Assessment of Wetland Ecosystem Health in the Source Region of Yangtze,Yellow and Yalu Tsangpo Rivers of Qinghai Province

Assessment of wetland ecosystem health is the basis for wetland conservation,has an important role in guiding how to improve the management level of wetland ecological environment.As the world's unique large-area alpine wetland,the source region of Yangtze,Yellow and Yalu Tsangpo Rivers of Qinghai province is the ecological barriers of ecological environmental security and regional sustainable development for the middle and lower reaches of rivers in China and Southeast Asian countries.In this paper,taking the source region of Yangtze,Yellow and Yalu Tsangpo Rivers of Qinghai province as the study area,Landsat ETM+ remote sensing image data,meteorological data,DEM data,population data,GDP data,transportation,rivers,soil erosion and NPP data were the main data sources to extract the wetland distribution information.Based on pressure-state-response(PSR) conceptual model,integrated assessment index system of wetland health in the source region of Yangtze,Yellow and Yalu Tsangpo Rivers of Qinghai province was constructed.Taking 1 km× 1 km grid as the basic assessment unit,according to the needs of assessment model,combined with mathematical statistics and mathematical modeling methods,the necessary indicators of the wetland ecosystem health assessment were got.Then,according to the regional characteristics of the source region of Yangtze,Yellow and Yalu Tsangpo Rivers,by the use of AHP and GIS spatial analysis techniques,the health status of wetland in the region was assessed and mapped.With the reference to previous practice and the characteristics of various types of wetlands in the study area,the wetland ecosystem health levels of the region were established.Set 5 ranges of health standards to describe the corresponding wetland health status,which are very healthy,healthy,sub-healthy,unhealthy and sick.The results showed that the health levels of the wetlands ecosystem in the region decreased from southeast to northwest,which was combined effected by the pressure-state-response.Most of the wetlands in the region were healthy,which mainly located in the central and western parts of the region,accounting for 37.47% of the total area of the wetlands.The wetlands in eastern and central parts of the region were very healthy,and their area was 3 602 km2,accounting for 14.92% of the total area.Sub-healthy wetlands in the region were mainly located in the central and eastern parts,their area was 5 930 km2,accounting for 24.57% of the total area.Unhealthy and sick wetlands in the region were mainly located in northwest part,accounting for 19.96% and 3.08% of the total area respectively,which were affected by higher human pressure in this area,the vulnerable wetlands state,and strongly land degradation respond.The irrational human production activities,such as over-grazing and dewatering of the marshes,led to wetland degradation,water and soil loss and serious desertification.High fragile ecological environment,severe soil freeze-thaw erosion and opening of the Qinghai-Tibet railway have brought pollution pressure to the environment,making the region's wetlands in unhealthy and sick states.In addition,the relative variability of regional precipitation fluctuations,the decreasing water supply for the wetlands in the dry period,which result to decreasing surface runoff and declining groundwater levels,make the region's wetland ecosystems more vulnerable.Therefore,these areas should be strengthened on protection and scientific management of the wetlands.