古尔班通古特沙漠1970—2000年代生物结皮覆盖变化研究

Spatial Pattern of Biological Soil Crusts and its Changes in Gurbantunggut Desert during the 1970 to the 2000

生物结皮是古尔班通古特沙漠主要的地表覆盖类型,也是维持其地表稳定的重要生物因子。论文利用20世纪70年代中期、80年代末期及21世纪初的遥感影像,通过生物结皮指数提取了古尔班通古特沙漠在相应时期内的生物结皮空间分布。在此基础上,分析了研究区近30年来生物结皮空间分布的变化特征;利用景观分析软件Fragstats计算了各个时期内结皮覆盖的景观指数熏并对其变化特征进行了分析。结果表明:由于新疆气候增湿、增暖明显,近30年来结皮发育良好。但由于油田开采、水利工程建设、牲畜放牧等人类活动的加强,结皮发育受到较为严重的干扰,区域内结皮斑块破碎化程度加大。

The biological soil crusts,especially lichen crusts,are well developed in Gurbantunggut Desert,the largest fixed and semi-fixed sandy desert in China.Together with vascular plant,biological soil crusts become an important factor relating to sandy surface fixation.The objective of this paper is to analyze the variation of the biological soil crust distribution in Gurbantonggut desert from the 1970s through to the 2000s.In this study,43 samples including lichen dominated biological crust,bare sand,litter and green vegetation were collected.The reflectance spectra of these samples were measured and a new biological soil crust index（BSCI） was used to detect and map the lichen-dominated crusts by remotely sensed data including four Landsat ETM＋ images,four Landsat TM images and five Landsat MSS images,acquired in the 1970s,the 1980s and the 2000s respectively.Based on the maps of the biological soil crust distribution in the 1970s,the 1980s and the 2000s,we calculated the landscape indexes of biological soil crust using software Fragstats and analyzed the variations of the crust distribution and their landscape features.The results showed that： （1）the biological soil crust was mainly distributed in the southeast part of this desert,but became gradually sparse toward northern and western parts of this desert.The crusts in the southeast part decreased remarkably,while in the north and central parts of the desert it developed very well during the 1970s to the 1980s. （2）There was an increasing trend for crusted areas during the 1970s to the 1980s in general,and the crusted areas displayed a decreasing trend during the 1980s to the 2000s.The climate change and increasing human activities resulted in such a trend. （3）An increasing landscape fragmentation,irregularity of patch shape and bigger isolation between patches were observed during the 1970s to the 2000s because of the significant human disturbance.