Soil and vegetation response to land use/cover change in artificial oasis ecosystem: a case study of Beitun oasis.

Oasis is the core of ecosystem structure in arid area,especially the artificial oasis developed by irrigation has become an important area for people to survival in arid area.Research has shown that ecosystem degradation,land desertification,vegetation decline,and species diversity loss of oasis are all connected with unreasonable resources development and utilization,and human factors are the direct cause of ecosystem degradation in arid area.Therefore,deep analysis of land use/cover change of oasis caused by human activities,especially ecological effects caused by the change of soil and vegetation,has great significance for rational use of land resource and land quality maintenance of artificial oasis in arid area.This paper took typical artificial oasis,Beitun oasis,as the study area,based on remote sensing and geographic information system technology,deeply analyzed land use/cover changes of Beitun oasis in recent 16 years by processing remote sensing images in 1989 and 2005.Based on field investigation,laboratory analysis and "time-space substitution method" and other methods,the paper analyzed the response mechanism of soil and vegetation to land use/cover change in artificial oasis ecosystem.The results shown as follows:(1) cultivated land area and saline or alkaline land area are increasing,cultivated land and grassland are continuously converted to saline or alkaline land,and cultivated land converted to grassland,which means that land reclamation and land abandonment become two main process of land use/cover change in the study area;(2) land use changes have great effects to soil nutrients and pH value,soil nutrient content of cultivated land is higher than that of the abandoned land and waste land,and the pH value of cultivated land is lower than that of abandoned land and waste land;(3) soil salt content of cultivated land is lower than that of the abandoned land and waste land,soil salinization is one of the most important threaten in Beitun oasis,and soil salinization types of Beitun oasis are chlorinate-sulfate and sulfate;(4)with the change of land use type,community composition changed a lot,and the dominant species changed significantly.Because the original vegetation had been damaged and soil structure had deteriorated,generally,it is hard to restore to uncultivated state when cultivated land is abandoned.While,in our research we find that the abandoned land of Beitun oasis can restore to the state similar to uncultivated without the disturbance of human beings.