Remote Sensing Dynamic Change And Driving Force Analysis Of Ecological Environment Quality In Sanjiangyuan National Park From 1990 To 2020

Protecting the ecological environment and achieving sustainable development are arduous tasks facing the world.The rapid development of social economy and the excessive consumption of natural resources have caused a series of ecological and environmental problems.Therefore,how to use scientific methods to quantitatively evaluate the ecological environment is very important.Sanjiangyuan National Park is one of the first national parks in China.It is located in the hinterland of the Qinghai-Tibet Plateau and the south of Qinghai Province.In the past 30 years,it has been affected by climate change and human activities,and the ecosystem is extremely sensitive and fragile.Efficiently monitoring and protecting the ecological environment of Sanjiangyuan National Park is of great significance to the construction of ecological security in China.Based on the Google Earth Engine(GEE)platform,this paper obtains 16 Landsat image data in the vegetation growing season(June to September)of Sanjiangyuan National Park from 1990 to 2020 at an interval of 2 years,and masks the water body information.The ecological indexes of greenness,humidity,heat and dryness were extracted from the image,and the remote sensing ecological index(RSEI)time series data set of Sanjiangyuan National Park was constructed by principal component analysis.The coefficient of variation(CV),trend analysis,Hurst index and correlation analysis were used to analyze the dynamic changes and driving factors of Sanjiangyuan National Park,in order to provide a strong basis for the effective formulation of ecological protection policies and the improvement of ecological engineering evaluation methods in the future.The main findings are as follows:(1)The average contribution rate of the four indexes of greenness,humidity,heat and dryness extracted from the remote sensing images obtained based on the GEE cloud platform to the first principal component(PC1)is more than 70%,indicating that it is feasible to construct the remote sensing ecological index model of the Sanjiangyuan National Park according to PC1.Accurately obtain the spatial and temporal pattern and evolution trend of the ecological environment quality of the Sanjiangyuan National Park,and provide strong support for the implementation of ecological environment protection and high-quality development strategy in the region.(2)From 1990 to 2020,the RSEI of Sanjiangyuan National Park showed an overall upward trend.The mean value of RSEI in the study area is between 0.57 and 0.65,and the average growth trend is 0.0026/a.The ecological environment quality of the three parks showed a slight growth trend at the rates of 0.0034/a,0.0017/a and 0.0026/a.(3)In the 30 years,the change of RSEI in the study area was relatively stable,the change trend of ecological environment quality was mainly improved,and the future change trend was generally realized as continuous improvement.The coefficient of variation of the remote sensing ecological index of Sanjiangyuan National Park ranged from 0.013 to 0.645,with an average of 0.064.The coefficient of variation was mainly stable,and the total area accounted for more than 90%.The change trend of ecological environment quality in Sanjiangyuan National Park is that the area of improvement trend accounts for 82.08%,the degradation trend is the second,accounting for 8.16%,and the basically stable area accounts for 9.76%.Among the three parks,the improvement of ecological environment quality in the Yangtze River source park is the most obvious,followed by the Lancang River source park and the Yellow River source park.The change of ecological environment quality in Sanjiangyuan National Park was mainly continuous,accounting for 81.73%,followed by anti-continuous change,accounting for 8.35%.The area of continuous improvement accounted for 77.28%,and the area of continuous degradation accounted for 4.45%.The degraded areas were mainly distributed in the high altitude and bare land areas of the park.(4)The change of ecological environment quality in Sanjiangyuan National Park is affected by many factors.The fluctuation of land use change and ecological environment quality change is similar.Forest and grassland have a major impact on the change of ecological environment quality,while other land use types have little effect on it.The changes of ecological environment quality in the three parks are affected by different altitudes,slopes and aspects.The changes of ecological environment quality in the Yangtze River and Yellow River source parks are easily affected by high altitude factors,and the ecological environment quality in the Yangtze River source park shows a more obvious degradation trend in high altitude areas.The change of ecological environment quality in Lancang River source park is mainly affected by low altitude area and part of slope aspect.The increase of temperature,precipitation and night light index can affect the change of ecological environment quality in the park to a certain extent.The mean RSEI of the Yangtze River source park was positively correlated with temperature and nighttime light index.The mean RSEI of the Yellow River source park was slightly negatively correlated with precipitation and potential evapotranspiration,and slightly positively correlated with annual average temperature and nighttime light index.The mean RSEI in the Lancang River source park was significantly positively correlated with the nighttime light index,and slightly negatively correlated with precipitation and potential evapotranspiration.