1. Trait‐based approaches are key to develop mechanistic understanding of differences in plant species performance under environmental change. While mean trait values have been widely used to link functional traits to species performance, the contribution of intraspecific trait variation and trait plasticity remains unclear. Moreover, environmentally induced changes in species biomass are caused by changes in the number of individuals and individual growth rate, both of which should be influenced by trait differences and plasticity. Our goal in this study is to use trait‐based information to explain species performance via changes in species abundance and individual weight.
2. We measured the mean, intraspecific variation and plasticity of nine above‐ground plant traits, and a further three mean root traits from 10 common species in a precipitation manipulation experiment in semi‐arid grassland. We used this trait information to explain differences in the responses of species biomass, abundance and mean individual weight to changing precipitation. Species responses were calculated as the normalised slopes of the regressions between species biomass, abundance and individual weight with the manipulated precipitation amount.
3. We found strong differences in species responses to changing precipitation for species biomass, abundance and mean individual weight. Reduced precipitation decreased biomass, abundance and mean individual weight for some species, but increased them for others. Biomass and mean individual weight of species with resource‐acquisitive traits, such as shallow rooted species, showed stronger positive responses to changing precipitation compared to resource‐conservative traits, like those with deep roots. For above‐ground traits, trait plasticity was the strongest predictor of species responses compared to mean traits and intraspecific trait variation. In addition, trait plasticity regulated changes in species biomass more via changes in species abundance than mean individual weight.
4. These results indicate that trait plasticity is a key driver for determining species‐specific responses to changing precipitation and needs more consideration for understanding and predicting ecosystem structure and functioning in future climate scenarios.

中文翻译：

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物种对降水变化的反应取决于性状的可塑性，而不是性状的平均值和种内变异

1. 基于特征的方法是发展对环境变化下植物物种表现差异的机械理解的关键。虽然平均性状值已被广泛用于将功能性状与物种表现联系起来，但种内性状变异和性状可塑性的贡献仍不清楚。此外，物种生物量的环境诱导变化是由个体数量和个体生长速率的变化引起的，这两者都应受到性状差异和可塑性的影响。这项研究的目标是使用基于特征的信息通过物种丰度和个体重量的变化来解释物种表现。
2. 我们在半干旱草原的降雨操纵实验中，测量了9种地上植物性状的均值，种内变异和可塑性，以及10种常见树种的另外3个平均根性状。我们使用此特征信息来解释物种生物量，丰度和平均个体重量对降水变化的响应差异。物种响应计算为物种生物量，丰度和个体重量与受控降水量之间回归的标准化斜率。
3. 我们发现，物种对生物量，丰度和平均个体重量变化的降水的反应差异很大。减少降水会减少某些物种的生物量，丰度和平均个体重量，但会增加其他物种的生物量，丰度和平均个体重量。具有资源获取性状的物种（例如，浅根物种）的生物量和平均个体重量，与具有深部根源的资源保守性相比，对降水变化表现出更强的正响应。对于地上性状，与平均性状和种内性状变异相比，性状可塑性是物种反应的最强预测因子。此外，性状可塑性通过物种丰度的变化比平均个体重量更多地调节物种生物量的变化。
4. 这些结果表明，性状可塑性是决定物种对降水变化的特定反应的关键驱动力，需要更多的考虑来理解和预测生态系统的结构以及未来气候情景中的功能。