念青唐古拉山东南坡植被群落数量生态分析及群落多样性

Quantitative Ecology and Species Diversity of the Vegetation in Southeast Slope of the Nyenchentanglha Mountain

研究沿海拔梯度对植被群落的影响,有助于人们进一步理解未来气候变化背景下,高寒生态系统结构和功能的响应模式。选择念青唐古拉山东南坡的典型生境,包括从海拔4 775 m到5 305 m全部范围内的植物群落。沿着海拔梯度每隔约30m设置1个样带,并在各个样带上随机设置样方,调查样方内物种数、物种高度、物种盖度、物种频度。采用群落多样性指数、应用双向指示种分析法(TWINSPAN)和除趋势对应分析(DCA)等方法,对西藏念青唐古拉山东南坡高山草甸植物群落进行了分析。TWINSPAN将所有植物群落划分为5种类型,分别为:香柏(Sabina pingii var.wilsonii)+高山嵩草(Kobresia pygmaea)灌丛草甸群落;高山嵩草+圆穗蓼(Polygonum macrophyllum)草甸群落;高山嵩草+矮生嵩草(Kobresia humilis)草甸群落;高山嵩草草甸群落;流石滩冰缘植被群落。这些群落分别位于不同的海拔高度。分类结果很好地反映了植物群落类型分布与地形、海拔的关系,并在DCA二维排序图上得到了较好的验证。念青唐古拉山东南坡草地植物群落多样性在高海拔、低海拔地区较低,中间海拔高度地区较高。植物群落多样性指数呈现出草本层>灌丛层>流石滩冰缘的特征。多样性指数与海拔高度之间的趋势模拟均呈负二次函数关系,单峰式函数关系能较好地表达不同海拔梯度植物群落多样性和均匀度与海拔之间的分布格局。

Study on the response of vegetation to altitude gradient is helpful for us to understand how alpine ecosystems will response to future climate change. We chose to study the vegetation along the south slope of the Nyenchentanglha Mountain, with the altitude gradient from 4 775 m to 5 305 m. Along the altitude gradient, samples were set every 30 meters and species, with plant height, coverage and species frequency investigated in each samples. Double gaps indicator species analysis (TWINSPAN), and Detrended correspondence analysis (DCA) were applied to analysis the community types and species diversity along the altitude gradient of the southeast slope of the Nyenchentanglha Mountain. TWINSPAN divided the plant communication into 5 types:Sabina pingii var. wilsonii+Kobresia pygmaea meadow community, Kobresia pygmaea+Polygonum macrophyllum meadow community, Kobresia pygmaea + Kobresia humilis meadow community, Kobresia pygmaea community and stone beach periglacial vegetation communities. The result of vegetation’s classification by TWINSPAN reflected the relation between community’s location, topography and altitude, which were verified in pattern map of DCA very well. The species was lower in high and low altitude area compared with the middle of slope of mountain, which formed a hump cure. The species diversity index from high to low of community was herb layer >shrub layer > periglacial stone-community. The model of diversity index and altitude was negatively quadratic function.