Department of Plant Biology and Ecology, College of Life Science, Nankai University, No. 94 Weijin Road, Tianjin 300071, PR China.
College of Agronomy & Resources and Environment, Tianjin Agricultural University, No. 22 Jinjing Road, Tianjin 300384, PR China.
Sci Total Environ. 2022 Jan 10;803:149950. doi: 10.1016/j.scitotenv.2021.149950. Epub 2021 Aug 27.
Understanding relationships between biodiversity and ecosystem functions (BEF) and the way in which ecosystem functions respond to changing climatic conditions or community composition is useful for predicting ecological consequences of global changes. However, how soil moisture condition, plant species richness interactively affect ecosystem functions in shrub-encroached grasslands is poorly understood. We conducted a soil moisture × species richness microcosm experiment using semi-arid grassland species with a N-fixing shrub Caragana microphylla Lam. as the dominant species to evaluate how soil moisture and plant species richness affected ecosystem functions directly or indirectly via regulating community functional structure, such as community-weighted mean values (CWM) and functional dispersion (FDis). Soil moisture and species richness interactively affected soil functions (soil C-, N-, P cycles and soil multifunctionality), with greater species richness buffering the adverse effects of soil drought. Soil moisture and species richness showed opposite effects on FDis but similar effects on CWM. FDis mediated the indirect effect of soil moisture and species richness on ecosystem functions, while CWM only mediated the indirect effect of soil moisture. More specifically, both soil moisture and plant species richness were negatively associated with soil P cycle, and the CWM contributed by traits related to resource-conservative strategy was positively associated with soil N cycle. Species richness showed a positive direct effect on total shoot biomass, which was mainly contributed by the complementarity effect of neighbor species richness. This study provides strong empirical support of how biomass and soil nutrient cycles respond to the changes of soil moisture and plant species richness in C. microphylla shrub-encroached grasslands, and insights on the mechanisms underlying the interactive effects of soil condition and community species composition on multiple ecosystem functions in N-fixing shrub encroached grasslands in semi-arid grassland regions.
理解生物多样性和生态系统功能（BEF）之间的关系，以及生态系统功能对气候变化条件或群落组成变化的响应方式，有助于预测全球变化对生态系统的影响。然而，在灌木侵入的草原中，土壤水分条件和植物物种丰富度如何相互作用影响生态系统功能，这一点还知之甚少。我们使用半干旱草原物种进行了一个土壤水分×物种丰富度的微宇宙实验，其中以固氮灌木柠条（Caragana microphylla Lam.）为优势种，以评估土壤水分和植物物种丰富度如何通过调节群落功能结构（如群落加权平均值（CWM）和功能离散度（FDis））直接或间接影响生态系统功能。土壤水分和物种丰富度交互作用影响土壤功能（土壤碳、氮、磷循环和土壤多功能性），丰富的物种多样性缓冲了土壤干旱的不利影响。土壤水分和物种丰富度对 FDis 表现出相反的影响，但对 CWM 的影响相似。FDis 介导了土壤水分和物种丰富度对生态系统功能的间接影响，而 CWM 仅介导了土壤水分的间接影响。更具体地说，土壤水分和植物物种丰富度均与土壤磷循环呈负相关，而与资源保守策略相关的性状所贡献的 CWM 与土壤氮循环呈正相关。物种丰富度对总地上生物量表现出正向直接效应，这主要是由相邻物种丰富度的互补效应贡献的。本研究为柠条灌木侵入草原中生物量和土壤养分循环对土壤水分和植物物种丰富度变化的响应机制提供了强有力的实证支持，并为半干旱草原地区固氮灌木侵入草原中土壤条件和群落物种组成对多个生态系统功能的相互作用机制提供了新的见解。
