藏北高寒草原群落维持性能对封育年限的响应

针对近年来退化高寒草原的恢复和合理利用的问题,对自然放牧、封育3年和7年的藏北申扎高寒草原设置样地,采用群落调查、收割法收集地上生物量,根钻法收集地下生物量等,比较分析不同封育年限下草地群落各生态指标。结果表明,高寒草原围栏封育后,随自然放牧到3年禁牧再到7年禁牧,植被高度持续增加,地上地下生物量、总盖度、物种多样性维持性能增加再降低,Pielou 均匀度指数在自然放牧草地最大。随封育年限延长,禾草类及莎草类植物功能群生物量及重要值显著增加,杂草类功能群生物量及重要值显著降低,说明封育措施有利于群落的正向演替。但通过对群落总盖度、地上生物量及群落种类组成与封育年限间关系进行统计分析表明,藏北高寒草原封育达3到5年后以1.23只羊单位/hm²的放牧强度放牧为佳。

Response of the maintain performance in alpine grassland to enclosure on the Northern Tibetan Plateau

In order to improve the management of degraded grasslands, the characteristics of the plant communities (structure and biomass) were investigated under three grazing treatments; unrestricted grazing, 3-year enclosure and 7-year enclosure in Shenzha, Northern Tibet. The result showed that, after enclosure, vegetation height gradually increased as the duration of enclosure increased. Above-ground and below-ground biomass, vegetation coverage and community species diversity were highest in the 3-year enclosure treatment, and Pielou evenness index was the largest in the natural-grazing. Biomass and the important value of grass and sedge functional groups increased with extended enclosure time, while values for the forbs functional groups decreased significantly, indicating that enclosure promoted plant community succession. Analyzing the relationship among plant coverage, above-ground biomass, community composition and enclosure time suggested that three-five years of enclosure at a stocking rate of 1.23 sheep/ha is appropriate for the degraded alpine grasslands in this region.