Study On The Effect Of The Plant Community And Soil Nutrient Of Alpine Grassland On Yak Grazing Intensity

White yak pasture of alpine grassland in Tianzhu was used as material to study plant community characteristics and soil nutrient in three sample of different seasonal pasture, which is grazing intensity gradually aggravating(Nannigou, Daiqian and Wushaoling). Above-ground biomass, species diversity and soil nutrient were analyzed, and provide preliminary basis for health of grassland. The results showed that:1. Above-ground biomassWith aggravation of grazing intensity, Above-ground biomass was gradually decreased in summer pasture of Nannigou, Daiqian and Wushaoling. There were 3783.3㎏/hm~2, 2317.6㎏/hm~2, 1588.2㎏/hm~2, the difference reached utmost obvious lever (P<0.01), In winter pasture of Nannigou and Daiqian, the difference not reached obvious lever (P>0.05). There was extremely negative correlativity between above-ground biomass and grazing intensity, y= -1097.6x + 4758.1 (R~2 =0.964), which showed grazing intensity was heavy.2. Underground phytomassOvergrazing directly led to decreased of above-ground biomass and underground phytomass. It showed the change of underground phytomass mainly different in 0～10cm soil. There was extremely positive correlativity between above-ground biomass and underground phytomass. In summer pasture: y = 18.928x -3153.8 (R~2 = 0.996), winter pasture: y = 17.402x -3684.9 (R~2 =0.981).3. Species diversityWith aggravation of grazing intensity, the indices of biodiversity was lowered in pasture summer, Nannigou >Daiqian> Wushaoling, the difference reached obvious lever (P<0.05); Daiqian higher more Nannigou in winter pasture. The indices of richness and evenness were similar to indices of biodiversity. There was extremely negative correlativity between the indices of biodiversity and grazing intensity, (y = -0.295x +2.306,R~2 = 0.988);but the difference not reached obvious lever (P>0.05) in winter pasture. There was extremely positive correlativity between the indices of biodiversity and indices of richness. In summer pasture: y =0.6733x +0.5407 (R~2 =0.946), in winter pasture, y =0.4161x +0.9001 (R2 =0.905).4. Dominance plant speciesIn summer pasture, some species that had strong endure trampling and reproduced ability...