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（Resource competition theory）的研究焦点长期以来多集中于与植株体型无关的资源获取性状（resource-acquisition traits），例如单叶、单根的性状，或是不同功能间的比例分配策略。然而，植物的最大潜在体型也存在差异，这一差异的影响可能远超构件级性状（module-level traits）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，以及体型与氮素供给（nitrogen supply）之间的交互作用机制。与“体型越大越有利”的传统认知相悖，本研究发现：植物的入侵成功率（invader success）与竞争能力均为最大潜在体型的单峰函数（unimodal functions），即体型过大（或过小）的植株会受到竞争的不成比例抑制。即便植物仅以体型对称竞争（size-symmetric competition）的方式竞争氮素，最优体型也会随氮素供给水平提升而增大；不过，当引入针对光照的体型非对称竞争（size-asymmetric competition）时，高氮环境下大体型植株的竞争优势会显著增强。植株体型与氮素供给间的这类复杂交互作用会催生极强的非线性效应，使得氮素的细微差异，能够在生产力梯度（productivity gradients）上对植物入侵成功率以及竞争的影响造成显著差异。