1997 Fiscal Year Final Research Report Summary
Competition and coexistence in plant community in relation to strategy of resource us
| Project/Area Number |
08454248
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
生態
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| Research Institution | Tohoku University |
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Principal Investigator |
HIROSE Tadaki Tohoku University, Graduate School of Science : Professor, 大学院理学研究科, 教授 (90092311)
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| Co-Investigator(Kenkyū-buntansha) |
HIKOSAKA Kohki Tohoku University, Graduate School of Science : Assistant Prof., 大学院理学研究科, 助手 (10272006)
SAKAI Satoki Tohoku University, Graduate School of Science : Associate Prof., 大学院理学研究科, 助教授 (90272004)
HIKOSAKA Kohki Tohoku University, Graduate School of Science : Assistant Prof. (10272006)
HIKOSAKA Kohki Tohoku University, Graduate School of Science : Assistant Prof. (10272006)
HIKOSAKA Kohki Tohoku University, Graduate School of Science : Assistant Prof. (10272006)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Competition / Coexistence / resoure / acquisition / Environmental variability / Female-bias / Sexual allocation / Sink-limited growth |
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| Research Abstract |
A plant community consists of individuals and species which are different in size from each other. We studied how those individuals and species acquire and use limiting resources in the community to elucidate the mechanism of competition and coexistence among species and individuals. In the Miscanthus sinensis grassland meadow at Kawatabi, Miscanthus dominated upper layrs of the canopy, while many smaller subordinate species such as Potentila and Lysimachia coexisted in the understory. Although those subordinate understory species absorbed much smaller amounts of PPFD than dominant Miscanthus, they have larger leaf area relative to aboveground biomass and consequently the PPFD absorbed per unit aboveground biomass was closer to that of Miscanthus. This suggests that a similar efficiency of light acquisition per unit investment of aboveground biomass is a necessary condition for species coexistence in a plant community. We studied a natural stand of Xanthium canadense at the shore of La
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ke Kamahusa as a competition system. Tall individuals were in the upper layr and absorbed large amounts of available PPFD.Difference in the leaf area ratio between individuals in upper and lower layrs was limited and consequently the efficiency of light acquisition of the individuals in the upper layr was still larger than that in the lower layr individuals. This made a strong contrast against the coexistence system given above. From a comparison between stands different in the growth stage, it was shown that plant height and light climate controlled leaf area development of individuals. We further studied photosynthetic characteristics of leaves in a canopy established experimentally at two nitrogen availabilities. Leaf nitrogen concentration tended to be higher in leaves of plants in lower layrs when compared at a common light climate. However, nitrogen use in leaf photosynthesis depended solely on the light climate of the leaf.
We developed optimal-allocation models to investigate bet-hedging on ovule production as an evolutionary strategy in environments where either pollinator availability or resource availability is unpredictable. We showed that large variability in pollinator or resource availability does not always select for an increase in the number of ovules produced by the plant. Rather, the plant decreases its I ovule number in habitats where pollinator or resource availability is more variable. To explain female-biased sexual allocation in cosexual plants, we developed a game theoretic model incorporating a source-sink relationship of flower/fruit growth. In this model, flower/fruit growth rate is either limited by its sink strength (the product of its potential relative growth rate and absolute size) or by the source strength (instantaneous amount of resources available) of the plant. We showed that female-biased sexual allocation is evolutionarily stable if fruit growth is sink-limited at least in the early stage of its growth. Less
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