Data from: Plant size and competitive dynamics along nutrient gradients

Resource competition theory in plants has focused largely on resource-acquisition traits that are independent of size such as traits of individual leaves or roots or proportional allocation to different functions. However plants also differ in maximum potential size which could outweigh differences in module-level traits. We used a community-ecosystem model called MONDRIAN to investigate whether larger size inevitably increases competitive ability and how size interacts with nitrogen supply. Contrary to the conventional wisdom that bigger is better we found that invader success and competitive ability are unimodal functions of maximum potential size such that plants that are too large %28or too small%29 are disproportionately suppressed by competition. Optimal size increases with nitrogen supply even when plants compete only for nitrogen in a size-symmetric manner although adding size-asymmetric competition for light does substantially increase the advantage of larger size at high nitrogen. These complex interactions of plant size and nitrogen supply lead to strong nonlinearities such that small differences in nitrogen can result in big differences in plant invasion success and the influence of competition along productivity gradients.植物资源竞争理论的研究长期以来多聚焦于与个体大小无关的资源获取性状（resource-acquisition traits），例如单叶或单根的性状，抑或是不同功能间的比例分配。然而，植物的最大潜在体型差异同样可能超过模块级性状（module-level traits）间的差异。本研究采用一款名为MONDRIAN的群落-生态系统模型（community-ecosystem model），探究更大的体型是否必然提升竞争能力，以及体型如何与氮素供给产生交互作用。与“体型越大竞争力越强”的传统认知相悖，我们发现入侵成功率与竞争能力均为最大潜在体型的单峰函数（unimodal functions）：体型过大（或过小）的植物会受到竞争的不成比例抑制。即便植物仅以大小对称竞争（size-symmetric competition）的方式争夺氮素，最优体型也会随氮素供给增加而提升；不过，当加入针对光照的大小不对称竞争（size-asymmetric competition）后，高氮环境下大体型的竞争优势会显著增强。植物体型与氮素供给间的这些复杂交互作用会引发强烈的非线性效应（strong nonlinearities），使得氮素的微小差异即可导致植物入侵成功率产生巨大差异，并改变竞争沿生产力梯度（productivity gradients）的影响模式。