Effects of soil conservation measures on soil erosion in the Yunnan Plateau, southwest China

Soil and water conservation (SWC) measures are among the most important ways to control soil erosion in mountainous areas. However, little is known about the application of SWC measures on soil erosion over large areas. We developed a new framework for investigating the distribution of engineering measures by using high-resolution remote sensing images at a large scale, and we assessed the soil conservation effects of those measures on the Yunnan Plateau (YP) in China using the Chinese Soil Loss Equation (CSLE). We detected 43,398 km(2) of soil conservation measures on the YP, accounting for 53% of farmland. The area of conservation measures decreased with an increase in slope gradient. Different types of engineering measures had different spatial distribution patterns, and together they conserved 5.08 x 10(8) t of soil each year on the YP. The effects of engineering measures on soil erosion decreased with an increase in slope. Furthermore, more than 82% of soil loss from farmlands was attributed to areas without engineering measures, and steep-slope farmland without such measures was the main source of soil erosion on the YP. Our results suggest that engineering measures were effective in soil conservation, but the effects varied with topography on theYP. We suggest that further studies focus on the relationships between the soil erosion and grain supply of farmlands without engineering measures to provide a basis for the formulation of land use planning policy in China.