The Coupling Study Of Ecological Risk Evaluation And Ecological Health In Typical Alpine Pastoral Areas

Gannan Tibetan Autonomous Prefecture (hereinafter referred to as Gannan) is located in southern Gansu, as the important alpine forage base in northwest china with relatively fragile ecological environment. Because of special natural environment and the requirement of human economic sustainable development, lead to unreasonable use of the nature resources. The ecological environment of Gannan facing an unprecedented challenge:the frequent occurrence of rodent damage, the decline of water conservation capability, serious loss of soil and water, degradation and desertification of grassland, the decrease of biodiversity.In this study, based on GIS (Geographic Information System) and RS (Remote Sensing), the TM images, population, economics, temperature and precipitation data of Gannan from2005to2010(may to October) were used and GIS spatial interpolation and spatial overlay analysis technology were employed to evaluate the ecological risk. The temperature, precipitation, rodent damage, water and soil erosion, overload rate of grazing and urbanization were selected as the source of risk, then the normalized value of the each risk source was overlaid to estimate the ecological risk. According to the integrity of ecological structure, the strength of system recovery ability and the significant degree of ecological problems, the ecological risk was classified to five levels by using grade model:lower, low, medium, high, and higher. Moreover, the ecological health assessment index system was established based on PSR model and with status, response, pressure index as the rule layer, which contains22indicators such as afforestation area, per-capita production value, economic density and urbanization rate etc. The weight of each index was calculated by use of AGA-AHP analysis method, the comprehensive evaluation model was determined finally. Then the ecological health of Gannan was analyzed by the same method used in ecological risk, Similar to the results of ecological risk.2000points were random sampled and the values of ecological health and ecological risk of them were extracted to analyze the relationship between ecological risk and ecological health by use of cluster analysis method year by year.The results show that the ecological risk status of Gannan includes five levels in2005,2006,2007,2009and2010. But in2008, just includes four levels which are lower, low, medium, high level. The lower level is mainly located in northwest of Maqu. And higher level is spread over periphery of Zhouqu town from2005to2010. The results of ecological health assessment indicate that2005,2006,2007,2009and2010includes five levels,2008includes four levels (lower, low, medium, high). When the ecological risk in the higher state and the ecological health in the lower state, the development trend of ecological risk is maintaining its original state or even tends to decrease; when the ecological health is little more than (approximately equal to) ecological risk, the ecological risk will be reduce; when the ecological health is slight less than ecological risk, the ecological risk also will be reduce; When the ecological health is higher and ecological risk is lower, the ecological risk have no obvious variation trend. Overall, ecological health and ecological risk show a negative correlation.