Study on Contents of Soil Nutrients in Different Grazing Intensities on Subei Alpine Steppes

Na,Fe,Mn,Cu and Zn contents in soil samples in 0-10,10-20 and 20-30 cm layers in Subei alpine steppe were studied under four kinds of grazing intensities,i.e.,no grazing,light grazing,middle grazing and high grazing.The results indicated that: 1) grazing intensity had consistent effect on soil physical,chemical and biological fertilities,which were associated with each other and determined the evolution direction of soil fertility;2) With the increase of steppe grazing intensity,soil bulk density at both 0-10 cm and 10-20 cm layers increased,while soil porosity and moisture content decreased significantly,steppe grazing intensity influenced soil moisture content more strongly than soil porosity;3) Soil organic matter and total N contents of light grazing steppes were higher than those of middle grazing and high grazing steppes,soil available N,P and K contents increased with the increase of steppe standard of grazing intensity;4) The nutrient content order was NaFeMnCuZn,they shared the same changing order,i.e.,light grazingno grazingmiddle grazinghigh grazing;5) With the increase of steppe grazing intensity,the decreasing extent of soil nutrients was 10-20cm0-10cm20-30cm.