农牧交错区生态环境质量遥感动态监测——以宁夏盐池为例

以26 a（1989-2015年）4期Landsat TM/OLI遥感数据为基础，提取不同年份的湿度指数、植被指数、地表温度以及土壤指数，利用主成分分析法，构建盐池县4个时期遥感生态指数（RSEI）和生态环境质量综合指数（ESI），对其生态环境质量进行了评价，探讨区域生态环境的时空变化特征。结果表明：（1）湿度、绿度对区域生态环境质量起正面作用，而热度和干度则起负面作用，其中代表绿度指标的植被覆盖度（NDVI）对生态指数的贡献最大。（2）1989-2015年间，4个年份RSEI均值分别为0.41、0.54、0.51、0.57，生态环境质量呈上升-下降-上升且整体变好的特征。26 a间研究区生态环境明显转好的面积约占全县面积的20.01%，而生态环境质量中明显变差的面积仅占全县面积的1.64%。改善区域主要分布在研究区北部的盐池县城-高沙窝镇-王乐井乡以及惠安堡镇以南-麻黄山地区，中部的冯记沟乡生态环境质量有所变差。（3）盐池县生态环境质量受气候影响明显，退耕还林还草、草地禁牧以及禁止乱砍乱伐等措施对生态环境质量的提升起到了重要的促进作用。

Dynamic monitoring of ecology and environment in the agro-pastral ecotone based on remote sensing:a case of Yanchi County in Ningxia Hui Autonomous Region

The ecological environment is closely related to human life. Rapid and effective evaluation of regional ecological environment quality and spatial-temporal changes is helpful to understand the status of regional ecological environment, and provide the basis of development trends for the regional ecological environment protection and sustainable development. In the past few years, remote sensing ecological index(RSEI)based on PCA has been increasingly more widely applied to ecological environment evaluation of different fields and achieving good results. In this paper, based on Landsat TM/OLI remote sensing data of 4 periods in 26 years(1989-2015), four ecological evaluation indicators including wetness, greenness, heat and dryness were retrieved, which were the important ecological indicators frequently used in assessing regional ecology. Four indicators were developed RSEI and ESI(ecological environment quality synthetical index)of different periods using PCA method. Yanchi County ecological environmental quality from 1989 to 2015 was evaluated and spatial-temporal evolution characteristics of ecological environmental were discussed based on RSEI and ESI. Firstly, using remote sensing images based on pre-treatment, four indicators was obtained from Tasseled Cap Transformation, including WET, NDVI (Normalized Difference Vegetation Index), LST(Land Surface Temperature)and NDSI(Normalized Difference Soil Index). Then these four remote sensing ecological indices were used to build the RSEI with PCA. Based on RSEI, five levels of ecological zones were identified using equal interval method and ESI was calculated. Finally, RSEI change detection of Yanchi County during different periods were classified to five levels and mapped. The results show:(1)The humidity degree and green degree have a positive effect on promoting the ecological environment quality of the region, while the heat degree and dry degree have a restraining effect on the regional ecological environment quality, and NDVI which represents green degree has the most contribution to ecological index.(2)The whole situation of ecological environment quality in Yanchi County has been improved apparently from 1989 to 2015, and the mean value of RSEI was 0.41, 0.54, 0.51, 0.57 in 1989, 1999, 2006, 2015 respectively, which indicated that in 1989, 1999 and 2006, the level of overall regional ecological status of Yanchi County was general level, but in 2015, it was good level. The ecological environmental quality of the study area showed the characteristics of rise-decline-rise, the overall ecological environment quality has been improved apparently. The area of significantly improvement of ecological environment quality accounted for 20.01% of total area; howerver, the area of significantly deterioration of ecological environment quality just accounted for 1.64% of total area during the 26 years. The improved regions mainly distributed in the area of Yanchi-Gaoshawo-Wanglejing which was in the north of the county, and Mahuangshan area which was in the south of the county, the deteriorated regions mainly distributed in the middle of Fengjigou-Dashuikeng.(3)The precipitation had significant impact on change of ecological environmental quality of the study area, and desertification control measures such as returning farmland to forests and pastures, forbidding grazing grassland and prohibiting deforestation played an important role in promoting the ecological environmental quality.