Determinants of the reproductive yield of competing plants in a stand

林分中竞争植物繁殖产量的决定因素

基本信息

批准号：
11440225
负责人：
HIROSE Tadaki
金额：
$ 7.94万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

We studied the effect of CO_2 elevation on the reproductive yield of Xanthium canadense. Although the plant growth and total reproductive yield (seeds plus capsules) increased with CO_2 elevation, seed production did not increase. Analysing N use in plant growth, we found retranslocation of N from leaves to seeds was retarded at high CO_2 due to increased longevity of leaves and low temperature. Translocation was lowered by lower air temperature at later growing season. Thus seed production was constrained by the availability of N.We developed a new method to separate the effect of self-shading from that of shading from neighbors and applied it to stands of Xanthium canadense established with different densities. We estimated (1) the intensity of shading for plants in the stand and (2) self-shading for plants isolated from the stand. Shading from neighbors was estimated as a subtraction of (2) from (1). We found that the interaction among individuals was strong in a stand and that the intensity increased with increasing plant densities.From an analysis of trade-off between size and number in seed production, we proposed a sink-limiting growth model, where contraints in the absorption rate of resources from mother plants were assumed with a loss of resources due to maintenance respiration. This model predicts that seed size does not increase reciprocally to the reduction in seed number. This is because an efficiency in using storage substance decreases with a smaller number of seeds and thus benefits increasing seed number at the expense of seed size. The optimal seed size is smaller than that predicted by Smith and Fretwell.

我们研究了CO_2升高对加拿大苍耳繁殖产量的影响。尽管植物生长和总繁殖产量（种子加蒴果）随CO_2升高而增加，但种子产量并未增加。分析植物生长中的氮利用，我们发现，由于叶子寿命的延长和低温，在高CO_2条件下，氮从叶子到种子的再转移受到阻碍。生长季节后期气温较低，易位减少。因此，种子产量受到氮的可用性的限制。我们开发了一种新方法，将自遮荫的影响与邻居遮荫的影响分开，并将其应用于以不同密度建立的加拿大苍耳林。我们估计了（1）林分中植物的遮荫强度和（2）从林分中分离出来的植物的自遮荫程度。来自邻居的阴影被估计为（1）减去（2）。我们发现林分中个体之间的相互作用很强，并且强度随着植物密度的增加而增加。通过对种子生产中大小和数量之间的权衡分析，我们提出了一个库限制生长模型，其中限制假设母植物的资源吸收率是由于维持呼吸造成的资源损失。该模型预测种子大小不会随着种子数量的减少而增加。这是因为使用储存物质的效率随着种子数量的减少而降低，因此有利于以种子尺寸为代价增加种子数量。最佳种子尺寸小于 Smith 和 Fretwell 的预测。