Influence of Different Grazing Intensity to Soil Fertility in the Subei Alpine Steppes

Characteristics of soil fertility variation and their relationships were studied in Subei alpine steppes.According to the classification standard of grazing intensity,we investigated four kinds of steppes(no grazing,light grazing,middle grazing and high grazing) and soil samples in 0-10 cm,10-20 cm,20-30 cm layers were collected by a soil auger in steppes with different grazing intensity in each sampling area.The results were listed as follows:(1) Under the ecological conditions of the Subei alpine steppes,steppes grazing intensity had consistent effects on soil physical,chemical and biological fertilities.These soil physical,chemical and biological fertilities were associated with each other and set the direction of soil fertility evolvement in the alpine steppes.(2) With increased steppe grazing intensity soil bulk density at both 0-10 cm and 10-20 cm layers showed a increased trend,while soil porosity and moisture content decreased significantly although steppe grazing intensity influenced soil moisture content more than soil porosity.(3) Soil organic matter and total N contents of light grazing steppes was higher than middle grazing and high grazing steppes,soil available N,P and K showed a increasing trend with steppe standard of grazing intensity.(4) Soil samples in 0-10 cm,10-20 cm,20-30 cm layers,soil organic matter content as well as the soil pH,total N and P contents were increased trend with the soil depth,but soil available K showed a decreasing trend.