民勤绿洲土地荒漠化动态监测

解译1998年和2003年的卫星影像数据表明:5年间,民勤绿洲荒漠化土地面积从337126.71hm2增加到341221.21hm2,增加了4094.50hm2。其中风蚀荒漠化土地增加了5857.24hm2,盐渍荒漠化土地减少了1762.74hm2。风蚀荒漠化土地中沙化耕地的面积增加了11035.49hm2,而沙化林地、沙化草地分别减少了2749.12hm2、2556.82hm2。其荒漠化程度正在由中轻度向重度和极重度逐步加剧发展。民勤绿洲荒漠化发展变化集中表现为在原有耕地和新开荒的弃耕以及有林地、沙化林地、沙化草地、盐渍化土地被无序的开荒而转变为沙化耕地。造成民勤绿洲荒漠化目前形式的原因主要有两点:一是石羊河上游来水量持续减少和地下水持续超采造成的绿洲水资源环境的逐步恶化,地下水持续下降,造成其天然植被退化消亡;二是随着人口压力的增加,人为过度开荒和弃耕造成的地表植被无法恢复,引起的土地荒漠化。

Dynamic Monitoring of Land Desertification in Minqin Oasis

The monitor result by satellite image data shows that the desertification area of Minqin Oasis increased by 4,094.50hm2from 337,126hm2 to 341,221hm2 representing 0.90% of studied area,from 1998 to 2003,for which the wind erosion land increased by 5,857.24hm2 and salinized land decreased by 1,762.74hm2.In the wind erosion desertified area,the sandified cropland increased by 11,035.49 hm2 while the sandified forestland and grassland decreased by 2,749.12 and 2.556.82,indicating intensifying desertification from light and moderate levels to severe and extreme levels.Minqin Oasis desertification occurred mainly in the cropland,newly reclaimed cropland and forest/grassland land.Two causes are prominent for the desertification in Minqin Oasis: on the one hand,continuous decrease of water flow from the Shiyang River and over exploration of groundwater led to deterioration of oasis water resources and environmental quality decline;on the other hand,the population pressure with excessive cropland reclamation and farmland abandonment made the revegetation degenerated.