区域尺度绿洲稳定性评价

论文在区域尺度上,探讨了绿洲稳定性的内涵,并以新疆三工河流域绿洲为例,从绿洲所处的地理位置、绿洲与外围荒漠和山地系统之间的相互作用等方面评价了绿洲的区域稳定性。结果表明:①冲洪积扇型绿洲稳定性最高,其次是位于地下水溢出带下方的冲积平原型绿洲,稳定性最差的是湖滨三角洲或散流干三角洲上发育的绿洲;②绿洲的冷岛效应和植被指数可较好地表征绿洲与外围荒漠和山地系统之间的相互作用和评价绿洲的区域稳定性的时间变化。绿洲规模的扩大及绿洲水分和植被的增加将加强绿洲的冷岛效应,提高绿洲的稳定性;归一化差异植被指数增加,表明绿洲内植被覆盖密度增大和植物生物量提高,绿洲的稳定性增强。

Evaluation of the stability of the oasis at the regional scale

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.