抚仙湖流域植被覆盖度时空分异及其与坡度的关系

摘要

Vegetation coverage change is not only an important indicator to reflect the growth of terrestrial vegetation, but also it is the essential fundamental data for ecological system study.It partly indicates the dynamic changes of the regional ecological environment and plays an important role in global change research.Using Landsat image as main data, combined with geographic information data, administrative zone boundary, thematic information provided by the relevant departments, and then using normalized difference vegetation index (NDVI) to calculate and graded the vegetation cover of study area.Finally, the spatio-temporal change of vegetation cover is obtained by transfer matrix in Fuxian Lake watershed for nearly 40 years.The results show that: (1) The area change of grade I is a little, while the gradeⅡ~Ⅳ is not stable and have several times valley and peak value, but the grade Ⅴ is linear increasing in nearly 40 years in Fuxian Lake watershed;(2) The slope, derived by DEM(2 meters interval), was classified as follows: 0°~8°,8°~15°,15~25°,25°~35°,35°~90°.Based on accounting the each year and each grade vegetation coverage ratio, it can reveal that the low vegetation coverage mainly distribute in relatively flat ground (0°~15°), while high vegetation coverage is almostly in steep ground;(3) The largest area is the gradeⅠin each year, and the area of the gradeⅡand Ⅲ are more than Ⅳ and Ⅴ in 1974, 1977, 1989 and 1996.While the area of the change subtly in each grade exclude grade Ⅰ from 2000, and the area of vegetation coverage at levels Ⅳ and Ⅴ is greater than Ⅱ and Ⅲ in 2006, 2009, 2012 and 2014.%采用像元二分模型,以1974-2014年间的10期Landsat 5/8影像和DEM数据,对抚仙湖流域植被覆盖动态变化进行监测,并结合基础地理信息数据、行政区划界资料、行业部门专题资料等,分析流域植被覆盖时空分异及其与坡度的关系.结果表明:(1)1974-2014年,抚仙湖流域裸地(Ⅰ级)面积波动极小,低植被覆盖(Ⅱ级)、中低植被覆盖(Ⅲ级)、中高植被覆盖(Ⅳ级)面积变化波动大,变化趋势线数次出现谷值和峰值,高植被覆盖(Ⅴ级)面积则呈增加趋势.(2)坡度较小、地势较平缓的区域(0°~15°)以裸地和低植被覆盖为主;中低植被覆盖度、中高植被覆盖和高植被覆盖度主要分布在地势比较陡峭的区域(>15°).(3)抚仙湖流域各年份植被覆盖度Ⅰ级面积最大,1974,1977,1989,1996年Ⅱ,Ⅲ级面积较大,而Ⅳ,Ⅴ级面积较小;2000年后的Ⅱ,Ⅲ,Ⅳ级面积变化较小;2006,2009,2012,2014年Ⅳ,Ⅴ级的面积较大,Ⅱ,Ⅲ级的面积较小.