Spatial-temporal Evolution of the Oasis in Shiyanghe River Basin in 1975-2010

Basing on the technology of RS(Remote sensing) and GIS(Geographic information system),taking the oasis in the Shiyanghe River Basin as the research object,we monitored its spatial-temporal dynamic changes from 1975 to 2010,and discussed the reasons for the change of the oasis with climate,surface runoff and human activities data.Results show that the oasis scale in the Shiyanghe River Basin presented fluctuation trend in recent 35 years.The areas of oasis in 1975,1990,2000 and 2010 were 7 563.06,7 730.62,7 131.56 km2 and 7 459.43 km2,respectively.Through analyzing the transformation between oasis and desert,we found the transformation experienced the process of oasification-desertification-oasification and the area of oasis reduced by 103.63 km2.The area of cultivated land,residential land and water area expanded obviously,but the forest land and grassland reduced.The variation of oasis area was affected by natural factors and human activities together,but the population increase,economic development and the change of surface runoff had significant influence on the evolution of oasis.