1986—2015年民勤县绿洲时空变化分析

Spatiotemporal Change of the Oasis in Minqin County during the Period from 1986 to 2015

以1986—2015年7期Landsat TM/OLI影像为数据源,提取民勤县绿洲分布情况,分析其时空变化特征及成因。结果表明:近30 a民勤县绿洲面积除2005—2010年大幅度退缩外,其余时期均呈现扩张趋势,面积由1986年的767 km2增长到2015年的1 360 km2,30 a增长了77.3%。绿洲与荒漠间的相互转化也很剧烈,1990—2000年是绿洲与荒漠间转化最剧烈的时期;扩张绿洲主要集中在有水源保障的区域,多为移民及市场驱动所导致;退缩绿洲在2005年之前主要分布于绿洲尾闾及河道两侧,多为水资源短缺及自然因素所引起,2005年之后全区域均大面积出现退缩,主要为生态治理等政策因素所导致,近30 a来民勤绿洲整体呈现出向南迁移的趋势;易变化绿洲主要分布于主体绿洲外围及荒漠中的零星绿洲。

In this paper,seven Landsat TM/OLI images during the period from 1986 to 2015 were used as the data sources to extract the distribution of the oasis in Minqin County,Gansu Province,on which the spatiotemporal characteristics and the causes resulting in the oasis change were analyzed. The results showed that the development of the oasis in Minqin County was trended growth except during the period of 2005-2010,and the area was enlarged from 767 km2 in 1986 to 1 360 km2 in 2015 and expanded by 77. 3% in recent 30 years. The oasis area was changed significantly,at the same time,the transformation between the oasis and desert was also very intense,especially during the period of 1990-2000. The expanded areas were mainly distributed in the upper reaches where it was relatively rich in water resources,which was mostly driven by immigration and economic interests,especially in Nanhu Township located in the southeastern part of the main oasis,this expansion was very obvious. Before2005,the shrunk areas of the oasis were mainly distributed in the tail of the oasis and the flood land along both riversides,which was mostly caused by abandoned land and the degradation of natural oasis. After 2005,the oasis was shrunk in large area in the whole region due to mainly the ecological governance policy factors. In the recent 30 years,the central position of the Minqin Oasis was migrated southward by a migration distance of 3. 861 3 km. The regions without change formed the main body of the oasis in Minqin County,and the areas with easy change were mainly distributed in the peripheral zone of the main oasis and scattered in the desert.