Analysis On Fractional Vegetation Cover Change And Driving Factors In The Agro-pastoral Ecotone Of China From 2000 To 2019

As an important component of terrestrial ecosystems,vegetation connects the atmosphere,soil,water and other elements,and plays a critical role in climate regulation,carbon cycling,wind and sand control,soil conservation and hydrological processes.Therefore,vegetation change can be used as a sensitive indicator of land degradation and ecosystem health.Monitoring vegetation cover change and exploring its driving forces can improve the understanding of surface processes and vegetation-atmosphere interactions,and provide scientific references for formulating ecological conservation policies and optimizing land use management.The Liao River Basin spans across the arid,semi-arid,and semi-humid regions of China,representing a transitional zone between monsoon and continental climates.Furthermore,it is a convergence point of livestock and agricultural activities in China.The vegetation status in this area undergoes rapid change due to the influence of climatic changes and human activities.Therefore,comprehending the dynamics of FVC and response characteristics to natural and anthropogenic factors in the Liaohe River basin over the past two decades is crucial in understanding the regional ecological change in the context of global change.However,existing studies on this topic have been inconsistent in results due to differences in data sources and research methods,leading to no consensus on the factors that influence vegetation cover changes.In this study,we employed normalized vegetation index,meteorological data,topography and geomorphology,solar radiation,population data,and nighttime lights to quantitatively analyze the spatial-temporal distribution,and change characteristics of the FVC in the Liaohe River basin from 2000 to 2019 using trend analysis,MK test,Hurst index,Bayesian linear regression,Pearson correlation coefficient,and Geo-detector model.Additionally,we investigated the potential factors affecting FVC change and their driving mechanisms.The results of the study are as follows:(1)In the past 20 years,the vegetation cover of the basin shows a spatial pattern of high in the east and low in the west,and the average value of FVC in the Liaohe River basin from2000 to 2019 is 0.69,with vegetation cover at a high level overall.The vegetation cover in the basin shows a slow upward trend in time,and the magnitude of the increase is ranked as follows:pastoral area > agro-pastoral area > agricultural area.The FVC in the agricultural area has shown the least fluctuation over the past 20 years,while the FVC in the pastoral area has shown the greatest fluctuation.(2)The increase of vegetation cover in the basin is mainly located in the low hill areas in the southwest and the grassland areas in the central and west of the basin,accounting for about85% of the total area of the basin,while the decrease of vegetation cover is mainly located in the horqin sands in the central part of the basin and the urban clusters and suburban areas such as Shenyang-Jinzhou-Yingkou in the southeast of the basin,accounting for about 15% of the total area.In the future,16.1% of the vegetation cover of the Liaoning River basin will be in an anti-continuous improvement state,18.9% in an anti-continuous degradation state,40.3% in a continual improvement state and 24.7% in a continual degradation state.The overall vegetation cover of the Liaohe River basin will show an improving trend in the future,but there are still small areas where the vegetation cover will be degraded in the future.(3)The linear regression results show that the influence of natural factors is greater than that of human activities on the change in vegetation cover across the basin,with precipitation having the most pronounced effect.We also found that the influence of socio-economic factors increased sharply in the agricultural areas,probably because the vegetation types in the agricultural areas are mainly artificial crops,and human cultivation activities are more active in the agricultural areas than in the pastoral areas,and the frequent human activities also have some influence on the regional vegetation change.(4)Geographical factor detection shows that natural factors have more explanatory power on FVC than socio-economic factors throughout the basin.Precipitation has the most significant influence on FVC in all areas of the basin except pastoral areas,and the gradient change in precipitation influences the degree to which other factors explain FVC,with the fit of each factor to FVC increasing as annual precipitation increases.Geographic interaction detection shows that a combination of natural and socio-economic factors driving changes in the FVC of the catchment.In both office and pastoral areas,interactions between natural factors(semipastoral: precipitation and elevation;pastoral: temperature and precipitation)play a dominant role in FVC variation,while FVC variation in agricultural areas is mainly attributed to synergistic effects between natural factors(precipitation)and human activities(night lighting).