To examine the role of plant functional traits and phylogenetic relationships in predicting plant community species coexistence and diversity maintenance, we measured 73 species and six functional traits along a slope aspect gradient on the Qinghai-Tibetan plateau. We calculated the net relatedness index (NRI), the nearest taxon index (NTI), phylogenetic diversity (PD), functional diversity, and analysed phylogenetic signals. The results show that the species richness, plant composition, and PD changed substantially from northern to southern aspects, and the phylogenetic structure of the community changed from clustering to over-dispersion. Weak phylogenetic signals in plant height, leaf nitrogen content, and leaf potassium content were recorded. We conclude that the influencing factor(s) of species coexistence on northern and north-western aspects is limiting similarity (interspecific competition), whereas on southern and south-western aspects, habitat filtering (environmental effect) is predominant. On western aspects, the influencing factors are driven by three processes: limiting similarity, habitat filtration, and random processes. Results suggest that niche processes (including habitat filtration and limiting similarity) are the main mechanisms for species coexistence and diversity maintenance on aspects of the alpine meadow in the northeast of the Qinghai-Tibetan plateau, while random processes appear at the transitional zone (the western aspect in our study) between aspects.

为了研究植物功能性状和系统发育关系在预测植物群落物种共存和多样性维持中的作用，我们在青藏高原沿坡向梯度测量了 73 个物种和 6 个功能性状。我们计算了净相关性指数 (NRI)、最近分类群指数 (NTI)、系统发育多样性 (PD)、功能多样性，并分析了系统发育信号。结果表明，从北到南，群落的物种丰富度、植物组成和PD发生了较大的变化，群落系统发育结构由聚集向过度分散转变。记录了植物高度、叶氮含量和叶钾含量的弱系统发育信号。我们得出结论，北部和西北部物种共存的影响因素是限制相似性（种间竞争），而在南部和西南部，栖息地过滤（环境效应）占主导地位。在西方方面，影响因素由三个过程驱动：限制相似性、栖息地过滤和随机过程。结果表明，生态位过程（包括生境过滤和限制相似性）是青藏高原东北部高寒草甸物种共存和多样性维持的主要机制，而过渡带（西部我们研究中的方面）在方面之间。栖息地过滤（环境影响）占主导地位。在西方方面，影响因素由三个过程驱动：限制相似性、栖息地过滤和随机过程。结果表明，生态位过程（包括生境过滤和限制相似性）是青藏高原东北部高寒草甸物种共存和多样性维持的主要机制，而过渡带（西部我们研究中的方面）在方面之间。栖息地过滤（环境影响）占主导地位。在西方方面，影响因素由三个过程驱动：限制相似性、栖息地过滤和随机过程。结果表明，生态位过程（包括生境过滤和限制相似性）是青藏高原东北部高寒草甸物种共存和多样性维持的主要机制，而过渡带（西部我们研究中的方面）在方面之间。