Evaluation of the stability of the oasis at the regional scale
区域尺度绿洲稳定性评价

This paper discusses the meaning of the oasis stability at the regional scale,and taking oasis of Sangong River Watershed as an example,analyzes the oasis stability from its geographic location and reciprocity between the oasis and its surrounding deserts and mountain systems.The results show that: (1)As long as the oasis moisture keeps stable and its efficiency gradually improves (at least no decline),which will result in continuous increase in primary productivity,and nonobviously decline (at least keeping relatively stable)of natural primary productivity,we can consider that oasis is stable and sustainable at the regional scale. (2)The main geomorphologic locations at which the oases can develop include alluvial-diluvial-fan,alluvial-plain and lake-shore delta or dry delta.From the capability of the oasis water capturing,the oasis in alluvial-diluvial-fan type is most powerful and its stability is the highest, next is the oasis in alluvial-plain type which stands below the overflow belt of groundwater,and the lowest is the oasis in the lake-shore delta type or dry delta type. (3)The cold-island effect and vegetation index of the oasis may be used to represent the in-teraction between the oasis and its surrounding deserts and mountain systems as well as the time change in the stability of the oasis.Enlargement of the oasis and increase of the moisture and vegetation in the oasis will certainly enhance the cold-island effect of the oasis,which is advantageous to increase the stability of the oasis.Conversely,the stability of the oasis will be redu-ced.When NDVI of the oasis increases,which indicates the increase of plant cover density and the primary productivity in the oasis,the stability of the oasis will enhance.Conversely,the stability of the oasis will be reduced.