川西北高寒典型沙区植被恢复动态遥感监测研究

Research on dynamic monitoring of vegetation restoration in typical high cold sand areas of northwest Sichuan

近几十年来,土地退化、沙化问题威胁着川西北地区草原生态环境和群众生产生活。为获取并定量分析沙区治理的植被恢复动态及趋势,探讨典型沙区的生态修复变化机制,本文以红原县瓦切镇典型沙区1984、2000和2021年3期长时序Landsat遥感影像为数据源,在ENVI 5.3和ArcGIS 10.2软件的支持下,通过植被覆盖指数(NDVI)与光谱混合分析(NDVI-SWA)相结合的方法提取植被覆盖度(FVC),运用土地动态度空间分析模型和转移矩阵分析川西北高寒典型沙区植被恢复变化特征。结果表明:(1)研究区植被覆盖度等级结构以高度植被覆盖度为主(占50%以上),且不同植被盖度类型存在明显空间差异;(2)1984年研究区植被覆盖情况最差,2021年植被覆盖情况最好,中度及以下植被覆盖度面积仅占4.71%。1984-2021年,变化幅度最大的是中度以下植被覆盖度情况,占比呈现出先增加后降低的趋势,相对而言,中高度、高度植被覆盖度处于较为稳定的变化状态。(3)各级FVC转移矩阵分析中,具体转化方向较为一致,主要是向高植被覆盖方向转化,表现为:中高等级向高等级转化;低等级向中低、中等级转化。

In recent decades,land degradation and desertification have threatened the grassland ecological environment and people's production and life in the northwest of Sichuan.To obtain and quantitatively analyze the dynamics and trends of vegetation restoration in sand area management,and explore the mechanisms of ecological restoration changes in typical sand areas.Based on the 1984,2000 and 2021 long time series remote sensing images of the typical sand area in Wache Town,Hongyuan County,supported by ENVI 5.3 and ArcGIS 10.2,the vegetation coverage(FVC)was extracted by NDVI and spectral mixture analysis(NDVI-SWA),and the vegetation restoration and change characteristics of the typical alpine sand area in northwest Sichuan were analyzed by land dynamics Spatial analysis model and Transition matrix.The research showed that:(1)the vegetation coverage level structure is mainly characterized by high vegetation coverage,accounting for over 50%of the study area,and there were significant spatial differences among different vegetation coverage types;(2)The vegetation coverage in the research area was the worst in 1984,and the best in 2021,with moderate and below vegetation coverage accounting for only 4.71%of the area.From 1984 to 2021,the most significant change was in vegetation coverage below moderate levels,with a trend of first increasing and then decreasing in proportion.Relatively speaking,medium to high and high vegetation coverage remained in a relatively stable state of change.(3)In the analysis of FVC stochastic matrix at all levels,the specific transformation direction was relatively consistent,mainly towards the direction of high vegetation coverage,manifested as:transformation from mid high level to high levels,and convert from bottom level to mid bottom and mid level.