西藏珠峰-卓奥友峰普士拉地区高山稀疏植被的群落特征及小地形的影响

Community structure of alpine sparse vegetation and effects of micro-topography in Pushila, Everest-Choyu region, Tibet, China

在西藏定日县珠穆朗玛峰 -卓奥友峰附近的普士拉地区的一山坡上 (海拔 5 176 - 5 390m) ,设置 13个样方 ,进行群落调查、小地形测定和土壤剖面调查 ,分析该地区高寒植被的群落特征及其与小地形的关系。 13个样方 (面积 2 5 - 2 0 0m2 不等 )中 ,共记载物种 80个 (含变种和亚种 ) ,分别隶属于 4 7个属。出现频度较高的种有高山嵩草(Kobresiapygmaea)、矮兔耳草 (Lagotishumilis)、楔叶委陵菜 (Potentillacuneata)、华马先蒿 (Pedicularisoederivar.sinensis)、高山委陵菜 (Potentillapolyschista)、密生雪灵芝 (Arenariadensissima)等 ;含物种数较多的属有 :虎耳草属 (Saxifraga)、风毛菊属 (Saussurea)、嵩草属 (Kobresia)、委陵菜属 (Potentilla)、龙胆属 (Gentiana)、葶苈属 (Dra ba)等。随着海拔降低 ,物种和属的丰富度呈现出上升的趋势。在该地区 ,植被盖度能较好地指示生境条件。等级聚类的结果也支持了这一观点。随着植被盖度的增加 ,转换物种丰富度 (TSR)和转换属丰富度 (TGR)增加 ,而物种多样性指数 (Shannon Wiener指数 )减小。利用物种矩阵以及海拔、坡度、坡向、土壤深度、植被盖度等环境变量进行CCA排序 ,结果分出 4类生境类型 ,它们较好地反映了群落特征与地形的关系。

A total of 13 plots were set along a transect from the altitude of 5176 m to 5390 m in Pushila, Everest-Choyu region, Tibet, to investigate community structure of alpine sparse vegetation and effects of micro-topography. A total of 80 higher plant species, belonging to 47 genera, were identified. The most prevalent species were Kobresia pygmaea, Lagotis humilis, Potentilla cuneata, Pedicularis oederi var. sinensis, Potentilla polyschista, and Arenaria densissima. Several genera were highly species rich, such as Saxifraga, Saussurea, Kobresia, Potentilla, Gentiana, and Draba. As altitude decreased, richness of both species and genera tended to increase. Vegetation coverage was found to be a good indicator for habitat conditions. Cluster analysis supported this finding. With increasing vegetation coverage, transformed species richness (TSR) and transformed genus richness (TGR) increased, while Shannon-Wiener index decreased. Four habitat types that reflected a good correlation between community structure and micro-topography were identified based on CCA analysis using species matrix and five variables (altitude, slope, aspect, soil depth, and vegetation coverage).