拉萨河谷山地灌丛草地物种多样性随海拔升高的变化特征

Variation in the biodiversity of montane shrub grassland communities along an altitudinal gradient in a Lhasa River basin valley

以拉萨河谷达孜县新仓村沟域的山地灌丛草地为研究对象,采用样方调查法探究了随海拔升高（3992-4940m）灌丛草地群落结构、物种多样性、功能性状Rao指数的变化特征。结果表明,1）随海拔升高灌丛生物量和盖度呈先增加后降低的变化趋势,但草地盖度（71±14）%和生物量（49.18±19.17）g/m^2变化不明显（P〉0.05）;2）随海拔升高群落物种组成存在差异,但共优种高山嵩草（0.591±0.034）和青藏苔草（0.326±0.061）的优势度无显著变化（P〉0.05）;3）随海拔升高草地物种丰富度、Shannon-Wiener多样性指数呈先增加后降低的＂单峰曲线＂变化特征;4）以株高测算的草地群落功能性状Rao指数随海拔升高而降低。物种丰富度、功能性状以及地上净初级生产力沿海拔升高的变化特征存在差异,为维持高原河谷山地灌丛草地的生态安全,未来应重视三者相互关系及其生态学机制的相关研究。

A field survey was carried out to measure the variation in the biodiversity of montane shrub grassland communities along an altitudinal gradient in the Xincang village valley,Taktse County in the Lhasa River basin.Community assembly and functional trait diversity were assessed using the Raoindex.The aboveground biomass and total coverage of shrubs initially increased and then decreased with increasing altitude.Variation in aboveground biomass（49.18±19.17g/m^2）or total coverage（71%±14%）for alpine meadows among plots along the altitudinal gradient was not high.Species composition indices varied along the altitudinal gradient;Kobresia pygmaea（0.591±0.034）and Carex moorcroftii（0.326±0.061）were the two most dominant species.Species diversity of the shrub-grassland community revealed a unimodal variation pattern along the altitudinal gradient;both species richness and the Shannon-Wiener diversity index initially increased and then decreased from 3992 to 4940m.Conversely,the Raoindex for plant height decreased with increasing altitude.Being the most important factor in the ecological security of the Lhasa river basin,montane shrub grassland should be afforded more scientific attention,particularly the interactions between and the mechanisms underlying species richness,functional traits and ecological processes.