新疆生态质量变化趋势遥感分析

新疆是我国西部生态环境问题比较突出的区域,开展生态状况调查评估、及时掌握生态质量状况及其变化特征是环境保护的一个研究重点。以遥感数据为基础,根据构建垂直干旱指数(Perpendicular Drought Index, PDI)的思想,改变土壤基线所经过的原点,提出表征土壤湿度的垂直湿度指数(Perpendicular Moisture Index,PMI)。基于代表绿度的垂直植被指数(Perpendicular Vegetation Index, PVI)、代表湿度的垂直湿度指数PMI和代表热度的地表温度(Land Surface Temperature, LST),利用空间几何原理创建了植被-湿度-温度生态指数(Vegetation-Moisture-Temperature Ecological Index, VMTEI)。利用MODIS数据计算了新疆2000—2018年的VMTEI,并进行趋势分析。结果表明:VMTEI集成了植被、湿度和热度的信息,能很好地反映新疆生态质量的空间分布和时间变化趋势。新疆生态质量状况总体空间分布格局变化不大,与植被分布特征比较一致,呈现出纬向伸展的变化,不同生态系统VMTEI均值差异明显,湿地生态系统生态质量状态最好,VMTEI均值为0.43左右,其次为森林生态系统;最差的是荒漠生态系统,VMTEI仅为0.28。近20年来,新疆生态状况总体上得到改善,其中,生态状况明显改善的区域占2.332%,主要集中在塔里木河干流、伊犁河、额敏河和天山北坡绿洲经济带,以农田、聚落生态系统为主,主要原因为三北防护林建设、风沙治理、城市绿地面积增加造成的生态质量状况改善;生态状况严重退化的区域占0.430%,主要集中在塔克拉玛干沙漠外围、博斯腾湖、艾比湖以及零星分布于新疆的不同地区,以湿地生态系统为主,主要由于人为因素和气候变化造成平原湖泊以及部分水库的生态退化。

Remote sensing analysis of ecological quality change in Xinjiang

Xinjiang is a region with vulnerable eco-environment in western China. It is of significance to carry out eco-environment survey, assessment and timely grasp the ecological status and its changing characteristics for environmental protection. To meet this requirement, this paper developed a Vegetation-Moisture-Temperature Ecological Index (VMTEI) for measuring of region ecology. As an index for assessment of region ecological status, the VMTEI synthesized three important ecological indicators which were frequently used in evaluating ecology. These are greenness, wetness and heat. The three indicators can be represented respectively by three remote sensing indices or components, which are the perpendicular vegetation index (PVI), perpendicular moisture index (PMI), and land surface temperature (LST). Instead of a simple addition or weighted addition of the three indicators, the 3D spatial geometry principle was utilized to compress the three indicators into one to develop the VMTEI for assessing ecological status. The VMTEI of Xinjiang from 2000 to 2018 was calculated and the trend analysis was carried out by Sen+Mann-Kendall method. The results showed that VMTEI synthesized information on vegetation, soil moisture, and heat could well reflect the spatial distribution and temporal change of Xinjiang''s ecological quality. The overall spatial distribution pattern of eco-environment in Xinjiang had little change, which is consistent with the distribution of vegetation with the change of latitudinal extension. The mean value of VMTEI in various ecosystems was obviously different. The eco-environment of wetland ecosystem was the best, the mean values of its VMTEI is 0.43, and followed by forest ecosystems. The worst was the desert ecosystem with VMTEI only 0.28. In the past 20 years, Xinjiang''s ecological status has been improved overall. The area with obvious improvement of ecological quality status accounted for 2.332%, mainly concentrated in the farmland and settlement ecosystem which distributed in the Tarim River mainstream, Yili River, Emin River, and Tianshan North Slope Oasis Economic Belt. The main reasons of improvement were the construction of the Three-North Shelter Belt, sand management and the increase of urban green space. The area witnessed eco-degradation was 0.430%, mainly located in the wetland ecosystem which distributed in the periphery of the Taklimakan Desert, Bosten Lake, Aibi Lake and scattered in different regions of Xinjiang mainly due to eco-degradation of plain lakes and some reservoirs to human factors and climate change.