Evaluation of ecological carrying capacities in Gannan based on PSR model

Ecological carrying capacity refers to the natural ecosystems to maintain their service functions and health potential in a certain socioeconomic conditions. The evaluation system of the ecological carrying capacity was established by using satellite imagery (TM, ETM+) and the census data in Gannan region. The 22 indexes including average vegetation coverage, area of cultivated land per capita, grazing overload rate etc. were determined by using the PRS (PressureStateResponse) ecological safety evalutation model. On this basis, the AGAAHP was used to calculate the weight value of each index. Then the ecological carrying capacity of each county of Gannan region in 2000, 2004 and 2008 was assessed with help of the State Space Method. The results indicated that the ecological carrying capacities of Maqu, Diebu, Zhouqu, Lintan County and Hezuo City were overloaded in 2000, 2004 and 2008. The ecological carrying capacity of Xiahe County was overloaded in 2000 and 2004, but that was in an ideal state in 2008. The ecological carrying capacity in Zhuoni County was 1.081 0 in 2000, while that was 0.934 8 and 0.924 3 in 2004 and 2008, respectively, in which indicated the ecological carrying capacity was improved in 2004 and 2008. The ecological carrying capacity of Luqu County was in an ideal state in 2004, while that was excesses capacity in 2000 and 2008. This study provided an effective method for evaluation of alpine pastoral ecological carrying capacities.