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| Assessment on soil conservation value of the returning farmland to forestland and grassland project based on GIS and RS:Taking the Simianyaogou Watershed of Wuqi,Shaanxi as the example |
| Qin Wei,Zhu Qingke,Liu Zhongqi,Xue Zhide,Zhao Leilei,Li Yang |
| Key Lab.of Soil & Water Conservation and Desertification Combating,Ministry of Education,Beijing Forestry University,100083,Beijing,China |
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Abstract The benefit of soil conservation is an important ecological benefit of returning farmland to forestland and grassland.Assessing value of soil conservation can provide an important reference for founding ecological compensation mechanism of returning farmland to forestland and grassland.The Simianyaogou Watershed of Wuqi County,a demonstration area of returning farmland to forestland and grassland in China,was chosen as a study case.The type and area of returning farmland to forestland and grassland were monitored using RS and GIS techniques.The improved L factor of the Revised Universal Soil Loss Equation(RUSLE) was presented,which considers the effect of land cover for erosion.Based on RUSLE and GIS,the dynamic changes of soil erosion were assessed due to returning farmland to forestland and grassland.Then,soil conservation value of returning farmland to forestland and grassland was calculated using method of opportunity cost and replacement price.The results showed that in period from 1997 to 2004,the total area of returning farmland to forestland and grassland was 1 895.8 hm2,of which the afforestation in wasteland was 369.99 hm2,returning farmland to forestland was 357.48 hm2,returning farmland to grassland was 901.72 hm2 and closure measure was 266.61 hm>2.The annual modulus of soil erosion reduced by 4 644.04 t/(km2·a).The intensity of soil erosion fell from very strong grade into moderate grade.The annual soil conservation value of returning farmland to forestland and grassland was up to 13.24 million yuan,of which 0.08 million yuan for reducing soil loss,11.8 million yuan for reducing fertility loss,1.24 million yuan for reducing sediment deposition and 0.12 million yuan for increasing soil nutrient.
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Received: 16 June 2008
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