Competition and coexistence in plant community in relation to strategy of resource us

植物群落由大小不同的个体和物种组成。研究了群落中个体和物种如何获取和利用有限资源，以阐明物种和个体之间的竞争与共存机制。川边芒草草甸中，芒草在冠层上层占主导地位，而在林下则有许多较小的从属种，如Potentila和Lysimachia。虽然从属林下种对PPFD的吸收量远低于优势芒草，但相对于地上生物量，它们的叶面积更大，因此单位地上生物量吸收的PPFD更接近芒草。这表明，相似的每单位地上生物量的光获取效率是植物群落中物种共存的必要条件。我们研究了加拿大苍耳（Xanthium canadense）在La海岸的天然林分，并将其作为竞争系统。高大的个体处于上层，吸收了大量的有效PPFD。上层和下层个体的叶面积比差异有限，因此上层个体的光获取效率仍然大于下层个体。这与上面给出的共存系统形成了强烈的对比。不同生育期林分的比较表明，株高和光照气候对单株叶面积发育有一定的控制作用。我们进一步研究了在两种氮效度条件下实验建立的冠层叶片的光合特性。与普通光照气候下相比，低层植物叶片氮浓度有较高的趋势。然而，叶片光合作用中的氮利用仅取决于叶片的光气候。我们开发了最优分配模型来研究在传粉者可用性或资源可用性不可预测的环境中，对胚珠生产的下注对冲作为一种进化策略。我们发现传粉者或资源可用性的大变异性并不总是选择增加植物产生的胚珠数量。相反，在传粉者或资源可用性变化较大的生境中，植物会减少其胚珠数。为了解释雌雄同体植物的雌性偏向性分配，我们建立了一个包含花/果生长源库关系的博弈论模型。在这个模型中，花/果的生长速度要么受到其汇强度（其潜在相对生长速度和绝对大小的乘积）的限制，要么受到植物的源强度（瞬时可用资源量）的限制。我们发现，如果果实生长受到汇限制，至少在其生长的早期阶段，雌性偏向性分配是进化稳定的。少

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 … More 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