Human activities markedly modify diversity patterns of plant communities and their response to environmental conditions, with subsequent consequences for ecosystem functions. We measured 11 key functional traits of 47 plant species and assessed both taxonomic and functional composition as well as above-ground biomass (AGB) of plant communities from 127 plots in the Lake Dongting wetland. Using a generalized multilevel path model, we examined the cascading effects of hydrological gradients on plant diversity and ecosystem functions in two distinct habitat types (short grassland with a natural community dominated by Carex spp. and tall grassland with a managed artificial community dominated by Triarrhena lutarioriparia and Phragmites australis). We found significant differences in the response of plant diversity and AGB to hydrological gradients. Species richness, Shannon–Wiener diversity, multiple-trait functional diversity measures (i.e., functional richness, functional dispersion & Rao's quadratic entropy) and community-weighted mean (CWM) of shoot height were all significantly higher and functional divergence and CWM of tuber significantly lower in tall grassland. AGB was significantly higher in short grassland, largely driven by variations of functional diversity rather than of taxonomic diversity. Moreover, we found a significant cascading effect of elevation and soil moisture on AGB, directly or indirectly induced by changes in functional diversity in the short grassland, while only direct effects of elevation on AGB were observed in the tall grassland. Therefore, our study provides strong evidence that human-induced changes in habitat types uncoupled the cascading effects of hydrological gradients on ecosystem functions mediated by either the taxonomic or the functional diversity.

中文翻译：

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人类活动解耦了水文梯度对洞庭湖湿地植物多样性和生态系统功能的连锁效应

人类活动显着改变了植物群落的多样性模式及其对环境条件的反应，进而对生态系统功能产生影响。我们测量了洞庭湖湿地 127 个地块的 47 个植物物种的 11 个关键功能性状，并评估了植物群落的分类和功能组成以及地上生物量 (AGB)。使用广义的多级路径模型，我们检查了水文梯度对两种不同栖息地类型（以Carex spp为主的自然群落的短草地和以Triarrhena lutarioriparia为主的人工群落的高草地）中植物多样性和生态系统功能的级联效应和芦苇）。我们发现植物多样性和 AGB 对水文梯度的响应存在显着差异。物种丰富度、Shannon-Wiener 多样性、多性状功能多样性度量（即功能丰富度、功能离散度和 Rao 二次熵）和茎高的群落加权平均值（CWM）均显着较高，块茎的功能发散度和 CWM 显着增加在高大的草地上较低。AGB 在短草地中显着更高，主要是由功能多样性而不是分类多样性的变化驱动的。此外，我们发现海拔和土壤水分对 AGB 有显着的级联效应，直接或间接地由矮草地的功能多样性变化引起，而在高草地中仅观察到海拔对 AGB 的直接影响。所以，