Dynamic assessment of alpine pasture grassland ecosystem health——A case study from the Gannan region

The “Pressure-State-Response” (PSR) model considers the 3 ecosystem aspects of pressure, state, and response. Seventeen indicators were chosen to build a PSR indicator system for the assessment of alpine grassland ecosystem health in Gannan. Using the application of Analytic Hierarchy Process (AHP) and GIS/RS, alpine grassland ecosystem health was assessed from 2001 to 2013. Meanwhile, the spatial and temporal variation characteristics of ecosystem health assessment were analyzed. We found that grassland ecosystem health level can be graded as one of the following levels of health: very low, low, medium, high, and very high, which respectively amount to 3.82%, 23.5%, 0.82%, 53.06%, and 18.81% of the total area. Grassland ecosystems of Zhuoni, Zhouqu, Diebu, Maqu, and Luqu were found to be very high in their level of health, while those of Hezuo, Lintan, and Xiahe were of low health. We also found that the Gannan alpine grassland ecosystem health showed an obviously declining trend over the past 13 years, with 68.01% of the total area deteriorating in health, 27.75% staying the same, and only 4.18% improving.