Ecosystem Health Assessment Of Alpine Wetland In Gannan Prefecture And Northwest Sichuan

Gannan prefecture and northwest Sichuan are located on the eastern edge of the Qinghai-Tibet Plateau,which are sensitive areas for climate change and ecological environment in China.Since the 19th National People's Congress,the construction of ecological civilization has been listed as a millennium plan,and the strategic layout of"eco-protection and high-quality development of the Yellow River Basin"has been proposed.As an important ecological barrier of the upper reaches of the Yangtze River and the Yellow River,Gannan prefecture and northwest Sichuan region are important water conservation areas and wetland ecological areas of the source of the Yellow River,and play an important role in the regional and even the middle and lower reaches of the Yangtze River and the Yellow River.In recent years,due to climate change and overgrazing,the structure and function of the alpine wetlands in Gannan prefecture and northwest Sichuan have deteriorated,which has caused a series of ecological problems and also restricted the sustainable development of the regional economy.Based on the DPSIR model,this paper constructs a health evaluation index system for the alpine wetland ecosystem in Gannan prefecture and northwest Sichuan,quantitatively evaluates the health of the alpine wetland ecosystem in Gannan prefecture and northwest Sichuan from 1990 to 2015.This paper analyzes the temporal and spatial distribution rule and landscape pattern change of alpine wetland,evaluates the habitat suitability of flagship species,and puts forward the Zoological method for the health diagnosis of alpine wetland.The main conclusions are as follows:(1)The health value of wetland ecosystem in Gannan prefecture and northwest Sichuan was between0.12-0.72 from 1990 to 2015.The health status of wetland ecosystem in Ruoergai and Maqu counties in Heihe and Baihe basins was the best;and the health status of wetland ecosystem was the worst in the northeastern Hezuo City,Xiahe County,Zhouqu County and Lintan County.According to the classification results of alpine wetland ecosystem health,the fluctuation of area with high-health level decreases from 11,169 km~2 to 2,503 km~2,a decrease of 77.59%,and the area with sub-health and pathological condition increases from 29725 km~2 to 88741 km~2.In 2015,high-health level areas accounted for 2.05%,medium-health areas accounted for 5.74%,low-health areas accounted for 14.69%,sub-health areas accounted for 38.37%,and pathological areas accounted for 39.15%,the regional alpine wetland's ecosystem health level declined seriously from 1990 to 2015.(2)Based on Slope trend analysis,the priority protection pattern of alpine wetlands in Gannan prefecture and northwest Sichuan is proposed.Ruoergai County and Maqu County are level?protection areas;Aba County is level?protection area;Rangtang County,Maerkang City,Li County,Xiaojin County and Songpan County are level III protected area;Xiahe County,Hezuo City,Zhuoni County,Lintan County,Luqu County,Diebu County,Zhouqu County,Jiuzhaigou County,Jinchuan County,Mao County and Wenchuan County are level IV protected areas;Heishui County and Hongyuan County are level?protected areas.There is a serious trend of ecosystem deterioration in the level?and level?protected areas,and the management and protection of wetlands need to be strengthened,implement ecological and engineering measures to mitigate the deterioration of the ecosystem.The trend of ecosystem changes in level III and level IV protected areas was mainly mild deterioration,and management and monitoring need to be strengthened to prevent further deterioration.The health of the ecosystem of level?protected areas has improved,and only the existing wetland management and protection policies need to be maintained.(3)Marsh wetland is the main type of wetland in Gannan prefecture and northwest Sichuan.Wetland resources are mainly distributed in Ruoergai County,Maqu County and Hongyuan County.The conversion between wetland and grassland is the main type of regional wetland transfer.The shrinkage of the alpine wetland area in Gannan prefecture and northwestern Sichuan from 1980 to 1995 is the main feature of the change of wetland pattern.Its patch number,maximum patch area,diversity index and evenness index have all declined to a certain extent.After 2000,the regional landscape aggregation index decreased,the patch density increased,the overall landscape heterogeneity increased,the degree of landscape fragmentation was further strengthened,the complexity of the wetland landscape pattern decreased,and a certain degree of landscape pattern structure degradation occurred.(4)Based on the comparison study of the species distribution models,it is found that the random forest model has the best prediction accuracy of the regional black-necked cranes habitat suitability,and the prediction effect of the decision tree,maximum entropy,and treenet model decreases in turn.The habitat prediction based on random forest can be used as a zoological method for alpine wetland ecosystem health assessment.The suitable habitats of black-necked cranes are mainly located in Ruoergai County,Maqu County,Hongyuan County,Luqu County and Aba County,and other areas are not suitable for the survival and reproduction of black-necked cranes.From 1990 to 2015,the habitat suitability index of black-necked cranes in Gannan prefecture and northwestern Sichuan decreased from 0.121 to 0.112,an overall decrease of 7.44%.The loss of black-necked cranes was mainly converted from low-suitable areas to unsuitable areas,and the number of patches increased from 89 to 249,the degree of landscape fragmentation increases,and the distribution of low-suitability areas gradually discretizes,which putting a certain pressure on the survival and reproduction of black-necked cranes.