Assessment of soil erosion under woodlands using USLE in China

Universal Soil Loss Equation (USLE), originally developed by the USDA for agricultural lands and then used throughout the world, was applied in mountainous forest terrain in China. The woodland area was divide into 100 m x 100 m grid cells. The ArcInfo 9.2 GIS software provided spatial input data was used to predict the spatial distribution of the average annual soil loss on grid basis. The average rainfall erositivity factor (R) for national woodlands was found to be 21-1798 MJ.mm.ha(-1).h(-1).a(-1). The soil erodibility factor (K) with a magnitude of 0.043 t.ha.h.ha(-1).MJ(-1).mm(-1) is the highest for Chinese woodland. Most of the slope length factors (LS) were less than 5 for the national woodland. The highest and lowest values of cover and management factor (C) were found out to be 0.0068 and 0.2550 respectively for coniferous woodland and orchard woodland. The value of conservation factor (P) was assigned to be 1 for Chinese woodlands because of scarcity of conversation practice data at the national scale. The average annual soil loss of the national woodland areas was 3.82 t.km(-2).a(-1). About 99.89% of Chinese woodland area was found out to be under slight erosion class, whereas it only resulted in about 41.97% of soil loss under woodland area, and 58.03% of soil loss occurred under high erosion potential zone, namely more than 5 t.ha(-1).a(-1). Therefore, those zones need immediate attention from soil conservation point of view. The results here are consistent with many domestic and oversea previous researches under mountainous forests or hilly catchments, thus we showed that the USLE can be applied to estimations of soil erosion for Chinese woodlands at the national scale.