毛乌素沙地生物土壤结皮与沙化土地的关系研究

生物土壤结皮在荒漠地区广泛分布,是固沙和促进沙地生态恢复的重要生物因子。利用1989,2002和2006年的Landsat遥感影像,分别通过生物土壤结皮指数和NDVI阈值法,提取了毛乌素沙地生物土壤结皮和沙化土地的空间分布,并分析了二者之间联系。结果表明:(1)研究区1989,2002和2006年结皮面积所占比例分别为54.77%,55.72%和64.29%,表现为持续增加趋势,结皮斑块间连接度在增强,结皮的稳定性进一步巩固。(2)1989—2006年区内沙化土地的程度逐渐减弱,沙化程度综合指数由1989年的3.24下降到2006年的2.65。(3)1989—2006年,中度和重度沙化土地结皮分布范围最为广泛,均在70%以上;极重度沙化土地内的结皮面积表现为持续下降,1989,2002和2006年分别为19.40%,5.76%和2.80%。(4)以1989年沙化土地的格局为基础,1989,2002和2006年极重度沙化土地内生物结皮的数量比例分别为19.40%,33.18%和45.21%,处于上升趋势。

Relationship of Biological Soil Crusts and Land Desertification in Mu Us Desert Lands

Biological soil crusts are widely distributed in the desert as an important biological factor to stabilize the sand dunes and promote restoration of sandy ecosystem.Landsat remote sensing images of Mu Us Desert in 1989,2002and 2006were used to extract spatial distribution of biological soil crusts and land desertification based on the biological soil crust index and NDVI threshold.Furthermore,the relationship between biological soil crusts and land desertification was discussed.The results show that the areas covered by biological crusts accounted for 54.77%,55.72%and 64.29% of the total area in the three study years,respectively,indicating biological soil crusts in the study area increased continuously.In addition,the connectivity among crust patches was enhanced,and the crust stability was further strengthened.In contrast,the degree of land desertification was gradually weakened during the study period,as the composite index of land desertification dropped to 2.65in 2006from 3.24in 1989.Biological soil crusts distributed most widely(over 70%)in the lands experienced moderate and severe desertification.However,the area of biological soil crusts continued to decline in extremely severely desertified lands,accounting for 19.40%,5.76% and 2.80% of the total area of the extremely severely desertified land in the three study years,respectively.The number of biological soil crusts was increasing in extremely severe desertification land,indicated by the ratio of 19.40%,33.18%and 45.21%in the three study years,respectively.