Abstract:

 Being fundamental for human life and development，the ecological function of soil conservation attracted more and more attention in scientific research Qinling Mountains，which is the vital water catchment area of middle route of South to North water transfer project，play an important role both in providing adequate access for water with a qualified water quality，and sediment retention with deposition reducing in rivers The InVEST model based on the USLE model improves the soil conservation by fully considering sediment removal through routing filtration and sedimentation in dead volume of reservoirs in the area Vegetation does not only keep sediment from eroding where it grows also traps sediment that has eroded upstream So we estimate how much of the sediment eroded on all pixels will be trapped by downstream vegetation based on the ability of vegetation in each pixel to capture and retain sediment We used the InVEST model (Sediment Retention Model step 1) to study the potential soil erosion and actual soil erosion of Qinling Mountains at the scales of the study area，watersheds and administrative regions And soil conservation service value was quantfied in this area by using the step 2 of the model The result indicates as follows. (1) the total potential soil erosion and actual soil erosion of Qinling Mountains in 2012 were 4588×108  t，152×108  t The five watersheds (Jialing River，Han River，Wei River，Dan River and Luo River) were mainly light erosion intensity and moderate erosion intensity Ziyang and Langao both in the south of Han River watershed had strong erosion intensity which suffered from serious soil erosion in 6323 t/(hm2[DK]·a) and 5869 t/(hm2[DK]·a)，respectively. (2) The amount of soil preserved by the ecosystems of Qinling Mountains was approximately 4337×108 t，and the average capacity per unit area was 71979 t/(hm2[DK]·a) for the entire region In 2012，the soil conservation service value of avoiding dredging and water quality in Qinling Mountains reached 4，187 million yuan，showing a rank of Dan River>Wei River>Han River>Jialing River>Luo River per unit area The soil conservation service value in each county was between 1 to 475 million yuan，and mainly distributed in 96 to 191 million. (3) Ensuring certain area of forest land is the prerequisite of preventing deterioration of large area soil erosion and increasing the ecological benefits in Qinling Mountains Meanwhile，keeping pushing the policy of returning farmland to forestry is necessary for slope farmland above 25°. (4) A major cause of any possible errors in this study is that the sediment retention value for each LULC class comes from the InVEST model But surely，as an important hydrologic process，traping sediment that has eroded upstream cannot be ignored Or，the amount of soil preserved by ecosystems of Qinling Mountains could have a deviation of 143×108 t at least