西藏色季拉山森林群落沿海拔梯度变化格局

Change Pattern of Forest Community along Altitude Gradient in Sejila Mountain,Tibet,China

为了揭示青藏高原森林群落系统发育结构在海拔梯度上的变化及其驱动因素,以西藏色季拉山森林群落为研究对象,采用群落系统发育α多样性Faith’s PD指数与系统发育β多样性PhyloSor指数对西藏典型森林群落的系统发育多样性进行分析,并结合净亲缘指数(net relatedness index)和最近亲缘指数(nearest taxon index),探讨色季拉山不同植被类型的森林群落系统发育结构沿海拔梯度的变化规律,进一步探究色季拉山沿海拔梯度的森林群落构建机制。从色季拉山海拔梯度的变化趋势来看,乔木群落的系统发育结构在高海拔和低海拔地区呈现聚集状态,在中海拔地区呈现离散结构。在所有空间尺度上,色季拉山系统发育的周转呈现出非随机状态,并且环境距离对系统发育的α及β多样性解释程度要显著高于空间距离。研究结果揭示,环境过滤在西藏色季拉山森林群落构建和生物多样性的维持中起到主导作用;随着海拔梯度变化,群落系统发育结构存在比较显著的差异性;不同群落间系统发育结构指数对于空间变量和环境变量的响应也是不一样的。本文同时从青藏高原独特的地理单元印证了生态群落构建过程中非随机过程的重要作用。

In order to reveal the changes of the phylogenetic structure of forest communities in the Qinghai-Tibet Plateau on the elevation gradient and its driving factors.This study took the Tibetan Sejila Mountain forest community as the research subjects,adopted the phylogenetic diversity Faith’s PD index and the phylogeneticβdiversity PhyloSor index to analyze phylogenetic diversity of typical forest communities in Tibet,and used the net relatedness index and the nearest taxon index to explore the phylogenetic structure of forest communities with different vegetation types and the variation along the elevation gradient.The results show that the phylogenetic structure(NRI and NTI)of the arbor community accumulates at low altitudes and high altitudes,and the discrete structures are presented in the mid-altitude regions.At all spatial scales,the phylogenetic turnover appears to be non-random,and the environmental distance is significantly higher than the spatial distance for the phylogeneticαandβdiversity.The results reveal that environmental filtration plays a leading role in the construction of forest communities and the maintenance of biodiversity in Sejila Mountain,Tibet.There is a significant change in the phylogenetic structure of the community along the elevation gradient.Different community phylogenetic structural indices respond differently to spatial and environmental factor variables.At the same time,it also confirms the crucial role of the non-random process in the process of ecological community construction from the unique geographical unit of the Qinghai-Tibet Plateau.