基于线性光谱混合模型(LSMM)的民勤绿洲荒漠化治理效果评价

民勤绿洲是干旱荒漠化的典型区域,生态系统脆弱,对该区域的荒漠化治理效果进行评价可以为其生态修复政策的制定和管理提供参考。采用线性光谱混合模型(LSMM),将Landsat影像中的土地覆盖信息进行有效分解,通过分解后光谱在直方图上的特征值,确定合适的阈值,对荒漠化土地进行分类,分析荒漠化土地类型的时空变化特征,对民勤绿洲1992-2017年荒漠化治理效果进行评价。结果表明:(1)1992-2005年民勤绿洲荒漠化加剧面积大于改善面积,两者相差175.47 km^2,荒漠化加剧,治理效果不明显。(2)2005-2017年荒漠化改善面积大于加剧面积,两者相差174.18 km^2,荒漠化改善,治理效果显著。(3)1992-2017年民勤绿洲荒漠化总体趋于改善,局部地区加剧。其中,坝区和泉山区的荒漠化改善面积大于加剧面积,两者分别相差47.63 km^2和52.79 km^2,荒漠化改善,治理效果显著;而湖区荒漠化加剧面积大于改善面积,两者相差36.83 km^2,荒漠化加剧,治理效果不明显。

Evaluation of Desertification Control Effect in the Minqin Oasis in Gansu,China, Based on LSMM

Minqin Oasis is a typical area of arid desertification with fragile ecosystem. The evaluation of desertification control effect in this area can provide reference for the formulation and management of ecological restoration policies. In this paper, the linear spectral mixture model (LSMM) was used to effectively decompose the land cover information in the Landsat image. The appropriate thresholds were determined by the eigenvalues of the decomposed spectra on the histogram, then the desertification land was classified and the temporal and spatial variation characteristics were analyzed. Finally, the desertification control effect in Minqin Oasis during 1992-2017 was evaluated. The results show that: (1) From 1992 to 2005, the worsening desertification area in the Minqin Oasis was greater than the improved area by 175.47 km². The desertification was aggravated and the governance effect was not obvious. (2) From 2005 to 2017, the improved area of desertification was greater than the worsening area by 174.18 km². Desertification was improved and the governance effect was remarkable. (3) From 1992 to 2017, desertification in the Minqin Oasis tended to be improved, and local areas intensified. Among them, the improved area of desertification in dam region and Quanshan region was greater than the worsening area, and the difference between the two areas was 47.63 km² and 52.79 km², respectively, which shows the improvement of desertification has achieved significant effect in dam region and Quanshan region. The worsening area in the lake region is greater than the improved area by 36.83 km². Desertification is aggravating and the governance effect is not obvious in the lake region.