四川省若尔盖县生态环境质量评价

Eco-environmental Quality Assessment of Ruoergai County in Sichuan Province Based on Multi-sources Remote Sensing Data

本文以2007、2009和2012年的5月和9月共6个时期的遥感影像,基于栅格数据和综合评价模型,对若尔盖县的生态环境质量状况进行了评价。首先,从影响生态环境质量的因子出发,选取归一化植被指数(NDVI)、地表温度、坡度、坡向、土地利用、湿度指数6项生态因子作为评价指标;然后,利用主成分分析法确定各评价指标的权重,根据综合指数评价模型计算出研究区的生态环境质量指数,同时,依据计算结果的大小把研究区的生态环境质量划分为优、良、中、差4个等级;最后,对若尔盖县的生态环境状况的空间分布规律进行分析。结果表明,2007-2012年若尔盖县生态环境质量良好,不同时相的生态环境综合指数的均值均在60左右,同时该区域的生态环境质量有变好的趋势;不同季节的评价结果稍有差异,但是同一季节不同年的变化趋势是一致的;不同等级的区域相间分布,较差区域主要集中在植被覆盖较差的区域,西北部居多,中部零星分布。

Compared with traditional methods for eco-environmental assessment, the method based on remote sensing imagery is more convenient and does not require huge amounts of statistical data. Satellite remote sens-ing has the advantages of efficient, economical, macro and dynamic monitoring of land surface and therefore is an excellent way in providing data for eco-environmental assessment. Scholars have deeply studied how to ex-tract ecological environment factors from remotely sensed data. In this paper, normalized difference vegetation index （NDVI）, land surface temperature, slope, aspect, land use and wetness index were selected as evaluation factors, and the eco-environmental quality of Ruoergai County of Sichuan Province in the years of 2007, 2009 and 2012 is assessed based on multi-sources remote sensing images （TM, HJ1B CCD1/CCD2, ASTER GDEM, and MODIS） and GIS technology. Firstly, the evaluation factors were extracted from remote sensing images. Sec-ondly, based on principal component analysis （PCA） method, the weight of each factor was determined and used to calculate the eco-environmental quality index of Ruoergai County with the comprehensive index evaluation model. Thirdly, according to the eco-environmental quality index, the study area is divided into four regions that are marked with four different degrees which corresponds to excellent quality, good quality, general quality and poor quality. Finally, the spatial analysis was integrated into the eco-environmental quality assessment. The re-sult shows：（1） the global eco-environmental quality of Ruoergai County is at the level of good quality, for all of the average quality indexes of 2007, 2009 and 2012 are around 60 which represents good quality. （2） For a given year, the average and minimum values of eco-environmental quality index in September are both larger than that in May. （3） The ecological environment in the east region and middle region is better, while the northwest region is worse than others.