari Shibata, Gaku Kudo

  American Journal of Botany 2023年09月05日 

  Abstract Premise Under uncertain pollinator visit conditions, plants often exhibit long flowering periods and generalized pollination systems. Flowering of the gynodioecious shrub Daphne jezoensis occurs early in spring in cool temperate forests. Pollination by nocturnal moths is expected due to tubular‐shaped flowers with sweet fragrance and nectar. However, the effectiveness of nocturnal moths under cool conditions remains unknown. In this study, we evaluated the relative importance of diurnal and nocturnal visitors as pollinators in early spring. Methods Flowering duration, flower visitors, and floral scents were investigated in a natural population. We experimentally exposed flowers to visitors only during daytime or nighttime by bagging treatments and evaluated the contributions of diurnal and nocturnal insects to fruit set, pollen dispersal distance, and paternity diversity using 16 microsatellite markers. Key results Female flowers lasted approximately 3 weeks, which was approximately 8 days longer than that of hermaphrodites. Various insects, including Coleoptera, Diptera, Hymenoptera, and Lepidoptera, visited the flowers during both daytime and nighttime. Flowers emitted volatiles, such as lilac aldehyde isomers and β‐ocimene, which are known to attract moths. Fruit‐set in the night‐open treatment was similar to or higher than in the day‐open treatment. However, the pollen dispersal distance in the night‐open treatment was shorter than in the day‐open treatment. Paternity diversity was similar in day‐open and night‐open treatments. Conclusions Early‐blooming plants ensure pollen receipt and dispersal by having a long flowering period and using both diurnal and nocturnal flower visitors, suggesting the importance of a generalized pollination system under uncertain pollinator visit conditions. This article is protected by copyright. All rights reserved.
• For the love of insects: gardening grows positive emotions (biophilia) towards invertebrates

  Amelie Vanderstock, Cecilia Grandi-Nagashiro, Gaku Kudo, Tanya Latty, Shoko Nakamura, Thomas E. White, Masashi Soga

  JOURNAL OF INSECT CONSERVATION 26 5 751 - 762 2022年10月 

  As growing urban populations have fewer chances to experience nature, i.e., 'the extinction of experience', the subsequent loss of emotional affinities for biodiversity (biophilia) pose major challenges to environmental conservation. Gardening, as an everyday nature interaction and window into invertebrate ecological functioning may offer opportunities to develop biophilia. However, the associations between gardening and biophilia/biophobia towards invertebrates remains untested. We conducted an online survey (n = 443) with adults in Japan about their nature and gardening experiences, demographics, and species identification knowledge in relation to their biophilia (like) and biophobia (dislike, fear, and disgust) towards invertebrates. We also asked participants about their perceptions of invertebrates as 'beneficials' or 'pests'. From responses, we ranked invertebrates according to the attitudes held towards them. We found that frequent gardeners were more likely to express biophilia and perceive invertebrates as beneficial, and generally less likely to express biophobia towards invertebrates. Frequency of visits to recreational parks, but not national/state parks was associated with increased biophilia and reduced dislike and fear of invertebrates. Our results suggest that gardening, in addition to localised nature experiences, acts as a possible pathway towards appreciation of invertebrate biodiversity. We recommend that policymakers and conservation organisations view urban gardening as a potential tool to minimise the negative impacts of the extinction of experience. Implications for insect conservation As people are more likely to conserve what they love, finding ways to nurture positive attitudes towards insects is critical for the public support needed for successful insect conservation. Considering gardening is a relatively accessible form of nature connection even in cities, our findings of the association between gardening and biophilia towards invertebrates holds promise for potential pathways towards fostering support for insect conservation now and into the future.
• Conservative seed fertility maintains hermaphrodites in gynodioecious Daphne jezoensis : a test of the sex‐differential plasticity hypothesis

  A. Shibata, G. Kudo

  Plant Biology 24 6 1022 - 1030 2022年08月04日
• Low seed fertility of hermaphrodites is maintained in a gynodioecious species throughout the distribution range in Japan

  Shibata A, Kameyama Y, Kudo G

  Plant Systematic and Evolution 307 55  2021年08月 [査読有り]
  
• Climate change shifts population structure and demographics of an alpine herb, Anemone narcissiflora ssp. sachalinensis (Ranunculaceae), along a snowmelt gradient

  Yuka Kawai, Gaku Kudo

  Population Ecology 63 3 260 - 271 2021年07月 [査読有り]
  
• Seasonal variation in air temperature drives reproductive phenology of entomophilous plants in a cool-temperate mire community

  Takashi Y. Ida, Gaku Kudo

  Botany 99 7 433 - 447 2021年07月 [査読有り]
   

  Phenological responses of plants to temperature dynamics are receiving attention due to the ongoing challenge with climate change. Most previous phenological studies have focused on flowering phenology rather than fruiting phenology. However, at mid-latitudes, the air temperature periodically changes during the growing period of plants. Hence, cool temperatures early and late in the growing period may affect reproductive success through pollination and fruit-development processes. To evaluate the linkages between reproductive phenology and success, we compared the phenologies, photosynthetic capacities, and fruit-set rates among 25 species within a cool-temperate community in northern Japan. The ambient temperature during the flowering periods of individual species increased with delays in flowering-onset time, whereas the ambient temperature during fruit-development periods was highest for species which bloomed in July. Fruit-set success among species was positively correlated with the ambient temperatures during the reproductive periods and with the photosynthetic capacity. Fruit production of early blooming species was limited by cool temperatures during the flowering period, presumably because of low pollinator activity, whereas that of late-blooming species was limited by cool temperatures during the fruit-development period because of slow fruit-development (i.e., sink limitation). Thus, limiting factors of fruit production varied depending on the flowering phenology of individual species within a community.
• Ecotypic differentiation of a circumpolar Arctic-alpine species at mid-latitudes: variations in the ploidy level and reproductive system of Vaccinium vitis-idaea

  Akimi Wakui, Gaku Kudo

  AoB PLANTS 13 3 2021年06月01日 [査読有り]
   

  Although plant species originated from Arctic regions commonly grow in alpine habitats at mid-latitudes, some populations of these species exist also in some specific habitats below the treeline. Local populations at lower elevations may have different origins, ploidy levels, mating systems and/or morphological traits from alpine populations, but comparative studies between alpine and low-elevation populations are scarce. We aimed to reveal the ecological and genetic differentiations between higher and lower populations of Vaccinium vitis-idaea in Hokkaido, northern Japan by comparing 22 populations growing in diverse environments. We analysed the ploidy level of individual populations using flow cytometry. Genetic differentiation among populations, and genetic diversity within populations were calculated using microsatellite markers. Fruit and seed production were recorded under natural conditions, and a pollination experiment was conducted to reveal the variations in mating system across populations. Furthermore, we compared shoot growth and leaf characteristics among populations. Most of the low-elevation populations were tetraploid, whereas all but one of the alpine populations were diploid. Tetraploid populations were clearly differentiated from diploid populations. Some tetraploid populations formed huge clonal patches but genetic diversity was higher in tetraploids than in diploids. Alpine diploids were self-incompatible and produced more seeds per fruit than tetraploid populations. In contrast, tetraploids showed high self-compatibility. Leaf size and foliar production were greater in tetraploid populations. Our results indicate that the genetic compositions of low-elevation tetraploid populations are different from those of alpine diploid populations. Most populations at lower elevations contained unique ecotypes suited to persistence in isolated situations. Local, low-elevation populations of typical alpine species maintain ecologically and genetically specific characteristics and could be valuable in terms of evolutionary and conservation biology. The present study demonstrates the biological importance of small and isolated populations at the edges of species distribution.
• Is increased male flower production a strategy for avoidance of predispersal seed predation in andromonoecious plants?

  Gaku Kudo, Akari Shibata

  Ecology and Evolution 11 10 5646 - 5656 2021年05月 [査読有り]
  
• Habitat-specific effects of flowering advance on fruit-set success of alpine plants: a long-term record of flowering phenology and fruit-set success of Rhododendron aureum

  Gaku Kudo

  Alpine Botany 131 1 53 - 62 2021年04月 [査読有り]
  
• Floral abundance and bee density affect species-specific foraging patterns of alpine bumble bees

  Akari Shibata, Gaku Kudo

  Arthropod-Plant Interactions 14 6 771 - 783 2020年12月 [査読有り]
  
• Belowground impacts of alpine woody encroachment are determined by plant traits, local climate, and soil conditions

  Courtney G. Collins, Marko J. Spasojevic, Concepción L. Alados, Emma L. Aronson, Juan C. Benavides, Nicoletta Cannone, Chatrina Caviezel, Oriol Grau, Hui Guo, Gaku Kudo, Nikolas J. Kuhn, Jana Müllerová, Michala L. Phillips, Nuttapon Pombubpa, Frédérique Reverchon, Hannah B. Shulman, Jason E. Stajich, Alexia Stokes, Sören E. Weber, Jeffrey M. Diez

  Global Change Biology 26 12 7112 - 7127 2020年12月 [査読有り]
  
• Geographical distribution, genetic diversity, and reproductive traits of mixed polyploid populations in Parasenecio kamtschaticus (Senecioneae; Asteraceae)

  Gaku Kudo, Akira S. Hirao

  Plant Systematics and Evolution 306 5 2020年10月 [査読有り]
  
• Dynamics of flowering phenology of alpine plant communities in response to temperature and snowmelt time: Analysis of a nine-year phenological record collected by citizen volunteers

  Gaku Kudo

  Environmental and Experimental Botany 170 103843 - 103843 2020年02月 [査読有り]
  
• Intraspecific differentiation in the root system of Potentilla matsumurae along a snow accumulation gradient in mid-altitude alpine environment

  Kobayashi Makoto, Gaku Kudo

  Arctic, Antarctic, and Alpine Research 52 1 408 - 415 2020年01月01日 [査読有り]
  
• The influence of garden flowers on pollinator visits to forest flowers: comparison of bumblebee habitat use between urban and natural areas

  Shoko Nakamura, Gaku Kudo

  Urban Ecosystems 22 6 1097 - 1112 2019年12月 [査読有り]
   

  As garden plants in urbanized environments provide considerable diverse floral resources to pollinators, the availability of floral resources has changed as a consequence of increasing urbanization. Although pollinators often forage at different sites in response to spatiotemporal variations in floral resources, little is known about the differences in pollinator foraging between urban and nearby natural environments. We monitored the foraging patterns of bumblebees in open and forest habitats in two areas with and without urban gardens with respect to flowering phenology and the availability of floral resources in each habitat. Floral richness in the forest habitat decreased as the season progressed, with a peak in late spring to early summer, whereas floral resources in the open habitat increased late in the season. Thus, floral resources in the open habitat could compensate for seasonal declines in forest floral resources. In the urban area, which contained green gardens, floral richness in the open habitat was much greater than that in the forest habitat. This resulted in a relatively high density of bumblebees in the open habitat in the urban area compared with those in the natural area, which lacked green gardens. Visitation frequency of bumblebees to forest flowers decreased as the floral richness of the open habitat increased. These results suggest that although urban gardens are important foraging sites for pollinators, the high attractiveness of garden flowers reduces pollinator visits to wildflowers in nearby forests. This may result in reduced pollination of native flowers.
• Theory of coevolution of cytoplasmic male-sterility, nuclear restorer and selfing

  Atsushi Yamauchi, Takahiro Yamagishi, Ross Booton, Arndt Telschow, Gaku Kudo

  Journal of Theoretical Biology 477 96 - 107 2019年09月 [査読有り]
  
• Habitat use and floral resource partitioning of native and alien bumblebees in the coastal grassland—rural landscape

  Yoko Nishikawa, Takashi Shimamura, Gaku Kudo, Kazuo Yabe

  Journal of Insect Conservation 23 4 677 - 687 2019年08月 [査読有り]
  
• When spring ephemerals fail to meet pollinators: mechanism of phenological mismatch and its impact on plant reproduction

  Gaku Kudo, Elisabeth J. Cooper

  Proceedings of the Royal Society B: Biological Sciences 286 1904 20190573 - 20190573 2019年06月12日 [査読有り]
   

  The flowering phenology of early-blooming plants is largely determined by snowmelt timing in high-latitude and high-altitude ecosystems. When the synchrony of flowering and pollinator emergence is disturbed by climate change, seed production may be restricted due to insufficient pollination success. We revealed the mechanism of phenological mismatch between a spring ephemeral ( Corydalis ambigua ) and its pollinator (overwintered bumblebees), and its impact on plant reproduction, based on 19 years of monitoring and a snow removal experiment in a cool-temperate forest in northern Japan. Early snowmelt increased the risk of phenological mismatch under natural conditions. Seed production was limited by pollination success over the 3 years of the pollination experiment and decreased when flowering occurred prior to bee emergence. Similar trends were detected on modification of flowering phenology through snow removal. Following snowmelt, the length of the pre-flowering period strongly depended on the ambient surface temperature, ranging from 4 days (at greater than 7°C) to 26 days (at 2.5°C). Flowering onset was explained with an accumulated surface degree-day model. Bumblebees emerged when soil temperature reached 6°C, which was predictable by an accumulated soil degree-day model, although foraging activity after emergence might depend on air temperature. These results indicate that phenological mismatch tends to occur when snow melts early but subsequent soil warming progresses slowly. Thus, modification of the snowmelt regime could be a major driver disturbing spring phenology in northern ecosystems.
• Ecotypic divergences of the alpine herb Potentilla matsumurae adapted to fellfield–snowbed habitats across a series of mountain sky islands

  Akira S. Hirao, Yoshiko Shimono, Kenji Narita, Naoya Wada, Gaku Kudo

  American Journal of Botany 106 6 772 - 787 2019年06月 [査読有り]
   

  PREMISE: Divergent selection due to environmental heterogeneity can lead to local adaptation. However, the ecological and evolutionary processes of local adaptation that occurs across multiple regions are often unknown. Our previous studies reported on the ecotypic divergence within a local area of variation of Potentilla matsumurae, an alpine herb adapted to the fellfield-snowbed environment. Here we investigated large-scale geographic patterns of ecotypic differentiation in this species to infer local adaptation and selective forces across multiple regions. METHODS: We compiled information on the overall distributions of fellfield and snowbed habitats on the mountains in Japan across the distribution of the species. Next, we conducted common garden experiments to test the adaptive divergence of the fellfield-snowbed plants derived from multiple regions. Finally, we evaluated phylogeographic structures based on cpDNA and allozyme variations and inferred the evolutionary history of ecotype differentiation. RESULTS: The mosaic distribution of the fellfield-snowbed ecotypes across isolated mountaintops constitutes indirect evidence for habitat-specific natural selection. The significant difference in survivorship between the ecotypes observed in a controlled snow environment provides more substantial evidence of local selection. Phylogeographic structures support the hypothesis that ecotypic divergence events from fellfield to snowbed populations occurred independently in at least two distinct regions. CONCLUSIONS: Ecotypic divergence of P. matsumurae has occurred across a series of mountain sky islands. Local selection in snowy environments is a driving force that maintains the divergent ecotypes across multiple mountain regions and can contribute to the diversification of plants in heavy-snow regions.
• Responses of photochemical efficiency and shoot growth of alpine dwarf-pine Pinus pumila to experimental warming, shading, and defoliation in Japan

  Amagai Yukihiro, Kudo Gaku

  ALPINE BOTANY 129 1 43 - 52 2019年04月 [査読有り][通常論文]
  
• Association between community assemblage of flower colours and pollinator fauna: a comparison between Japanese and New Zealand alpine plant communities

  Ishii Hiroshi S, Kubota Masahiro X, Tsujimoto Shohei G, Kudo Gaku

  ANNALS OF BOTANY 123 3 533 - 541 2019年02月15日 [査読有り][通常論文]
  
• Variations in ramet performance and the dynamics of an alpine evergreen herb, Gentiana nipponica, in different snowmelt conditions

  Kawai Yuka, Kudo Gaku

  AMERICAN JOURNAL OF BOTANY 105 11 1813 - 1823 2018年11月 [査読有り][通常論文]
  
• Changes in alpine plant communities under climate change: Dynamics of snow-meadow vegetation in northern Japan over the last 40 years

  Amagai Yukihiro, Kudo Gaku, Sato Ken

  APPLIED VEGETATION SCIENCE 21 4 561 - 571 2018年10月 [査読有り][通常論文]
  
• Altered morphologies and physiological compensation in a rapidly expanding dwarf bamboo in alpine ecosystems

  Kudo Gaku, Aoshima Yuta, Miyata Rie, Winkler Daniel E

  Arctic Antarctic and Alpine Research 50 1 2018年06月20日 [査読有り][通常論文]
   

  Dwarf bamboos are evergreen woody grasses that produce large clonal patches and dominate the understories of the montane to subalpine zones of northern Japan. Recently, dwarf bamboos have expanded their distribution to above the treeline and into alpine meadows. To clarify the mechanism of rapid invasion into the alpine, we compared the morphological performance, biomass allocation, photosynthetic activity, CO2 fixation ability, and sensitivity to temperature of dwarf bamboos in their native montane and expanding alpine sites in the Taisetsu Mountains. Alpine bamboo produced shorter but denser aboveground structures, where leaves were smaller and branching was more frequent. The total biomass of alpine bamboo was nearly half of that produced by montane bamboo. Montane bamboo produced more stems, while alpine bamboo invested more carbon in belowground structures. CO2 fixation per land area by alpine bamboo was 1.3 times higher than rates observed in montane bamboo. Optimal temperatures for photosynthesis were lower in alpine bamboo (15-20 degrees C) than in montane bamboo (20-25 degrees C), probably because of the rapid decrease in stomatal conductance at higher temperatures (>20 degrees C) observed in the alpine site. Overall, leaf transpiration rates were higher in alpine bamboo, but water-use efficiency was similar between sites. A high flexibility in both morphological and physiological characteristics enabled dwarf bamboos to expand into alpine environments in response to recent climate change.
• Restricted female function of hermaphrodites in a gynodioecious shrub, Daphne jezoensis (Thymelaeaceae)

  Akari Shibata, Yoshiaki Kameyama, Gaku Kudo

  Journal of Plant Research 131 2 245 - 254 2018年03月01日 [査読有り][通常論文]
   

  Gynodioecy is the coexistence of hermaphrodites and females in a population. It is supposed to be an intermediate stage in the evolutionary pathway from hermaphroditism to dioecy in angiosperm. Hermaphrodites gain fitness through both seed and pollen production whereas females gain fitness only through seed production. As females spread in a gynodioecious population, sexual selection prompts hermaphrodites to invest in male function and male-biased hermaphrodites prevail. In the gynodioecious shrub Daphne jezoensis (Thymelaeaceae), female frequency is stably around 50% in most populations, and fruit-set rate of hermaphrodites is commonly low. Therefore, D. jezoensis is likely at a later stage in the evolutionary pathway. Female function of hermaphrodites (fruit-set rate, selfing rate, seed size, and germination rate) was assessed in three populations under natural conditions. In order to evaluate the potential seed fertility and inbreeding depression by selfing in hermaphrodites, hand pollination treatments were also performed. Over a 2-year period under natural conditions, 18–29% of hermaphrodites and 69–81% of females set fruit. Across all three populations, the mean fruit-set rate ranged 9.5–49.2% in females and only 3.9–10.2% in hermaphrodites. Even with artificial outcross-pollination, 59–91% of hermaphrodites failed to set any fruit. When self-pollination was performed in hermaphrodites, both of fruit-set and germination rates were decreased, indicating early-acting inbreeding depression. In addition, more than half of the hermaphrodite seeds were produced by selfing under natural pollination, but pollinator service was still required. Totally, hermaphrodites performed poorly as seed producers because of the intrinsically-low fruiting ability and a combination of autogamous selfing and strong inbreeding depression, indicating the absence of reproductive assurance. These results indicate that the mating system of D. jezoensis is functionally close to dioecy.
• A linkage between flowering phenology and fruit-set success of alpine plant communities with reference to the seasonality and pollination effectiveness of bees and flies

  Yuki Mizunaga, Gaku Kudo

  OECOLOGIA 185 3 453 - 464 2017年11月 [査読有り][通常論文]
   

  To clarify the linkage between flowering phenology and pollination success in alpine plant communities, we quantified the seasonality of flower visitors, the temporal transition of floral resources, and the variation in pollination success of alpine plants in northern Japan. Bumble bees, syrphid flies, and non-syrphid flies were the predominant flower visitors. Foraging activity of bumble bees increased toward the late flowering period reflecting the life cycle of colony development. The activity of syrphid flies was sensitive to ambient temperature, while that of non-syrphid flies remained high throughout the season. Flower production of bee-pollinated plants fluctuated significantly between years with a bimodal pattern peaking in the early and late periods, while flower production of fly-pollinated plants was less variable between years. Fruit-set success of bee-pollinated plants increased considerably from the early to the late flowering period, while the trend for fly-pollinated plants was less marked. Three times more visits of dipteran insects are necessary for fly-pollinated plants to achieve fruiting success comparable to bee-pollinated plants. Bumble bees are potentially excellent pollinators, but the visitation frequency is low early in the season. Lower pollination ability of dipteran insects may be compensated for by abundant flower visits. The relationships between flowering phenology and fruit-set success of alpine plant communities highly depend on the type of pollinators.
• Degradation and recovery of an alpine plant community: experimental removal of an encroaching dwarf bamboo

  Gaku Kudo, Yuka Kawai, Yukihiro Amagai, Daniel E. Winkler

  ALPINE BOTANY 127 1 75 - 83 2017年04月 [査読有り][通常論文]
   

  The dwarf bamboo Sasa kurilensis has responded to recent climate change by expanding its distribution into alpine snow meadows in Japan. Tall, dense clonal patches of bamboo suppress alpine plant growth, alter ecosystem functioning, and reduce diversity. We aim to assess the ecological impacts of bamboo expansion and the effectiveness of bamboo control for restoring alpine vegetation and species diversity. We quantified the extent of bamboo expansion, its effects on an alpine ecosystem, and the recovery of species diversity by bamboo removal over 6 years in Daisetsuzan National Park, northern Japan. We established paired, experimental plots assigned to either removal or control treatments following an encroaching gradient from interior to terminal locations in a large bamboo patch. We monitored bamboo development and aboveground production, and its impact on soil moisture and species diversity to assess the recovery process of snow meadow species after its removal. In control plots, bamboo density consistently increased and accumulated biomass from year to year. In the removal treatment, bamboo culm density, height and biomass decreased through time at all locations. Furthermore, soil moisture increased in the removal plots and remained consistently higher than controls throughout the growing season. Dwarf bamboo strongly suppressed alpine plants and reduced species diversity. However, alpine snow meadow species rapidly recovered and diversity increased through time in the removal treatment. This study presents an effective management strategy for restoring alpine plant diversity impacted by bamboo expansion under global climate change.
• Degradation and recovery of an alpine plant community: experimental removal of an encroaching dwarf bamboo

  Gaku Kudo, Yuka Kawai, Yukihiro Amagai, Daniel E. Winkler

  ALPINE BOTANY 127 1 75 - 83 2017年04月 [査読有り][通常論文]
   

  The dwarf bamboo Sasa kurilensis has responded to recent climate change by expanding its distribution into alpine snow meadows in Japan. Tall, dense clonal patches of bamboo suppress alpine plant growth, alter ecosystem functioning, and reduce diversity. We aim to assess the ecological impacts of bamboo expansion and the effectiveness of bamboo control for restoring alpine vegetation and species diversity. We quantified the extent of bamboo expansion, its effects on an alpine ecosystem, and the recovery of species diversity by bamboo removal over 6 years in Daisetsuzan National Park, northern Japan. We established paired, experimental plots assigned to either removal or control treatments following an encroaching gradient from interior to terminal locations in a large bamboo patch. We monitored bamboo development and aboveground production, and its impact on soil moisture and species diversity to assess the recovery process of snow meadow species after its removal. In control plots, bamboo density consistently increased and accumulated biomass from year to year. In the removal treatment, bamboo culm density, height and biomass decreased through time at all locations. Furthermore, soil moisture increased in the removal plots and remained consistently higher than controls throughout the growing season. Dwarf bamboo strongly suppressed alpine plants and reduced species diversity. However, alpine snow meadow species rapidly recovered and diversity increased through time in the removal treatment. This study presents an effective management strategy for restoring alpine plant diversity impacted by bamboo expansion under global climate change.
• Environmental factors determining the distribution of highland plants at low-altitude algific talus sites

  Akimi Wakui, Masanao Sueyoshi, Ayuma Shimokawabe, Gaku Kudo, Junko Morimoto, Futoshi Nakamura

  ECOLOGICAL RESEARCH 32 2 183 - 191 2017年03月 [査読有り][通常論文]
   

  Algific talus is a micro-scale habitat type where highland plants (subalpine and alpine species) are found, disjunct from their typical range, in lowland forests. On algific talus, cold airflows from the interstices between talus fragments create a local microclimate colder than surrounding forests. Despite of the widely-known occurrence of unique vegetation on algific talus, critical environmental factors determining the distribution of highland species in this habitat type are unclear. In order to reveal the environmental factors enabling highland species to inhabit algific talus, we investigated the vegetation and environments of 26 algific talus sites and four reference (non-algific talus) sites in Hokkaido, northern Japan. Several algific talus sites were dominated by highland species, while some algific talus sites and all non-algific talus sites were dominated by lowland species. Community analysis based on detrended correspondence analysis (DCA) and canonical corresponding analysis (CCA) revealed that the algific talus sites dominated by highland species had lower ground temperature, more acidic soil, larger canopy openness, and less diverse vegetation than the sites dominated by lowland species. Highland plants might be maintained under conditions stressful for lowland plants, resulting in less competitive situation. Generalized linear models (GLM), used to evaluate the response of individual highland species to environmental factors, revealed that preferable environmental conditions for highland plants are highly species specific. These results indicate that the maintenance of diverse environments is crucial for the conservation of the unique vegetation and local populations of highland species in algific talus areas.
• Elevation alters ecosystem properties across temperate treelines globally

  Jordan R. Mayor, Nathan J. Sanders, Aimee T. Classen, Richard D. Bardgett, Jean-Christophe Clement, Alex Fajardo, Sandra Lavorel, Maja K. Sundqvist, Michael Bahn, Chelsea Chisholm, Ellen Cieraad, Ze'ev Gedalof, Karl Grigulis, Gaku Kudo, Daniel L. Oberski, David A. Wardle

  NATURE 542 7639 91 - + 2017年02月 [査読有り][通常論文]
   

  Temperature is a primary driver of the distribution of biodiversity as well as of ecosystem boundaries(1,2). Declining temperature with increasing elevation in montane systems has long been recognized as a major factor shaping plant community biodiversity, metabolic processes, and ecosystem dynamics(3,4). Elevational gradients, as thermoclines, also enable prediction of long-term ecological responses to climate warming(5-7). One of the most striking manifestations of increasing elevation is the abrupt transitions from forest to treeless alpine tundra(8). However, whether there are globally consistent above-and belowground responses to these transitions remains an open question(4). To disentangle the direct and indirect effects of temperature on ecosystem properties, here we evaluate replicate treeline ecotones in seven temperate regions of the world. We find that declining temperatures with increasing elevation did not affect tree leaf nutrient concentrations, but did reduce ground-layer community-weighted plant nitrogen, leading to the strong stoichiometric convergence of ground-layer plant community nitrogen to phosphorus ratios across all regions. Further, elevation-driven changes in plant nutrients were associated with changes in soil organic matter content and quality (carbon to nitrogen ratios) and microbial properties. Combined, our identification of direct and indirect temperature controls over plant communities and soil properties in seven contrasting regions suggests that future warming may disrupt the functional properties of montane ecosystems, particularly where plant community reorganization outpaces treeline advance.
• 気候変動に対する高山植物の応答

  工藤 岳

  日本地理学会発表要旨集 2017 100089 - 100089 公益社団法人 日本地理学会 2017年 

  高山生態系は最も気候変動に脆弱な生態系と考えられる。その理由として、寒冷環境に適応した生物群集から構成されていること、生態系の規模が小さく、隔離分布していること、多くの希少種・固有種から群集が構成されていること、生物の年生育期間が短いこと、微細なモザイク環境から生態系が構成されていることなどが挙げられる。日本の高山生態系は世界有数の豪雪地域に成立しており、高山生態系の生物多様性は、多様な積雪環境と雪解け時期の違いにより維持されている。したがって、気温変化のみならず、積雪環境の変動は、高山生態系に大きな影響をもたらすと予測される。気候変動に対する生物の応答は、(1) 生理的影響、(2) 分布変化、(3) 季節性の変化（フェノロジー）として現れ、その結果、生態系構造の変化や生物群集の多様性の変化が生じる。気候変動が高山生態系の構造と機能に及ぼす影響を検出・予測するには、長期モニタリングによるデータ集積が不可欠である。北海道大雪山系は日本最大の高山生態系であり、多くの高山植物が生育している。高山帯の年平均気温は近年、0.3 ºC / 10年のペースで上昇しており、雪解け時期は4日/ 10年のペースで早まっている。この変化と連動して、様々な生態系の変化が生じている。例えば、湿生植物群落（湿生お花畑）の急速な消失が報告されており、これは雪解けの早期化と夏季の気温上昇による土壌乾燥化の結果、湿生植物の種子生産が減少したためと考えられる（生理的乾燥ストレス）。また、森林帯に分布中心を持つチシマザサの分布域が急速に拡大し、高山植物群落への侵入が加速していることが示された。ササのような競合種の分布拡大は、高山植物群落の種多様性を低下させると危惧される。高山植物の種数はササの密度増大に伴い急速に減少し、ササの除去によって回復することが実験的にも示された。さらに、高山植物群落の開花フェノロジーは、気温や雪解け時期の変化に対して大きく変動することがモニタリング調査により明らかになった。シミュレーションの結果、夏の気温が１ºC上昇すると高山植物群落の開花ピーク期間（平年48.9日間）は5.7日短縮し、雪解けが10日早まることにより開花ピーク期間は7.8日短縮されると予想された。開花期間の短縮により、花資源を利用するマルハナバチなどの訪花昆虫も影響を受けることが予測される。以上の研究成果から、気候変動に伴う生物の個体群変動、分布域の変化、季節性の変化などがすでに高山生態系に現れていることが明らかとなった。気候変動を踏まえた高山生態系における生物多様性の減少、機能的影響評価、ならびに保全管理計画への取り組みが急務である。
• Size-dependent sex allocation and reproductive investment in a gynodioecious shrub

  Akari Shibata, Gaku Kudo

  AOB PLANTS 9 plw089 2017年 [査読有り][通常論文]
   

  In sexually dimorphic plants, resource allocation to reproduction often differs between sex morphs. In gynodioecious species, i.e. coexisting hermaphrodite and female plants within a population, females often produce more fruits than hermaphrodites. Since fruit production is costlier than flower production, hermaphrodites and females may regulate flower and fruit production differently in response to resource availability. To clarify the gender specific strategies of reproductive allocation, we assessed sexual dimorphism in reproductive traits, size-dependent resource allocation, morphological traits, and photosynthetic capacity in a natural population of a gynodioecious shrub, Daphne jezoensis. Hermaphrodites had larger flowers and increased flower number with plant size at a rate greater than females, but showed consistently smaller fruit production. Although females did not increase flower production as much as hermaphrodites did as their size increased, they produced 3.7 times more fruits than did hermaphrodites. Despite a large sexual difference in fruiting ability based on hand-pollination, total resource investment in reproduction (the sum of flower and fruit mass) was similar between sex morphs across plant sizes, and there was a little sexual difference in the cost of reproduction, i.e. the negative effect of current reproduction on future reproductive effort, in the natural population. In addition, there were no sexual differences in the resource allocation to vegetative organs (leaf and root mass) and photosynthetic capacity (light response photosynthetic rates). Under natural conditions, pollen limitation strongly restricted the fruit production of females, resulting in similar cost of reproduction between hermaphrodites and females.
• Genetic structure of Vaccinium vitis-idaea in lowland cool spot and alpine populations: microrefugia of alpine plants in the midlatitudes

  Ayuma Shimokawabe, Yuichi Yamaura, Masanao Sueyoshi, Gaku Kudo, Futoshi Nakamura

  ALPINE BOTANY 126 2 143 - 151 2016年10月 [査読有り][通常論文]
   

  Local cool spots (wind-holes) in lowland areas of midlatitudes may act as microrefugia for cold-adapted species outside of their typical alpine habitats. We examined the genetic structure of Vaccinium vitis-idaea, a common alpine species in Japan, in eight lowland wind-hole and five surrounding alpine populations. We collected leaf samples and genotyped seven microsatellite loci. Clonal patches (genets) were common in almost all populations. An analysis of annual shoot growth suggested that individuals in the wind-hole populations were long-lived (> 500 years old). Genetic diversity (allelic richness) and differentiation (F (ST)) of the wind-hole populations were lower and higher than those of the alpine populations, respectively. No significant isolation-by-distance trend in the genetic structure was detected for the wind-hole or alpine populations. All wind-hole populations had negative inbreeding coefficients (F (IS)), suggesting no tendency toward homozygosity due to inbreeding, regardless of the small populations geographically isolated from the large alpine populations. Therefore, wind-holes may harbor genetically isolated but stable populations due to clonal growth, limited gene flow, and abortion of selfed seeds by early acting inbreeding depression. Analysis of molecular variance demonstrated that genetic variations among and within populations contributed more to regional genetic diversity than those between wind-hole and alpine populations, suggesting that the wind-hole and alpine populations are important for maintaining the genetic diversity of midlatitude V. vitis-idaea populations. On the other hand, Bayesian clustering showed that some wind-hole populations geographically close to the alpine populations had mixed genetic compositions of the alpine and wind-hole populations.
• Seasonal dry-down rates and high stress tolerance promote bamboo invasion above and below treeline

  Daniel E. Winkler, Yukihiro Amagai, Travis E. Huxman, Masami Kaneko, Gaku Kudo

  PLANT ECOLOGY 217 10 1219 - 1234 2016年10月 [査読有り][通常論文]
   

  How species invasions impact ecosystem structure and function at important ecotones or boundaries is unknown, but may provide insight into the impacts of climate change and the mechanisms underlying community change. The dwarf bamboo, Sasa kurilensis, may be a good system to understand these issues, as the species impacts ecosystem features as it encroaches beyond treeline into alpine systems. We used remote sensing imagery spanning a 35 year period to quantify S. kurilensis expansion patterns across its range, measured growth and stress tolerances of S. kurilensis above and below treeline, and evaluated components of growth to reveal how shifts in light and water limitations influence the ontogeny of height, branching, and leaf production. We show that S. kurilensis more than doubled its abundance across its range, but more than tripled its abundance near and above treeline. Soil dry-down rates were a key driver of invasion above and below treeline, where growth rates decreased with more rapid rates of soil moisture dry-down. We found S. kurilensis responds to competition and climate stress by increasing allocation to belowground structures at high elevations. Further, it invests more carbon in fewer-yet taller and heavier-aboveground structures in low-light, low elevation environments. It appears this species' success is driven by considerable morphological and physiological flexibility, coupled with changes in water balance associated with snowmelt that in each habitat results in sites increasingly hospitable to bamboo. Overall, this study links resource allocation strategies and physiological responses to climate change and provides a mechanistic explanation of invasion success.
• Male-biased hermaphrodites in a gynodioecious shrub, Daphne jezoensis

  J. P. Sinclair, Y. Kameyama, A. Shibata, G. Kudo

  PLANT BIOLOGY 18 5 859 - 867 2016年09月 [査読有り][通常論文]
   

  Gynodioecy, a state where female and hermaphrodite plants coexist in populations, has been widely proposed an intermediate stage in the evolutionary pathway from hermaphroditism to dioecy. In the gynodioecy-dioecy pathway, hermaphrodites may gain most of their fitness through male function once females invade populations. To test this prediction, comprehensive studies on sex ratio variation across populations and reproductive characteristics of hermaphrodite and female phenotypes are necessary. This study examined the variation in sex ratio, sex expression, flower and fruit production and sexual dimorphism of morphological traits in a gynodioecious shrub, Daphne jezoensis, over multiple populations and years. Population sex ratio (hermaphrodite:female) was close to 1:1 or slightly hermaphrodite-biased. Sex type of individual plants was largely fixed, but 15% of plants changed their sex during a 6-year census. Hermaphrodite plants produced larger flowers and invested 2.5 times more resources in flower production than female plants, but they exhibited remarkably low fruit set (proportion of flowers setting fruits). Female plants produced six times more fruits than hermaphrodite plants. Low fruiting ability of hermaphrodite plants was retained even when hand-pollination was performed. Fruit production of female plants was restricted by pollen limitation under natural conditions, irrespective of high potential fecundity, and this minimised the difference in resources allocated to reproduction between the sexes. Negative effects of previous flower and fruit production on current reproduction were not apparent in both sexes. This study suggests that gynodioecy in this species is functionally close to a dioecious mating system: smaller flower production with larger fruiting ability in female plants, and larger flower production with little fruiting ability in hermaphrodite plants.
• 19pBW-1 地球温暖化によって高山生態系(植生)に生じる「レジームシフト」の数理モデル解析

  矢吹 哲夫, 工藤 岳

  日本物理学会講演概要集 71 3174 - 3174 一般社団法人日本物理学会 2016年
• Foraging responses of bumble bees to rewardless floral patches: importance of within-plant variance in nectar presentation

  Shoko Nakamura, Gaku Kudo

  AOB PLANTS 8 plw037 2016年 [査読有り][通常論文]
   

  Spatiotemporal variation in nectar distribution is a key factor affecting pollinator movements between flowers and plants within a population. Pollinators having systematic searching ability can flexibly respond to the reward condition of floral patches, and they tend to revisit rewarding patches. However, foraging behaviour may be influenced by the nectar distribution within populations. To evaluate the effects of unrewarding experiences and plant distribution, we compared bumble bee foraging behaviours between naturally rewarding and artificially rewardless (by nectary removal) patches in two aconite populations with different plant densities. Visitation frequency to the patches, number of successive flower visits within inflorescences, and successive inflorescence visits within patches were recorded. Nectar production and standing crop were also measured. Bumble bees increased the movements between neighbouring inflorescences instead of leaving the patches when they faced rewardless flowers. A large variance in nectar production existed among flowers within plants. This might explain the observed bumble bee behaviour, because they could be rewarded by moving to the adjacent inflorescences even after a rewardless experience. Our results imply that a highly variable nectar reward in a population might mask the disadvantage of completely rewardless individuals.
• Short-term responses in maximum quantum yield of PSII (Fv/Fm) to ex situ temperature treatment of populations of bryophytes originating from different sites in Hokkaido, Northern Japan

  Annika K. J�gerbrand, Gaku Kudo

  Plants 5 2 455 - 465 2016年 [査読有り][通常論文]
   

  There is limited knowledge available on the thermal acclimation processes for bryophytes, especially when considering variation between populations or sites. This study investigated whether short-term ex situ thermal acclimation of different populations showed patterns of site dependency and whether the maximum quantum yield of PSII (Fv/Fm) could be used as an indicator of adaptation or temperature stress in two bryophyte species: Pleurozium schreberi (Willd. ex Brid.) Mitt. and Racomitrium lanuginosum (Hedw.) Brid. We sought to test the hypothesis that differences in the ability to acclimate to short-term temperature treatment would be revealed as differences in photosystem II maximum yield (Fv/Fm). Thermal treatments were applied to samples from 12 and 11 populations during 12 or 13 days in growth chambers and comprised: (1) 10/5 & #176 C (2) 20/10 & #176 C (3) 25/15 & #176 C (4) 30/20 & #176 C (12 hours day/night temperature). In Pleurozium schreberi, there were no significant site-dependent differences before or after the experiment, while site dependencies were clearly shown in Racomitrium lanuginosum throughout the study. Fv/Fm in Pleurozium schreberi decreased at the highest and lowest temperature treatments, which can be interpreted as a stress response, but no similar trends were shown by Racomitrium lanuginosum.
• Habitat-specific responses of shoot growth and distribution of alpine dwarf-pine (Pinus pumila) to climate variation

  Yukihiro Amagai, Masami Kaneko, Gaku Kudo

  ECOLOGICAL RESEARCH 30 6 969 - 977 2015年11月 [査読有り][通常論文]
   

  Alpine dwarf-pine (Pinus pumila) in dominant in the alpine regions of Japan, and often forms the krummholz zone of stunted alpine forest. The distribution of P. pumila is strongly related to the distribution of snow, and shoot growth is also sensitive to weather conditions. Changes in temperature and snowmelt regimes may well affect the distribution patterns of the krummholz zone. P. pumila usually occupies the habitat between the fellfield and snowbed communities, and responses to climate change may differ depending on whether plants are close to the fellfield or the snowbed. We compared the distribution and shoot growth patterns of P. pumila close to both surrounding ecosystems in the Taisetsu Mountains, northern Japan. P. pumila has expanded its distribution area by 14 % toward both edges over the last 32 years. Annual shoot growth was positively affected by summer temperature and sunshine duration, but negatively related to spring temperature toward the fellfield side. Shoot growth was greater at the southeastern edge of patches, where snowdrifts were formed. The results indicated that shoot growth and distribution area increased in warm summers. However, warm springs might have a negative influence on shoot growth, probably because the earlier reduction in cold-resistance enhances the risk of frost damage in spring close to the fellfield side. This study suggests the importance of understanding the site-specific responses of shrubs to predict the impacts of climate change on alpine ecosystems.
• Warm temperature conditions restrict the sexual reproduction and vegetative growth of the spring ephemeral Gagea lutea (Liliaceae)

  Ninuola Sunmonu, Gaku Kudo

  PLANT ECOLOGY 216 10 1419 - 1431 2015年10月 [査読有り][通常論文]
   

  The responses of reproduction and growth to climate warming are important issues to predict the fate of plant populations at high latitudes. Spring ephemerals inhabiting cool-temperate forests grow better under cool conditions, but how reproductive performance is influenced by warm weather is unclear. The phenological and physiological responses of reproduction and vegetative growth to warm temperature and light conditions were evaluated in the spring ephemeral Gagea lutea. Leaf and bract physiological activities, bulb growth, and seed production were compared among reproductive plants grown in forest, open, and greenhouse (GH; warming manipulation in the open site) plots. In vitro pollen germination ability was tested under various temperatures. In the GH, leaf and bract photosynthetic activities decreased rapidly at the fruiting stage, but dark respiration rates remained high, resulting in higher carbon exhaust in warm conditions. Both leaf and bract sizes and their longevities were reduced in the GH. Annual bulb growth was largest in the forest plot and smallest in the GH plot. Pollen germination was strongly inhibited at high temperature (30 degrees C). Fruit and seed productions were decreased only in the GH plot. Both vegetative and reproductive activities were negatively affected by warm temperature, resulting in less vegetative growth and lower seed-set, whereas an understory habitat was beneficial for vegetative growth and showed similar seed production to an open habitat over the experimental period. Decreasing population dynamics of spring ephemerals was predicted in response to future warming climate not only by growth inhibition but also by restriction of seed production.
• Intrinsic and extrinsic factors acting on the reproductive process in alpine-snowbed plants: roles of phenology, biological interaction, and breeding system

  Yoshiaki Kameyama, Gaku Kudo

  PLANT SPECIES BIOLOGY 30 1 3 - 15 2015年01月 [査読有り][通常論文]
   

  Pollinator activity and competition for pollinators lead to quantitative and qualitative pollen limitations on seed production and affect the reproductive success of plant species, depending on their breeding system (e.g., self-compatibility and heterospecific compatibility) and genetic load (e.g., inbreeding depression and hybrid inviability). In alpine ecosystems, snowmelt regimes determine the distribution and phenology of plant communities. Plant species growing widely along a snowmelt gradient often grow with different species among local populations. Their pollinators also vary in their abundance, activity, and behavior during the season. These variations may modify plant-pollinator and plant-plant interactions. We integrated a series of our studies on the alpine dwarf shrub, Phyllodoce aleutica (Ericaceae), to elucidate the full set of intrinsic (species-specific breeding system) and extrinsic factors (snow condition, pollinator activity, and interspecific competition) acting on their reproductive process. Seasonality of pollinator activity led to quantitative pollen limitation in the early-blooming populations, whereas in the late-blooming populations, high pollinator activity ensured pollination service, but interspecific competition for pollinators led to qualitative and quantitative pollen limitation in less competitive species. However, negative effects of illegitimate pollen receipt on seed-set success might be reduced when cryptic incompatibility systems (i.e., outcross pollen grains took priority over self- and heterospecific pollen grains) could effectively prevent ovule and seed discounting. Our studies highlight the importance of species-specific responses of plant reproduction to changing pollinator availability along environmental gradients to understand the general features of pollination networks in alpine ecosystems.
• The consequences of demand-driven seed provisioning for sexual differences in reproductive investment in Thalictrum occidentale (Ranunculaceae)

  Takashi Y. Ida, Lawrence D. Harder, Gaku Kudo

  JOURNAL OF ECOLOGY 103 1 269 - 280 2015年01月 [査読有り][通常論文]
   

  1. Many iteroparous angiosperms may benefit from flexible annual resource allocation in response to variable reproductive opportunities induced by external conditions. If maximal reproductive investment is fixed, lack of reproductive sinks would cause resource redistribution to other sinks. Alternatively, reproductive investment may vary depending on the demand of reproductive sinks, changing source-sink relations. In particular, differential responses by males and females to the demands of flower and seed production may cause sexual dimorphism. 2. We assess the occurrence of demand-driven seed allocation by females and its implications for sexual differences in reproductive investment, including the dynamics of mass and carbon allocation and the physiological cost of reproduction, for a dioecious, perennial herb, Thalictrum occidentale. We specifically quantified allocation responses to partial defoliation, which reduced current resource supply, and partial flower/fruit removal, which reduced the aggregate demand of reproductive sinks. 3. During flowering, males preferentially invested carbon and mass in flowers at the expense of vegetative organs, whereas females allocated less mass to flowers and invested more in new rhizome production for future performance than males. In contrast, during early fruiting, both sexes had new rhizomes of similar size and a doubling of reproductive mass by females after flowering resulted in similar total reproductive investment for both sexes. Manipulation of the source-sink balance did not influence carbon allocation, except that partial fruit removal increased new rhizome mass compared with intact plants. 4. Females with many fertilized ovules invested proportionally more in seed number and mass per seed than females with few fertilized ovules, indicating both demand-driven seed maturation and its elimination of seed size-number trade-off. Furthermore, males consistently exhibited size-dependent flower production, whereas females exhibited size-dependent flower production only if they had not reproduced during the previous year. 5. Synthesis. This study demonstrates that sexual differences in policies of reproductive investment and the timing of the physiological costs of reproduction impose contrasting allocation schedules. Males invested in reproduction proportionally with their size, whereas females invested flexibly in seeds in response to the demand of developing embryos. Thus, the contrasting certainty and timing of reproductive resource requirements between the sexes contribute to sexual dimorphism.
• Variation in responses to temperature treatments ex situ of the moss Pleurozium schreberi (Willd. ex Brid.) Mitt. originating from eight altitude sites in Hokkaido, Japan

  Annika K. Jagerbrand, Juha M. Alatalo, Gaku Kudo

  JOURNAL OF BRYOLOGY 36 3 209 - 216 2014年09月 [査読有り][通常論文]
   

  Thermal acclimatisations are important for the survival and growth of individuals and populations but seldom studied for different populations of bryophytes. The aims of this study were to (I) investigate if responses to temperature treatments were independent of the site sampled or if the intra- and inter-population variation in responses were larger than the responses to the temperature treatments (control, press, and pulse), and to (II) examine if experimental responses varied, depending on the sampled sites. We collected samples of the circumpolar bryophyte species, Pleurozium schreberi (Willd. ex Brid.) Mitt., originating from eight altitude sites on Mt. Oakan in Hokkaido, Japan, and exposed them to three different temperature treatments ex situ for four weeks. Thermal acclimatisation was estimated by measuring responses in growth length increase, biomass increase, number of branches, and the maximum quantum yield of PS II (Fv/Fm). We found that responses to temperature treatments were dependent on the site sampled, and that differences were most pronounced in the length increase. Results also shows that the responses to experimental treatments may differ between sites. Our results therefore raise important concerns regarding the general validity of both ex situ and in situ experiments when performed on a single or a limited number of sites.
• Winter climate change in plant-soil systems: summary of recent findings and future perspectives

  Kobayashi Makoto, Takuya Kajimoto, Lina Koyama, Gaku Kudo, Hideaki Shibata, Yosuke Yanai, J. H. C. Cornelissen

  ECOLOGICAL RESEARCH 29 4 593 - 606 2014年07月 [査読有り][通常論文]
   

  The winter climate is changing in many parts of the world, and it is predicted that winter climate change will modify the structure and function of plant-soil systems. An understanding of these changes and their consequences in terrestrial ecosystems requires knowledge of the linkage between above- and below-ground components as well as the species interactions found in plant-soil systems, which have important implications for biogeochemical cycles. However, winter climate-change studies have focused on only a part of the ecosystem or ecological process. We summarize here recent findings related to the effects of winter climate and its changes on soil nitrogen (N) dynamics, greenhouse gas (N2O) emissions from the soil, N use by individual plants, vegetation development, and interactions between vegetation and pollinators to generate an integrative understanding of the response of the plant-soil system to winter climate change. This review indicates that the net effects on plants, soil microbes, pollinators, and the associated biogeochemical cycles are balanced among several processes and are highly variable depending on the context, such as the target species/functional group, original winter condition of the habitat, and type of climate change. The consequences of winter climate change for species interactions among plants, associated animals, and biogeochemical cycles are largely unknown. For further research, a large-scale comparative study to measure ecosystem-level functions is important, especially in less-cold ecosystems.
• Vulnerability of phenological synchrony between plants and pollinators in an alpine ecosystem

  Gaku Kudo

  ECOLOGICAL RESEARCH 29 4 571 - 581 2014年07月 [査読有り][通常論文]
   

  The relationship between flowering phenology and abundance of bumble bees (Bombus spp.) was investigated using 2 years of phenological data collected in an alpine region of northern Japan. Abundance of Bombus species was observed along a fixed transect throughout the flowering season. The number of flowering species was closely related to the floral resources for pollinators at the community scale. In the year with typical weather, the first flowering peak corresponded to the emergence time of queen bees from hibernation, while the second flowering peak corresponded to the active period of worker bees. In the year with an unusually warm spring, however, phenological synchrony between plants and bees was disrupted. Estimated emergence of queen bees was 10 days earlier than the first flowering date owing to earlier soil thawing and warming. However, subsequent worker emergence was delayed, indicating slower colony development. The flowering season finished 2 weeks earlier in the warm-spring year in response to earlier snowmelt. A common resident species in the alpine environment, B. hypocrita sapporoensis, flexibly responded to the yearly fluctuation of flowering. In contrast, population dynamics of other Bombus species were out of synchrony with the flowering: their frequencies were highest at the end of the flowering season in the warm-spring year. Therefore, phenological mismatch between flowers and pollinators is evident during warm years, which may become more prevalent in a warmer climate. To understand the mechanism of phenological mismatch in the pollination system of the alpine ecosystem, ground temperature, snowmelt regime, and life cycle of pollinators are key factors.
• How do sink and source activities influence the reproduction and vegetative growth of spring ephemeral herbs under different light conditions?

  Ninuola Sunmonu, Gaku Kudo

  JOURNAL OF PLANT RESEARCH 127 4 503 - 511 2014年07月 [査読有り][通常論文]
   

  Spring ephemeral herbs inhabiting deciduous forests commonly complete reproduction and vegetative growth before canopy closure in early summer. Effects of shading by early canopy closure on reproductive output and vegetative growth, however, may vary depending on the seasonal allocation patterns of photosynthetic products between current reproduction and storage for future growth in each species. To clarify the effects of sink-source balance on seed production and bulb growth in a spring ephemeral herb, Gagea lutea, we performed a bract removal treatment (source reduction) and a floral-bud removal treatment (sink reduction) under canopy and open conditions. Leaf carbon fixations did not differ between the forest and open sites and among treatments. Bract carbon fixations were also similar between sites but tended to decrease when floral buds were removed. Seed production was higher under open condition but decreased by the bract-removal treatment under both light conditions. In contrast, bulb growth was independent of light conditions and the bract-removal treatment but increased greatly by the bud-removal treatment. Therefore, leaves and bracts acted as specialized source organs for vegetative and reproductive functions, respectively, but photosynthetic products by bracts were flexibly used for bulb growth when plants failed to set fruits. Extension of bright period was advantageous for seed production (i.e., source limited) but not for vegetative growth (i.e., sink limited) in this species.
• Global assessment of experimental climate warming on tundra vegetation: heterogeneity over space and time (vol 15, pg 164, 2012)

  Sarah C. Elmendorf, Gregory H. R. Henry, Robert D. Hollister, Juha Alatalo, Robert G. Bjoerk, Anne D. Bjorkman, Terry V. Callaghan, Laura Siegwart Collier, Elisabeth J. Cooper, Johannes H. C. Cornelissen, Thomas A. Day, Anna Maria Fosaa, William A. Gould, Jarngerur Gretarsdottir, John Harte, Luise Hermanutz, David S. Hik, Annika Hofgaard, Frith Jarrad, Ingibjoerg Svala Jonsdottir, Frida Keuper, Kari Klanderud, Julia A. Klein, Saewan Koh, Gaku Kudo, Simone I. Lang, Val Loewen, Jeremy L. May, Joel Mercado, Anders Michelsen, Ulf Molau, Isla H. Myers-Smith, Steven F. Oberbauer, Sara Pieper, Eric Post, Christian Rixen, Clare H. Robinson, Niels Martin Schmidt, Gaius R. Shaver, Anna Stenstroem, Anne Tolvanen, Orjan Totland, Tiffany Troxler, Carl-Henrik Wahren, Marilyn D. Walker, Patrick J. Webber, Jeffery M. Welker, Philip A. Wookey

  ECOLOGY LETTERS 17 2 260 - 260 2014年02月 [査読有り][通常論文]
  
• Early onset of spring increases the phenological mismatch between plants and pollinators

  Gaku Kudo, Takashi Y. Ida

  ECOLOGY 94 10 2311 - 2320 2013年10月 [査読有り][通常論文]
   

  Climate warming accelerates the timing of flowering and insect pollinator emergence, especially in spring. If these phenological shifts progress independently between species, features of plant-pollinator mutualisms may be modified. However, evidence of phenological mismatch in pollination systems is limited. We investigated the phenologies of a spring ephemeral, Corydalis ambigua, and its pollinators (bumble bees), and seed-set success over 10-14 years in three populations. Although both flowering onset and first detection of overwintered queen bees in the C. ambigua populations were closely related to snowmelt time and/or spring temperature, flowering tended to be ahead of first pollinator detection when spring came early, resulting in lower seed production owing to low pollination service. Relationships between flowering onset time, phenological mismatch, and seed-set success strongly suggest that phenological mismatch is a major limiting factor for reproduction of spring ephemerals. This report demonstrates the mechanism of phenological mismatch and its ecological impact on plant-pollinator interactions based on long-term monitoring. Frequent occurrence of mismatch can decrease seed production and may affect the population dynamics of spring ephemerals.
• Responses of leafing phenology and photosynthesis to soil warming in forest-floor plants

  Ryo Ishioka, Onno Muller, Tsutom Hiura, Gaku Kudo

  ACTA OECOLOGICA-INTERNATIONAL JOURNAL OF ECOLOGY 51 34 - 41 2013年08月 [査読有り][通常論文]
   

  Phenological and physiological responses of plants to climate change are key issues to understand the global change impact on ecosystems. To evaluate the species-specific responses, a soil-warming experiment was conducted for seven understory species having various leaf habits in a deciduous forest, northern Japan; one evergreen shrub, one semi-evergreen fern, one summer-deciduous shrub, and four summer-green herbs. Soil temperature in the warming plots was electrically maintained 5 degrees C higher than control plots. Responses of leafing phenology highly varied among species: new leaf emergence of the evergreen shrub was delayed; senescence of overwintering leaves of the semi-evergreen fern was accelerated resulting in the shift to deciduousness; leaf shedding of the summer-deciduous shrub was accelerated. Among four summer-green species, only an earliest leaf-out species advanced growth initiation, but the period of growth season was not changed. Physiological responses to soil warming were also highly species-specific: the warming treatment increased the photosynthetic activity of the summer-deciduous shrub and one summer-green species, decreased that of the semi-evergreen fern, while other species did not show any changes in photosynthetic traits. Totally, the soil warming impacts on understory plants was apparent in spring. It was suggested that modification of snow conditions is important issue especially for plants with overwintering leaves. Responses of understory vegetation to climate change may highly vary depending on the composition of leaf habits in the cool-temperate forests. (C) 2013 Elsevier Masson SAS. All rights reserved.
• Photosynthetic compensation by the reproductive structures in the spring ephemeral Gagea lutea

  Ninuola Sunmonu, Takashi Y. Ida, Gaku Kudo

  PLANT ECOLOGY 214 2 175 - 188 2013年02月 [査読有り][通常論文]
   

  Growth and reproduction of spring ephemerals inhabiting deciduous forests progress simultaneously during a short period from snowmelt to canopy closure. To clarify the mechanism to mitigate the cost of reproduction, contributions of foliar and non-foliar photosynthetic products to seed production were examined in a spring ephemeral Gagea lutea. Leaf growth, foliar and non-foliar photosynthetic activities, and total assimilated products were compared among reproductive-intact, floral bud-removal, and vegetative plants. Translocation of current photosynthetic products to individual organs was quantified by (CO2)-C-13-trace experiment. Bulb growth was compared between hand-pollination and floral bud-removal treatments. Finally, seed set was compared between intact, leaf-clipping, and bract-clipping treatments. Fruit-forming plants retained leaves longer than vegetative and floral bud-removal plants, but the assimilative contribution of extended leaf longevity was negligible. Carbon supply by bract photosynthesis was large enough for fruit development, while carbon supply by fruit photosynthesis was offset by the high respiration loss. Foliar photosynthetic products were largely transported to bulbs, while translocation to reproductive functions was negligible. Because the floral bud-removal increased the bulb growth, lack of reproduction could lead to more storage. The leaf-clipping had no effect on seed production, while the bract-clipping significantly reduced the seed production. Therefore, current photosynthesis of leafy bracts might be a major carbon source for fruit development. This self-compensative mechanism of reproductive structure enables the continuous reproductive activity in this species.
• ELUCIDATIVE MECHANISM OF THE RECESSION OF ALPINE PLANTS AND THE INVASION OF DWARF BAMBOO KURILENSIS IN THE TAISETSU MOUNTAINS

  Buho Hoshino, Gaku Kudo, Masami Kaneko, Hidehisa Taniuchi, Tetsuo Yabuki

  2013 IEEE INTERNATIONAL GEOSCIENCE AND REMOTE SENSING SYMPOSIUM (IGARSS) 2778 - 2781 2013年 [査読有り][通常論文]
   

  Global warming's influence over the last 30 years, along with soil dehydration in the Taisetsu mountains has resulted in shrubbery such as Dwarf bamboo (Dwarf bamboo kurilensis), a species of dwarf bamboo, and Japanese Stone pine (Pinus pumila) (an indicator of soil dehydration), increase in area of distribution while many herbaceous species of alpine plants have reduced in distribution area to the extent where some extinction has occurred. This study, using multipolarization of ALOS satellite PALSAR L-band microwave (HH/HV) data, has developed a model to estimate soil moisture in densely vegetated areas to clarify factors in the seasonal variation of soil moisture in an area with fluctuating vegetation and so clarify factors in the casual relationship between soil dehydration and vegetation fluctuation in a wide area. Moreover, conducting this research will enable identification of potential areas where Dwarf bamboo may easily invade, and thus contribute to environmental measures.
• Demand-driven resource investment in annual seed production by a perennial angiosperm precludes resource limitation

  Takashi Y. Ida, Lawrence D. Harder, Gaku Kudo

  ECOLOGY 94 1 51 - 61 2013年01月 [査読有り][通常論文]
   

  The limits on annual seed production have long been characterized as restriction by either pollination success or resource provision to seed development. This expected dichotomy between pollen and resource limitation is based on the assumption that reproductive resources are fixed, which is reasonable for semelparous species. In contrast, iteroparity can ease the constraints on reproductive output per breeding season, if resources can be either mobilized from past storage or borrowed against future performance. For perennial plants, these options allow enhanced reproductive investment in response to unusually good pollination, so that annual seed production may not be pollen or resource limited. We assessed demand-governed reproductive investment by manipulating both resource supply capacity (partial defoliation) and resource demand (pollination quality: fully self-pollination, fully cross-pollination, or combinations of partial self-and cross-pollination within the inflorescence) for a forest herb, Stenanthium occidentale, which is subject to strong pre-dispersal inbreeding depression. Insensitivity to partial defoliation indicated that reproductive output was not source regulated. Instead, demand by developing seeds governs resource distribution, as demonstrated by elevated photosynthate translocation to fruits on fully cross-pollinated plants and the ability of completely defoliated plants to produce seeds. Such contingent resource allocation eliminates a simple dichotomy between pollen receipt and resource availability as limits on annual seed production. Instead, such flexible reproductive investment allows iteroparous perennials to participate maximally in current reproduction (as determined by ovule production) following superior pollination, or to conserve resources for future reproduction following poor pollination.
• Pollination linkage between canopy flowering, bumble bee abundance and seed production of understorey plants in a cool temperate forest

  Naoki Inari, Tsutom Hiura, Masanori J. Toda, Gaku Kudo

  JOURNAL OF ECOLOGY 100 6 1534 - 1543 2012年11月 [査読有り][通常論文]
   

  In forest ecosystems, canopy trees provide a large amount of floral resources for pollinators but flower production fluctuates highly from year to year. Temporal variation in floral resources may influence the population dynamics of pollinators. We investigated the relationship between the population dynamics of bumble bees (Bombus spp.) and canopy floral resources over 5 years in a cool temperate forest. We predicted that the yearly fluctuation of canopy resources affects colony development and queen production, resulting in the variation of the pollination success of understorey plants the following spring. Flower production of canopy trees showed clear biyearly fluctuations, synchronously among most species. Worker production of Bombus ardens and Bombus hypocrita were positively related to floral resources during colony establishment by overwintered queens, while that of Bombus diversus was positively related to floral resources during the worker-active period. An abundance of overwintered queens was positively related to both worker abundance and floral resources in the previous summer in B. ardens and to only previous-year worker abundance in B. hypocrita but was dependent on neither factor in B. diversus. These differences in causal effects on queen production among species might be a reflection of interspecific differences in the degree of dependence on canopy resources for queen production due to species-specific phenologies and/or foraging preferences of other species of flowers. The extent of pollen limitation in the spring-ephemeral Corydalis ambigua, which is exclusively pollinated by overwintered queens, was negatively correlated with the abundance of B. hypocrita queens. Thus, population dynamics of bumble bees has a crucial effect on seed production of understorey plants. Synthesis. The dynamics of flower production in overstory trees can indirectly affect the pollination efficiency of understorey plants in the next season via the population dynamics of pollinators. Our results suggest that a cascade effect occurs through pollination networks in a cool temperate forest ecosystem.
• Effects of neighboring vascular plants on the abundance of bryophytes in different vegetation types

  Annika K. Jagerbrand, Gaku Kudo, Juha M. Alatalo, Ulf Molau

  POLAR SCIENCE 6 2 200 - 208 2012年07月 [査読有り][通常論文]
   

  Due to the climate change, vegetation of tundra ecosystems is predicted to shift toward shrub and tree dominance, and this change may influence bryophytes. To estimate how changes in growing environment and the dominance of vascular plants influence bryophyte abundance, we compared the relationship of occurrence of bryophytes among other plant types in a five-year experiment of warming (T), fertilization (F) and T + F in two vegetation types, heath and meadow, in a subarctic-alpine ecosystem. We compared individual leaf area among shrub species to confirm that deciduous shrubs might cause severe shading effect. Effects of neighboring functional types on the performance of Hylocomium splendens was also analyzed. Results show that F and T + F treatments significantly influenced bryophyte abundance negatively. Under natural conditions, bryophytes in the heath site were negatively related to the abundance of shrubs and lichens and the relationship between lichens and bryophytes strengthened after the experimental period. After five years of experimental treatments in the meadow, a positive abundance relationship emerged between bryophytes and deciduous shrubs, evergreen shrubs and forbs. This relationship was not found in the heath site. Our study therefore shows that the abundance relationships between bryophytes and plants in two vegetation types within the same area can be different. Deciduous shrubs had larger leaf area than evergreen shrubs but did not show any shading effect on H. splendens. (C) 2012 Elsevier B.V. and NEPR. All rights reserved.
• Plot-scale evidence of tundra vegetation change and links to recent summer warming

  Sarah C. Elmendorf, Gregory H. R. Henry, Robert D. Hollister, Robert G. Bjork, Noemie Boulanger-Lapointe, Elisabeth J. Cooper, Johannes H. C. Cornelissen, Thomas A. Day, Ellen Dorrepaal, Tatiana G. Elumeeva, Mike Gill, William A. Gould, John Harte, David S. Hik, Annika Hofgaard, David R. Johnson, Jill F. Johnstone, Ingibjorg Svala Jonsdottir, Janet C. Jorgenson, Kari Klanderud, Julia A. Klein, Saewan Koh, Gaku Kudo, Mark Lara, Esther Levesque, Borgthor Magnusson, Jeremy L. May, Joel A. Mercado-Diaz, Anders Michelsen, Ulf Molau, Isla H. Myers-Smith, Steven F. Oberbauer, Vladimir G. Onipchenko, Christian Rixen, Niels Martin Schmidt, Gaius R. Shaver, Marko J. Spasojevic, Pora Ellen Porhallsdottir, Anne Tolvanen, Tiffany Troxler, Craig E. Tweedie, Sandra Villareal, Carl-Henrik Wahren, Xanthe Walker, Patrick J. Webber, Jeffrey M. Welker, Sonja Wipf

  NATURE CLIMATE CHANGE 2 6 453 - 457 2012年06月 [査読有り][通常論文]
   

  Temperature is increasing at unprecedented rates across most of the tundra biome(1). Remote-sensing data indicate that contemporary climate warming has already resulted in increased productivity over much of the Arctic(2,3), but plot-based evidence for vegetation transformation is not widespread. We analysed change in tundra vegetation surveyed between 1980 and 2010 in 158 plant communities spread across 46 locations. We found biome-wide trends of increased height of the plant canopy and maximum observed plant height for most vascular growth forms; increased abundance of litter; increased abundance of evergreen, low-growing and tall shrubs; and decreased abundance of bare ground. Intersite comparisons indicated an association between the degree of summer warming and change in vascular plant abundance, with shrubs, forbs and rushes increasing with warming. However, the association was dependent on the climate zone, the moisture regime and the presence of permafrost. Our data provide plot-scale evidence linking changes in vascular plant abundance to local summer warming in widely dispersed tundra locations across the globe.
• Plot-scale evidence of tundra vegetation change and links to recent summer warming

  Sarah C. Elmendorf, Gregory H. R. Henry, Robert D. Hollister, Robert G. Bjork, Noemie Boulanger-Lapointe, Elisabeth J. Cooper, Johannes H. C. Cornelissen, Thomas A. Day, Ellen Dorrepaal, Tatiana G. Elumeeva, Mike Gill, William A. Gould, John Harte, David S. Hik, Annika Hofgaard, David R. Johnson, Jill F. Johnstone, Ingibjorg Svala Jonsdottir, Janet C. Jorgenson, Kari Klanderud, Julia A. Klein, Saewan Koh, Gaku Kudo, Mark Lara, Esther Levesque, Borgthor Magnusson, Jeremy L. May, Joel A. Mercado-Diaz, Anders Michelsen, Ulf Molau, Isla H. Myers-Smith, Steven F. Oberbauer, Vladimir G. Onipchenko, Christian Rixen, Niels Martin Schmidt, Gaius R. Shaver, Marko J. Spasojevic, Pora Ellen Porhallsdottir, Anne Tolvanen, Tiffany Troxler, Craig E. Tweedie, Sandra Villareal, Carl-Henrik Wahren, Xanthe Walker, Patrick J. Webber, Jeffrey M. Welker, Sonja Wipf

  NATURE CLIMATE CHANGE 2 6 453 - 457 2012年06月 [査読有り][通常論文]
   

  Temperature is increasing at unprecedented rates across most of the tundra biome(1). Remote-sensing data indicate that contemporary climate warming has already resulted in increased productivity over much of the Arctic(2,3), but plot-based evidence for vegetation transformation is not widespread. We analysed change in tundra vegetation surveyed between 1980 and 2010 in 158 plant communities spread across 46 locations. We found biome-wide trends of increased height of the plant canopy and maximum observed plant height for most vascular growth forms; increased abundance of litter; increased abundance of evergreen, low-growing and tall shrubs; and decreased abundance of bare ground. Intersite comparisons indicated an association between the degree of summer warming and change in vascular plant abundance, with shrubs, forbs and rushes increasing with warming. However, the association was dependent on the climate zone, the moisture regime and the presence of permafrost. Our data provide plot-scale evidence linking changes in vascular plant abundance to local summer warming in widely dispersed tundra locations across the globe.
• Global assessment of experimental climate warming on tundra vegetation: heterogeneity over space and time

  Sarah C. Elmendorf, Gregory H. R. Henry, Robert D. Hollister, Robert G. Bjork, Anne D. Bjorkman, Terry V. Callaghan, Laura Siegwart Collier, Elisabeth J. Cooper, Johannes H. C. Cornelissen, Thomas A. Day, Anna Maria Fosaa, William A. Gould, Jarngerdur Gretarsdottir, John Harte, Luise Hermanutz, David S. Hik, Annika Hofgaard, Frith Jarrad, Ingibjorg Svala Jonsdottir, Frida Keuper, Kari Klanderud, Julia A. Klein, Saewan Koh, Gaku Kudo, Simone I. Lang, Val Loewen, Jeremy L. May, Joel Mercado, Anders Michelsen, Ulf Molau, Isla H. Myers-Smith, Steven F. Oberbauer, Sara Pieper, Eric Post, Christian Rixen, Clare H. Robinson, Niels Martin Schmidt, Gaius R. Shaver, Anna Stenstrom, Anne Tolvanen, Orjan Totland, Tiffany Troxler, Carl-Henrik Wahren, Patrick J. Webber, Jeffery M. Welker, Philip A. Wookey

  ECOLOGY LETTERS 15 2 164 - 175 2012年02月 [査読有り][通常論文]
   

  Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future biodiversity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations of this approach include the apparent site-specificity of results and uncertainty about the power of short-term studies to anticipate longer term change. We address these issues with a synthesis of 61 experimental warming studies, of up to 20 years duration, in tundra sites worldwide. The response of plant groups to warming often differed with ambient summer temperature, soil moisture and experimental duration. Shrubs increased with warming only where ambient temperature was high, whereas graminoids increased primarily in the coldest study sites. Linear increases in effect size over time were frequently observed. There was little indication of saturating or accelerating effects, as would be predicted if negative or positive vegetation feedbacks were common. These results indicate that tundra vegetation exhibits strong regional variation in response to warming, and that in vulnerable regions, cumulative effects of long-term warming on tundra vegetation and associated ecosystem consequences have the potential to be much greater than we have observed to date.
• 大雪山国立公園(<連載1>野外研究サイトから(21))

  工藤 岳

  日本生態学会誌 62 2 301 - 305 一般社団法人 日本生態学会 2012年
• 大雪山国立公園高山帯におけるマルハナバチ相のモニタリング調査

  工藤 岳, 井本 哲雄

  保全生態学研究 17 2 263 - 269 一般社団法人 日本生態学会 2012年 

  環境省生物多様性センターのモニタリングサイト1000では、2011年より高山帯におけるマルハナバチ相のモニタリング調査を開始した。最初の登録地である北海道大雪山国立公園における初年度の調査概要を報告する。赤岳登録地の森林限界から高山帯において、6月上旬から8月下旬にかけて、計12回のライントランセクトによるマルハナバチ相、ならびに訪花植物の調査を行った。調査シーズンを通して、総計473個体が確認された。その内訳は、エゾオオマルハナバチが60%、アカマルハナバチが18%、エゾヒメマルハナバチが14%、エゾナガマルハナバチが7%、エゾトラマルハナバチが1%であり、移入種のセイヨウオオマルハナバチは確認されなかった。出現頻度は、6月中旬と7月下旬以降に高くなる二山分布を示し、前者は越冬明けの女王バチ、後者は働きバチが多数を占めていた。季節を通して約40種の植物への訪花が観察され、マルハナバチ類は高山帯において重要な花粉媒介者であることが確認された。マルハナバチ活動最盛期に黒岳登録地とヒサゴ沼調査地で同様の調査を行なったところ、マルハナバチ相は顕著な地域差が見られた。黒岳登録地ではエゾヒメマルハナバチの頻度が50%と最も高かった。ヒサゴ沼調査地ではエゾオオマルハナバチの頻度が90%以上を占めていた。また、ヒサゴ沼調査地ではセイヨウオオマルハナバチの侵入が初めて観察された。気候変動や移入種の侵入による今後のマルハナバチ相の動向について、継続調査の重要性が示された。
• Effects of defoliation and shading on the physiological cost of reproduction in silky locoweed Oxytropis sericea

  Takashi Y. Ida, Lawrence D. Harder, Gaku Kudo

  ANNALS OF BOTANY 109 1 237 - 246 2012年01月 [査読有り][通常論文]
   

  Background The production of flowers, fruits and seeds demands considerable energy and nutrients, which can limit the allocation of these resources to other plant functions and, thereby, influence survival and future reproduction. The magnitude of the physiological costs of reproduction depends on both the factors limiting seed production (pollen, ovules or resources) and the capacity of plants to compensate for high resource demand. Methods To assess the magnitude and consequences of reproductive costs, we used shading and defoliation to reduce photosynthate production by fully pollinated plants of a perennial legume, Oxytropis sericea (Fabaceae), and examined the resulting impact on photosynthate allocation, and nectar, fruit and seed production. Key Results Although these leaf manipulations reduced photosynthesis and nectar production, they did not alter photosynthate allocation, as revealed by (13)C tracing, or fruit or seed production. That photosynthate allocation to reproductive organs increased >190% and taproot mass declined by 29% between flowering and fruiting indicates that reproduction was physiologically costly. Conclusions The insensitivity of fruit and seed production to leaf manipulation is consistent with either compensatory mobilization of stored resources or ovule limitation. Seed production differed considerably between the two years of the study in association with contrasting precipitation prior to flowering, perhaps reflecting contrasting limits on reproductive performance.
• ESTIMATED SOIL MOISTURE IN VEGETATED AREA USING MULTITEMPORAL MULTIPOLARIZATION DATA

  Buho Hoshino, Gaku Kudo, Masami Kaneko, Hidehisa Taniuchi, Hisae Iino, Tetsuo Yabuki

  2012 IEEE INTERNATIONAL GEOSCIENCE AND REMOTE SENSING SYMPOSIUM (IGARSS) 654 - 657 2012年 [査読有り][通常論文]
   

  Alpine ecosystem is the most sensitive terrestrial ecosystem to global climate change. Recently, a dwarf bamboo species, Sasa kurilensis, (Poaceae), has invaded into alpine snow-meadows in the wilderness area of the Taisetsu Mountains, northern Japan. The spatial distribution and seasonal changes in soil moistures are key parameter in numerous environmental studies at both regional and global scales including hydrological, ecological, climatic and agricultural fields. However, the natural variability and complexity of vegetation canopy and surface roughness significantly affect the sensitivity of backscatter from soil. This study indicates a new method to estimate surface soil moisture in high density vegetated area in the Taisetsu Mountains with an L-band dual-polarization (HH and HV) radiometer measurements. For dense vegetated surfaces, we used the multitemporal and multipolarization backscatter coefficient data and the subtraction methods to provide the estimation of vegetation effects. After the soil moisture corrected based on vegetation phenology, the surface soil moisture can be inferred by the estimated surface backscatter signals.
• A NEW METHOD FOR ESTIMATION OF SOIL MOISTURE FROM PALSAR POLARIZATION DATA IN HIGH DENSITY VEGETATED AREA

  B. Hoshino, G. Kudo, Y. Amagai, M. Kaneko, T. Yabuki

  The 32nd Asian Conference on Remote Sensing 3 - 7 2011年10月 [査読無し][通常論文]
  
• Invasion of dwarf bamboo into alpine snow-meadows in northern Japan: pattern of expansion and impact on species diversity

  Gaku Kudo, Yukihiro Amagai, Buho Hoshino, Masami Kaneko

  ECOLOGY AND EVOLUTION 1 1 85 - 96 2011年09月 [査読有り][通常論文]
   

  Recently, a dwarf bamboo species, Sasa kurilensis; Poaceae, has invaded into alpine snow-meadows in the wilderness area of the Taisetsu Mountains, northern Japan. This dwarf bamboo species has a wide distribution range from lowland to alpine sites of snowy regions. Because of the formation of dense evergreen culms and an extensive rhizome system, other plants are excluded following invasion by this dwarf bamboo, resulting in low species diversity. Dwarf bamboo originally inhabited the leeward slopes of alpine dwarf pine (Pinus pumila) clumps in alpine regions. During the last 32 years, however, dwarf bamboo has expanded its distribution area by up to 47% toward snow-meadows, especially on southeastern facing slopes. This rapid change may be related to the decrease in soil moisture and expansion of the annual growing period caused by the recent acceleration of snowmelt time. A multiyear census revealed that the density of bamboo culms increased 30 150% during 2 years, and the annual expansion of bamboo rhizomes was 39 cm on average. In addition to the expansion of bamboo clumps by vegetative growth, the possibility of migration by seed dispersal was also suggested by a genet analysis. With the increase in culm density, the species richness of snow-meadow vegetation decreased to less than one-quarter of the original level due to intense shading by dwarf bamboo. The rapid vegetation change in these almost pristine alpine environments isolated from the human activity implies that global climate change already influences the alpine ecosystem.
• Local differentiation of flowering phenology in an alpine-snowbed herb Gentiana nipponica

  Yuka Kawai, Gaku Kudo

  Botany 89 6 361 - 367 2011年06月 [査読有り][通常論文]
   

  Phenological events of alpine plants are strongly influenced by the seasonal thermal conditions at the local scale that are caused by heterogeneity in snowmelt time. Populations in late-snowmelt locations suffer from a short period for seed maturation, in which rapid flowering that occurs soon after snowmelt (i.e., a low thermal requirement for flowering) is advantageous. To test the possibility of local adaptation of flowering phenology, we compared reproductive phenology, the preflowering period, and the thermal requirement for flowering of the alpine-snowbed species Gentiana nipponica Maxim. between populations inhabiting early-and late-snowmelt sites within a local area. Plants in the late-snowmelt population showed a shorter preflowering period than in the early-snowmelt population nevertheless, they often failed to set fruit owing to the short growth period. To test the plasticity and genetic regulation of flowering phenology, we performed a reciprocal transplant experiment between early-and late-snowmelt populations. Although the preflowering period showed clear plastic responses depending on the transplanted habitats, the lower thermal requirement for flowering was retained in plants originating from the late-snowmelt populations, even after transplantation. Therefore, habitat-specific differentiation of flowering phenology was genetically determined between these local populations.
• Local differentiation of flowering phenology in an alpine-snowbed herb Gentiana nipponica

  Yuka Kawai, Gaku Kudo

  BOTANY-BOTANIQUE 89 6 361 - 367 2011年06月 [査読有り][通常論文]
   

  Phenological events of alpine plants are strongly influenced by the seasonal thermal conditions at the local scale that are caused by heterogeneity in snowmelt time. Populations in late-snowmelt locations suffer from a short period for seed maturation, in which rapid flowering that occurs soon after snowmelt (i.e., a low thermal requirement for flowering) is advantageous. To test the possibility of local adaptation of flowering phenology, we compared reproductive phenology, the preflowering period, and the thermal requirement for flowering of the alpine-snowbed species Gentiana nipponica Maxim. between populations inhabiting early- and late-snowmelt sites within a local area. Plants in the late-snowmelt population showed a shorter preflowering period than in the early-snowmelt population; nevertheless, they often failed to set fruit owing to the short growth period. To test the plasticity and genetic regulation of flowering phenology, we performed a reciprocal transplant experiment between early- and late-snowmelt populations. Although the preflowering period showed clear plastic responses depending on the transplanted habitats, the lower thermal requirement for flowering was retained in plants originating from the late-snowmelt populations, even after transplantation. Therefore, habitat-specific differentiation of flowering phenology was genetically determined between these local populations.
• Beringia, the phylogeographic origin of a circumpolar plant, Vaccinium uliginosum, in the Japanese Archipelago

  Hirao AS, Sato T, Kudo G

  Acta Phytotaxonomica et Geobotanica 61 3 155 - 160 The Japanese Society for Plant Systematics 2011年 [査読有り][通常論文]
  
• Clarification of the genetic component of hybrids between Phyllodoce caerulea and Phyllodoce aleutica (Ericaceae) in Hokkaido, northern Japan

  Yoshiaki Kameyama, Gaku Kudo

  PLANT SPECIES BIOLOGY 26 1 93 - 98 2011年01月 [査読有り][通常論文]
   

  Natural hybridization provides great opportunities to understand the interaction of genetics and ecology in determining species boundaries. We examined the genetic relationships of Phyllodoce taxa and revealed that most hybrids were fertile F(1)s and an extremely small number of backcross and no F(2) plants were established in natural conditions. Because this trend was irrespective of regions, we conclude that negative endogenous selection may act after the germination of F(1) seeds and prevent the establishment of later-generation hybrids. Based on these results, we discuss the ecological and evolutionary significance of natural hybridization in Phyllodoce taxa.
• POLLINATION EFFICIENCY OF BUMBLEBEE QUEENS AND WORKERS IN THE ALPINE SHRUB RHODODENDRON AUREUM

  Gaku Kudo, Akira S. Hirao, Yuka Kawai

  INTERNATIONAL JOURNAL OF PLANT SCIENCES 172 1 70 - 77 2011年01月 [査読有り][通常論文]
   

  Rhododendron aureum is a weakly self-compatible alpine shrub pollinated by bumblebees. Flower visitation frequency and foraging behavior differed between queen bumblebees and workers. Queens exhibited less frequent flower visits, longer flight distances between inflorescences, and a smaller number of sequential inflorescence visits within patches than did worker bees. Flowering in early-snowmelt populations occurred in June, when only overwintered queens were available, while flowering in late-snowmelt populations occurred from late July to August, when frequent visits by workers were common. The fruit to flower ratio per inflorescence was lower in early-snowmelt populations due to quantitative pollen limitation, while the seed to ovule ratio per fruit was lower in late-snowmelt populations. This is because geitonogamous pollination by workers was common later in the season, which resulted in a high abortion rate of self-pollinated seeds, that is, qualitative pollen limitation. Thus, pollination efficiency, or the type of pollen limitation, shifts during the flowering season, reflecting the seasonal life cycle of bumblebees in the ecosystem. Many of the self-fertilized seeds aborted due to high inbreeding depression, and the outcrossing rate was similar to 80% regardless of season.
• Habitat-Specific Responses of Alpine Plants to Climatic Amelioration: Comparison of Fellfield to Snowbed Communities

  Gaku Kudo, Mitsuhiro Kimura, Tetsuya Kasagi, Yuka Kawai, Akira S. Hirao

  ARCTIC ANTARCTIC AND ALPINE RESEARCH 42 4 438 - 448 2010年11月 [査読有り][通常論文]
   

  Because of the contrastive differences in environment and species composition climatic amelioration may affect alpine vegetation differently between fellfield and snowbed communities To test this prediction, the effects of warming on plant growth and vegetation structure were studied in two fellfield and two snowbed communities in northern Japan over 7 years using open-top-chambers (OTCs) OTCs increased the temperature by 1 1-1 8 degrees C, but the effects on snowmelt time and soil moisture were small Vegetation height and canopy volume increased substantially at both fellfield sites as a result of the use of OTCs Deciduous shrubs increased substantially at the lower fellfield and grammoids increased at the upper fellfield In contrast, the responses of snowbed plants to OTCs were not significant Because snowbed plants are snow covered until mid-summer, climatic amelioration during the snow-free period may influence plant growth only slightly if the snow-free period does not change Species richness and diversity were not changed by OTCs at any of the sites, indicating that the effect of warming alone may not be strong enough to change the species composition and diversity over several years These results indicate significant variation in the response among alpine communities to warming
• Seasonal patterns of carbon assimilation and allocation of a summer-green forest herb, Parasenecio auriculata (Senecioneae; Asteraceae)

  Takashi Y. Ida, Gaku Kudo

  PLANT ECOLOGY 210 1 181 - 193 2010年09月 [査読有り][通常論文]
   

  Summer-green herbs inhabiting deciduous forests often put out aerial shoots under bright conditions before tree-canopy closure and grow until late summer under the closed canopy. Some of them produce leaves continuously even after the initiation of canopy closure, indicating an exploitation of the low light period. The manner of carbon assimilation during bright and shade periods within a growth season should reflect the seasonal patterns of vegetative growth and reproductive allocation of individual species. We examined the seasonal patterns of assimilation, partitioning of photosynthate between reproduction and storage, and the budget of reproduction of a perennial understory herb, Parasenecio auriculata. Although photosynthetic rates per unit leaf area decreased with the seasonal reduction in light level, net assimilation at the whole-plant level was maintained at a high level even after canopy closure owing to the increase in the total leaf area. Stored resource in tubers contributed to the rapid development of aerial shoots in the early season, and annual tuber growth was completed before flowering. Instant photosynthetic products considerably contributed to the maintenance of flowers but not to fruit development because of low assimilation rate during fruiting. These findings indicated that carbon assimilation during flowering contributes to sexual reproduction without influencing the development of storage organs. Stable carbon assimilation over summer by shade-acclimatized leaves enabled the maintenance of high productivity associated with high sexual reproduction.
• Modification of bumblebee behavior by floral color change and implications for pollen transfer in Weigela middendorffiana

  Takashi Y. Ida, Gaku Kudo

  EVOLUTIONARY ECOLOGY 24 4 671 - 684 2010年07月 [査読有り][通常論文]
   

  Flowers of Weigela middendorffiana change the color from yellow to red. The previous study revealed that red-phase flowers no longer have sexual function and nectar, and bumblebees selectively visit yellow-phase flowers. The present study examined how retaining color-changed flowers can regulate the foraging behavior of bumblebees and pollen transport among flowers within (geitonogamous pollination) and between (outcrossing pollination) plants and how the behavior is influenced by display size (i.e., number of functional flowers) and visitation frequency. The visitation frequencies of bumblebees to plants and successive flower probes within plants were observed in the field using plants whose flower number and composition of the two color-phase flowers had been manipulated. To evaluate pollination efficiency over multiple pollinator visits, a pollen transport model was constructed based on the observed bumblebee behavior. In the simulation, three flowering patterns associated with display size and existence of color-changed flowers were postulated as follows: Type 1, large display (100 functional flowers) and no retention of color-changed flowers; Type 2, small display (50 functional flowers) and retention of color-changed flowers (50 old flowers), and; Type 3, large display (100 functional flowers) and retention of color-changed flowers (100 old flowers). Color-changed flowers did not contribute to increasing bumblebee attraction at a distance but reduced the number of successive flower probes within plants. Comparisons of pollen transfer between Types 1 and 3 revealed that the retention of color-changed flowers did not influence the total amount of pollen exported when pollinator visits were abundant (> 100 visits) but decreased geitonogamous pollination. Comparisons between Types 2 and 3 revealed that the discouragement effect of floral color change on successive probes accelerated in plants with a large display size. Overall, the floral color change strategy contributed to reduce geitonogamous pollination, but its effectiveness was highly sensitive to display size and pollinator frequency.
• Carbon source for reproduction in a spring ephemeral herb, Corydalis ambigua (Papaveraceae)

  Gaku Kudo, Takashi Y. Ida

  FUNCTIONAL ECOLOGY 24 1 62 - 69 2010年02月 [査読有り][通常論文]
   

  P>1. The carbon source for reproduction in plants may differ between flowering and fruiting stages. To clarify how spring ephemerals use current photosynthetic products for reproduction, the allocation patterns of photosynthate at flowering and fruiting and the effects of resource limitation on reproductive performance in Corydalis ambigua were assessed. 2. A 13C tracing experiment revealed that about 20% of the current photosynthetic carbon was used for reproduction at both flowering and fruiting. The proportion of 13C allocated to fruits was constant irrespective of the light level. In contrast, 13C translocation to tubers increased at fruiting, and this trend was accelerated when plants were shaded. 3. Defoliation treatment significantly reduced nectar production and tuber mass, while seed production was not affected. Therefore, when carbon assimilation was limited, carbon was preferentially allocated to current reproduction (seeds) rather than to pollinator attraction (nectar) or storage (tuber). 4. If seed production is partly supported by carbohydrate reserved in the old tissue of tubers, nectar and seed production may not compete strongly for carbon sources. In contrast to the ability of high seed production, the susceptibility of nectar production to current photosynthesis indicates that seed production of this species is basically limited by pollen capture. 5. Therefore, temporal separation of resource pool for reproduction may mitigate the joint limitation of seed production between pollinator attraction and resource availability. Temporal variation of the sink-source balance of storage organ is crucial to understand the cost of reproduction in perennial plants.
• Flowering phenology influences seed production and outcrossing rate in populations of an alpine snowbed shrub, Phyllodoce aleutica: effects of pollinators and self-incompatibility

  Yoshiaki Kameyama, Gaku Kudo

  ANNALS OF BOTANY 103 9 1385 - 1394 2009年06月 [査読有り][通常論文]
   

  Because of differences in snowmelt time, the reproductive phenologies of alpine plants are highly variable among local populations, and there is large variation in seed set across populations. Temporal variation in pollinator availability during the season may be a major factor affecting not only seed production but also outcrossing rate of alpine plants. Among local populations of Phyllodoce aleutica that experience different snowmelt regimes, flowering phenology, pollinator availability, seed-set rate, and outcrossing rate were compared with reference to the mating system (self-compatibility or heterospecific compatibility with a co-occurring congeneric species). Flowering occurred sequentially among populations reflecting snowmelt time from mid-July to late August. The visit frequency of bumble-bees increased substantially in late July when workers appeared. Both seed set and outcrossing rate increased as flowering season progressed. Although flowers were self-compatible and heterospecific compatible, the mixed-pollination experiment revealed that fertilization with conspecific, outcrossing pollen took priority over selfing and hybridization, indicating a cryptic self-incompatibility. In early snowmelt populations, seed production was pollen-limited and autogamous selfing was common. However, genetic analyses revealed that selfed progenies did not contribute to the maintenance of populations due to late-acting inbreeding depression. Large variations in seed-set and outcrossing rates among populations were caused by the timing of pollinator availability during the season and the cryptic self-incompatibility of this species. Despite the intensive pollen limitation in part of the early season, reproductive assurance by autogamous selfing was not evident. Under fluctuating conditions of pollinator availability and flowering structures, P. aleutica maintained the genetic composition by conspecific outcrossing.
• MORPHOLOGICAL AND GENETIC VARIATIONS OF POTENTILLA MATSUMURAE (ROSACEAE) BETWEEN FELLFIELD AND SNOWBED POPULATIONS

  Yoshiko Shimono, Mikio Watanabe, Akira S. Hirao, Naoya Wada, Gaku Kudo

  AMERICAN JOURNAL OF BOTANY 96 4 728 - 737 2009年04月 [査読有り][通常論文]
   

  Identifying ecological factors associated with local differentiation of populations is important for understanding microevolutionary processes. Alpine environments offer a unique opportunity to investigate the effects of habitat-specific selective forces and gene flow limitations among populations at a microscale on local adaptation because the heterogeneous snowmelt patterns in alpine ecosystems provide steep environmental changes. We investigated the variation in morphological traits and enzyme loci between fellfield and snowbed populations of Potentilla matsumurae, a common alpine herb with a wide distribution along snowmelt gradients in northern Japan. We found significant differences in morphological traits between fellfield and snowbed habitats in a northern distribution region. These differences were maintained when plants were grown under uniform conditions in a greenhouse. Allozyme variations among 15 populations from geographically separated regions with different historical backgrounds showed that the populations are more genetically differentiated between the fellfield and snowbed habitats within a region than between populations occupying the same habitat type in different regions. These results suggest that variation in snowmelt regimes could be a driving force creating local adaptation and genetic differentiation of alpine plant populations.
• Comparison of light harvesting and resource allocation strategies between two rhizomatous herbaceous species inhabiting deciduous forests

  Takashi Y. Ida, Gaku Kudo

  JOURNAL OF PLANT RESEARCH 122 2 171 - 181 2009年03月 [査読有り][通常論文]
   

  Light conditions on the floor of deciduous forests are determined by the leaf dynamics of canopy trees and gap formation. Such spatiotemporal variations of light availability should affect the resource partitioning strategies of understory herbs. Although rhizomatous species are common in understory, relationships between rhizome structure, vegetative growth, and sexual reproduction are unclear in terms of carbon allocation. We compared the photosynthetic characteristics and carbon translocation patterns in the under-canopy and light-gap sites between two summer-green perennial species: Cardamine leucantha with an annual long rhizome, and Smilacina japonica with a perennial short rhizome system. Flowering of both species occurs in early summer under decreasing light availability. In the light-gap, C. leucantha maintained high photosynthetic activity due to continuous leaf production, resulting in higher seed production than in the under-canopy. In contrast, the photosynthetic rate of S. japonica, producing leaves simultaneously, decreased with time irrespective of light conditions, resulting in stable seed production in both sites. Although seasonally decreasing light availability commonly restricts carbon assimilation of understory herbs, the responses of resource partitioning to variations in light availability depend greatly on the belowground structure of individual species.
• Investigation on the water stress in alpine vegetation using Hyperspectral Sensors

  Buho Hoshino, Gaku Kudo, Tetsuo Yabuki, Masami Kaneko, Sumiya Ganzorig

  2009 IEEE INTERNATIONAL GEOSCIENCE AND REMOTE SENSING SYMPOSIUM, VOLS 1-5 1856 - 1858 2009年 [査読有り][通常論文]
   

  The effect of global warming may be seen even on the top of the Mt. Daisetsuzan National Park (DNP) in Japan's northernmost island of Hokkaido where communities of alpine plants having been greatly suffered from the expansion of alien species. Alpine of the Mt. Daisetsu is in protected zone of the DNP and has no direct human influence. So far, this happening might indicate the negative effects of global scale climate changes in high mountainous ecosystem. Seriousness of that phenomenon is that it is completely changing the local vegetation. Due to the global warming, increased temperature causes rapid melting of the snow coverage at DNP and soil is quickly losing its moisture. In this study, alpine meadow vegetation in DNP was photographed with aid of the hyper-spectral sensors mounted on the airplane. Simultaneously, ground observations were also made. Hyperspectral sensors are having 60 bands with wavelength from 400 to 1000 nm, and resolution of 10 nm. Ground observations were made using the Field Spec devices for spectral measurement, GPS for mapping. Plant species, coverage, and soil moisture were investigated.
• Effectiveness of buzz pollination in Pedicularis chamissonis: significance of multiple visits by bumblebees

  Yuka Kawai, Gaku Kudo

  ECOLOGICAL RESEARCH 24 1 215 - 223 2009年01月 [査読有り][通常論文]
   

  Pollination success of plants is highly susceptible to the frequency of visits and foraging behavior of pollinators. Pollination of the nectarless flowers of Pedicularis species depends on bumblebee workers collecting pollen by vibrating the anthers (buzz pollination). However, little is known about the efficiency of the pollination system. Foraging behavior, pollen removal from anthers and pollen deposition on stigmas of P. chamissonis were studied to assess the effectiveness of buzz pollination in an alpine snowbed population of northern Japan. Although bumblebees tended to visit most of the flowers open at a given time within inflorescences during a single visit, pollen removal rate at the first visit was about 20%, and buzzing period decreased with increasing number of previous visits, resulting in a decreasing proportion of pollen removed per visit as the number of visits increased. These trends enable plants to provide pollen for more pollinators. The number of pollen grains deposited on stigmas was not saturated during the first visit and increased with additional visits. Irrespective of weak self-compatibility, evidence of interference between self and outcross pollen was lacking for seed production. Therefore, buzz pollination in P. chamissonis acts as a mechanism that improves the chance of cross-pollination upon multiple visits if pollinator visitation is frequent.
• Combined effects of inflorescence architecture, display size, plant density and empty flowers on bumble bee behaviour: experimental study with artificial inflorescences

  Hiroshi S. Ishii, Yuimi Hirabayashi, Gaku Kudo

  OECOLOGIA 156 2 341 - 350 2008年05月 [査読有り][通常論文]
   

  Pollen dispersal by pollinators is governed by the extent to which diverse effects on pollinator behaviour act independently or augment or moderate each other. Using artificial inflorescences, we assessed the behavioural responses of bumble bees to inflorescence architecture (raceme, panicle, and umbel), inflorescence size (7 or 13 flowers), inter-inflorescence distance and the proportion of empty flowers per inflorescence. The advantage of large inflorescences in terms of attractiveness was larger for racemes and umbels than for panicles, whereas the effect of inter-inflorescence distance on the number of successive probes was smaller for racemes than for panicles and umbels. The number of flowers probed per visit increased almost proportionally with display size when fewer flowers were empty, whereas the number increased less when many flowers were empty. Our results suggest that display size and the spatial arrangement of flowers and nectar within inflorescences can contribute to efficient pollination by affecting pollinator behaviour interactively.
• The effect of segregation of flowering time on fine-scale spatial genetic structure in an alpine-snowbed herb Primula cuneifolia

  A. S. Hirao, G. Kudo

  HEREDITY 100 4 424 - 430 2008年04月 [査読有り][通常論文]
   

  The flowering phenology of alpine-snowbed plants varies widely depending on the time of snowmelt. This variation may cause spatial and temporal heterogeneity in pollen dispersal, which in turn may influence genetic structure. We used spatial autocorrelation analyses to evaluate relative effect of segregation in flowering time and physical distance on fine-scale spatial genetic structure (SGS) of a snowbed herb Primula cuneifolia sampled in 10-m grids within a continuous snow patch (110 x 250 m) using nine allozyme loci. Although the individual flower lasts for <= 10 days, flowering season varied over 50 days from late June to the middle of August within the plot. The effect of flowering phenology on SGS was assessed using spatial autocorrelation analyses based on the pairwise kinship coefficients for all sampled plants (control pairs), plants with flowering overlap (co-flowering pairs) and plants with separate flowering season (non-co-flowering pairs). The degree of SGS increased as the extent of flowering segregation increased: co-flowering pairs < control pairs < non-co-flowering pairs, indicating substantial effect of restriction in gene flow due to phenological heterogeneity. Flowering segregation caused by snowmelt timing is a critical factor for reinforcing the fine-scale SGS in this species.
• A hybrid zone dominated by fertile F(1)s of two alpine shrub species, Phyllodoce caerulea and Phyllodoce aleutica, along a snowmelt gradient

  Y. Kameyama, T. Kasagi, G. Kudo

  JOURNAL OF EVOLUTIONARY BIOLOGY 21 2 588 - 597 2008年03月 [査読有り][通常論文]
   

  In alpine ecosystems, the steep environmental gradients produced by the difference in snowmelt timing create a dynamic selective regime for alpine plants. As these gradients directly alter flowering phenology, they can affect pollen-mediated gene flow among populations of single and related species. In northern Japan, we found a hybrid zone dominated by fertile F(1)s of two alpine shrub species, Phyllodoce caerulea and P. aleutica, along a snowmelt gradient. Seed germination confirmed the fertility of F-1 hybrid, making the rarity and absence of backcross and F-2 plants puzzling. The long-term clonal perpetuation of F-1 hybrids (at least a few thousand years ago) contributes the maintenance of this unique hybrid zone. The distribution patterns of chloroplast DNA haplotypes suggest that F-1 formation might be caused by directional pollen flow between parental species along the snowmelt gradient. Based on these results, we discuss the ecological and evolutionary significance of this unique hybrid zone.
• Timing of canopy closure influences carbon translocation and seed production of an understorey herb, Trillium apetalon (Trilliaceae)

  Takashi Y. Ida, Gaku Kudo

  ANNALS OF BOTANY 101 3 435 - 446 2008年02月 [査読有り][通常論文]
   

  Background and Aims The light availability on a temperate, deciduous-forest floor varies greatly, reflecting the seasonal leaf dynamics of the canopy trees. The growth and/or reproductive activity of understorey plants should be influenced by the length of the high-irradiance period from snowmelt to canopy closure. The aim of the present study was to clarify how spring-blooming species regulate the translocation of photosynthetic products to current reproduction and storage organs during a growing season in accordance with the changing light conditions. Methods Growth pattern, net photosynthetic rate, seed production, and shoot and flower production in the next year of Trillium apetalon were compared between natural and experimentally shaded conditions. Furthermore, translocation of current photosynthetic products within plants was assessed by a labelled carbon-chase experiment. Key Results During the high-irradiance period, plants showed high photosynthetic ability, in which current products were initially used for shoot growth, then reserved in the rhizome. Carbon translocation to developing fruit occurred after canopy closure, but this was very small due to low photosynthetic rates under the darker conditions. The shading treatment in the early season advanced the time of carbon translocation to fruit, but reduced seed production in the current year and flower production of the next year. Conclusions Carbon translocation to the storage organ had priority over seed production under high-irradiance conditions. A shortened bright period due to early canopy closure effectively restricts carbon assimilation, which greatly reduces subsequent reproductive output owing to low photosynthetic products for fruit development and small carbon storage for future reproduction. As populations of this species are maintained by seedling recruitment, acceleration of canopy closure timing may influence the maintenance and dynamics of populations.
• Linkages between phenology, pollination, photosynthesis, and reproduction in deciduous forest understory plants

  Gaku Kudo, Takashi Y. Ida, Tomokazu Tani

  ECOLOGY 89 2 321 - 331 2008年02月 [査読有り][通常論文]
   

  Light availability in the understory of deciduous forests changes drastically within the growing season due to the foliage dynamics of canopy trees. Because flowering phenology, photosynthetic characteristics, and fruiting success respond to such strong seasonality in light availability, we hypothesized that understory plants in such ecosystems should describe distinct phenological groups or syndromes where "syndrome'' is defined only as a set of characteristics that co-occur. To identify these phenological syndromes, we studied the flowering phenology, fruit or seed set, and photosynthetic characteristics for 18 perennial understory herbaceous species that differed in reproductive strategy over eight years in a deciduous forest in northern Japan. Three phenological groups emerged from this study: (1) spring bloomers, flowering and fruiting before the completion of canopy closure; (2) early-summer bloomers, flowering during the progress of canopy closure and fruiting after canopy closure; and (3) late-summer bloomers, flowering and fruiting after canopy closure. The spring bloomers had high photosynthetic rates and high fruiting abilities, but the flowering time varied considerably among years due to yearly fluctuations of snowmelt date. Bumble bee-pollinated species of spring bloomers showed variable seed-set success, while fly-pollinated species showed relatively stable seed sets over the years. The early-summer bloomers showed low fruiting abilities irrespective of pollination success, reflecting severe resource limitation with decelerating light availability during fruit development. Although the late-summer bloomers showed low photosynthetic rates under low-light conditions, high fruit-set success was attained if pollination was sufficient. These results support our hypothesis that phenological syndromes may be found in deciduous forest understory plants. Given that reproductive success of bee-pollinated spring bloomers is highly susceptible to seasonal fluctuation, climate change may have its strongest impacts on this group.
• 地球温暖化と森林生態系 : フェノロジーを介した生物間相互作用への影響

  工藤 岳

  森林科学 52 14 - 18 日本森林学会 2008年
• 送粉系生態学のこれまでの経過と最近の動向 (コメント,宮地賞受賞者総説)

  工藤 岳

  日本生態学会誌 58 3 168 - 170 一般社団法人 日本生態学会 2008年
• Size-dependent sex allocation in a monocarpic perennial herb, Cardiocrinum cordatum (Liliaceae)

  Guo-Xing Cao, Gaku Kudo

  PLANT ECOLOGY 194 1 99 - 107 2008年01月 [査読有り][通常論文]
   

  The size-dependent sex allocation model predicts that the relative resource allocation to female function often increases with plant size in animal-pollinated plants. If size effects on reproductive success vary depending on the environmental conditions, however, the size dependency may differ among populations. We tried to detect site-specific variation in size-dependent sex allocation of a monocarpic hermaphrodite with reference to light availability. Multiple flowers and fruits were sampled from the individuals of Cardiocrinum cordatum, a monocarpic understory herb, and pollen, ovule and seed production were measured with reference to the plant size in two populations. Furthermore, frequency and foraging behavior of pollinator visitation was observed. Ovule production per flower increased with plant size in both populations, while pollen production per flower increased with size only in the population under sparse canopy. Therefore, proportional allocation to male function decreased with plant size in the population under closed canopy, but did not change in the population under sparse canopy. Pollinators usually visited only one flower per plant, indicating the negligible geitonogamous pollination in this species. Although seed production under closed canopy was lower than that under sparse canopy, seed-set rate per flower and seed mass per fruit were independent of plant size in either of the populations. Size-dependent sex allocation in this species was site-specific, suggesting that not only resource storage before reproduction (i.e., plant size) but also resource availability of environment throughout the reproductive process (i.e., light availability) affect reproductive performance in this species.
• Floral sex allocation in a hermaphrodite herb with 1-day flowers, Hosta rectifolia (Liliaceae)

  Guo-Xing Cao, Gaku Kudo, Takashi Y. Ida

  PLANT SPECIES BIOLOGY 22 3 191 - 196 2007年12月 [査読有り][通常論文]
   

  The size-dependent sex allocation theory predicts that a female-based sex allocation is accelerated with increasing resource status in insect-pollinated hermaphrodite plants. However, variations in the mating environment among flowers, which are caused by pollinator movements and temporal fluctuation in the floral sex ratio, may cause diverse patterns in sex allocation among flowers within inflorescences. We examined the floral sex allocation among plants and among flowers within inflorescences in a perennial hermaphrodite species with 1-day flowers, Hosta rectifolia Nakai. Flowering progresses sequentially from basal to distal positions within an inflorescence with little flowering overlap among flowers. At the plant level, both pollen and ovule production per flower increased with plant size. Within inflorescences, both ovule and pollen production per flower declined from basal to distal positions, indicating decreasing resource availability per flower. The probability of fruit-set success under natural conditions also decreased from basal to distal positioned flowers within inflorescences. However, the pollen to ovule ratio of individual flowers remained constant, regardless of floral position and plant size. Constant sex allocation at the flower level is consistent with the prediction of the mating environment theory; every positioned flower seemed to have a similar potential of pollination success because there was no geitonogamous pollination.
• A test of the effect of floral color change on pollination effectiveness using artificial inflorescences visited by bumblebees

  Gaku Kudo, Hiroshi S. Ishii, Yuimi Hirabayashi, Takashi Y. Ida

  OECOLOGIA 154 1 119 - 128 2007年11月 [査読有り][通常論文]
   

  Floral color change has been recognized as a pollination strategy, but its relative effectiveness has been evaluated insufficiently with respect to other floral traits. In this study, effects of floral color change on the visitation pattern of bumblebees were empirically assessed using artificial flowers. Four inflorescence types were postulated as strategies of flowering behavior: type 1 has no retention of old flowers, resulting in a small display size; type 2 retains old flowers without nectar production; type 3 retains old flowers with nectar; and type 4 retains color-changed old flowers without nectar. Effects of these treatments varied depending on both the total display size (single versus multiple inflorescences) and the pattern of flower-opening. In the single inflorescence experiment, a large floral display due to the retention of old flowers (types 2-4) enhanced pollinator attraction, and the number of flower visits per stay decreased with color change (type 4), suggesting a decrease in geitonogamous pollination. Type-4 plants also reduced the foraging time of bees in comparison with type-2 plants. In the multiple inflorescence experiment, the retention of old flowers did not contribute to pollinator attraction. When flowering occurred sequentially within inflorescences, type-4 plants successfully decreased the number of visits and the foraging time in comparison with type-2 plants. In contrast, floral color change did not influence the number of visits, and it extended the foraging time when flowering occurred simultaneously within inflorescences but the opening of inflorescences progressed sequentially within a plant. Therefore, the effectiveness of floral color change is highly susceptible to the display size and flowering pattern within plants, and this may limit the versatility of the color change strategy in nature.
• Cost of reproduction in a spring ephemeral species, Adonis ramosa (Ranunculaceae): Carbon budget for seed production

  Satoshi Horibata, Shigeaki F. Hasegawa, Gaku Kudo

  ANNALS OF BOTANY 100 3 565 - 571 2007年09月 [査読有り][通常論文]
   

  Background and Aims Spring ephemerals have a specific life-history trait, i.e. shoot growth and sexual reproduction occur simultaneously during a short period from snowmelt to canopy closure in deciduous forests. The aim of this study is to clarify how spring ephemerals invest resources for seed production within a restricted period. Methods In order to evaluate the cost of reproduction of a typical spring ephemeral species, Adonis ramosa, an experiment was conducted comprising defoliation treatments (intact, one-third and two-thirds leaf-cutting) and fruit manipulations (control, shading and removal) over two growing seasons. In addition, measurements were made of the movements of carbon assimilated via C-13 tracing. Key Results Survival rate was high irrespective of treatments and manipulations. The proportion of flowering plants and plant size decreased as a result of the defoliation treatments over 2 years, but the fruit manipulations did not affect flowering activity or plant size. Seed set and seed number decreased as a result of fruit shading treatment, but the defoliation treatments did not affect current seed production. Individual seed weight also decreased in the second year due to fruit shading. The 13C tracing experiment revealed that young fruits had photosynthetic ability and current photosynthetic products from leaves were mainly transferred to the below-ground parts, while translocation to fruit was very small even when fruit photosynthesis was restricted by the shading treatment. Conclusions Current foliage photosynthetic products are largely stored in the below-ground parts for survival and future growth, and about one-third of the resources for seed production may be attained by fruit photosynthesis. Therefore, the trade-off between current seed production and subsequent growth is weak. The cost of seed production may be buffered by sufficient storage in the below-ground organs, effective photosynthesis under high irradiation and self-assimilation ability of fruits.
• Eight microsatellite markers for sympatric alpine shrubs, Phyllodoce aleutica and P-caerulea (Ericaceae)

  Y Kameyama, T Kasagi, G Kudo

  MOLECULAR ECOLOGY NOTES 6 2 402 - 404 2006年06月 [査読有り][通常論文]
   

  Phyllodoce aleutica and Phyllodoce caerulea are sympatric alpine-snowbed plants in northern Japan. They compete for pollinators (bumblebees) each other and the competitive situation varies depending on snow conditions. We isolated and characterized eight microsatellite loci in these species. Additionally, one of 13 primers developed for Rhododendron metternichii was available in these species. The expected heterozygosity of these nine markers ranged from 0.06 to 0.93 in P. aleutica and from 0.09 to 0.96 in P. caerulea. These markers may be useful to reveal the mating system evolution, patterns of pollen flow and the process of natural hybridization in these Phyllodoce species.
• Seasonal changes in pollinator activity influence pollen dispersal and seed production of the alpine shrub Rhododendron aureum (Ericaceae)

  AS Hirao, Y Kameyama, M Ohara, Y Isagi, G Kudo

  MOLECULAR ECOLOGY 15 4 1165 - 1173 2006年04月 [査読有り][通常論文]
   

  In alpine ecosystems, microscale variation in snowmelt timing often causes different flowering phenology of the same plant species and seasonal changes in pollinator activity. We compared the variations in insect visitation, pollen dispersal, mating patterns, and sexual reproduction of Rhododendron aureum early and late in the flowering season using five microsatellites. Insects visiting the flowers were rare early in the flowering season (mid-June), when major pollinators were bumblebee queens and flies. In contrast, frequent visitations by bumblebee workers were observed late in the season (late July). Two-generation analysis of pollen pool structure demonstrated that quality of pollen-mediated gene flow was more diverse late in the season in parallel with the high pollinator activity. The effective number of pollen donors per fruit (N-ep) increased late in the season (N-ep = 2.2-2.7 early, 3.4-4.4 late). However, both the outcrossing rate (t(m)) and seed-set ratio per fruit were smaller late in the season (t(m) = 0.89 and 0.71, seed-set ratio = 0.52 and 0.18, early and late in the season, respectively). In addition, biparental inbreeding occurred only late in the season. We conclude that R. aureum shows contrasting patterns of pollen movement and seed production between early and late season: in early season, seed production can be high but genetically less diverse and, during late season, be reduced, possibly due to higher inbreeding and inbreeding depression, but have greater genetic diversity. Thus, more pollinator activity does not always mean more pollen movement.
• Significance of nectar distribution for bumblebee behaviour within inflorescences, with reference to inflorescence architecture and display size

  Yuimi Hirabayashi, Hiroshi S. Ishii, Gaku Kudo

  ECOSCIENCE 13 3 351 - 359 2006年 [査読有り][通常論文]
   

  Because pollinator behaviour within plants affects the mating outcomes of animal-pollinated plants, plants may regulate the pollinator behaviour by controlling floral design and display to maximize pollination efficiency. We assessed how extent of the display size, inflorescence architecture, and nectar distribution within inflorescences alter bumblebee behaviour (number of flowers visited, time of stay, and nectar intake efficiency) under controlled conditions using artificial inflorescences. The effect of display size on bumblebee attraction was also measured. Eighteen types of artificial inflorescences, two display sizes (large and small) x three architectures (particle, umbel, and raceme) x three nectar distributions (constant nectar content in every flower, gradual changes in nectar content, and random distribution of empty and rewarded flowers) were visited by bumblebees. The mean nectar amount per flower was set as 3 mu L in 2003 and 1 mu L in 2004. Although the inflorescence architecture had little effect on bumblebee behaviour, the random nectar distribution decreased the number of successive flower visits (both 3 mu L and 1 mu L) and staying time (only 3 mu L) during a single visit and increased the foraging efficiency (both 3 mu L and 1 mu L). These features may contribute to decreases in the geitonogamous pollination and pollen loss during pollinator movements. Display size did not influence the attraction of bumblebees in this study. Our results suggest that nectar distribution within inflorescences can be a strategy for efficient pollination by manipulating pollinator behaviour.
• Seasonal pattern of leaf production and its effects on assimilation in giant summer-green herbs in deciduous forests in northern Japan

  T Tani, G Kudo

  CANADIAN JOURNAL OF BOTANY-REVUE CANADIENNE DE BOTANIQUE 84 1 87 - 98 2006年01月 [査読有り][通常論文]
   

  Understory vegetation of northern deciduous forests in far eastern Asia is characterized by giant summer-green herbs. We examined the patterns of height growth, leaf accumulation, photosynthetic characteristics, daily net assimilation, and dry matter allocation within aboveground parts of six giant summer-green herbs with reference to light conditions in deciduous forests. Plant height, leaf number, and total leaf area per plant increased with progressing tree-canopy closure in five species (Cacalia hastata L. subsp. orientalis Kitam., Cirsium kamtschaticum Ledeb., Filipendula kamtschatica (Pall.) Maxim. f. kamtschatica, Senecio cannabifolius Less., and Urtica platyphylla Wedd.) that had continuous leaf production throughout the growing season, whereas one species (Veratrum album L. subsp. oxysepalum Hulten) with early leaf production, completed leaf production mostly before the beginning of tree-canopy closure. Maximum photosynthetic and dark respiration rates decreased seasonally in all species. Species with continuous leaf emergence accumulated leaves acclimatized to shade conditions, which offset the decreasing photosynthesis of individual leaves with progressing tree-canopy closure, resulting in stable carbon gain even under decreasing light availability. In contrast, V. album assimilated vigorously during the short period of high irradiance before tree-canopy closure, and decreased its assimilation rate continuously thereafter.
• Habitat-specific responses in the flowering phenology and seed set of alpine plants to climate variation: implications for global-change impacts

  G Kudo, AS Hirao

  POPULATION ECOLOGY 48 1 49 - 58 2006年01月 [査読有り][通常論文]
   

  The timing of the snowmelt is a crucial factor in determining the phenological schedule of alpine plants. A long-term monitoring of snowmelt regimes in a Japanese alpine area revealed that the onset of the snowmelt season has been accelerated during the last 17 years in early snowmelt sites but that such a trend has not been detected in late snowmelt sites. This indicates that the global warming effect on the snowmelt pattern may be site-specific. The flowering phenology of fellfield plants in an exposed wind-blown habitat was consistent between an unusually warm year (1998) and a normal year (2001). In contrast, the flowering occurrence of snowbed plants varied greatly between the years depending on the snowmelt time. There was a large number of flowering species in the fellfield community from mid- to late to late June and from mid- to late July. The flowering peak of an early-melt snowbed plant community was in the middle of the flowering season and that of a late-melt snowbed community was in the early flowering season. These habitat-specific phenological patterns were consistent between 1998 and 2001. The effects of the variation in flowering timing on seed-set success were evaluated for an entomophilous snowbed herb, Peucedanum multivittatum, along the snowmelt gradient during a 5-year period. When flowering occurred prior to early August, mean temperature during the flowering season positively influenced the seed set. When flowering occurred later than early August, however, the plants enjoyed high seed-set success irrespective of temperature conditions if frost damage was absent. These observations are probably explained based on the availability of pollinators, which depends not only on ambient temperature but also on seasonal progress. These results suggest that the effects of climate change on biological interaction may vary depending on the specific habitat in the alpine ecosystem in which diverse snowmelt patterns create complicated seasonality for plants within a very localized area.
• Microscale variations in the mating system and heterospecific incompatibility mediated by pollination competition in alpine snowbed plants

  G Kudo, T Kasagi

  PLANT SPECIES BIOLOGY 20 2 93 - 103 2005年08月 [査読有り][通常論文]
   

  The effects of pollination competition between related species on pollen limitation, selfing ability and heterospecific incompatibility were studied in the alpine snowbed shrubs, Phyllodoce caerulea and Phyllodoce aleutica (Ericaceae) along local snowmelt gradients. The flowering season of these species highly overlapped and they shared the same method of pollination (via bumblebees). The floral density and nectar production were higher in P. caerulea in the early snowmelt habitat, but they were higher in P. aleutica in the late snowmelt habitat, reflecting the species-specific sensitivity to a short growing season. Bumblebee preference shifted from P. caerulea to P. aleutica along the snowmelt gradient, reflecting the changes in the relative reward level between the species. The extent of pollen limitation of P. caeruea was severe in the late snowmelt habitat, whereas that of P. aleutica was obvious in the early snowmelt habitat. A pollination experiment revealed that P. caerulea showed a consistently low selfing ability, whereas P. aleutica showed a high selfing ability in the early snowmelt habitat and shifted to an obligate outcrosser in the late snowmelt habitat. The frequency of interspecific bumblebee movement for P. caerulea from P. aleutica increased in the late snowmelt habitat. To the contrary, the frequency of interspecific movement for P. aleutica from P. caerulea decreased along the snowmelt gradient. P. caerulea did not indicate heterospecific incompatibility to P. aleutica pollen. In contrast, P. aleutica indicated heterospecific incompatibility to P. caerulea pollen, reflecting the high risk of receiving heterospecific pollen as a result of interspecific bumblebee movement. However, heterospecific compatibility of P. aleutica disappeared in the late snowmelt habitat, where the risk of heterospecific pollen receipt was low. Therefore, changes in interspecific bumblebee movement might have been responsible for the variation in heterospecific incompatibility among P. aleutica populations. The local snowmelt gradient creates diverse biological interactions and mating system evolution in the alpine ecosystem.
• Floral and inflorescence effects on variation in pollen removal and seed production among six legume species

  G Kudo, LD Harder

  FUNCTIONAL ECOLOGY 19 2 245 - 254 2005年04月 [査読有り][通常論文]
   

  1. Most flowering plants display multiple flowers, so that the interaction with pollinators that determines their mating success can vary with both the characteristics of individual flowers and aggregate properties of the entire floral display, especially the number of open flowers (floral display size). These effects are seldom examined in concert and their collective consequences for interspecific differences in reproductive performance have not been considered previously. 2. In this paper, we characterize the relation of pollen removal and seed production to differences in floral and inflorescence characteristics among six species of herbaceous legumes (Fabaceae). 3. Several aspects of reproductive performance varied significantly among species with either plant traits or aspects of pollinator behaviour that depend on plant traits. Pollinator visitation, as measured by the ratio of pollen removal during 24 h to first-visit removal, varied positively with both nectar production per flower and floral display size. Bumble-bees visited more flowers per inflorescence on species with large floral displays, with no increase in the proportion of flowers visited. Pollen removal during a flower's first visit varied negatively among species with the mean number of flowers visited by bees per inflorescence. 4. These results indicate that floral and inflorescence traits act together to influence both pollinator energetics, which affects a plant species' attractiveness, and the rate of pollen removal, which should affect pollen export. In contrast, neither pollen removal during 24 h, nor female fecundity varied significantly with floral or display characteristics.
• Comparisons of growth schedule, reproductive property and allocation pattern among three rhizomatous Polygonatum species with reference to their habitat types

  T Hasegawa, G Kudo

  PLANT SPECIES BIOLOGY 20 1 23 - 32 2005年04月 [査読有り][通常論文]
   

  Phenology, reproductive traits and dry matter allocation were compared among three rhizomatous Polygonatum species (Liliaceae) growing in different habitats. Polygonatum odoratum var. maximowiczii grows mainly on the floor of deciduous forests; Polygonatum involucratum at forest edges with patchy light spots; and Polygonatum humile in moist grasslands with sparse vegetation cover. The purpose of this study was to describe the growth patterns and reproductive traits of related species for the consideration of habitat-specific responses of life-history traits. The leaf emergence and reproductive phenology of P. odoratum progressed more rapidly and the growth season was shorter in comparison with other species, reflecting seasonal changes in light conditions in the understory. Every species showed very low selfing ability but the evidence of pollen limitation was negligible under natural pollination. Dry matter allocations to above- and below-ground parts were similar among species but the patterns of annual resource allocation varied greatly: P. odoratum showed large annual shoot production but annual rhizome growth was small (3-4 cm/year). The lifespan of rhizomes was >8 years in this species, whereas it was 34 years in other species. The annual growth of rhizomes in P. humile was large (15.5 cm/year) and branching was frequent, indicating rapid vegetative expansion under unstable conditions. The leaf/stem ratio was large in P. humile and small in P. odoratum. The allocation and growth pattern of P. involucratum were intermediate. Such differences in growth and allocation patterns among the three Polygonatum species could reflect the possible directions of life-history strategy against specific light conditions and habitat stability, although phylogenetic constraints should be taken into account for the interspecific comparison.
• Interspecific pollinator movements and heterospecific incompatibility: comparisons between Phyllodoce caerulea and Phyllodoce aleutica along snowmelt gradients (vol 7, pg 73, 2005)

  T Kasagi, G Kudo

  EVOLUTIONARY ECOLOGY RESEARCH 7 3 504 - 504 2005年03月 [査読有り][通常論文]
  
• Comparisons of germination traits of alpine plants between fellfield and snowbed habitats

  Y Shimono, G Kudo

  ECOLOGICAL RESEARCH 20 2 189 - 197 2005年03月 [査読有り][通常論文]
   

  We examined the seed-germination responses of 27 alpine species with reference to habitat type (fellfield and snowbed), temperature (five regimes), and light requirement. About 70% of species showed > 40% germination at warm temperatures without cold stratification. However, a moist-chilling treatment markedly improved the germination percentages in most species, especially under cool conditions. Thus, cold stratification effectively reduced the temperature requirement for germination. Patterns of germination response within species were not consistent between the fellfield and snowbed habitats for species inhabiting both habitats. For interspecific comparisons, there were no significant differences in germination responses to the temperature regimes and the cold stratification between the fellfield and snowbed species. Also, germination speed and the length of germinating period did not differ between fellfield and snowbed species. Most species (86%) showed a requirement for light for germination without cold stratification. Although the extent of the light requirement was reduced after cold stratification in some species, the light requirement of most small-seeded species remained. The combination of cold stratification and the light requirement is a major factor determining the seedling emergence and formation of seed banks in alpine plants. However, habitat-specific patterns of germination traits were less clear, suggesting similar germination traits in fellfield and snowbed plants, at least under controlled conditions in the laboratory.
• Resource allocation pattern under simulated environmental change and seedling establishment of alpine dwarf shrubs in a mid-latitude mountain

  S. Suzuki, G. Kudo

  PHYTON-ANNALES REI BOTANICAE 45 4 409 - 414 2005年 [査読有り][通常論文]
   

  SUZUKI S. & KUDO G. 2005. Resource allocation pattern under simulated environmental change and seedling establishment of alpine dwarf shrubs in a mid-latitude mountain. - Phyton (Horn, Austria) 45 (4): (409)-(414). We set up 11 open-top chambers (OTCs) on a fell-field (1680 in a.s.l.) in the Taisetsu Mountains, northern Japan to assess responses to warming of circumpolar plants growing around their southern distribution margins. The OTCs increased the daily mean air-temperature by 1.7 degrees C throughout the growing season. For five alpine species - two deciduous shrubs: Arctous alpinus and Vaccinium uliginosum and three evergreen shrubs: Ledum palustre subsp. decumbens, Vaccinium vitis-idaea, and Empetrum nigrum var. japonicum - effects of artificial warming on reproductive components were investigated during five (for flower production) or four (for fruit production) years. In addition, seedling establishments were compared among the three vegetation types and bare ground. Flower production in the OTCs was enhanced significantly in both deciduous species over that of control plots. In contrast, comparison to the control plots showed a significant decrease in flower production in the OTCs in two of the evergreen species. Fruit production of V. uliginosum and L. palustre was enhanced in the OTCs relative to the control plots. Both deciduous species allocated their resources to reproduction rather than to vegetative growth. Seedling establishment was very rare and was restricted on bare ground in this study site. We concluded that the difficulty of seedling establishment gives advantage to some species, which show active vegetative growth under global warming, to develop their vegetation cover.
• Overwintering leaves of a forest-floor fern, Dryopteris crassirhizoma (Dryopteridaceae): A small contribution to the resource storage and photosynthetic carbon gain

  T Tani, G Kudo

  ANNALS OF BOTANY 95 2 263 - 270 2005年01月 [査読有り][通常論文]
   

  Background and Aims Dryopteris crassirhizoma is a semi-evergreen fern growing on the floor of deciduous forests. The present study aimed to clarify the photosynthetic and storage functions of overwintering leaves in this species. e Methods A 2-year experiment with defoliation and shading of overwintering leaves was conducted. Photosynthetic light response was measured in early spring (for overwintering leaves) and summer (for current-year leaves). Key Results No nitrogen limitation of growth was detected in plants subjected to defoliation. The number of leaves, their size, reproductive activity (production of sori) and total leaf mass were not affected by the treatment. The defoliation of overwintering leaves significantly reduced the bulk density of rhizomes and the root weight. The carbohydrates consumed by the rhizomes were assumed to be translocated for leaf production. Photosynthetic products of overwintering leaves were estimated to be small. Conclusion Overwintering leaves served very little as nutrient-storage and photosynthetic organs. They partly functioned as a carbon-storage organ but by contrast to previous studies. their physiological contribution to growth was found to be modest, probably because this species has a large rhizome system. The small contribution of overwintering leaves during the short-term period of this study may be explained by the significant Storage ability of rhizomes in this long-living species. Other ecological functions of overwintering leaves, such as suppression of neighbouring plants in spring, are suggested. (C) 2004 Annals of Botany Company.
• Interspecific pollinator movements and heterospecific incompatibility: comparisons between Phyllodoce caerulea and Phyllodoce aleutica along snowmelt gradients

  T Kasagi, G Kudo

  EVOLUTIONARY ECOLOGY RESEARCH 7 1 73 - 87 2005年01月 [査読有り][通常論文]
   

  Relationships between interspecific pollinator movements and heterospecific incompatibility were investigated in two co-flowering alpine-snowbed shrubs, Phyllodoce caerulea and Phyllodoce aleutica, among plots arranged along snowmelt gradients. Bumblebees, the predominant pollinator of these species. preferred P caerulea in early- to middle-snowmelt plots but P aleutica in late-snowmelt plots. This switching of preference reflected the changes in the relative floral densities of these species along the snowmelt gradients. The frequency of bumblebee movements from P aleutica to P caerulea flowers increased at late-snowmelt plots, whereas that from P caerulea to P. aleutica flowers decreased at late-snowmelt plots. Thus, the risk of heterospecific pollen receipt increased in P caerulea but decreased in P aleutica from early- to late-snowmelt habitats. Phyllodoce caerulea showed similar seed-set rates among conspecific, heterospecific and species-mixed pollination treatments throughout the plots, indicating that there is no mechanism to avoid hybridization at P aleutica pollen. On the other hand, P aleutica pollinated with P. caerulea pollen showed a very low seed set in comparison with that pollinated with conspecific pollen in early- and middle-snowmelt plots. However, the seed set of P aleutica did not differ among the treatments at late-snowmelt plots. Therefore, P aleutica showed heterospecific incompatibility with P caerulea pollen only in the early-to middle-snowmelt populations. Changes in interspecific bumblebee movements might be responsible for the variation in heterospecific incompatibility among the P aleutica populations.
• Climate change and shoot elongation of alpine dwarf pine (Pinuspumila regel): Comparisons between six Japanese mountains

  N. Wada, K. Watanuki, K. Narita, S. Suzuki, G. Kudo, A. Kume

  PHYTON-ANNALES REI BOTANICAE 45 4 253 - 260 2005年 [査読有り][通常論文]
   

  In northern to central Japan, alpine dwarf pine (Pinus pumila Regel) is a principal component of vegetation in the alpine life zone above the timberline. In this study, we examined interannual variations in the shoot elongation of P. pumila growing on the summits of six Japanese mountains and analysed the relationships between climatic factors and shoot growth during the period from 1980 to 2003. A significant increment of annual shoot elongation over the last 24 years was detected in three populations studied in central Japan, showing synchronization between the populations. However, such a trend was not found in the populations in northern Japan. In central Japan, interannual increasing trends in summer temperatures during the period were observed at meteorological stations near the populations. In the three populations of northern Japan, however, similar trends were not obvious, but a significant decreasing trend in summer sunshine duration was observed at a meteorological station located near the northernmost population. Summer sunshine duration, as well as summer temperature, was significantly positively correlated with shoot elongation of P. pumila in four out of six populations. We discuss these geographical variations in interannual shoot elongation of P. pumila between the six populations in relation to climate change in Japan.
• Landscape genetics of alpine-snowbed plants: comparisons along geographic and snowmelt gradients

  AS Hirao, G Kudo

  HEREDITY 93 3 290 - 298 2004年09月 [査読有り][通常論文]
   

  The genetic structure of three snowbed-herb species (Peucedanum multivittatum, Veronica stelleri, and Gentiana nipponica) was analyzed using allozymes across nine populations arranged as a matrix of three snowmelt gradients x three geographic locations within 3 km in the Taisetsu Mountains, northern Japan. Phenologically asynchronous populations are packed within a local area in alpine snowbeds, because flowering season of alpine plants depends strongly on the timing of snowmelt. Moderate genetic differentiation was detected among local populations in every species (F-ST = 0.03 - 0.07). There was a significant correlation between the geographic distance and genetic distance in the P. multivittatum populations, but not in the V. stelleri and G. nipponica populations. On the other hand, a significant correlation between the phenological distance caused by snowmelt timing and genetic distance was detected in the V. stelleri and G. nipponica populations, but not in the P. multivittatum populations. The snowmelt gradient or geographic separation influenced hierarchical genetic structure of these species moderately (F-RT <0.04). Restriction of gene flow due to phenological separation and possible differential selection along the snowmelt gradient may produce genetic clines at microgeographic scale in these species.
• Flowering phenology of tropical-alpine dwarf trees on Mount Kinabalu, Borneo

  G Kudo, S Suzuki

  JOURNAL OF TROPICAL ECOLOGY 20 563 - 571 2004年09月 [査読有り][通常論文]
   

  The flowering phenology of five alpine dwarf-tree species was observed in the summit region (3900-3950 m elevation) of Mt. Kinabalu on Borneo Island from March.1.998 to November 2001. For each target species, 20-50 individual plants were numbered in two observation plots and the number of inflorescences was monitored at 23-mo intervals. The flowering patterns varied among species. Rhododendron buxifolium bloomed extensively every March-May at the main plot but the flowering pattern at the subplot was less predictable. Mass flowering occurred in March 1998 when drought stress was very severe due to an El Nino event. Rhododendron ericoides showed continuous flowering throughout the year and high synchrony between the plots. Extensive flowering of Leptospermum recurvuin occurred synchronously within and between plots in the early half of 1999, then flowering activity decreased greatly. Photinia davidiana showed an annual flowering cycle but the timing of the peak flowering differed between the plots. Vaccinium stapfianum showed synchronous flowering between the plots and the flowering peak appeared at longer than 1-y intervals. Plant size was positively correlated with mean flower production in all species, and with the flowering frequency of R. ericoides, R. buxifoilium, and V. stapfianum at one of the plots at least. Two fleshy-fruited species, P. davidiana and V. stapfianum, had high selfing ability for fruit production and showed relatively low flowering synchrony among individuals in comparison with the other species. These results indicate that the trigger for initiation of flowering may differ among sympatric species in a tropical-alpine ecosystem at least in normal years.
• Does seed production of spring ephemerals decrease when spring comes early?

  G Kudo, Y Nishikawa, T Kasagi, S Kosuge

  ECOLOGICAL RESEARCH 19 2 255 - 259 2004年03月 [査読有り][通常論文]
   

  To predict the effect of global warming on plant reproductive success, seed-sets of spring ephemerals were compared between a year of extremely warm spring (2002) and normal years at cool-temperate deciduous forests in northern Japan. The spring of 2002 was the warmest in the last 40 years and most spring-ephemeral plants bloomed 7-17 days earlier than usual. The seed-set of bumblebee-pollinated Corydalis ambigua drastically decreased in 2002 in every population. The small bee-pollinated Gagea lutea also significantly decreased in 2002. However, the seed-sets of two fly pollinated species, Adonis ramosa and Anemone flaccida, were not influenced by early flowering. These results indicat that the effect of global warming on seed production of spring ephemerals differs between species depending on the type of pollinators, and that bee-pollinated species can have serious impacts on reproductive success as a result of climate change.
• Floral sex allocation in Corydalis ambigua populations visited by different pollinators

  G Kudo, T Kasagi

  ECOSCIENCE 11 2 218 - 227 2004年 [査読有り][通常論文]
   

  We studied variations in reproductive success, pollinator behaviour, and intra-inflorescence sex allocation of Corydalis ambigua between populations having different pollinator types. This species is self-incompatible and predominantly pollinated by bumblebees. Bombus hypocrita subsp. sapporoensis was a dominant flower visitor in lowland populations. It behaved as a nectar robber but contributed as a pollinator. A legitimate pollinator, Bombus hypnorum subsp. koropokkrus, was common in mountainous areas. Seed production in lowland populations was intensively restricted by pollen limitation caused by low pollination efficiency of robber-like pollinators, whereas the extent of pollen limitation was small in mountain populations. Seed-set success under natural pollination significantly decreased in upper flowers within inflorescences in every population. Pistil mass, ovule number, and corolla mass decreased from bottom to top flowers in every population, corresponding to the seed-set pattern. Stamen mass and pollen number were almost identical among flower positions in lowland populations, whereas they increased from bottom to top flowers in mountain populations. Legitimate pollinators showed larger pollen removal per visit and tended to visit more flowers during a single stay than robber-like pollinators, resulting in more geitonogamous pollen flow (i.e., self pollination between flowers). When geitonogamy is intense, higher allocation to male function in upper flowers should increase donation success because bumblebees tend to leave an inflorescence, from upper flowers. These results suggest that pollinator behaviour is a strong selective force causing variations in the sex allocation of plants.
• Floral color change in Weigela middendorffiana (Caprifoliaceae): reduction of geitonogamous pollination by bumble bees

  TY Ida, G Kudo

  AMERICAN JOURNAL OF BOTANY 90 12 1751 - 1757 2003年12月 [査読有り][通常論文]
   

  We examined the significance of retaining color-changed flowers in pollination success of Weigela middendorffiana through a single visit of bumble bees. Inner parts of flowers changed color with age from yellow to red. In an investigation of the mating system, duration of each color phase, reproductive ability of each of the color-phase flowers, and the effects of color-changed flowers on bumble bee behavior (1) flowers of this species were self-incompatible, (2) color-changed flowers provided little reward to pollinators and little residual reproductive ability, (3) the timing of floral color change was delayed with the progress of flowering season within individual plants, while the duration of the red phase shortened with the progress of flowering season, and (4) red-phase flowers did not attract bumble bees at a distance but did contribute to reducing the number of successive flower visits during a single stay within the plants. Red-phase flowers seemed to indicate the low reward level of old flowers and functioned as a cue to discourage pollinators from staying longer on the same plant. Our results predict that the retention of color-changed flowers without sexual function can enhance the pollination success of a whole plant through male function by reducing successive flower visits during a single stay of pollinators, i.e., geitonogamous pollination.
• Variations in bumble bee preference and pollen limitation among neighboring populations: comparisons between Phyllodoce caerulea and Phyllodoce aleutica (Ericaceae) along snowmelt gradients

  T Kasagi, G Kudo

  AMERICAN JOURNAL OF BOTANY 90 9 1321 - 1327 2003年09月 [査読有り][通常論文]
   

  Two alpine-snowbed shrubs, Phyllodoce caerulea and P. aleutica (Ericaceae), co-occur in locales in northern Japan with early to late snowmelt, but they have different mating systems. Phyllodoce caerulea is an obligate outcrosser in any population, whereas the selfing ability of P. aleutica is highly variable among neighboring populations along snowmelt gradients: it shows high self-compatibility in early to middle snowmelt populations but low self-compatibility in late snowmelt populations. We investigated the relationships between pollinator availability and mating systems of these species along three snowmelt gradients. Relative abundance of flowers and nectar standing crop of P. caerulea decreased from early to late snowmelt plots. Bumble bees preferred P. caerulea to P. aleutica in early and middle snowmelt plots, while their preference shifted to P. aleutica in late snowmelt plots. Pollen limitation was severe in P. aleutica in early to middle snowmelt plots but it was severe in P. caerulea in late snowmelt plots. Seed-set success under natural conditions of P. aleutica was higher than that of P. caerulea in all plots. Thus, we infer that the setting ability of P. aleutica under pollinator limitation acts as a reproductive assurance. We conclude that the interaction through pollination between the sympatric species is strong enough to cause a phenotypic change in mating system even within a local area.
• Anther arrangement influences pollen deposition and removal in hermaphrodite flowers

  G Kudo

  FUNCTIONAL ECOLOGY 17 3 349 - 355 2003年06月 [査読有り][通常論文]
   

  1. Effects of anther arrangement on pollen deposition and removal in hermaphrodite flowers were experimentally quantified to assess the ecological significance of stamen structure. The anther arrangement of Brassica rapa was modified into six types with respect to anther number and the spatial arrangement of long and short stamens. Each anther treatment was combined with a nectar-intact and nectar-depleted treatment. After single visits by bumblebees in a glasshouse, the visit duration to each flower and the number of pollen grains deposited on stigmas and pollen grains remaining in long and short anthers were measured. 2. Visits were significantly shorter in nectar-depleted flowers. Short anthers also extended visit duration, but modification of the long anther arrangement had no effect. Pollen deposition on stigmas depended on the number of long anthers and on visit duration. Although an increase in long anther number accelerated self-pollination, removal of short anthers did not influence pollen deposition. 3. Pollen removal from long anthers depended on anther treatment and visit duration, but not on nectar availability. Any modification of anther arrangement tended to increase pollen removal during single visits. Long anthers contributed to the decrease in pollen removal per visit, while pollen removal from short anthers depended only on visit duration. Short anthers appeared to have a different function from the restriction of pollen removal during single visits by bumblebees. 4. Thus, long and short anthers made different contributions to pollination efficiency of nectar-feeding bumblebees. The maintenance of different types of stamens in Brassicaceae plants (tetradynamous stamens) may reflect functional advantages for a diverse pollination syndrome if the pollination efficiency of long and short anthers varies depending on the type of pollinator.
• Warming effects on growth, production, and vegetation structure of alpine shrubs: a five-year experiment in northern Japan

  G Kudo, S Suzuki

  OECOLOGIA 135 2 280 - 287 2003年04月 [査読有り][通常論文]
   

  Warming effects on shoot growth, production, reproductive activity, and vegetation structure of alpine shrubs were measured over 5 years in a mid-latitude alpine fellfield in northern Japan. Open-top chambers (OTC) increased the daily mean air-temperature by 1.5-2.3degreesC throughout the growing season but the effect on soil temperature was small. Two evergreen species, Ledum palustre and Empetrum nigrum, tended to increase their annual shoot production and aboveground-mass accumulation in the OTCs, whereas flower production did not differ. Two deciduous species, Vaccinium uliginosum and Arctous alpinus, increased their flower production in the OTCs, whereas the vegetative growth and mass accumulation did not change. No significant differences in vegetative and flower production were detected in Vaccinium vitis-idaea between the OTCs and control plots. The shoot survival and growth in terms of height of most species increased in the OTCs relative to the control treatment, and the growth rate was significantly different among species. As a result, interspecific competition seemed to be accelerated in the OTCs, and the less competitive V. vitis-idaea was suppressed by other plant species. The response to the warming observed in this study was rather different from that seen in arctic and subarctic plants even within the same species, indicating that the warming effect may cause different responses between arctic and mid-latitude alpine ecosystems. We concluded that the artificial warming over 5 years accelerated the growth of a few restricted species and lead to the change in vegetation structure in the mid-latitude alpine ecosystem.
• Variations in leaf traits and susceptibility to insect herbivory within a Salix miyabeana population under field conditions

  G Kudo

  PLANT ECOLOGY 169 1 61 - 69 2003年 [査読有り][通常論文]
   

  Variations in leaf traits (toughness, total nitrogen and total phenolic concentrations) and susceptibility to herbivory in Salix miyabeana were studied among individual trees within a population under field conditions. Leaf quality clearly decreased as season progressed, i.e. increases in leaf toughness and total phenolics and decrease in leaf nitrogen. Seasonal pattern and extent of herbivore attack were similar between years. Significant correlation between leaf traits and susceptibility to herbivore attack was detected, while effects of sex and plant size on leaf traits and herbivory were less clear. There was a negative correlation between total nitrogen and total phenolics, and a positive correlation between leaf toughness and total phenolics among trees. Trees with high quality leaves tended to suffer from frequent herbivore attack and leaf damage. Such a clear relationship between leaf traits and susceptibility to herbivory may be related with a life-history strategy of willows, which are rapid-growing pioneer species and generally respond to herbivorous damage not by induced resistance but by compensative growth.
• Storage ability of overwintering leaves and rhizomes in a semi-evergreen fern, Dryopteris crassirhizoma (Dryopteridaceae)

  T Tani, G Kudo

  ECOLOGICAL RESEARCH 18 1 15 - 24 2003年01月 [査読有り][通常論文]
   

  Dryopteris crassirhizoma is a rhizomatous semi-evergreen fern growing in the understory of deciduous forests. Although the top portion of the overwintering leaves began to wither in early winter, intensive senescence occurred in the spring, concurrently with new leaf development. Dry weight comparisons between organs revealed that the rhizome occupied the largest proportion of the total mass, followed by the pinnae. To assess the storage ability of overwintering leaves and the rhizome, seasonal changes in nitrogen content and the dry mass of pinnae and the rhizome were measured. Nitrogen (36.6%) was resorbed from winter-withering pinnae, but not from spring-withering pinnae. In contrast, a similar decrease in dry mass per unit area occurred between winter- and spring-withering pinnae (similar to15%). These results indicate that overwintering leaves serve as a carbohydrate storage organ, but do not serve as a nitrogen storage organ. Nitrogen was not translocated from the rhizome during the early growing season, but translocation did occur in late summer and autumn. The dry mass of the rhizome decreased by 18.4% in spring, at the time of new leaf expansion. The amount of exported dry matter from the rhizome was threefold larger than that from senescent pinnae. Therefore, the rhizome is a major carbohydrate storage organ in this species, although overwintering leaves also act as a carbohydrate storage organ.
• Intraspecific variations in seedling emergence and survival of Potentilla matsumurae (Rosaceae) between alpine fellfield and snowbed habitats

  Y Shimono, G Kudo

  ANNALS OF BOTANY 91 1 21 - 29 2003年01月 [査読有り][通常論文]
   

  Potentilla matsumurae has a wide distribution from wind-blown fellfields to snowbeds in alpine regions of Japan. The environmental factors influencing seedling establishment differ between the fellfield and snowbed habitats plants growing in each habitat may therefore have different germination strategies. Using a reciprocal sowing experiment, patterns of seedling emergence and survivorship were examined in both habitat types in the Taisetsu Mountains, Japan. Seeds derived from a fellfield population germinated earlier than did those derived from a snowbed population at both habitats, and the germination of fellfield seeds continued throughout the growing season. The timing of seedling emergence greatly affected subsequent survival at the fellfield. Seedlings that emerged in the first half of the growing season had low survivorship during the first year because of frost and drought damage, but the remaining seedlings had high survivorship during the winter: seedlings that emerged in the latter half of the growing season showed the opposite trend. At the snowbed, seedling survival was high throughout the growing season. Germination experiments in the laboratory highlighted a difference in the sensitivity of seeds from the fellfield and snowbed populations to fluctuating, temperatures. These results indicate that intraspecific variation in emergence and survivorship may occur over a small scale in in alpine environment. (C) 2003 Annals of Botany Company.
• Relationships between flowering phenology and fruit-set of dwarf shrubs in Alpine Fellfields in northern Japan: A comparison with a subarctic heathland in northern Sweden

  G Kudo, S Suzuki

  ARCTIC ANTARCTIC AND ALPINE RESEARCH 34 2 185 - 190 2002年05月 [査読有り][通常論文]
   

  Relationships between flowering phenology and fruit-set of 10 ericaceous species were studied in three alpine fellfields in the Taisetsu Mountains, northern Japan. Flowering season varied from late May to early August among species. There was a positive correlation between flowering time and fruit-set under natural conditions. Pollinator exclusion by net-bagging and hand-pollination revealed that very low fruit-set in early-flowering species was caused by severe pollen limitation, while late-flowering species tended to have high fruit-set with slight pollen limitation. Such seasonal patterns reflect the changes in seasonal activity of pollinating insects, which are highly influenced by ambient temperature. A similar research program was conducted in a subarctic heathland in northern Sweden with almost similar species composition. In Sweden, however, there was no positive correlation between flowering time and fruit-set. The difference between the alpine fellfields and the subarctic heathland may be caused by the specific seasonal pattern of temperature change in either region. A steep increase in air temperature from early to mid-summer in the alpine fellfields in Japan may cause all increase in pollinator availability with progress of season.
• Flowering phenology of tropical-alpine plants on Mount Kinabalu: preliminary report of two-years observation

  Kudo Gaku, Suzuki Shizuo

  Sabah Parks Nature Journal 5 143 - 152 2002年 [査読有り][通常論文]
  
• Leaf-trait variation of tundra plants along a climatic gradient: an integration of responses in evergreen and deciduous species

  G Kudo, U Molau, N Wada

  ARCTIC ANTARCTIC AND ALPINE RESEARCH 33 2 181 - 190 2001年05月 [査読有り][通常論文]
   

  To understand response patterns of leaf traits in tundra plants against decreasing annual season length comprehensively, a graphic model based on carbon balance theory was presented. The model predicted that leaves with very short life-span and high nitrogen concentration (N-mass) or leaves with very long lift-span and small N-mass will be dominate under the conditions of a short growing season. To test this prediction, leaf life-span and other leaf traits of 26 tundra species were compared among four sites selected along a gradient of climatic harshness: a subalpine site at Abisko in northern Sweden, two nearby mid-alpine sites at Latnjajaure with early and late snowmelt, and a site at Ny-Alesund (Svalbard) in the High Arctic. In herbaceous and deciduous shrub species, leaf life-span and/or leaf mass per unit area (LMA) tended to decrease, and leaf N-mass tended to increase along the climatic gradient with decreasing growing season and lower temperatures. In evergreen shrub species, both leaf life-span and leaf N-mass tended to increase under harsh conditions, but the response pattern of LMA was less clear. Deciduous species produced short-lived leaves with a low construction cost and probably high photosynthetic potential, whereas evergreen species produced long-lived leaves. The contrastive patterns of leaf-trait variation between the deciduous and evergreen plants observed in this study were concordant with the prediction of the model.
• Variation in floral sex allocation and reproductive success within inflorescences of Corydalis ambigua (Fumariaceae): pollination efficiency or resource limitation?

  G Kudo, T Maeda, K Narita

  JOURNAL OF ECOLOGY 89 1 48 - 56 2001年02月 [査読有り][通常論文]
   

  1 The variation of floral sex allocation with flower position within inflorescences was investigated in the spring ephemeral, Corydalis ambigua. Investment in female function (pistil), attraction (corolla) and nectar production decreased from bottom to top flowers, whereas male investment (stamen) did not differ. 2 This self-incompatible species appears to set seeds as a result of visitation by nectar robbing bumblebee queens. The tendency of bees to visit lower flowers first and then move upwards within an inflorescence should result in directional pollen flow from bottom to top flowers. 3 Naturally pollinated upper flowers set fewer seeds than intermediate and lower flowers due to pollen limitation. The lack of differences in seed set and seed mass per pod following artificial outcrossing indicated that resource limitation did not explain the variation in seed production of flowers in different positions. Pollen viability also did not differ significantly between flower positions. 4 A model of pollination was developed that incorporated the visitation pattern of bumblebees and observed variations in nectar distribution between flower positions. This predicted that receipt of outcross pollen would decrease from bottom to top flowers, but that pollen export to other plants would not differ between flower positions provided that the pollen exchange rate of pollinators was either small or positively correlated with nectar content of each flower position. The observed pattern of floral sex allocation would then be parallel to relative success of pollen export and import between flower positions within inflorescences.
• Pattern of seedling emergence of alpine plants: comparisons between fellfield and snowbed habitats

  Shimono Yoshiko, Kudo Gaku

  Memoirs of National Institute of Polar Research, Special Issue 54 467 - 478 2001年 [査読有り][通常論文]
   

  We observed the germination pattern of alpine plants at a fellfield (three species) and a snowbed (four species) in relation to environmental differences between the habitats. Emergence patterns of seedlings varied among species within each habitat, especially at the fellfield, which has a relatively long growing season. At the fellfield, the peak of seedling emergence occurred early in the growing season for Potentilla matsumurae, mid-season for Patrinia sivirica, and late season for Bupleurum ranunculoides. At the snowbed, germination of Peucedanum multivittatum started immediately after snowmelt, germination of P. matsumurae and Primula cuneifolia were concentrated in early July, and germination of Arnica unalaschcensis was common in mid-July in 1998. Species which produced large seeds tended to have a short period for seedling growth, while species which produced small seeds tended to continue seedling growth as long as they could. Temperature requirements for germination of P. matsumurae differed between the habitats. Seeds in the snowbed population needed a warmer temperature regime for germination than seeds in the fellfield population. These results indicate that germination traits may differ between habitats even within the same species.
• Responses of alpine shrubs to simulated environmental change during three years in the mid-latitude mountain, northern Japan

  S Suzuki, G Kudo

  ECOGRAPHY 23 5 553 - 564 2000年10月 [査読有り][通常論文]
   

  Effects of artificial warming on phenology, individual leaf traits, vegetative growth, and reproduction of five alpine species (two deciduous and three evergreen shrubs) were investigated during three years in the mid-latitude alpine, northern Japan. Eleven open-top chambers (OTCs) were set up on a fellfield (1680 m a.s.l.) in the Taisetsu Mountains by which air temperature at plant height was increased by ca 2 degreesC. Vaccinium uliginosum (deciduous shrub) showed earlier leaf emergence in every season and earlier flowering only in the first season in the OTCs. By contrast, acceleration of leaf emergence in the OTCs was not clear for other species, i.e. Arctous alpinus (deciduous shrub), Ledum palustre, V. vitis-idaea, and Empetrum nigrum (evergreen shrub). Both deciduous species showed longer leaf life-span in the OTCs every season. All evergreen species had higher leaf survival rates in the OTCs, indicating extension of leaf life-span. Leaf nitrogen concentration and leaf mass per unit leaf area (mg cm(-2)) generally tended to decrease in the OTCs. Relationships between the individual leaf traits and cumulative air temperature during the leaf developing period were not clear. Total leaf production during the three seasons increased in the OTCs in A. alpinus, L. palustre, V. vitis-idaea, and E. nigrum. All evergreen shrubs showed larger shoot growth in the OTCs but both deciduous shrubs did not show significant changes. In contrast to the vegetative growth, deciduous shrubs produced more flowers in the OTCs. Fruit production was not influenced by the OTCs for all species. The extension of photosynthetic period in the OTCs may contribute to the larger vegetative growth or flower production.
• Wind pollination and insect pollination of two temperate willow species, Salix miyabeana and Salix sachalinensis

  S Tamura, G Kudo

  PLANT ECOLOGY 147 2 185 - 192 2000年04月 [査読有り][通常論文]
   

  Pollination systems of Salix miyabeana and Salix sachalinensis were studied at a riverside in northern Japan in order to measure the balance of wind pollination and insect pollination. In 1996, 19 clones of each species were selected, and seed-set success by a net-bagging (to exclude insect visitation) and an artificial pollination (to remove pollen limitation) were compared to by natural pollination. For S. miyabeana, the same experiment was repeated in two populations in 1997. Proportion of seed set through wind pollination dominated in both species in this study. Pollen limitation was common under natural conditions, and S. sachalinensis relied more on insect pollination for seed production than S. miyabeana. Meteorological factors such as precipitation and hours of sunshine during the flowering season influenced the potential reproductive activity of the willow between years. In the wet and cloudy spring of 1996, clones which obtained high seed set depended more on insect pollination for both species, whereas in the dry and sunny spring of 1997, such clones depended more on wind pollination for S. miyabeana. Because the efficiency of wind pollination seemed to be more sensitive to fluctuating weather conditions than insect pollination, insect pollination was considered to play an assurance role for seed production in these willows.
• Variations in reproductive traits at inflorescence and flower levels of an arctic legume, Astragalus alpinus L.: Comparisons between a subalpine and an alpine population

  Gaku Kudo, Ulf Molau

  Plant Species Biology 14 3 181 - 191 1999年12月 [査読有り][通常論文]
   

  The reproductive traits of Astragalus alpinus L. between a subalpine and an alpine population in northern Sweden were compared. This species was physiologically self-incompatible and mainly pollinated by bumblebees. Mean flower size was larger and anthesis was longer in the alpine population than in the subalpine population. There were no significant differences in ovule fertilization rate and seed predation rate per inflorescence between the populations. However, the abortion rate of fertilized ovules was higher in the alpine population, probably because of resource limitation. The difference in seed production per inflorescence was small between the populations. Dense ovule packing within each flower may have compensated for the lower fruit production in the alpine population, where pollinator activity was low. Although the alpine population produced a smaller number of mature seeds per inflorescence, total seed mass per inflorescence did not differ between the populations due to larger seed size in the alpine population. Within an inflorescence, upper flowers had a smaller size, a relatively larger allocation to stamens, lower seed production (for both populations) and higher pollen viability (only for the alpine population) than did lower flowers. Thus, reproductive values through male and female functions may differ among flowers within an inflorescence.
• 個葉特性変異と環境傾度 : ツンドラ植物を中心に

  工藤 岳

  日本生態学会誌 49 1 21 - 35 一般社団法人 日本生態学会 1999年 

  Although various leaf traits (such as photosynthetic capacity, leaf mass per area (LMA), longevity, nitrogen content and toughness) are highly influenced by changes in environmental conditions, strong correlations exist among leaf traits. Photosynthetic productivity and leaf persistence are negatively correlated, i.e., short-lived leaves often have higher photosynthetic activity and lower defensive ability than long-lived leaves. There are two major hypotheses for explaining the observed variation of leaf longevity: the nutrient use efficiency theory and the carbon balance theory. The theories differ in their viewpoints of the factors limiting photosynthetic activity, i.e. mineral limitation and carbon limitation. In general, plants living in tundra environments suffer from a short growing season, and the extent of this stress changes along the altitudinal, latitudinal and snowmelt gradients in arctic and alpine ecosystems. As season length decreases, deciduous plants produce shorter-lived, lower-LMA and nitrogen-richer leaves, whereas evergreen plants produce longer-lived leaves within and among specics. This contrasting pattern of changes in leaf traits can be explained by a simple graphic model based on the carbon balance theory. The ecological significance of leaf-trait variations should be applied to the fields of reproductive ecology and biological interactions between plants and herbivores.
• Flowering phenology of alpine plant communities along a gradient of snowmelt timing.

  Kudo Gaku, Suzuki Shizuo

  Polar Bioscience 12 100 - 113 1999年 [査読有り][通常論文]
   

  Flowering phenology of alpine plant communities was observed at seven sites (two fellfields, two alpine meadows, and three snowbeds) in 1996 and 1997 in the Taisetsu Mts., northern Japan. These sites were selected along a gradient of snowmelt time. In total, flowering phenologies of 39 species were compared across the seven sites. The length of flowering season within communities decreased with lateness of snowmelt from 88 days at the fellfield site to 32 days at the snowbed site. The onset of flowering varied among species at the early snowmelt sites, and it became concentrated within narrow periods among species at the later snowmelt sites. Interspecific overlap of anthesis was large in the late flowering season at the earliest snowmelt site, whereas it was large in the early flowering season at the snowbed sites. Such changes in flowering patterns at community level along the snowmelt gradient were considered to be induced by the difference in temperature sequence after snowmelt among the sites, i. e., the increasing pattern of the effective cumulative temperature. Thus, the time of snowmelt affects not only the flowering phenology of individual species but also the flowering pattern of a whole community. Some species growing in the fellfields changed the temperature-demand for onset of flowering which was considered as an adjustment to decrease the interspecific overlap of anthesis within the community.
• Effects of snowmelt timing on leaf traits, leaf production, and shoot growth of alpine plants: Comparisons along a snowmelt gradient in northern Sweden

  G Kudo, U Nordenhall, U Molau

  ECOSCIENCE 6 3 439 - 450 1999年 [査読有り][通常論文]
   

  Effects of snow-melt timing on leaf traits (for five deciduous and five evergreen species), shoot growth, and leaf production (for five evergreen species) of tundra plants were studied along a snow-melt gradient in an alpine snowbed in northern Sweden. In deciduous plants, leaf life-span and leaf mass per area (LMA) decreased, and nitrogen concentration (leaf N) increased with decreasing growing season, whereas in evergreen plants, both leaf life-span and leaf N increased with decreasing growing season. By extending leaf life-span, evergreen plants are able to have a large leaf mass, which may contribute to maintain net annual carbon gain in short snow-free seasons. In two predominantly boreal evergreen species, Empetrum hermaphroditum and Vaccinium vitis-idaea, leaf lifespan was negatively correlated with both annual leaf production and shoot growth, but there were no similar significant correlations for the other three, strictly arctic-alpine evergreen species (Cassiope tetragona, Loiseleuria procumbens, and Dispensia lapponica). Based on these results, we predict that extension of season length will decrease leaf N of both deciduous and evergreen species, and will accelerate leaf turnover of evergreen plants. Although annual leaf production and shoot growth of boreal species may increase with an extension of season length, they will remain unchanged in strictly arctic-alpine species.
• Size-dependent variation of phenotypic gender and functional gender of a spring ephemeral, Anemone debilis Fisch.

  Gaku Kudo, Toshihiko Maeda

  Plant Species Biology 13 2-3 69 - 76 1998年 [査読有り][通常論文]
   

  The effect of plant size on phenotypic gender and functional gender was studied within a population of a hermaphroditic perennial herb, Anemone debilis, which had only one perfect flower on a plant. Seed-set under natural conditions was 69-89%, and the selfing rate by autodeposition was 49% of maximum possible seed-set. Phenotypic gender calculated from the stamen and ovule numbers changed with individual flower size measured by dry weight large plants having larger flowers allocated more to female function (ovule number) than small plants. Matured seed number increased linearly with flower size, whereas estimated sired seed number indicated a saturating pattern. Functional gender calculated from the produced seed number and the estimated sired seed number changed with flower size, where large plants succeeded relatively better as mother plants and some small plants succeeded as pollen donors only. Thus, size-dependent sex allocation between the male and female functions at a flowering stage seemed to reflect the paternal and maternal success for seed production.
• Short-term effects of simulated environmental change on phenology, leaf traits, and shoot growth of alpine plants on a temperate mountain, northern Japan

  S Suzuki, G Kudo

  GLOBAL CHANGE BIOLOGY 3 108 - 115 1997年12月 [査読有り][通常論文]
   

  In order to assess the responses of circumpolar and semicircumpolar plants growing around their southern distribution margins to artificial warming, we set up 11 open-top chambers (OTCs) on a fell-field (1680 m a.s.l.) in the Taisetsu Mountains, northern Japan. The OTCs increased mean air temperature by 1.3 degrees C through the growing season (June-September) and extended the length of the growing season. We examined phenology and leaf traits of plants in the OTCs and control plots during the first season under artificial warming treatment using two deciduous and three evergreen species. Ledum palustre (evergreen shrub), Vaccinium uliginosum, and Arctous alpinus (deciduous shrubs) showed earlier leaf emergence and/or flowering in the OTCs. Deciduous shrubs had longer individual leaf longevity and an extended foliage period in the OTCs than in the control plots. There were no significant differences in specific leaf area and leaf size for many species between the OTCs and the control plots. Vaccinium vitis-idaea (evergreen shrub), L. palustre, A. alpinus, and Empetrum nigrum (evergreen shrub) had lower leaf nitrogen concentration in the OTCs than in the control plots, whereas it was higher in V. uliginosum. Only E. nigrum showed larger annual shoot growth in the OTCs. No clear differences in response to the warming effect were detected between evergreen and deciduous species in the first season. Circumpolar plants growing in temperate alpine regions may be more affected by season length rather than temperature itself.
• Herbivory pattern and induced responses to simulated herbivory in Quercus mongolica var grosseserrata

  G Kudo

  ECOLOGICAL RESEARCH 11 3 283 - 289 1996年12月 [査読有り][通常論文]
   

  Seasonal changes in leaf traits and the herbivory pattern of Quercus mongolica var. grosseserrata were studied, and simulated herbivory experiments were carried out in order to evaluate leaf trait responses. Leaves of Q. mongolica emerged simultaneously in spring and most were retained until autumn. Nitrogen concentration was highest when leaves first emerged and decreased rapidly with leaf age. Leaf mass per area (LMA) increased with leaf age. Herbivore attack was concentrated in the first 20 days after bud-break, which corresponded to the high nutritional value of the leaves for herbivores at this time. Simulated herbivory experiments indicated that LMA increased with artificial leaf damage, suggesting an increase in leaf toughness, and that nitrogen concentration decreased later in the season in comparison with intact leaves. As a result, herbivore attack following artificial leaf damage decreased with increasing initial leaf damage. However, leaf longevity was not affected by initial leaf damage. These responses were considered to be a strategy to disperse herbivory damage among leaves.
• Intraspecific variation of leaf traits in several deciduous species in relation to length of growing season

  G Kudo

  ECOSCIENCE 3 4 483 - 489 1996年 [査読有り][通常論文]
   

  Effects of growing season length on leaf traits were studied in three deciduous species found along an alpine snowmelt gradient (snow-free period ranging from 69 to 117 days), and in four deciduous species found along an altitudinal gradient (ranging from 140 m to 1900 m) in northern Japan. Along these gradients, leaf life-span generally decreased while specific leaf area (SLA) and nitrogen concentration (leaf N) increased with a shorter growing season. In each species, there was a negative correlation between leaf life-span and SLA, and between leaf life-span and leaf N, respectively. A positive correlation was found between SLA and leaf N. Production of high nitrogen leaves which had a lower initial carbon investment (leaf construction cost) was considered to be a response to maintain the carbon balance under the condition of a short growing season.
• ALTITUDINAL EFFECTS ON LEAF TRAITS AND SHOOT GROWTH OF BETULA-PLATYPHYLLA VAR JAPONICA

  G KUDO

  CANADIAN JOURNAL OF FOREST RESEARCH-REVUE CANADIENNE DE RECHERCHE FORESTIERE 25 11 1881 - 1885 1995年11月 [査読有り][通常論文]
   

  Leaf demography, shoot growth, and seasonal changes of leaf size, specific leaf area, and leaf nitrogen (N) concentration of Betula platyphylla var. japonica Hara were compared at two altitudes (140 and 700 m above sea level). At the higher site, where the length of growing season was restricted, leaf life-span was shorter and leaf N concentration was higher throughout the growing season than at the lower site. Leaf size did not differ between sites. Production of short-lived and high N concentration leaves was considered adaptive under the condition of short growing season. At the higher site, N was translocated from senescing early leaves to late leaves in mid-September, whereas a significant increase in late leaf N concentration was not observed at the lower site. There were no differences in shoot growth, bud size, late leaf number on long shoots between sites, probably because of effective N use at the higher site.
• LEAF TRAITS AND SHOOT PERFORMANCE OF AN EVERGREEN SHRUB, LEDUM PALUSTRE SSP DECUMBENS, IN ACCORDANCE WITH LATITUDINAL CHANGE

  G KUDO

  CANADIAN JOURNAL OF BOTANY-REVUE CANADIENNE DE BOTANIQUE 73 9 1451 - 1456 1995年09月 [査読有り][通常論文]
   

  Individual leaf traits, leaf age structure, and leaf dry mass of Ledum palustre ssp. decumbens were compared at three sites along a latitudinal gradient: temperate mountain (43 degrees 30'N), taiga (62 degrees 10'N), and arctic tundra (71 degrees 25'N). At the arctic site, L, palustre produced leaves having longer life-span, higher nitrogen concentration, and smaller size and specific leaf area (SLA) in comparison with that at the temperate mountain site. Although current leaf number and annual shoot growth were smaller, leaf dry mass per stem was larger at the arctic site than at the temperate mountain site. At the taiga site, those traits were within the range of the other two sites, with the exception of leaf size and total leaf number per stem, which were largest at the taiga site. Leaf life-span was negatively correlated to SLA and annual leaf number per stem and positively correlated to leaf nitrogen concentration. Thus, with increasing latitude, L. palustre produced fewer but more costly leaves and retained them for longer. Old leaves might have a resource storage function supporting new leaf production.
• EFFECTS OF THE LENGTH OF THE SNOW-FREE PERIOD ON LEAF LONGEVITY IN ALPINE SHRUBS - A COST-BENEFIT MODEL

  K KIKUZAWA, G KUDO

  OIKOS 73 2 214 - 220 1995年06月 [査読有り][通常論文]
   

  Leaf longevities of three woody dwarf-shrub species were investigated in relation to the length of the snow-free period in a mountain area in Hokkaido, northern Japan. Leaf longevity of a deciduous species, Sieversia pentapetala, slightly increased with increasing length of the snow free period. In contrast, the leaf life-span of two evergreen species, Phyllodoce aleutica and Rhododendron aureum, decreased with increasing snow-free period. These trends are consistent with a cost-benefit model for leaf longevity as a function of the changing length of the yearly period favorable for photosynthesis. Hence the plastic changes in leaf longevity with varying snow-free periods were concluded to be adaptive traits for maximizing photosynthetic gain for the plants.
• ECOLOGICAL SIGNIFICANCE OF FLOWER HELIOTROPISM IN THE SPRING EPHEMERAL ADONIS-RAMOSA (RANUNCULACEAE)

  G KUDO

  OIKOS 72 1 14 - 20 1995年02月 [査読有り][通常論文]
   

  Flower heliotropism could increase reproductive success in Adonis ramosa by increasing pollination, fertilization success, and/or seed development. Mean gynoecium temperature of heliotropic flowers was 5.5 degrees C warmer than the ambient. Under natural conditions, seed set was restricted by pollen limitation. Activity of pollinating insects was temperature-dependent and the visiting frequency was higher in heliotropic flowers than in non-heliotropic ones. As optimal temperature for pollen germination and pollen tube growth was higher than the ambient temperature, heliotropic warming might facilitate greater fertilization success after pollination. Experiments combining hand-pollination and petal removal showed that both seed set and individual seed weight decreased when heliotropic effects were removed. Thus, all three hypotheses were supported in this study. Advantages of out-crossing through heliotropic movements was not clear in this study, because there was no significant difference in individual seed weight between selfed and out-crossed flowers.
• Relationship between Flower Number and Reproductive Success of a Spring Ephemeral Herb, Anemone flaccida (Ranunculaceae)

  YOKO NISHIKAWA, GAKU KUDO

  Plant Species Biology 10 2 111 - 118 1995年 [査読有り][通常論文]
   

  Abstract Flowering phenology and reproductive traits of Anemone flaccida were compared between ramets having one, two, and three flowers. We evaluated the flowering pattern and the reproductive function of each flower within a ramet and discussed the ecological significance of flower number. Early‐blooming flowers had larger numbers of pistils and stamens, higher seed‐set, and heavier seeds than the later‐blooming flowers within a ramet under natural conditions. These differences remained after flowers were hand‐pollinated. When one flower was removed from a ramet with two flowers, seed‐set and seed weight of the remaining flower did not increase. Because flowering occurs sequentially within a ramet, anthesis per ramet was extended with flower number. Production of the second and the third flowers was considered for plants to reduce entire failure in setting seeds under the condition of unpredictable pollinator activity. However, it was thought that having more than three flowers makes it hard to complete the life‐cycle during the growing season (mid‐April to early June). Copyright © 1995, Wiley Blackwell. All rights reserved
• RELATIONSHIP BETWEEN FLOWERING TIME AND FRUIT-SET OF THE ENTOMOPHILOUS ALPINE SHRUB, RHODODENDRON-AUREUM (ERICACEAE), INHABITING SNOW PATCHES

  G KUDO

  AMERICAN JOURNAL OF BOTANY 80 11 1300 - 1304 1993年11月 [査読有り][通常論文]
   

  Flowering phenology, fruit set, and pollinator frequency of the ericaceous alpine dwarf shrub, Rhododendron aureum, were compared among three quadrats arranged along a snowmelt gradient on a slope. Bagging and self-pollination experiments showed that R. aureum was physiologically self-compatible, but pollinator visitation highly enhanced fruit set. Depending on the lateness of snowmelt, flowering time varied from mid-june to late July among quadrats. Pollinator visitation increased as the flowering season progressed, and fruit set was significantly higher in the quadrat with latest snowmelt. Emasculation experiments suggested that later flowering might promote cross-pollination. Thus, later flowering was advantageous for effective pollination. On the other hand, later-flowering plants often failed to set fruits because of the onset of autumn frost and snow before fruit maturation.
• HEAT-PRODUCTION AND CROSS-POLLINATION OF THE ASIAN SKUNK CABBAGE SYMPLOCARPUS-RENIFOLIUS (ARACEAE)

  S UEMURA, K OHKAWARA, G KUDO, N WADA, S HIGASHI

  AMERICAN JOURNAL OF BOTANY 80 6 635 - 640 1993年06月 [査読有り][通常論文]
   

  The Asian skunk cabbage Symplocarpus renifolius has an exothermic spadix on which about 100 flowers bloom in very early spring when effective pollinators such as bees and drone flies are inactive. This species is protogynous; female phase and male phase took 6.8 +/- SD 5.8 days and 16.7 +/- 5.7 days, respectively, with a short transitional phase of bisexuality (2.1 +/- 0.9 days). The spadices produced heat 24 hours/day throughout female and bisexual phases, but temperature dropped quickly after the beginning of male phase. Although self-compatibility was expected from the flower structure, the basipetal flowering, and the absence of effective pollinators, bagging tests demonstrated that they rarely produce seeds without crossing. The spadices were visited by small numbers of invertebrates throughout the flowering season. Of these invertebrates, house flies, rove beetles, and mosquitos were the likeliest pollinators, since they are probably attracted both to the pollen produced in male phase and to the stench or carbon dioxide in female phase. On two female spadices with immature male flowers, we fortuitously collected a rove beetle and a mosquito that carried some pollen grains; these had to have been transported from other S. renifolius spadices. This infrequent and ineffective pollination appears to explain why as low as 13% of spadices set seeds in a natural population. We examine alternative hypotheses to explain production of heat in spadices of skunk cabbage.
• 定山溪漁入ハイデの風穴植生

  佐藤 謙, 工藤 岳, 植村 滋

  日本生態学会誌 43 2 91 - 98 一般社団法人 日本生態学会 1993年 

  Cool-spots site vegetation was surveyed at Izariiri-Heide, near Sapporo, northern Japan. Along the gradient of soil temperature, vegetation height and species richness decreased towards the central area of Heide, where many cool-spots are distributed. Soil temperature in the central area was as low as about 4℃ even in late September, suggesting that the low temperature had enabled the subalpine Pinus pumila vegetation to become established locally in the mixed forest zone. Some stand groups in the central area were characterized by relatively abundant species richness in spite of the cool conditions. In such habitats, various forms of microrelief due to the physical characteristics of the bedrock andesite support the growth of many plant species : e. g., Sphagnum squarrosum and Sphagnum girgensohnii in wet depressions, and Vaccinium ovalifolium var. coriaceum and seedlings of Picea glehnii on dry mounds.
• Size‐dependent Resource Allocation Pattern and Gender Variation of Anemone debilis Fisch.

  GAKU KUDO

  Plant Species Biology 8 1 29 - 34 1993年 [査読有り][通常論文]
   

  Abstract Size‐specific effects on the resource allocation pattern and gender variation at the flowering stage were studied in a perennial hermaphrodite, Anemone debilis. With an increase of plant size, allocations to inflorescence and roots decreased, while those to leaves and stem were constant allocations to rhizome increased. A negative correlation between sexual reproduction and survival or vegetative reproduction was suggested. There was a trade‐off in resource allocation between male function (androecium) and female function (gynoecium) within an inflorescence. Gender of A. debilis gradually shifted to femaleness with size increment. This size‐specific sex allocation pattern agrees with the prediction of the theoretical model for entomophilous hermaphroditic plants. Copyright © 1993, Wiley Blackwell. All rights reserved
• PERFORMANCE AND PHENOLOGY OF ALPINE HERBS ALONG A SNOW-MELTING GRADIENT

  G KUDO

  ECOLOGICAL RESEARCH 7 3 297 - 304 1992年12月 [査読有り][通常論文]
   

  Responses of plants to the length of the growing season were studied in an alpine snow-bed by setting five plots along a snow-melting gradient. Performance and phenology were compared between the plots for five herbaceous species (Peucedanum multivittatum, Primula cuneifolia, Veronica stelleri var. longistyla, Solidago virga-aurea var. leiocarpa and Potentilla matsumurae). Performance characteristics measured were flower height, leaf height, leaf number, flower number and fruit number. In the late exposed plots with short snow-free periods, fruit-set was reduced in many species due to the decrease in flower number and/or the short growing season for fruit development. Veronica stelleri var. longistyla and Solidago virga-aurea var. leiocarpa, which decreased in flower and leaf numbers due to the short snow-free period, were sensitive to the short growing season. Peucedanum multivittatum was vigorous in the late exposed plots, but its slow flowering and fruiting prevented the fruit-set from developing in the last exposed plot. Primula cumeifolia and Potentilla matsumurae, quick flowering species that maintained their flower number throughout the snow-melting gradient, were considered the most successful species in late exposed habitats.
• EFFECT OF SNOW-FREE DURATION ON LEAF LIFE-SPAN OF 4 ALPINE PLANT-SPECIES

  G KUDO

  CANADIAN JOURNAL OF BOTANY-REVUE CANADIENNE DE BOTANIQUE 70 8 1684 - 1688 1992年08月 [査読有り][通常論文]
   

  Leaf life-spans and specific leaf weights of four plant species, Pyllodoce aleutica, Rhododendron aureum, Sieversia pentapetala, and Potentilla matsumurae were compared along a gradient of decreasing snow-five duration in alpine snow beds. Life-span was obtained by observation from emergence to senescence for deciduous plants and was estimated from leaf age distributions for evergreen plants. Along the gradient, the evergreen shrubs Ph. aleutica and R. aureum had extended leaf life-spans, whereas the deciduous shrubs S. pentapetala and the deciduous herb Po. matsumurae had reduced leaf life-spans. Specific leaf weights, obtained by dry weight per unit leaf area, increased in Ph. aleutica but decreased in S. pentapetala and Po. matsumurae along the gradient. These phenomena are considered adaptive adjustments for maintaining a positive carbon balance under the conditions of limited photosynthetic season.
• PLANT-DISTRIBUTION IN RELATION TO THE LENGTH OF THE GROWING-SEASON IN A SNOW-BED IN THE TAISETSU MOUNTAINS, NORTHERN JAPAN

  G KUDO, K ITO

  VEGETATIO 98 2 165 - 174 1992年02月 [査読有り][通常論文]
   

  The distribution pattern of plants was studied in an alpine snow-bed in six plots along a snow-melting gradient. Each plot consisted of two habitats with respect to the microtopography; the flat habitat and the mound habitat. The number of species per plot decreased with the shortened snow-free period. In the flat habitat, the dominant growth forms changed from the early exposed plots to the late exposed ones as follows; lichens <-> evergreen and deciduous shrubs <-> forbs <-> graminoids <-> bryophytes. In the mound habitat, evergreen and deciduous shrubs prevailed widely along the gradient because of the ability to exploit new habitat by creeping over exposed rocks. For shrubs, the existence of mounds contributed to the expansion of the distribution ranges. Forbs and graminoids shifted their distribution modes to the late exposed plots where shrubs decreased in cover. Deciduous shrubs and forbs completely disappeared in the latest exposed plot.
• EFFECTS OF SNOW-FREE PERIOD ON THE PHENOLOGY OF ALPINE PLANTS INHABITING SNOW PATCHES

  G KUDO

  ARCTIC AND ALPINE RESEARCH 23 4 436 - 443 1991年11月 [査読有り][通常論文]
   

  Phenology of alpine plants was studied with reference to the time span of snow-free period by setting six quadrats along a snowmelt gradient. Of the 56 species, 17 inhabited four or more quadrats and their phenology was observed for 3 yr, 1988 to 1990. Contraction of the snow-free period reduced flowering and seeding rates. Phenology of the alpine plants was controlled primarily by (1) growth form, (2) the span of preflowering, and (3) the term for the maturity of seeds. Shrub species, especially evergreen shrubs, took longer for maturing their seeds. They abandoned sexual reproduction and reproduced vegetatively by layering in the short snow-free habitats. Forb and graminoid species opened their flowers even in the short snow-free habitats. Some graminoid species shifted their leaf habit from summergreen to semievergreen in these short snow-free habitats. This is considered a strategy to extend the photosynthetic period.
• ウラジロタデの生態的変異について(第二報) : 生活史特性の比較

  工藤 岳

  日本生態学会誌 41 1 25 - 30 一般社団法人 日本生態学会 1991年 

  Life-history of a pioneer plant species, Aconogonon weyrichii, was studied at two habitats, and open site and an alder-forest site by setting three quadrats (1×1m in each size) at the former and two at the latter, in Yufutsu Mire, northern Japan. At the open site, the majority of shoots, which developed in spring, were retained until early October. Shoot growth stopped in early June and flowering occurred from early June and flowering occurred from early July to early September. At the forest site shoots emerged densely in spring but shoot density gradually decreased with the decrease in ambient light intensity due to alder leaf emergence. From early June to early July, shoots grew rapidly and completely suppressed other forest-floor plants, but shoot longevity was shorter than that at open site. Flowering occurred simultaneously in early July, and flowering duration was shorter (about 60 days) than that at open site (80-90 days). Therefore, A. weyrichii growing at open site are considered to be adapted as "ruderals" whereas those growing at forest site are adapted as "competitors". Individuals transplanted from the open site to the forest population initially showed rapid growth but by late July had died due to shading. Individuals transplanted from the forest site to the open site showed a similar growth pattern and growth form to open site types. It is assumed that the observed between-site variation in A. weyrichii is and example of ecological plasticity.
• ウラジロタデの生態的変異について

  工藤 岳

  日本生態学会誌 39 1 37 - 44 一般社団法人 日本生態学会 1989年 

  Ecological variation in Aconogonon weyrichii was studied at 3 sites. Comparisons of morphological characteristics were done at an open highland site, an open lowland site and an alder-forest site, Biomass and resource allocation comparisons were done at the open lowland site and the alder-forest site. Both open sites had oligotrophic mineral soil with low vegetation cover, whereas the forest site had eutrophic organic soil with high vegetation cover. Morphological characters were relatively similar at both open sites, and A. weyrichii populations had the same life-cycles. At the forest site, A. weyrichii was much larger in size and biomass than that at the lowland open site. The open site type had very deep vertical rhizomes which produced aerial shoots at the same locations every year. The forest site type had very dense and dynamic horizontal rhizomes which had many dormant buds, and actively produced large, dense ramets. The open site type allocated much resource expenditure to flower production, whereas the forest site type allocated much resource expenditure to aerial stems. High resource allocation to aerial stems and rhizome differentiation (vertical vs. horizontal) relative to forest type are adaptations which enable A. weyrichii, originally growing at unstable open sites, to grow in the alder-forest.
• Rhizome development of Phragmites australis in a reed community

  Gaku Kudo, Koji Ito

  Ecological Research 3 3 239 - 252 1988年12月 [査読有り][通常論文]
   

  Variations in the height, shoot density, biomasses of above- and below-ground parts and rhizome distributions of Phragmites australis were investigated along a line-transect in a reed community at Yufutsu Mire, Hokkaido. Relationships of performance of the reed plants to soil conditions and species compositions were also examined. Three types of rhizome development were recognized in reed plants (1) the central part of the reed community, characterized by well developed rhizomes and dense aerial shoots, (2) the intermediate part, characterized by development of rhizomes along both the peat and surface layers and very dense aerial shoots, and (3) the marginal part, characterized by development of rhizomes only along the peat layer and sparse aerial shoots. Observation showed that rhizomes in the surface layer actively produced aerial shoots, whereas rhizomes in the peat layer contributed to the spreading of their distribution range. With the growth of rhizomes, organic debris originating from dead rhizomes and roots accumulated in the mineral soil to promote organic soil formation. In dense parts of the reed stand, species composition was poor because of the shading and litter accumulation by reed plants. The effects of microtopography and water level on the establishment of reed seedlings were also considered. © 1988 Ecological Society of Japan.

MISC

• 27pAH-8 大雪山の急激な高山植生遷移のモデル解析 : レジームシフトのパラメータ解析(27pAH 環境物理(放射線,エネルギー,環境評価,地球システム),領域13(物理教育,物理学史,環境物理))

  矢吹 哲夫, 永田 麻莉, 工藤 岳 日本物理学会講演概要集 69 (1) 445 -445 2014年03月05日
• 高山植物群落の開花フェノロジー構造の場所間変動と年変動 : 市民ボランティアによる高山生態系長期モニタリング調査

  工藤 岳, 横須賀 邦子 保全生態学研究 17 (1) 49 -62 2012年05月30日 

  高山生態系は地球温暖化の影響を最も受けやすい生態系であり、気候変動は高山植物群落の生物季節(フェノロジー)を変化させると予測される。北海道大雪山国立公園では、市民ボランティアによる高山植物群落の開花状況調査が長期間行われている。風衝地2カ所と雪田2カ所の計4群落で6年間に渡って記録された開花日のデータを解析し、群落構成種の開花に要する温度要求性(有効積算温度)、開花日の群落間変動、年変動を解析した。高山植物の開花は、種や個体群に特有の有効積算温度で表すことができた。風衝地群落の開花は気温の季節的推移によって規定されており、温暖気候であった2010年にはほとんどの種で開花開始日の早期化と群落レベルの開花期間の短縮が生じていた。一方で、雪田群落の開花は局所的な雪解け時期とその後の温度変化の双方で規定されていた。すなわち、気温の季節推移と雪解けパターンから植物群落の開花構造が予測できることが示された。しかし、生育期の気温と雪解け開始時期に明確な対応関係は認められず、雪田の雪解け時期は場所や年によって変動した。寒冷な夏は雪田プロット内の雪解け進行速度を緩やかにし、その結果、種間の開花重複が高くなる傾向があった。一部の種では開花に要する温度有効性に個体群間変異が認められ、開花特性の分化が起きていることが示唆された。以上の結果より、気候変動が高山植物群落のフェノロジー構造に及ぼす影響を予測するには、気温の季節推移、雪解けパターンの地域性、個体群特有の温度要求性を考慮することの重要性が示唆された。
• 山岳生態系における植生変動の定量化に関する研究 : ─北海道大雪山系五色ヶ原を例として

  星野 仏方, 工藤 岳, 米森 舞乃, 雨谷 教弘, 金子 正美, 矢吹 哲夫 酪農学園大学紀要. 自然科学編 35 (1) 47 -53 2010年10月 [査読無し][通常論文]
  
• 地道なモニタリングが暴きだすエキサイティングな相互作用 : 気候変動がもたらすフェノロジカルミスマッチ

  工藤 岳 日本生態學會誌 60 (1) 13 -14 2010年03月31日
• ミヤマキンバイにおける平行進化的なエコタイプ分化

  平尾章, 下野嘉子, 和田直也, 成田憲二, 工藤岳 日本生態学会大会講演要旨集 57th 2010年
• Effects of simulated environmental change on dynamics of alpine dwarf shrubs in the mid-latitude mountain, northern Japan

  Suzuki, S, Kudo, G Proceedings of the 4th International Workshop on Global Change: Connection to the Arctic 2003 (GCCA4) 151 -155 2004年 [査読無し][通常論文]
  
• 樹木開花量に関連したマルハナバチの空間分布,個体数,および季節変動 北海道苫小牧の冷温帯落葉広葉樹林において

  稲荷尚記, 加藤悦史, 工藤岳, 日浦勉, 戸田正憲 日本生態学会大会講演要旨集 49th 215 2002年03月25日 [査読無し][通常論文]
  
• 開放型温室を用いた環境操作に対する高山植物の反応 大雪山での2年間の研究

  鈴木静男, 工藤岳 日本生態学会大会講演要旨集 44th 13 1997年03月 [査読無し][通常論文]
  
• 遠音別岳高山帯と亜高山帯アカエゾマツ林床におけるイソツツジ・コケモモの個葉特性と枝伸長量の比較

  鈴木静男, 工藤岳 遠音別岳原生自然環境保全地域調査報告書 79 -87 1997年 [査読無し][通常論文]
  
• 環境圧の緩和は高山植物の成長・葉の特性にどのような効果をもたらすのか?―高山風衝地での操作実験

  鈴木静男, 工藤岳 日本生態学会大会講演要旨集 43rd 188 1996年03月 [査読無し][通常論文]
  

書籍等出版物

• Structure and Function of Mountain Ecosystems in Japan

  工藤 岳 (担当:共編者(共編著者))
  Springer 2016年
• 高山植物学 高山環境と植物の総合科学

  共立出版 2009年
• 登山道の保全と管理

  古今書院 2008年
• 生態系と群集をむすぶ

  京都大学学術出版会 2008年
• Ecology and Evolution of Flowers

  (担当:共著)
  Oxford University Press 2006年
• 森林の科学—森林生態系科学入門—

  朝倉出版 2005年
• 高山植物の自然史：お花畑の生態学

  北海道大学図書刊行会 2000年
• 大雪山のお花畑が語ること：高山植物と雪渓の生態学

  京都大学学術出版会 2000年

所属学協会

• 日本生態学会   種生物学会   The Society for the Study of Species Biology   

共同研究・競争的資金等の研究課題

• 地域集団の遺伝的多様性と気候変動へのレジリエンス：高山植物を用いた地域間比較

  日本学術振興会：科学研究費助成事業

  研究期間 : 2022年04月 -2026年03月 

  代表者 : 工藤 岳, 和久井 彬実, 和田 直也, 甲山 哲生
• 固着性生物の種内変異が種間共存に及ぼす影響の長期観測に基づく解明

  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 : 甲山 隆司, 金子 正美, 野田 隆史, 相場 慎一郎, 工藤 岳, 久保 拓弥

   

  陸上植物や沿岸付着動物のような、固着性生物では、定着環境の変異に対応して個体間変異が大きい。同じ固着性の他種と共存するメカニズムと、種内個体間変異がどのよおうに関係するかは未解明の課題である。本研究は、森林樹木・低木・沿岸フジツボを対象に、継続観測データに基づいて、種内の生活史変異を解析した。個体間変異の時間積算が、種レベルの回転率の遅速トレードオフをもたらし、共存に貢献することを見出した。
• フェノロジカルミスマッチの発生メカニズムと送粉系機能への影響評価

  日本学術振興会：科研費

  研究期間 : 2017年04月 -2020年03月 

  代表者 : 工藤 岳
• 気候変動による急速な高山植生変化の検出とそのメカニズム解明のモデル構築データ解析

  日本学術振興会：科学研究費助成事業

  研究期間 : 2015年04月 -2019年03月 

  代表者 : 矢吹 哲夫, 金子 正美, 工藤 岳, 星野 仏方, 原 登志彦, 田中 成典, 蛯名 邦禎, 田中 歩

   

  気候変動（地球温暖化）によって生じている可能性の高い大雪高山生態系の遷移（レジームシフト）のモデル解析をフィールド現場での測定及び生態系回復実験のデータと照合しつつ定量的なモデル解析を行なった。初期土壌水分量を積雪量で除した値等複数の無次元パラメータを用いて、ササ刈取りによる翌シーズンの初期土壌水分量の経年変化（上昇）を理論解析し、それに伴う高山植生の安定相の相構造変化をグラフを使ってシミュレーション解析することで、ササ刈取り前の土壌水分量とササ刈取り最中のシーズン最初の初期土壌水分量の測定値から、高山植生が安定的に回復するまでに必要なササ刈取りの継続年数を推定する方法論を見出した。
• ハナバチ送粉系の生態系機能の解明：植物群集の開花構造と形質進化

  日本学術振興会：科研費

  研究期間 : 2015年04月 -2019年03月 

  代表者 : 工藤 岳
• 植物群集における双翅目ポリネーターの生態系機能評価：訪花行動と花粉流動の解析から

  日本学術振興会：科学研究費助成事業

  研究期間 : 2015年04月 -2018年03月 

  代表者 : 石井 博, 工藤 岳, 丑丸 敦史

   

  双翅目ポリネーターの割合が異なる植物群集間で、花形質の組成を比較した。その結果、翅目ポリネーターの割合が多く、結果としてポリネーターの多様性が小さい地域ほど、植物群集における花形質の多様性も低くなる傾向が見出された。一方、ポリネーターの体表花粉及び柱頭付着花粉の分析からは、双翅目ポリネーターに受粉を依存している植物種であっても、膜翅目ポリネーターに受粉を依存している植物種とほぼ同等に、同種植物種の花粉を受け取っていることが示された。また、双翅目訪花者にも色の好みが存在し、それが種類ごとに異なることがわかった。これらの結果は、双翅目ポリネーターの送粉機能が高いことを示唆するものであった。
• 気候変動による高山お花畑消失メカニズムの解明

  日本学術振興会：科研費

  研究期間 : 2012年03月 -2016年03月 

  代表者 : 工藤 岳
• 高山生態系の特性を利用した、送粉ネットワーク構造の解析

  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 : 石井 博, 工藤 岳, 丑丸 敦史

   

  北アルプス高山帯の送粉群集を解析した結果、ネスト構造とモジュール構造が認められた。しかし、ネスト構造は種の観察数の偏りによってもたらされており、モジュール構造ではモジュールに当てはまらないリンク（相互作用が観察された訪花者と植物の組み合わせ）が多く存在した。そこで、訪花者と植物種を一定の基準でグループ分けし、各グループの訪花昆虫種が、数個の植物種グループを訪花すると仮定して解析したところ、説明できないリンクの数が激減した。この結果は、送粉群集を新しいネットワークモデルで説明することが妥当であることを示唆している。
• 開花フェノロジー構造の形成メカニズム：送粉系生物間相互作用の機能評価

  日本学術振興会：科研費

  研究期間 : 2011年04月 -2015年03月 

  代表者 : 工藤 岳
• 気候変動に対する森林帯ー高山帯エコトーンの多様性消失の実態とメカニズム

  環境省：環境研究特別推進費

  研究期間 : 2009年04月 -2012年03月 

  代表者 : 工藤 岳
• 気候変動に対する高山植物群集動態の定量化とそのメカニズムの解明

  日本学術振興会：科研費

  研究期間 : 2009年04月 -2012年03月 

  代表者 : 工藤 岳

   

  気候変動に伴う環境変化が高山植生変化を引き起こしている現状の評価と、そのメカニズム解明を目的とした。ササの分布拡大や土壌乾燥化により、高山植物の多様性が急速に低下し、高山植生が衰退する実態とその原因を解明した。植生変化と広域スケールの環境変化の定量化手法の開発し、チシマザサとハイマツの分布変化の定量化との広域スケールでの土壌水分変化を解析した。さらに、急速な植生変化が生じる状況についての数理モデルによる予測を行った。
• ポリネーション競争を反映した花粉流動と植物の繁殖様式の進化

  日本学術振興会：科学研究費助成事業

  研究期間 : 2007年 -2008年 

  代表者 : 亀山 慶晃, 工藤 岳

   

  高山生態系では雪解け時期を反映した連続的な開花現象が認められ、傾度に沿って花粉媒介者や近縁他種との関係が変化する。北海道大雪山系におけるツガザクラ属植物では、雪解け傾度に沿って雑種第一代が優占する広大な交雑帯が形成されており、雑種と親種の間で花粉媒介者を巡る競争が生じていた。親種の受粉成功は開花時期や年によって大きく変動し、繁殖成功(他殖率)に多大な影響を及ぼしていた。
• 電熱線大規模埋設実験による落葉広葉樹林生態系の温暖化に対する応答の解明

  日本学術振興会：科学研究費助成事業

  研究期間 : 2007年 -2008年 

  代表者 : 日浦 勉, 工藤 岳, 笠原 康裕, 彦坂 幸毅

   

  1、ミズナラの最大光合成速度は温暖化処理によって変化しなかったが、窒素含量は低下したため窒素利用効率は上昇した。イオン交換樹脂法によって土壌中の無機体窒素量がどのように変化したかは現3定量中である。 2、葉中の窒素含量の低下と硬さの指標が上昇したため、植食性昆虫による食害は低下した。 3、ミズナラの堅果生産量は枝の温暖化処理によって3〜5倍に上昇した。そのメカニズムは今のところ不明である。 4、土壌中のバクテリアの量や組成は2年間の実験では変化が見られなかった。 5、林床植物の総植被率は、林冠閉鎖が完了する6月中旬に最大となり、その後低い値で安定する傾向が見られた。林床に到達する光エネルギーとの対応関係が示された。夏緑性植物の地上部生育開始時期は、温暖化により早まる傾向が見られたが、その程度は種により異なっていた。一方で、秋の生育終了時期には明瞭な違いが認められなかった。すなわち、生育初期に温暖化の効果が大きいことが示された。半常緑性植物のオシダの越冬葉は、温暖区ではほとんどが冬の間に枯死していた。これは、温暖区では積雪がほとんどないため凍害による損傷が強かったためと考えられた。さらに、当年シュートの伸長は温暖区で遅くなる傾向が見られた。越冬葉の損失により、新葉生産のための養分や資源転流がなくなったことが影響していると予測される。土壌温暖化による積雪環境の変化は、冬期の越冬環境を変化させ、植物の生育にマイナスの効果をもたらす可能性が示唆された。 以上の結果より、温暖化が植物にもたらす影響は、種や生活形により多様であることが示された。温暖化の影響予想には、個々の植物が有する生理特性を考慮する重要性が示された。
• 鮮苔類の地球環境変化に対する応答について

  日本学術振興会：科学研究費助成事業

  研究期間 : 2007年 -2008年 

  代表者 : 工藤 岳, JAGERBRAND Annika K., JAGERBRAND AnnikaK.

   

  北海道の亜高山帯から高山帯にかけて分布する鮮体類(シモフリゴケ・タチハイゴケ・イワダレゴケ)を指標にし、生育環境や標高の違いに対する成長応答と生理活性を現地調査ならびに室内実験により計測した。2年間に及ぶ野外での成長解析の結果、温度変化に対する成長の感受性は、種間・個体群間で大きく異なっていた。例えば、森林帯に主な分布域を持つタチハイゴケは、温度増加に対して伸長生長を増加させる傾向があった。一方で、高山帯に主な分布域を持つシモフリゴケは、高温域で生長の低下が見られた。また、北海道内に広く分布するタチハイゴケを6つの山域で比較した結果、成長速度、分枝パターン、蛍光光合成活性(Fv/Fm比)、窒素含有量いずれにも地域間で違いが見られたが、標高変化に対する感受性は様々であり、明瞭な傾向は認められなかった。室内実験により同一環境で生育させても、鮮体類の温度応答は山域により異なり、遺伝的な差異の存在が示唆された。冷温帯から寒帯地域にかけて広く分布する鮮体類の成長応答を詳細に計測した研究例は、これまでに非常に少ない。本研究成果は、気候変動に対する鮮苔類の応答を予測する際に、個体群あるいは地域固有の応答を考慮する重要性を示唆するものである。以上の研究成果は、現在3つの学術論文として投稿準備中である。また、気候変動に対する鮮苔類の応答についての総説を投稿中である。
• 日本と北米大陸における第3紀起源ユリ科(広義)植物の比較生活史研究

  日本学術振興会：科学研究費助成事業

  研究期間 : 2006年 -2008年 

  代表者 : 大原 雅, 林 一彦, 工藤 岳, 工藤 洋, 北村 系子

   

  日本と北米大陸に現在隔離分する広義のユリ科植物の中でも、日本の近縁種に関して、これまで詳細な生活史研究が行われてきた生態的背景がわかっている種群を対象に、繁殖様式ならびに個体群構造に関する、詳細な野外調査と分子マーカーを活用した遺伝解析を行った。その結果、さまざまな種群について有益なデータを得ることが出来た。特に、カタクリ属(Erythronium)、スズラン属(Convallaria)、バイケイソウ属(Veratrum)に関しては、繁殖特性に関わる集団間ならびに集団内の他殖率の変異性、および個体群統計遺伝学の側面から、種子繁殖と栄養繁殖の寄与に関して、環境と生活史形質の変異の関係を明らかにすることが出来た。
• 長期モニタリングと個体群統計遺伝学による植物個体群の存続可能性の評価と保全

  日本学術振興会：科学研究費助成事業

  研究期間 : 2004年 -2006年 

  代表者 : 大原 雅, 工藤 岳, 高田 壮則, 和田 直也, 亀山 慶晃

   

  本研究は、植物個体群の存続可能性(viability)を、個体群統計学的(demographic)側面と遺伝学的(genetic)側面の両側面を考慮することで評価することを目的として行った。具体的には、低地から高山帯のさまざまな環境に生育する多様な植物群を対象に、それらの存続可能性を以下の内容に関する研究を行った。 1.これまで各研究者が蓄積してきた、多様な環境に生育するさまざまな種に関する貴重な長期個体群モニタリング・データ(5年〜23年)を集約し、正確な個体群統計学的情報を整理する。 2.個体群動態調査に基づく各個体の時間的・空間的情報をもとに、生活史段階の異なる各個体(実生、未成熟個体、成熟個体)を対象として酵素多型ならびにAFLP解析を行い、集団の遺伝的構造を把握する。 3.統計学的情報と遺伝学的情報を集約した数理モデルを構築し、個体群の存続可能性を定量的に評価する。 4.本研究で行う長期モニタリング調査法、遺伝解析法、数理解析法の一連の解析による「植物個体群の存続可能性評価法」に関するマニュアル作成を行う。 これまで多年生植物の個体群に関しては、長期モニタリングに基づく正確な個体群動態に関するデータの欠如していた。また遺伝学的側面に関しても、種内にみられる遺伝的多様性のパターンを解明することが中心であった。本研究により、個体群を各種の生活史を反映したさまざまな個体の集合として捉える概念が確立し、多様な環境に生育する植物個体群の存続可能性に関する正確な評価を行うことが可能になった。
• 花粉散布様式から見た虫媒花植物の繁殖戦略と交配システムの再評価

  日本学術振興会：科学研究費助成事業

  研究期間 : 2003年 -2005年 

  代表者 : 工藤 岳, 大原 雅, 石井 博

   

  本研究は、植物の多様な繁殖システムをポリネーションの見地から解明することを目的とした。 植物の花蜜分布がポリネーターの行動に及ぼす影響を、人工花序を用いた屋内実験により調べた.様々な花蜜分布に対するマルハナバチの花序内移動パタンと滞在時間を詳細に記録して解析した結果、花蜜分配様式は昆虫の行動に強く作用し、その影響は花序形態により変化することが示された。すなわち花蜜分泌様式は、花粉散布戦略であることが示された。 野外実験では以下の事柄について調べた。1.花色変化するウコンウツギへのマルハナバチの訪花様式を解析し、花色変化は植物の花粉散布であることを解明した。2.盗蜜型と正当訪花型のマルハナバチがエゾエンゴサクの繁殖成功に及ぼす影響について解析し、花序内性配分様式が個体群間で異なることを見いだした。3.開花時期が自殖率や花粉親多様度に及ぼす影響を高山植物キバナシャクナゲ個体群で調べた。季節的な訪花昆虫の行動の違いは、送粉効率や生産種子の遺伝的多様度に大きく影響することが示された。4.森林性植物で種子生産の制限要因を調べた。春植物は一般に高い結実率を達成しているが、マルハナバチ媒花はハエ媒花植物に比べて結実率の年変動が大きかった。初夏に開花する植物は一般に結実が低く、光資源により結実が制限されていた。林床が暗くなってから開花結実する夏〜秋咲き植物は一般に結実率が高いが、ハチ媒花植物は花粉制限を受け易かった。光環境に応じた開花フェノロジーグループ毎に共通の結実特性が認められた。5.クローナル植物スズランを対象として繁殖戦略に関わる調査を行った。人工交配実験の結果、同一クローン内の花序間の受粉ではほとんど種子は結実しなかった。また、結実率は近隣にある和合花粉を持つ異なるクローンの花数により大きく左右されていた。クローン成長の程度は、花粉媒介者を誘引する花密度に影響を及ぼし、和合花粉の供給効率や種子繁殖を通じた個体の繁殖成功に影響を及ぼすことが示された。
• 無季節環境下での個葉・シュート特性のトレードオフと植物生活形多様性

  日本学術振興会：科学研究費助成事業

  研究期間 : 2002年 -2004年 

  代表者 : 甲山 隆司, 寺島 一郎, 工藤 岳, 高橋 耕一, 鈴木 英冶, 東 正剛, 北山 兼弘

   

  熱帯山地は、温度と乾燥のストレスもかかりにくい、植物にとってもっとも恒常的な環境であり、植物の生活形多様性が高い。そこでは、適応的分化を反映する明瞭な生理機能レベルのトレードオフが存在すると推測される。本研究では、個葉およびシュートモジュールレベルのトレードオフが、同じ地域の恒常的な環境下での多様化を促進しているという仮説に立って、葉およびシュートの生理機能の分化を解析した。本研究が主対象としたのは、西ジャワ州のハリムン山国立公園であり、対照として、屋久島の照葉樹林においてもセンサスも行なった。 ハリムンでは、110種の葉寿命の観測を3年間にわたって行なった。葉の窒素利用効率は、葉の原形質成分と細胞壁成分に分けて分析し、葉の寿命と、葉の構造維持にかかわると想定される細胞壁成分の窒素分画の増加について分析を行なう。着生大型シダのオオタニワタリや、つる性ヤシ科のロタンなどでは、詳細な成長解析を実施した。種間で、当年葉展開時の水分配や、生活形によるシュート間の分配制御の違い、肥大成長とシュート伸長成長のあいだの分配を観測して、種間・生活形間の分化の適応をあきらかにした。 屋久島では、116種の葉試料について、葉齢分布、LMA,C/Nの分析を行い、予測した1年葉以上の種での窒素含量と葉寿命の無相関を、生活形にまたがって検出した。照葉樹の葉配置に認められる疑似輪生配置と二列生配置の二系について、シュート形態と葉特性との対比が存在することもあきらかにした。
• 多雪環境における高山植物集団の時空間的動態の解析と地球環境変化の影響予測

  日本学術振興会：科学研究費助成事業

  研究期間 : 2001年 -2003年 

  代表者 : 大原 雅, 高田 壮則, 和田 直也, 工藤 岳

   

  本研究は高山生態系における雪解け時期の変動が、そこに生育する植物個体群の時空間的動態ならびに遺伝的構造に及ぼす影響を定量的に評価し、さらに、得られた結果をもとに、数理モデルを用いて変動環境における植物個体群の動態を予測することを目的として行った。野外調査ならびに室内遺伝実験は、大雪山、立山、ロッキー山脈の3地域に関して行った。 大雪山では、さまざまな高山植物個体群間で、交配システム変異と花粉散布による遺伝的交流の程度を明らかにするために、アロザイム分析ならびにマイクロサテライト遺伝子を用いた種子の遺伝解析を行った。その結果、いずれの種においても局所個体群は遺伝的に分化している傾向が認められ、遺伝構造は地理的距離もしくは雪解け傾度の影響を受け、階層的に構築されている傾向が示された。 立山では、周北極要素の高山植物・チョウノスケソウについて,立山の一ノ越個体群と水晶岳の個体群について,10酵素18遺伝子座でアロザイム分析を行った。その結果,両個体群ともすべての遺伝子座において,変異が全く無いことが分かった。また,立山一ノ越個体群において花の形質を調べたところ,北極圏の個体群に比べて雌しべに対する雄しべへの投資比が高いことが分かった。 ロッキー山脈では、カタクリ(Erythronium grandiflorum)を対象に、消雪時期の変動と集団間・集団内の遺伝的分化を調査した。酵素多型分析の結果、高山性カタクリ集団において消雪時期の不均一性が開花フェノロジーを変動させ、花粉流動を妨げることにより、遺伝的構造を生じさせることが明らかになった。 このほか、野外生態調査と平行して、多年生植物の動態を記述する数理モデルに関する研究を行い、密度依存性がある動態の場合の環境変動に対する集団の応答を評価する方法を新たに開発した。
• 冷温帯林の送粉系ネットワーク機能の解明

  日本学術振興会：科学研究費助成事業

  研究期間 : 1999年 -2002年 

  代表者 : 戸田 正憲, 工藤 岳, 日浦 勉

   

  本研究では「樹木開花量の年変動により送粉者個体群が年変動し,それにより送粉者を共有する林床植物の結実率も年変動する」という仮説を証明するために次の3項目について調査し,以下の知見を得た。 1.虫媒性樹種の開花量:マルハナバチ利用樹種8種を含む,約20種の樹木の開花量の年変動を定量化した。とくに開花量の年変動が大きいアオダモについてはその繁殖システムを明らかにした。またハクウンボクについては光合成産物のトレースを行い,非繁殖シュートから繁殖器官への転流が開花量決定に重要な役割を果たしていることを明らかにした。 2.マルハバチの個体数:森林調査区においては,春期の越冬女王の個体数(標識再捕獲法による)は彼女らが生まれた前年の樹木開花量と,ワーカー個体数(ウィンドウトラップ採集法による)は当年の樹木開花量とそれぞれ同調した年次変動パタンを示した。マルハナバチと樹木開花量の垂直分布の季節変化パタンから,マルハナバチが林冠木の開花量と関連して飛翔空間を決定することが示唆された.森林と草原におけるワーカー個体数の季節変化から,コマルハナバチの草原と森林の利用割合が季節変化しないが,オオマルハナバチは季節によりいずれか一方の生息地に特化するという生息地利用における種間の違いが認められ,これが両者の年次変動パタンの違いに関連していることが示唆された。 3.林床性草本の繁殖成功:10種の繁殖特性と結実成功を4年間評価し,エゾエンゴサクを含む林床性植物の繁殖システムの概要を評価できた。また,光環境の異なる林縁と林内での林床植物の結実率を比較することにより,資源制限と花粉制限の影響を相対的に評価した。 本研究により初めて温帯林で送粉系の年次変動が定量的に記述され,上記の仮説が部分的に支持された。このことは,送粉系の動的側面を適切に評価するためには長期的モニタリングがきわめて重要であることを示唆する。
• 森林における炭素バランス

  日本学術振興会：科学研究費助成事業

  研究期間 : 1999年 -2001年 

  代表者 : 甲山 隆司, 田中 教幸, 東 正剛, 岩熊 敏夫, 工藤 岳, 大崎 満

   

  2001年度には,既設の森林プロットの再測を実施した.3年間の樹高・幹直径関係の推移を測定している幌内川河畔林では,まだ明瞭な方向的推移を得るには至っていない.18年生と45年生の二次林での初期生長を,ミズナラ・イタヤカエデとカラマツ(植林樹)について,樹幹解析によって比較解析したところ,種間で応答挙動が違うことが示唆された.落葉分解観測については,ミズナラがすでに終了しているが,イタヤカエデとオオイタドリ(遷移初期種)について,幌内川河畔林内および有珠山の遷移初期植生で比較観測を実施した. 森林土壌から放出される二酸化炭素の空間的なばらつきや時間的な変動の詳細を明らかにすることを目的として空間スケールの異なる4つのサイトを設営し,内部に等間隔の100個の格子点上でチャンバー法による土壌CO_2フラックスの季節変化を2001年6月から11月まで毎月観測した.その結果,大きくばらつくフラックスの値は正規分布で近似できることがわかった.CO_2フラックスの季節変動の大きさは全ての観測点で一定の傾向を持っているとは限らず,また観測地点によって最大10〜40倍の差が見られた.季節変動から求めた温度係数Q10は約2〜9,平均値約5.2という値を示した. 土壌分解系の機能を探る目的で,冷温帯、温帯、暖温帯の広葉樹林と針葉樹林において,落葉・土壌・土壌動物のδ15Nとδ13Cを求めた.安定同位体比には,落葉<土壌<土壌動物の関係が見られ,土壌動物の中でも落葉食者よりも肉食者で大きな値を示した.土壌中の安定同位体比は,δ15Nとδ13Cのいずれも南方ほど高く,有機物の分解速度植物を介した炭素や窒素の流れが速いことを反映していた. モデル研究では,既存モデルの適用と,シュートモジュール機能モデルの定量化を実施した.米国モンタナ大学テラダイナミクスシュミレーション研究グループの開発したBIOME-BGCモデルを苫小牧タワーサイトに導入し,水・炭素・窒素の循環と貯蔵を日間隔でシュミレートした.ほぼ妥当な純一次生産速度に対して,現存量が実測推定に対して過少に出る傾向があった.葉・シュートレベルの生態生理過程から,個体と個体群の挙動を記述するモデル(PipeTree)は,北方性モミ属個体群を想定したデータマッチングを行い,今まで報告されてきた自己間引きにともなう変化など個体群過程を再現するのに成功した.
• 東南アジア多雨林生態系の地球環境変化に対する応答

  日本学術振興会：科学研究費助成事業

  研究期間 : 1998年 -2000年 

  代表者 : 甲山 隆司, 工藤 岳, 中静 透, 鈴木 英治, 大崎 満, 小林 繁男, 東 昭雄, 柴田 英昭, TURNER Ian

   

  東南アジアの熱帯低地多雨林は,有機物蓄積量でも,一次生産速度においても,もっとも巨大な生態系である.この自然生態系は人間活動により急激に変貌しつつあり,さらに大気二酸化炭素濃度の上昇と気候変化に対応して生態系諸機能の加速的変化を遂げつつある.したがって,熱帯多雨林の変化過程を高い精度で追跡観測することは,地球環境の変化を予測していく上できわめて重要な課題である.本調査は,すでに典型的な気候極相である低地混交フタバガキ林および貧栄養な立地上に成立する内陸泥炭湿地林・ヒース林に設定されている永久調査区を対象として,森林動態パラメータの変化を観測し,熱帯低地多雨林における有機物空間パターンの変容過程を抽出することを目的とした. 主なフィールド調査は,ボルネオ島南部中央カリマンタン州のヒース林と泥炭湿地林で実施した.同州都パランカラヤ市周辺に散在する保護区域内のヒース林と泥炭湿地林に設置した1ヘクタール規模の永久調査区を調査対象として,一連の環境・森林生態系調査を実施した.とりわけ,1997年のエルニーニョによる乾燥影響が把握できるデザインとなった. また,すでに1992年来設定している西カリマンタン州ランダック川中流部のスリンブの混交フタバガキ林の追跡データから,森林のギャップ動態・サイズ分布動態を再現するモデルを提出した.さらに,本研究では,マレーシア領サバ州のキナバル山の植生と,サラワク州での予備調査,またブルネイ領のタセック・マリンブン保護地における泥炭湿地林の調査区設営など,ボルネオ島の森林タイプを広くカバーする野外調査を実施した. これら永久調査区の同時追跡データによって,きわめて急速に進行している森林の人為的な衰退が,ボルネオ熱帯林のポテンシャルに及ぼしつつある影響が,今回のセンサスと今後のその継続によって的確に把握できるものと考えている.
• 生存戦略としての高山植物の種子発芽特性の評価

  日本学術振興会：科学研究費助成事業

  研究期間 : 1998年 -1999年 

  代表者 : 工藤 岳

   

  北海道大雪山系の高山帯で,高山植物実生の発生時期と生存パターンについての調査を2年間行った。また,現地で採取した10数種の種子を用いて実験室内で発芽試験を行い,発芽の温度特性を比較した。野外での観察の結果,雪解けの早い風衝地植物群落では生育シーズンを通しての発芽が認められたのに対して,雪解けの遅い雪田植物群落では雪解け直後に発芽が集中していた。風衝地では生育シーズン初期の乾燥による死亡と越冬期の死亡が高かったが,雪田環境では発芽実生の死亡率は低かった。実験室での様々な温度制御下での発芽試験の結果、風衝地植物の発芽は種内においても様々な温度特性を示したのに対して,雪田植物の発芽はある温度域に集中していた。また,一般に風衝地植物の発芽開始積算温度は雪田植物に比べて低い傾向が認められた。これらの傾向は,風衝地から雪田まで広い分布域をもつミヤマキンバイの個体群間でも認められた。以上の結果より,風衝地は植物にとって変動環境にあり,生育シーズン初期の乾燥や冬季の死亡率が実生の定着を制限していることが推測された。早く発芽した実生は乾燥による死亡の危険性が高いが,長い生育期間を確保できるために根茎の発達がよく,冬季の死亡の危険性が低いというトレードオフの関係が認められた。このような環境では,発芽時期に変異を持たせる危険分散によって,実生集団の絶滅確率を低くするような発芽パターンが適応的であると考えられる。異なる積雪環境にある個体群間では,発芽特性に作用する選択圧が異なっていることが本研究によって示唆された。
• ボルネオ多雨林生態系の地球環境変化に対する応答

  日本学術振興会：科学研究費助成事業

  研究期間 : 1997年 -1997年 

  代表者 : 甲山 隆司, 工藤 岳, 田中 教幸, 高橋 英紀, 東 正剛, 岩熊 敏夫

   

  本研究は,IGBP-GCTEのコアリサーチ「モンスーンアジア陸域生態系における地球変化のインパクト」(TEMA)の熱帯低地多雨林観測体制を担う目的で行なった.TEMAの観測体制は,熱帯低地雨林生態系のステーションが欠けていた.本研究は,インドネシア・マレーシアとの共同研究としてボルネオにおけるTEMAステーションの整備・立ちあげを行なった.気候的極相である低地混交フタバガキ林生態系とともに,内陸泥炭湿地林および海岸湿地林といった地形的・土壌的成因による貧栄養生態系にも調査ステーションを設けて,低地生態系の全体像を把握することに重点を置いた.ボルネオ島南部の内陸低地には木質泥炭が深く堆積する特殊な森林生態系が広く分布する.中央カリマンタン・パランカラヤ市近郊のラヘイ地区およびその周辺に設営したステーションでは,泥炭湿地林と,泥炭が欠落した珪砂質栄養土壌上のケランガス林に森林調査プロットを設営し,毎木調査と同定のための標本採取の他,リタートラップと分解実験のためのリターバッグ(葉および細枝)も設置した.さらに土壌のガス交換特性を調べるために,採気による温室効果ガスの測定を開始した.また,広域の集水域特性をみるために,パランカラヤからタンジュンプティ国立公園にかけての陸水学的予備センサスを行なった. また,並行してマレーシア・サバ州タビン保護区に海岸湿地林生態系のステーションを設置し,すでにTEMA観測が進行しているキナバル山でもプロットの再測定と,特に高標高地域の植物の繁殖過程を行なった.2月上旬にはTEMA共同研究をひとつの柱とした札幌のシンポジウムに参加するとともに,3月中旬に開催されたGCTE-LUCC国際会議に出席してTEMAの成果を発表し,今後の観測体制について討議した.
• 北方林の林床多年生草木群集の多様性を支える生活史シンドローム

  日本学術振興会：科学研究費助成事業

  研究期間 : 1996年 -1997年 

  代表者 : 甲山 隆司, 工藤 岳, 植村 滋, 大原 雅, 佐藤 利幸, 露崎 史朗

   

  北海道の低標高域に残存する北方混交林は、その緯度帯の森林植生としては植物種多様性が高い系である。本研究では、北海道の北方混交林を対象に、多年生草本の種多様性が維持されるメカニズムを解き明かすことを目的とした。 前年度に引き続き、札幌市東郊の野幌森林公園内と、北海道大学苫小牧演習林内およびその近郊を中心に調査を継続した。苫小牧では2年間の林床草本群集のフェノロジーについてデータを蓄積し、融雪と林冠の展葉開始の年変動にともなって、積算受光量を一定に調節するような季節性の変化が存在することを見いだした。さらに季節に沿った各部分重の間の相対生長関係を6種について追跡調査し、種差が少なく葉に多くを分配するパターンを記録した。繁殖に注目した調査としては、一回繁殖型植物のオオウバユリ個体群の空間パターンを継時的に解析した。また、あらたに円盤接触法を考案して、葉群の垂直構造の定量的解析を行なった。選択的な採食圧にともなう群集の変化の解析を、夏季の馬の林間放牧系で調査した。さらに、対象地域の広域分布特性を空間スケール依存性として把握するために、シダ植物群について分析を行なった。 以上の基礎調査で明かにした群集パターンに基づいて、共存する種間の形態、繁殖持性、季節戦略、そして微環境のあいだのシンドロームについて、考察を行なった。
• 訪花昆虫と植食性昆虫の季節性が高山植物の繁殖成功に及ぼす効果について

  日本学術振興会：科学研究費助成事業

  研究期間 : 1995年 -1995年 

  代表者 : 工藤 岳

   

  高山植物の開花・結実フェノロジーと繁殖成功との関係を,訪花昆虫や種子食害昆虫の季節性の効果に着目し調査した.北海道大雪山系の雪田で,雪解け時期の異なる4箇所に20×20mの調査プロットを設定し,セリ科多年生草本のハクサンボウフウの開花・結実状況を,5月下旬から10月上旬まで定期的に観察した.プロット間で雪解け時期は6月上旬から8月下旬と大きく異なり,ハクサンボウフウの開花時期も7月中旬から9月中旬までと大きく異なっていた. 雪解け時期の早い場所では,開花時期の気温が低く,訪花昆虫の活性が低くために結実が花粉不足によって制限されていた.また,双翅目昆虫の幼虫による果実の食害が頻繁に観察された.雪解けが中程度の場所では,開花期の訪花昆虫の活性が高く,種子の食害も非常に低いために,高い種子生産を示していた.一方,雪解けの遅い場所では,受粉成功は高いが種子成熟期間が制限されているために,ほとんど結実できなかった.以上の結果より,雪解け時期の違いによって引き起こされた開花フェノロジーの変異は,種子生産成功度に大きく影響することが示された. ハクサンボウフウは,同一個体上に雄花と両性花を持つ雄性両全同株(andromonoecy)である.プロット間で各個体の両性花と雄性花の構成比を比較したところ,雪解けの遅いプロットほど両性花の割合が高くなっていた.このような性表現の変異は,それぞれのハビタットにおける訪花昆虫の活性や生育期間の制限に起因していると考えられる.雄器官・雌器官を通しての繁殖成功度が変化するときの最適両性/雄性花生産比を求めるESSモデルを作り,実際の野外データに当てはめたところ,モデルを支持する傾向が得られた. 以上得られた成果のうち,野外データについてはOpera Botanicaに掲載予定であり,モデルの当てはめについて現在論文作成中である.
• 高山植物の積雪に対する反応と適応

  日本学術振興会：科学研究費助成事業

  研究期間 : 1990年 -1990年 

  代表者 : 工藤 岳