放牧强度对青藏高原东部高寒草甸植物群落特征的影响

Effect of grazing intensity on characteristics of alpine meadow communities in the eastern Qinghai-Tibetan Plateau

通过对青藏高原东部玛曲高寒嵩草草甸植物群落在3个放牧梯度下的特征比较,分析了该类草甸主要群落特征对放牧强度差异的响应。结果表明,随着放牧强度的增加,草甸群落的高度、盖度和地上生物量都呈现显著降低的趋势;草甸群落中优势种群的莎草科和禾本科物种的优势度逐渐降低,被一些杂草类物种(黄帚橐吾和火绒草)所取代。放牧强度的增加,导致了禾草类和莎草类功能群生物量比例的显著降低,及豆科类、毒草类和杂草类功能群生物量比例的显著增加。中度放牧下的草甸群落表现出了最高的物种丰富度指数、多样性指数和均匀度指数,排序为中牧草甸>重牧草甸>禁牧草甸。随着放牧干扰强度的增加,高寒草甸群落将经历一个由上层的莎禾草类为主的草甸群落→上层莎禾草类+中层杂草类共存的草甸群落→中下层杂草类为主的草甸群落的演替过程。

A comparative study on community characteristics with different grazing intensitie was conducted in alpine meadows of the eastern Qinghai-Tibetan Plateau （Maqu county, Gansu province）. With increased grazing intensity, vegetation height, total cover and above-ground biomass all showed a significant decrease. The importance of species of Cyperaceae and Gramineae families fell and their dominances were replaced by some forbs species （Ligularia virgaurea and Leontopodiurn leontopodioides）. For plant functional groups, the biomass proportions of the germinal species group and the sedge species group were significantly reduced by increased grazing intensity, but the biomass proportions of leguminous species group, forbs species group and noxious species group were significantly increased. Richness index （R）, Shannon-Wiener diversity index （H） and Evenness index （E） of alpine meadow communities reached a maximum under the middle grazing intensity in the moderately-grazed plot〉heavily-grazed plot〉non-grazed plot. Results suggest that with increased grazing, alpine meadow communities will undergo a succession from ＂dominated by tall germinal and sedge species＂ to ＂dominated by tall germinal and sedge species＋middle forbs species＂, then to ＂dominated by middle and lower forbs species＂.