Research On Prairie Wetlands Ecological Environment Evaluation Method Based On Remote Sensing Technology

Wetlands, found at the interface between terrestrial and aquatic areas, are a class of ecosystems with characteristics which can’t be covered in neither terrestrial nor aquatic ecology. Ruoergai prairie wetlands are the world’s largest plateau alpine marsh wetlands. They are the important water conservation district of Yangtze River and Yellow River, and they are also the concentrated area of important pasture in China. The wetlands are extremely fragile and vulnerable, due to the high altitude, cold weather, remarkable spatial heterogeneity, abundant biodiversity but unitary of vegetation community structure, the great effects of topographic relief, and weak capability of anti-disturbance. Therefore, it is meaningful and of practical significance to monitor and evaluate the state of ecological environment.In this study, on the basis of domestic and international satellite remote sensing data and field investigation, with the help of ENVI, ArcGIS and Fragstats software, the comprehensive evaluation method was used to evaluate the ecological environmental conditions of Ruoergai County, which locates in Sichuan Province, and then the spatial distribution and driving forces were analyzed. The major contents and accomplishments are listed as follow.(1) Through the analysis of the characteristics of Ruoergai prairie wetlands, the Pressure-State-Response(P-S-R) model was chosen as the fundamental framework, and satellite remote sensing images as the main data source. The evaluation index system was established by considering climate, topography, vegetation, land use, and landscape pattern.(2) Evaluation index such as land use types, vegetation coverage were obtained by processing Landsat and HJ satellite remote sensing images in the year of 1994, 2000, 2007 and 2012. And remote sensing technology and geographic information system technology were used to images processing.(3) Weighting of evaluation index was determined by Analytic Hierarchy Process(AHP), and then a comprehensive evaluation method was used to evaluate the eco-environmental quality of Ruoergai County. Results showed that the average evaluation value of Ruoergai County was around 0.6, which means they were mainly in the II level or III level. The value from 2000 to 2007 had been reduced, while the value went back to that of 2000 in 2012. Seen from spatial distribution of the classes, they alternated distribution and there was no obvious line, and the proportion of each level was different with dynamic changes. Seen from spatial distribution, the ecological environment with worse conditions were mainly located in the northern and some central areas, while the areas of better ecological environment quality are mainly concentrated along the river and eastern regions.(4) Through analyzing the driving forces of ecological environment change, we concluded that human activities and natural factors led to change together in the study area. The natural factors are intrinsic factors with long-term effects, while human activities are extrinsic factors with characteristics of active and significant.