Study On The Spatio-Temporal Distribution Characteristics And Driving Factors Of Soil Erosion In Longnan City

Water erosion,a principal type of soil degradation,constitutes a grave risk to our global ecological systems.Approximately 24%of the world’s landmass is mountainous,and these areas,owing to their distinct geological structures and topographic conditions,are especially susceptible to soil erosion.China,recognized as one of the countries experiencing the highest rates of water erosion globally,sees over 40%of its total water erosion occurring in its mountainous regions.This loss of soil in these areas is an irreversible process,considerably more destructive and expensive to manage compared to other regions,emphasizing the immediate need to bolster land resource protection in these regions.Situated at the crossroads of the Loess Plateau,the Qinghai-Tibet Plateau,and the Qinba Mountains,Longnan City is a prototypical highland mountainous region.This city plays a crucial role as a major water conservation area and an ecological buffer for the Jialing River and the upper reaches of the Yangtze River.It is also a national priority area for soil erosion prevention.As such,preserving the ecological health of Longnan City holds tremendous significance for the sustainable management and development of the Jialing River and even the entirety of the Yangtze River’s upstream.Therefore,investigating the spatiotemporal evolution characteristics of soil erosion in Longnan City and quantifying the impacts of natural and anthropogenic factors on soil erosion is vital for safeguarding water and soil resources.This study employed the Revised Universal Soil Loss Equation（RUSLE）and the Sediment Delivery Ratio（SDR）model to estimate the volume of soil erosion in Longnan City from 2000 to 2020.To uncover the spatiotemporal evolution pattern of soil erosion in Longnan City,we conducted a gravity center shift model,spatial autocorrelation analysis,and hot/cold spot analysis.We utilized the Geographically Weighted Regression model（GWR）and path analysis model to quantify the effects of natural and human influences on soil erosion.The key findings are as follows:（1）From 2000 to 2020,the spatial distribution of precipitation and vegetation cover（NDVI）exhibited a pattern of low values in the northwest and high values in the southeast.Precipitation demonstrated a gradual increase over time with fluctuations,while vegetation growth significantly escalated.The primary land uses in Longnan City include forest,grassland,and cropland,accounting for 98%of the total study area.Cropland is predominantly located in the northern Xili Mountains and Huicheng Basin,with forests and grasslands primarily distributed in the south.Between 2000 and 2020,there was a gradual decrease in cropland and grassland areas,while construction land and forest areas saw a corresponding increase.（2）Between 2000 and 2020,the annual average rate of soil erosion in Longnan City fluctuated between 30-110 t·ha^-1·a^-1,displaying a trend of decline.Tolerable erosion was the dominant soil erosion type,comprising 48.92%of the total study area.Areas with the highest soil erosion intensity coincided with the"high-high"aggregation areas and were primarily located in the central Bailongjing River basin of Longnan City,characterized by higher precipitation,steeper slopes,and less robust vegetation cover.As the erosion intensity level increased,the distribution of gravity centers shifted from north to south,according to the gravity center shift model for different levels of erosion intensity.Apart from tolerable and slight erosion,all other erosion levels exhibited a westward trend from 2000 to 2020.（3）The hierarchy of erosion intensity across different land uses is as follows:grassland>forest>cropland>unused land≥construction land.The GWR model highlighted the significant spatial heterogeneity of different driving factors’impacts on erosion,ordered as slope>NDVI>precipitation>soil erodibility.The path analysis model indicated that NDVI is the primary direct control factor for erosion,followed by soil erodibility,slope,and precipitation.（4）Reflecting the current situation and characteristics of soil loss,landforms,and hydrogeology in Longnan City,this study classifies the city into three distinct areas of soil erosion:high mountain valleys,loess hills,and hilly basins.For each area,we propose governance suggestions such as"prioritizing soil erosion control and defending against erosion-induced natural disasters,""synchronizing governance with development for an ecological-economic win-win,"and"ensuring comprehensive soil erosion control aligns with agricultural production."This study elucidates the spatiotemporal distribution characteristics of soil erosion and sediment export in typical mountainous areas of China,alongside the driving mechanisms of soil erosion in these regions.The findings provide a practical scientific foundation for local soil erosion prevention and control and offer valuable guidance for formulating strategies to tackle soil loss in larger plateau mountainous regions.