Effects of Vegetation Coverage Change on Soil Conservation Service of Typical Steppe in Inner Mongolia

China is one of the countries suffering severely from soil wind erosion in the world,especially in the typical northern steppe.Xilingol League in Inner Mongolia is a part of the typical steppe zone.Ever since Beijing-Tianjin Dust Storms Sources Control Project was established in 2002,the grassland degradation situation has been controlled.The change of vegetation coverage can affect the ecological function of windbreak and sandfixation.In order to prepare the prevention and control measures for regional ecological restoration,to understand the practical significances of sustainable development of grassland ecosystem,and to control soil wind erosion,in this study,based on the meteorology and remote sensing data,combined with grassland degradation and recovery in Xilingol League,the Revised Wind Erosion Equation(RWEQ) was applied to quantitatively evaluate the spatio-temporal variations of soil conservation service function since the 1990s and to reveal the effects of the change of vegetation coverage on soil wind erosion control service.The results are shown as follows.The intensity of soil wind erosion was low in the most regions of Xilingol League,Especially in the eastern,central and southern regions,with higher vegetation coverage,lower wind field intensity,and abundant rainfall.The wind erosion regions with medium and higher soil wind erosion intensity were mainly distributed in the western desert steppe and Otindag Sandy Land,and the area of these regions decreased progressively as the erosion intensity increased.The distribution pattern of soil retention was similar to soil wind erosion modulus.The distribution characteristics of the soil retention rate were similar to the vegetation coverage,indicating a gradually increasing trend from northwest to southeast.Under the comprehensive influence of the warming-drying climate and the implementation of Beijing-Tianjin Dust storm Source Control Project,the vegetation coverage decreasing regions dominated by slight and micro erosion intensity turned into vegetation coverage increasing grassland dominated by slight and micro erosion intensity; the grassland having mild,medium or severe degree of vegetation coverage reduction turned into the grassland with balanced vegetation coverage.The decrease or increase of vegetation coverage can significantly intensify or mitigate the soil wind erosion.Additionally,the soil retention rate showed a significant positive relationship with the grassland vegetation coverage in the spring seasons in most regions(r0.6,p0.05).