Effects of different land-use types on soil carbon and nitrogen contents in the northern region of Qinghai Lake.

Four different land-use types,fenced and ungrazed(FU),fenced and seasonal grazed(FG),perennial pasture(PP) and crop land(CL) in the Sanjiao Cheng Sheep Breeding Farm located in the northeastern part of Qinghai Lake,were used to investigate underground biomass,soil particle size,soil organic carbon and total nitrogen contents of the 0-10,10-20,20-30 cm soil layers.Soil organic carbon and total nitrogen storage were different under different land-use types.The storage of soil organic carbon per unit area varied in the order of PPFUFGCL.The soil organic carbon in the perennial pasture was significantly(P0.05) higher than that in cropland,but no significant difference was found between the other two types(P0.05).The changes of total nitrogen were similar to those of organic carbon.In the 0-30 cm soil depth,the underground biomass varied in the order FUFGPPCL,with values of 2 416.67,1 688.25,1 224.50,and 1 290.75 g/m2 respectively.In the 0-10 cm soil layer the soil clay content of PP was significantly(P0.05) higher than in the other three types.The soil clay content of the 10-20 cm soil layer was in the order PPCLFUFG.No significant differences in soil clay contents were found in the 20-30 cm soil layer under different land-use types.The soil silt contents of the four different land-use types were not significantly different in the same soil layer.