| Soil erosion is a primary cause of the continuous loss of soil especially that of fine particles near the surface,and considerably decreases the soil water-holding capacity and productivity,aggravates the scarcity trend of land.This process severely affects the agricultural production,environmental quality,ecological security,and sustainable development in arid and semiarid regions.Moreover,nutrients?nitrogen,phosphorus,potassium and organic?are eroded along with these fine soil particles,leading to considerable loss in soil nutrients,soil degradation,and desertification,threatening the robustness of oasis ecosystems.Therefore,accurately evaluating the dynamic changes of soil erosion?wind and water erosion?and available nutrients,explaining the driving mechanism are the foundation of soil erosion prevention and control and the advance of implementing ecological environmental protection project.Based on remote sensing,geographic information system and field survey,the meteorological,topographic,soil and other data from 1982 to 2015 were comprehensively collected to reconstruct the spatial-temporal information of key elements in Hexi region?92°13?E-104°46?E,36°31?N-42°57?N?for 34 years.In order to simulate the water erosion rate,the revised universal soil loss equation?RUSLE?was integrated with the transport limited sediment delivery?TLSD?.The wind erosion rate was simulated by the revised wind erosion equation?RWEQ?.And the response characteristics of soil erosion and available nutrients under multi factor coupling were revealed.The main results of this study are as follows:The RUSLE-TLSD model could reliably simulate the soil erosion process in Hexi region.The potential water erosion rate was between 6.24 and 31.01 t·ha-1·a-1from 1982 to 2015,and the net water erosion rate showed a downward trend and in the range of soil loss tolerance.Spatially,the water erosion rate was strong in the south and weak in the north,mainly concentrated in the Qilian Mountains.The areas with strong erosion were mostly located on the steep slope section?more than 20°?above 1500 m sea level.Slope,precipitation and NDVI were the primary factors affecting water erosion in Hexi region,and the contribution of slope was the largest.Sediment deposition was mostly at the foot of steep slope.Extreme precipitation directly aggravated the water-erosion risk,and this factor should be given increased attention particularly in arid and semi-arid regions.The“Grain to Green Program”?GTGP?effectively reduced water soil erosion caused by extreme precipitation and improved water retention and soil consolidation in Hexi region.The Potential wind erosion rate?PWER?decreased remarkably from 1982 to2015(annual average of 67.7 t·ha-1·a-1 for the entire region).A severe and a mild wind erosion period occurred from October to May and from June to September,respectively.Spatially,the PWER was strong in the eastern,western,and northern regions?especially in the west?and less severe in the central and southern regions,and there was a decreasing tendency in 95%of the area.The PWER of Subei Mongolian Autonomous County was highest,while that of Minle was lowest.Climatic factors primarily determined the PWER in Hexi region,among which wind speed was the main factor controlling the intensity of wind erosion,and the coupling of temperature,gale days and NDVI jointly dominated the wind erosion rate in Hexi region.Meanwhile,the total area with a changing land cover was less than 2%of the study area,and mainly occurred in the inner oasis and near the oasis-desert transition zone.Therefore,the inhibiting effect of LUCC process on wind erosion was limited to the oasis with a small area and did not significantly affect the PWER in the short term. |
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