The effects of natural grazing intensity on plant community and soil nutrients in alpine meadow.

Grazing is significant factor impacting the ecological processes of grassland ecosystems.This study was conducted to investigate the effects of natural grazing intensity on plant community and soil nutrients in alpine meadow.Using comparative experiments,research was initiated under different grazing intensities to provide a theoretical basis for defining the reasonable stocking rate of alpine meadow.Our results showed that: Both above-ground biomass and species richness of plant community were the highest in fencing than that in light and moderate grazing,and the least in heavy grazing treatment;Shannon-Wiener diversity index was not significantly different among fencing,light and moderate grazing;the above-ground biomass and cover of palatable herbages(grasses and sedges) was reduced with grazing intensity increasing,while the forbs in heavy grazing treatment had higher above-ground biomass than that in fencing,light and moderate grazing;over three growing stages,soil moisture decreased with grazing intensity enhancing in May,but increased in July and September;the soil bulk density in moderate grazing was significantly lower than that in other three grazing treatment(P0.05);the pH value was the highest(pH 7.31) in heavy grazing and was not significantly different among fencing,light and moderate grazing treatment;soil organic carbon was reduced with increasing grazing intensity in plant growing stages;soil total nitrogen was not significant different among light,moderate and heavy grazing treatment.However,soil ammonium-N and nitrate-N increased along the increasing of grazing intensities over the whole plant growing stages;soil available phosphorus shared the same trend as total phosphorus that they had the highest value under moderate grazing.Our result suggested that the moderate grazing was effective way to protect biodiversity and improve grassland productivity,while fencing is beneficial for recovering of the degraded alpine meadow.