Ecological Environmental Quality Assessment Of The Yellow River Source Based On Remote Sensing Ecological Index

Three rivers source is the birthplace of the Yangtze River,Yellow River and Lancang River.It has dense rivers,numerous lakes and marshes,and widely distributed snow mountains and glaciers.Among the three rivers source,the area above Duoshi Gorge in Maduo County of Qinghai Province is the source of the Yellow River,which is the second longest river in China and the most important birthplace of Chinese civilization.Historically,the source of the Yellow River had a good ecological environment and rich species.However,in recent decades,due to the impact of human activities and global warming,the source of the Yellow River has experienced ecological problems such as soil erosion and grassland degradation.In 2005 and 2011,The State Council approved the General Plan for Ecological Protection and Construction of the Three Rivers Source Nature Reserve in Qinghai Province,and established the Qinghai Three Rivers Source National Comprehensive Experimental Zone for Ecological Protection.In 2014,the second phase of the Sanjiangyuan Protection and Construction Project was launched,aiming to fully restore the ecological environment of the three rivers source.Only by evaluating the ecological environment quality scientifically and objectively,and finding out the driving forces affecting the ecological environment,can people have a clearer understanding of the local ecological environment and take active measures to improve the ecological environment quality.In this paper,Landsat remote sensing image data of the Yellow River source in2000,2010 and 2020 were used to extract four indicators of greenness,wetness,dryness and heat,and principal component analysis method was used to integrate all the indicators to obtain the remote sensing ecological index distribution map of the Yellow River Source in 2000,2010 and 2020,and the classification was conducted with an spacing of 0.2.The ecological environment quality of the source of the Yellow River is divided into five levels to analyze and evaluate.In terms of time,the change of ecoenvironmental quality in the past 20 years is analyzed.In terms of space,the difference of eco-environmental quality in different geographical locations is analyzed based on the basic evaluation unit of county area.Then,geographical detector is used to select seven detection factors,namely land use type,temperature,precipitation,elevation,slope,population density and GDP,to explore the spatial differentiation between impact factors and remote sensing ecological index and the interaction between the two factors.Through analysis and research,the following results are obtained:(1)From 2000 to 2020,the greenness index of the Yellow River source increased gradually from northwest to southeast;Wetness index showed little change,and also showed a gradual upward trend from northwest to southeast.The index of dryness decreased gradually from northwest to southeast.The heat index rose first and then decreased,and the high heat area was concentrated in the southeast.(2)From 2000 to 2020,the ecological environment quality of the Yellow River source has gradually improved.The area area with excellent grade increased from 14.39%to 16.66% during 20 years,and the area with good grade increased from 17.16% to25.87%.The area of the average grade increased from 23.39% to 24.78% in 20 years,the area of the poor grade decreased from 22.73% to 18.11%,and the area of the poor grade decreased from 22.33% to 14.58% in 20 years.(3)After driving factor detection by geographic detector,among the seven detection factors of land use type,temperature,precipitation,elevation,slope,population density and GDP,the interpretation efforts of remote sensing ecological index were ranked as follows: land use type > precipitation > temperature > elevation >population density > slope >GDP.After the interaction detection,each two factors have the enhancement effect.Temperature ∩ precipitation,temperature ∩ slope,slope∩population density and slope∩GDP have the double factor nonlinear enhancement effect,while the other two factors have the double factor enhancement effect.