Monitoring and Evaluation of Dynamic Vegetation Change in Peng Zhou City Based on RS and GIS
|School||Sichuan Normal University|
|Course||Cartography and Geographic Information Systems|
|Keywords||earthquake damaged vegetation vegetation restoration ecological environment evaluation|
Natural ecological environment is the foundation of human survivaland development. Protecting and constructing our ecological environment is not onlycan make us get benefits, but also can give our children a good living environment. Inthe natural ecological environment, vegetation is one of the most important ingredientsin natural ecosystem. Vegetation can provide us oxygen and food, and at the same time,vegetation is the important index of natural ecological environment.In2008, Peng zhoucity was one of the disaster areas, which were hit by the significant Wen chuanearthquake. Earthquake not only makes huge damage to vegetation, but also changes theecological environment. Analyzing the vegetation damaged in the earthquake helps usto understand the damaged area and its results. After the earthquake, in2012, finding ofvegetation recovery, as well as the evaluation of ecological environment can guide thereconstruction of vegetation and the rebuilding of ecological environment.In this paper, on the basis of referring to a large number of related literature athome and abroad, with the geographical condition of this research area, We research onthe damage and vegetation recovery to the vegetation. We use the ETM+, CBERS-02Bremote sensing images and the images of environmental disaster mitigation to extractdamaged vegetation and extract the areas of vegetation recovery.First, we build a model of damaged vegetation and vegetation restoration, then countevery level of elevation、slope and aspect. According to the principle of selecting factorsof ecological environmental evaluation, We select four factors as the criterion layer andmain factors as index level, which are landform、meteorological factor、forest land use/vegetation cover, and human activities. Set up the evaluation index system of ecologicalenvironment in the study area. Determine each index’s weigh with analytic hierarchyprocess, with the spatial analysis of GIS technology and grid computing, we evaluatethe ecological environment. Build the model of the ecological environment evaluation, and classify the ecological environment of Peng zhou city. Below are the conclusions:(1) When extracting vegetation, we focus on analyzing the hillshade. Throughanalyzing of spectrum sampling of different ground objects, we found that themountain shadow values are less than other ground objects in each band. So we canextract the hillshade by using the total of all bands less than some value. In thehillshade, we test and determine the value of NDVI. In this case, we can exactvegetation from the hillshade.(2) By building the model of damaged vegetation, we find the area of damagedvegetation is112.64km2, it is about7.9%of the total area. Analyzing the severelydamaged area, the moderately damaged area, and the slightly damaged area.Afterthe study, we find that spatial distribution of damaged vegetation is significantpositive correlation with elevation and slope, and have little relationships withaspect.(3) By building the model of vegetation restoration, through comprehensive analysis ofall area, mainly influence factors of vegetation restoration are elevation and slope,and the influence of slope is less than the two factors.(4) Select seven indexes to evaluate ecological environment after the earthquake, theevaluation results of ecological environment are divided into five grades. Therecovery of ecological environment is mainly in general and better grades. After theanalyzing, we can draw a conclusion: the level of forest land, shrubland’s vegetationrestoration is optimal, slope is less than35°and the level of ecological environmentis good.Those intersection is the best level of ecological restoration.(5) According to the results of vegetation recovery and evaluation, it can help relevantdepartments to timely grasp the changes in the study area. And also providescientific reference for the study area of vegetation restoration and thereconstruction of the ecological environment.