Impact of different grazing intensity on soil physical properties and plant biomass in Qinghai-Tibet Plateau alpine meadow ecosystem

In Qinghai-Tibet Plateau grassland, human disturbances are becoming more and more strongly, especially with the increase of grazing intensity, the grassland ecosystems are in face of seriously degradation. In order to analysis the impacts of yak grazing on Qinghai-Tibet Plateau alpine meadow ecosystem and to determine the appropriate yak grazing intensity, four different grazing intensities and one control treatment were set up in Hongyuan County located in eastern part of Qinghai-Tibet Plateau. The soil water content and soil bulk density, plant biomass and coverage, the weight increase rate of yak were determined after one growing season. The results showed that, with the increasing of yak grazing intensity, the soil water content decreased and the soil bulk density did not change. The above-ground and below-ground biomass firstly increased then decreased with the increasing of yak grazing intensity, and the Poaceae and Cyperaceae biomass showed the same pattern as the total biomass, but the fabaceae and others grass biomass showed no significant difference. The weight increase rate of yak slowed with the increasing of yak grazing intensity. The combined results indicated that the appropriate yak grazing intensity was between 1.016~1.284 head·ha-1 in this region. The study can provide theoretical basis for the restoration of the degraded alpine grassland and the ecological livestock reducing engineering programs in Qinghai-Tibet Plateau.