A central principle in trait‐based ecology is that trait variation has an adaptive value. However, uncertainty over which plant traits influence individual performance across environmental gradients may limit our ability to use traits to infer ecological processes at larger scales. To better understand which traits are linked to performance under different precipitation regimes, we measured above‐ and belowground traits, growth, and reproductive allocation for four annual and four perennial species from a coastal sage scrub community in California under conditions of 50%, 100%, and 150% ambient precipitation. Across water treatments, annual species displayed morphological trait values consistent with high rates of resource acquisition (e.g., low leaf mass per area, low root tissue density, high specific root length), and aboveground measures of resource acquisition (including photosynthetic rate and leaf N concentration) were positively associated with plant performance (reproductive allocation). Results from a structural equation model demonstrated that leaf traits explained 38% of the variation in reproductive allocation across the water gradient in annual species, while root traits accounted for only 6%. Although roots play a critical role in water uptake, more work is needed to understand the mechanisms by which root trait variation can influence performance in water‐limited environments. Perennial species showed lower trait plasticity than annuals across the water gradient and were more variable as a group in terms of trait–performance relationships, indicating that species rely on different functional strategies to respond to drought. Our finding that species identity drives much of the variation in trait values and trait–performance relationships across a water gradient may simplify efforts to model ecological processes, such as productivity, that are potentially influenced by environmentally induced shifts in trait values.

中文翻译：

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植物性状与半干旱生态系统中的性能差异相关

基于特征的生态学的中心原则是特征变异具有适应性价值。但是，不确定哪些植物性状会影响整个环境梯度下的个体表现，可能会限制我们使用这些性状推断较大规模的生态过程的能力。为了更好地了解哪些性状与不同降水方式下的性能相关，我们在50％，100％的条件下，测量了加利福尼亚沿海鼠尾草灌丛社区的四个年度和四个多年生物种的地上和地下性状，生长和繁殖分配。 ，以及150％的环境降水量。在各种水处理中，一年生物种的形态特征值与高资源获取率相一致（例如，单位面积叶片质量低，根组织密度低，比根长高），资源获取的地上措施（包括光合速率和叶片氮浓度）与植物生长（生殖分配）呈正相关。结构方程模型的结果表明，叶片性状解释了一年生物种跨水梯度的生殖分配变化的38％，而根性状仅占6％。尽管根在水分吸收中起着至关重要的作用，但还需要做更多的工作来了解根特质变化可在缺水环境中影响性能的机制。在水梯度上，多年生物种的可塑性比年生物种低，并且在特征-性能关系方面作为一个整体变化更大，这表明物种依赖于不同的功能性策略来应对干旱。