Spatio-temporal variability of soil organic C and nutrients in the oasis of the northern slope of the Tianshan Mountains
天山北坡绿洲土壤有机碳和养分时空变异特征

The relationship between soil organic C and land use change is one of the important fields in the study on global change.In the past 20 years,with the rapid economic development and population increase in China,large-scale land reclamation resulted in oasis expansion and natural desert vegetation decrease,especially in Xinjiang.Taking the oasis of Sangong river watershed as a study case,we have evaluated the spatio-temporal variability of soil organic C and nutrients.The results show that:(1) The soil OC contents was roughly equivalent in 1982 and 2003,but lower in 1999 than in 1982 and 2003.The AN,AP and AK contents tended to increase with cultivation time.(2) The nugget-to-sill ratio of soil OC changed from 53.3% to 70.3%,suggesting that the spatial correlation belongs to moderate class.However,the nugget-to-sill of AN,AP and AK is higher,suggesting that the spatial correlation belongs to low class.Influenced by soil types and planting crops of the study area,the anisotropies of soil OC were obvious,while those of AN,AP and AK were weaker.(3) The results estimated by Kriging and IDW showed that soil OC declined from 1982 to 1999,and then increased from 1999 to 2003.AN,AP and AK increased significantly from 1982 to 1999,while decreased from 1999 to 2003 due to balanced fertilization application.In conclusion,soil OC had been increasing with the cultivation time in the Sangong river watershed,indicating that oasis soil presented C sink.This also indicates that the human activities in the oasis were reasonable and the environment of the oasis was improved.