放牧对西藏高寒嵩草草甸地上生物量空间分布的影响

以西藏自治区工布江达县的高寒嵩草（Kobresia）草甸为研究对象，利用地上生物量测定法对草地群落进行实地调查，并结合γ分布模型，从空间异质性角度来探索放牧对西藏高寒草甸地上生物量及其空间分布格局的影响，以期为高寒牧区退化草地的恢复及生产力的提高提供理论指导。结果表明：未放牧区（N）、适度放牧区（M）和重度放牧区（H）植物种地上生物量的空间分布与γ模型均具有很好的吻合性；样方内的平均生物量随着放牧强度的增大而减少，且适度放牧、重度放牧与未放牧区生物量之间均差异极显著（P<0.01）；群落的空间异质性表现为N>H>M，且草地植物种的生物量与其空间异质性负相关。因此在草地的管理与利用中，应有效控制植物群落的空间异质性来提高草地生产力，实现草畜平衡。

Effects of Grazing Intensity on the Spatial Distribution of Aboveground Biomass of Alpine Kobresia Meadow in Tibetan

The grassland community of alpine Kobresia meadow in the Gongbujiangda county of Tibet Autonomous District was investigated with the method of "aboveground biomass". From the view of spatial heterogeneity, the effects of grazing intensity on the aboveground biomass and spatial distribution alpine Kobresia meadow were analyzed with gamma distribution model to provide a theoretical basis for recovering and increasing the productivity of degraded grasslands in alpine pastoral region. Results indicated that the spatial distribution of aboveground biomass under non-grazing, medium grazing and heavy grazing fitted the gamma distribution model very well. The average biomass of tested plots decreased along with the increase of grazing intensity. The aboveground biomass of medium grazing plot significantly differed from non-grazing plot (P<0.01), whereas no significantly differed from heavy grazing plot. The spatial heterogeneity of community in the non-grazing plot was higher than that in the grazing plots, and there was a negative correlation between the spatial heterogeneity and aboveground biomass. Therefore, the spatial heterogeneity of plant community should be effectively controlled to improve grassland productivity and keep forage-animal balance in the management and utilization of grassland.