Schmid College of Science and Technology, Chapman University, Orange, California, 92866, USA.
Department of Plant Sciences, University of California, Davis, California, 95616, USA.
Ecology. 2021 May;102(5):e03318. doi: 10.1002/ecy.3318. Epub 2021 Apr 16.
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.
基于特征的生态学的一个核心原则是，特征变异具有适应性价值。然而，由于不确定哪些植物特征会影响跨环境梯度的个体表现，这可能限制了我们利用特征在更大尺度上推断生态过程的能力。为了更好地理解哪些特征与不同降水条件下的表现有关，我们在加利福尼亚州沿海莎草灌丛群落中，对四个一年生和四个多年生物种进行了地上和地下特征、生长和生殖分配的测量，条件分别为环境湿度的 50%、100%和 150%。在所有水分处理中，一年生物种表现出与高资源获取率一致的形态特征值（例如，低叶面积比、低根组织密度、高比根长），而资源获取的地上测量值（包括光合速率和叶片氮浓度）与植物表现（生殖分配）呈正相关。结构方程模型的结果表明，在一年生物种的水分梯度中，叶片特征解释了生殖分配变化的 38%，而根系特征仅占 6%。尽管根在水分吸收中起着关键作用，但仍需要更多的工作来理解根特征变化如何影响水分限制环境中的表现的机制。多年生物种在水分梯度上的表现比一年生物种的特征可塑性低，而且在特征-表现关系方面作为一个群体更加多变，这表明物种依赖不同的功能策略来应对干旱。我们的研究结果表明，物种身份在很大程度上决定了特征值和特征-表现关系在水分梯度上的变化，这可能会简化对生态过程（如生产力）的建模工作，这些过程可能受到环境诱导的特征值变化的影响。
