Effects of banning grazing and delaying grazing on species diversity and biomass of alpine meadow in northern Tibet.

Banning grazing and delaying grazing are reasonable grassland management measures for restoring the degraded alpine grassland.In this study,5 treatment plots including banning grazing for 3 years(JM3),for 5 years(JM5),for 7 years(JM7),delaying grazing for 5 years(XM5) and continuous grazing(FM) plots were devised in Nagqu to investigate the effects of banning grazing and delaying grazing on alpine meadow in Northern Tibet.Based on the quadrant method,community species diversity,height,coverage,aboveground biomass and underground biomass within areas of 0.5 m×0.5 m quadrant of alpine meadow in Northern Tibet were recorded.The result showed that the richness index and diversity index in banning grazing plots were significantly higher than those in XM5 and FM.JM3 and JM5 were significantly higher than JM7.But the evenness index in JM3 was significantly lower than that in JM5 and JM7.The important values of the grasses and sedges in JM3 were higher than other plots.The aboveground biomass of JM5 was 84.2 g/m2 and higher than other plots.The ratio of underground biomass and aboveground biomass of JM5 was the least in all plots.Thus,binning grazing for 5 years could maintain higher species diversity and significantly increase the productivity of alpine meadow,but binning grazing for over 5 years would go against maintaining higher species diversity and meadow available biomass.