Trait-based coexistence theories are useful to explain community processes. The aim was to distinguish which theory played a more important role in explaining the invasion mechanism of Caragana microphylla into communities in the Eurasian semi-arid grassland region. We conducted a water condition (WC) × neighbouring plant diversity (NSD) experiment, measured functional dispersion (FDis) and biomass of neighbours, absolute and hierarchical distances between neighbours and C. microphylla for plant height, specific leaf area and leaf dry matter content (LDMC), and explored the relative effect of each predictor on neighbour-effect intensity index (NIntA) on C. microphylla. Significant effect of NSD was direct or mediated by cascading effects between FDis and biomass of neighbours, significant effect of WC was direct or mediated by LDMC hierarchical distance, shoot biomass of neighbours mediated indirect effects of both NSD and WC on the NIntA on C. microphylla. None of the trait absolute distances was employed to explain the variability of the NIntA on C. microphylla. The reduction of NSD or water could decrease the inhibitory effects of neighbours on C. microphylla by increasing vacant niches or increasing the LDMC hierarchical distance between neighbours and C. microphylla, respectively, suggesting that vacant niches and competition-trait hierarchy played more important roles than competition-trait similarity in explaining shrub invasion processes in the Eurasian semi-arid grassland region.

中文翻译：

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空位生态位和竞争特征等级都有助于解释小叶锦鸡儿入侵半干旱草原

基于特征的共存理论有助于解释社区过程。目的是区分哪种理论在解释欧亚半干旱草原地区小叶锦鸡儿入侵群落的机制方面发挥了更重要的作用。我们进行了水分条件 (WC) × 相邻植物多样性 (NSD) 实验，测量了相邻植物的功能分散 (FDis) 和生物量、相邻植物与小叶 C. microphylla 之间的绝对和等级距离，用于植物高度、比叶面积和叶片干物质含量(LDMC)，并探讨了每个预测因子对 C. microphylla 的相邻效应强度指数 (NIntA) 的相对影响。NSD 的显着影响是直接的或由 FDis 和邻居生物量之间的级联效应介导的，WC 的显着影响是直接的或由 LDMC 等级距离介导的，邻居的枝条生物量介导 NSD 和 WC 对 C. microphylla 的 NIntA 的间接影响。没有使用性状绝对距离来解释 NIntA 对 C. microphylla 的变异性。NSD 或水的减少可以分别通过增加空位或增加邻居与小叶 C. microphylla 之间的 LDMC 等级距离来降低邻居对 C. microphylla 的抑制作用，表明空位和竞争性状等级比起更重要的作用。竞争性状相似性在解释欧亚半干旱草原地区灌木入侵过程中的作用。没有使用性状绝对距离来解释 NIntA 对 C. microphylla 的变异性。NSD 或水的减少可以分别通过增加空位或增加邻居与小叶 C. microphylla 之间的 LDMC 等级距离来降低邻居对 C. microphylla 的抑制作用，表明空位和竞争性状等级比起更重要的作用。解释欧亚半干旱草原地区灌木入侵过程的竞争性状相似性。没有使用性状绝对距离来解释 NIntA 对 C. microphylla 的变异性。NSD 或水的减少可以分别通过增加空位或增加邻居与小叶 C. microphylla 之间的 LDMC 等级距离来降低邻居对 C. microphylla 的抑制作用，表明空位和竞争性状等级比起更重要的作用。竞争性状相似性在解释欧亚半干旱草原地区灌木入侵过程中的作用。