长期放牧对青藏高原高寒灌丛植被的影响

Effect of Long-term Grazing on Alpine Shrub Vegetation in Qinghai-Tibet Plateau.

通过在青藏高原对放牧第18年的植物种多样性、群落结构、地上现存生物量和草场质量的研究结果表明:随放牧率增加,植物种多样性指数的变化是一个典型的单峰曲线模式。长期重度放牧使高寒灌丛群落结构简化,地上现存生物量特别是优良牧草的现存量减少。植物群落的高度、总盖度和枯草盖度随着放牧强度的降低而增加,绿色植物的盖度在中度放牧样地最高。从轻牧到重牧,灌木和禾草的优势地位被典型杂类草替代。长期重度放牧在青藏高原草场退化过程中起重要作用,在青藏高原实施"取半留半"的放牧原则,对于防止草场退化,提高牧草利用率,维持较高的生物多样性都有益处。

A long - term grazing experiment with different grazing intensities in alpine Potentilla fruticosa shrubland was carried out at Haibei Alpine Meadow Ecosystem Research Station, the Chinese Academy of Sciences. Effects on plant species diversity, community structure, standing above - ground biomass and rangeland quality were analyzed after 18 years grazing. The results suggested that the change of the biodiversity index as stocking rate increased was a typical unimodal curve. Long - term heavy grazing simplified the alpine shrub community and decreased the standing above - ground biomass, especially palatable herbage plants. The heights, total coverage and dead material coverage of plant communities increased as the stocking rate decreased, however, the live shoot coverage of the moderately grazed plot was greater than those of other plots. From light grazing to heavy grazing, the dominant shrub and graminoid species were replaced by typical forbs and the index of rangeland quality decreased. It is concluded that long - term heavy grazing plays an important role on alpine rangeland degradation in Qinghai - Tibet Plateau. The standard grazing rule of 'take half leave half' is recommended as a conservative management tool to prevent rangeland degradation, to improve grass utilization, and to sustain higher biodiversity in Qinghai - Tibet Plateau.