近15年来共和盆地土地沙质荒漠化动态变化及原因分析

在野外调查和前人研究的基础上，建立了青海共和盆地沙漠化土地遥感分类分级的指标系统，并在地理信息系统支持下，对该区1990年和2005年的TM影像进行了目视解译，分析了该区近15 a来土地沙漠化时空变化规律和原因。结果表明:①研究区沙质荒漠化依然严重，共有各类沙化土地7 419.62 km²，占研究区总面积的62.84%，以轻度和中度为主；②较为严重的沙质荒漠化主要发生在中部和南部气温较高的地区；③沙质荒漠化总体趋势为整体面积缩小，恶化和逆转并存，程度略有加强；④气候变化导致的蒸发量增加对研究区土地沙质荒漠化有一定的促进作用，而20世纪90年代后期以来耕地面积和农牧业人口急剧减少是研究区土地沙质荒漠化面积略有减少的主要原因；⑤研究区沙质荒漠化趋势虽然得到一定程度的控制，但沙质荒漠化形势仍然相当严峻，控制人口密度，调整土地利用结构，控制超载过牧，加强土地管理和生态环境建设势在必行。

Dynamic Changes of Sandy Desertification and Its Causes in the Gonghe Basin During the Last 15 Years

Based on the field investigation and summarizing experiences from other studies, this article taking the Gonghe basin as the study area, established classification and interpretation criterions of sandy desertified land, detected spatial-temporal evolution of desertification from 1990 to 2005 in the study area through visual interpretation of Landsat TM images, with the support of geographic information system (GIS), and analyzed its causes. The results showed that: ① The sandy desertified land of the study area was 7 419.62 km² in 2005, occupying 62.84% of the whole region, and the most is in light and middle grades. ② Although desertification takes place in the whole region, it is the most severe in the south and middle district with high annual mean temperature. ③ The dynamics of land sandy desertification are decreasing on the whole, reversing and developing in local, and the desertification degree is becoming intensifying. ④ Although increasing of evaporation resulted from climate change promotes sandy desertification, the abrupt reduction of farmland and agricultural population since 1996 are the important anthropogenic factors of decreasing land sandy desertification. ⑤ Sandy desertification in the study area was in a dynamic change progress with slight change, but not basically controlled. Therefore, it is imperative to control agricultural population and livestock increase speed, to adjust the land use structure and to reform the land use system, to enhance the management of land resource, and to strengthen the eco-environment construction.