Remote Sensing Dynamic Monitoring And Influencing Factors Of Ecological Environment Quality In The Beiluo River Basin

The construction of ecological civilization is of fundamental importance for the sustainable development of the Chinese nation.Since the 18th National Congress of the Communist Party of China(CPC),there has been a notable improvement in the eco-environment quality has been significantly improved.With the rapid development of remote sensing technology,collaborating multivariable data,rapid and real-time ecoenvironment quality monitoring and evaluation is conducive to promote the modernization of ecoenvironment governance system and capacity.The Beiluo River Basin is located in the hinterland of the Loess Plateau and has the ecosystem service functions.Meanwhile,the watershed has fragile ecoenvironment and is the key area for comprehensive control of soil erosion in China.Since the end of the 20th century,a series of ecological projects such as returning farmland to forest(grass)and soil and water conservation,which significantly improved the eco-environment quality of the watershed.Accurate and objective evaluation of eco-environment quality with a long-term has an important role in protecting the ecological environment and accelerating sustainable development in the Beiluo River Basin Moreover,it was also meaningful for establishing a strong ecological security shield in the Loess Plateau.Hence,the ecoenvironment quality of the Beiluo River Basin was conducted based on Google Earth Engine(GEE)from 1990 to 2021.The Landsat remote sensing images of summer(June to September)was selected in the GEE platform and four ecological index(greenness(NDVI),wetness(WET),dryness(NDBSI),and heat(LST))were calculated after removing the cloud pixels and masking the water body information.And the remote sensing-based ecology index(RSEI)was established quickly based on Principal Component Analysis(PCA)Meanwhile,the trend analysis and spatial autocorrelation methods were used to analyze the interannual trend changes and spatial pattern distribution of eco-environment quality in the Beiluo River Basin during the past32 years.The future prediction of RSEI was conducted based on the grey prediction model(GM(1,1)).Moreover,the Geographic detector and Multiscale Geographic Weighted Regression(MGWR)methods were used to explore the driving factors influencing spatial stratified heterogeneity of RSEI in the Beiluo River Basin.The main finding of this paper are as follows:(1)The average contribution rate of WET,NDVI,NDBSI and LST on the first principal component(PC1)was 88.61%.The correlations between RSEI and these four indicators were higher than the correlation between the four indicators.RSEI was well in integrate information from various indicators and was feasible to be used to evaluate eco-environment quality in the Beiluo River Basin.(2)From 1990 to 2021,the eco-environment quality of the Beiluo River Basin was at a medium level,(RSEI=0.58),and the mean RSEI showed a fluctuating rising trend with 0.29%/a.The trend analysis showed that the significantly improved area of eco-environment quality accounted for 32.65% of the total area,while the significantly degraded area accounted for 11.36% in the past 32 years.From the perspective of different landforms,the eco-environment of the loess hilly-gully area had significantly improved,with an increasing trend of 57%/a.However,the mean RSEI fluctuated between 0.70 and 0.85 with no significant trend of change in the earth-rock mountain forest area.(3)The spatial distribution of eco-environment quality in the Beiluo River Basin exhibited obvious regional characteristics.RSEI showed the characteristic of “high-high” and “low-low” aggregation.The earth-rock mountain forest area showed “high-high” aggregation and was dominated by excellent ecoenvironment quality,which accounting for 62.43% of the total area of the landform.However,the loess hillygully area presented "low-low" aggregation,and the eco-environment quality was dominated by comparatively poor grade,accounting for 38.09% of the total area.The eco-environment quality was dominated by medium and good grades in the terraced plain area and in the loess plateau gully area,respectively.Besides,the area of high RSEI level continuously expanded,while fluctuations existed within the region.The area of low RSEI level gradually decreased and the eco-environment quality had improved.According to the key point of RSEI trend change(2001a,2006 a and 2009a),the spatial transformation of RSEI level was mainly slight changes and concentrated in the terraced plain area,loess hilly-gully area and Loess plateau gully area during the different periods.Especially,from 2009 to 2012,it was critical period for the change of RSEI levels,and the eco-environment quality significantly improved and was dominated by excellent level after 2012.(4)The spatial stratified heterogeneity of RSEI was influenced by both natural and human factors with different affected degrees in the Beiluo River Basin.The vegetation coverage(VC)exerted the greatest impact on spatial heterogeneity of RSEI,explaining 60.1% of the variation.The impacts of SLOPE,ASPECT,SOIL and WID were all below 10%,indicating weaker influences on the spatial heterogeneity of ecoenvironment.Meanwhile,the explanatory degree of human factors on the spatial heterogeneity of ecoenvironment quality was above 18.9%.Human activity intensity(HAI)had a greater impact than other human factors with an explaining 27.8% on the spatial heterogeneity of RSEI.Besides,the eco-environment quality had different responses to land use.The mean RSEI value was highest in forestland(0.81),while the mean RSEI value was relatively poor in cropland(0.53)and construction land(0.30).From the perspective of different landforms,the mean value of RSEI different land use was higher in the earth-rock mountain forest area and loess plateau gully area than those in the loess hilly-gully area and terraced plain area.Moreover,multi-factor detection analysis showed that the explanatory degree of VC∩POP was the highest(68%)on the spatial heterogeneity of RSEI.(5)There was spatial heterogeneity in the intensity of influence of the same factor on RSEI in the Beiluo River Basin.The regression coefficient between VC and RSEI was relatively high in the western of earthrock mountain forest area(beta>0.82,p<0.05).Precipitation mainly improved the eco-environment quality,while there had a weak negative correlation between PRE4 and RSEI.There is a significant positive correlation between ELEVATION and RSEI in the terraced plain area(beta>0.28;p<0.05).Altitude showed a significant positive correlation with RSEI in the terrace plain areas.Besides,POP was negatively correlated with RSEI in the upper and middle reaches of the Beiluo River,while it was mainly positively correlated with them in the terraced plain area.Positive correlation was obtained between the GDP and RSEI in the loess hilly-gully area,indicating that economic development and sufficient material foundation are conducive to the improvement of the eco-environment quality.Especially,the intensity of human activities had a greater negative impact on the eco-environment quality in the Huangqiao Mountain area.