Data from: Interspecific competition alters leaf stoichiometry in 20 grassland species

The extensive use of traits in ecological studies over the last few decades to predict community functions has revealed that plant traits are plastic and respond to various environmental factors. These plant traits are assumed to predict how plants compete and capture resources. Variation in stoichiometric ratios both within and across species reflects resource capture dynamics under competition. However, the impact of local plant diversity on species-specific stoichiometry remains poorly studied. Here, we analyze how spatial and temporal diversity in resource-acquisition traits affects leaf elemental stoichiometry of plants (i.e., the result of resource capture) and how flexible this stoichiometry is depending on the functional composition of the surrounding community. Therefore, we assessed inter- and intraspecific variations of leaf carbon (C), nitrogen (N), and phosphorus (P) (and their ratios) of 20 grassland species in a large trait-based plant diversity experiment located in Jena (Germany) by measuring leaf elemental concentrations at the species-level along a gradient in plant trait dissimilarity. Our results show that plants showed large intra- and interspecific variation in leaf stoichiometry, which was only partly explained by the functional group identity (grass or herb) of the species. Elemental concentrations (N, P, but not C) decreased with plant species richness, and species tended to become more deviant from their monoculture stoichiometry with increasing trait dissimilarity in the community. These responses differed among species, some consistently increased or decreased in P and N concentrations; for other species, the negative or positive change in P and N concentrations increased with increasing trait difference between the target species and the remaining community. The strength of this relationship was significantly associated to the relative position of the species along trait gradients related to resource acquisition. Trait-difference and trait-diversity thus were important predictors of how species’ resource capture changed in competitive neighbourhoods.

近几十年来，性状在生态学研究中被广泛用于预测群落功能，这一研究范式揭示了植物性状（plant traits）具有可塑性，并可响应多种环境因子。此类植物性状被认为可用于预测植物的竞争能力与资源获取策略。种内与种间的元素化学计量比（stoichiometric ratios）变异，反映了竞争条件下的资源获取动态。然而，本地植物多样性对物种特异性化学计量特征的影响仍鲜有深入探讨。本研究依托位于德国耶拿（Jena）的大型基于性状的植物多样性实验，沿植物性状差异梯度测定物种水平的叶片元素浓度，分析了资源获取性状的时空多样性如何影响植物叶片元素化学计量比（leaf elemental stoichiometry，即资源获取的结果），以及该化学计量比的可塑性如何取决于周边群落的功能组成。为此，我们对该实验中的20个草原物种的叶片碳（C）、氮（N）、磷（P）及其比值的种内与种间变异进行了评估。研究结果显示，植物叶片化学计量比存在显著的种内与种间变异，且该变异仅部分由物种所属的功能群（禾本科或草本）所解释。元素浓度（N、P，而非C）随植物物种丰富度升高而降低；且随着群落内性状差异的增大，物种与其单作群落（monoculture）条件下的化学计量比的偏离程度趋于升高。这类响应因物种而异：部分物种的P、N浓度持续升高或降低；而对于其他物种，其P、N浓度的正负变化幅度随目标物种与剩余群落间的性状差异增大而增强。该关联的强度与物种沿资源获取相关性状梯度的相对位置显著相关。因此，性状差异与性状多样性是预测物种在竞争群落中资源获取方式变化的重要因子。