基于光谱混合分解的民勤生态治理效果评价

作为退化绿洲典型,甘肃民勤生态治理效果的评价对全球干旱区土地退化防治具有重要借鉴作用。使用Landsat系列遥感数据,基于光谱混合分解模型,采用土地覆被/利用分类后比较和端元丰度值差值的方法,对民勤生态工程第二阶段初期(2010—2015年)的治理效果进行了定性和定量研究。结果表明:民勤县土地退化面积为39 712.14hm^2,恢复面积为101 503.44hm^2,恢复面积大于退化面积,呈现出恢复的态势。沙地面积减少,沙地的沙化程度降低;盐碱地面积虽有增加,但盐碱地的盐渍化程度有所下降;林草地相较耕地、夏作耕地相较春作耕地成为当地优势植被地类;水域面积虽有减少,但水域的水含量有所增加。民勤经过近20年的生态修复治理,已经进入良性修复阶段。

Ecological Restoration Assessment in Minqin Based on Spectral Mixture Analysis

At the beginning of the 21st century, China launched a number of key ecological restoration projects (KERPs) unprecedentedly. Minqin is a typical degrading oasis, and its success and lessons of KERPs are helpful to global dryland land degradation control. This article obtained multi-seasonal Landsat data in 2010 and 2015, and conducted a spectral mixture analysis on each-season remote sensing data. Based on the spectral mixture analysis results, we implemented land cover/use classification in 2010 and 2015. The combination of post-classification comparison and endmember abundance difference in invariant land was then adopted to analyze ecological restoration status in Minqin during the initial period of the second ecological restoration stage (2010-2015). The results show that the land degradation area is 39 712.14 hm², and the area of restoration is 101 503.44 hm². The area of land restoration is larger than that of degradation, which indicates Minqin reached the zero net land degradation goal from 2010 to 2015, and was in a relative recovery situation. Accordingly, sand land area and sandification degree in invariant sand land decreased. Although the area of salinized land has increased, the salinization degree of invariant region decreased. Forest and grass land compared to cropland, and summer crop compared to spring crop are preponderant vegetation cover types. Water area is somewhat reduced, but the water content in invariant region increased. This research shows that Minqin has already enter into virtuous restoration phase after nearly 20-year ecological restoration governance.