Effects of Simulated Land Use Change on Soil Erosion in the Maotiao River Watershed of Guizhou Province

Land use and cover change(LUCC) and its environmental effects are the central research topics of Land Change Science(LCS).In fragile karst geological environments such as in southwest China,which are characterized by extremely poor soil cover,low rates of soil formation,and highly fragmented terrain and physiognomy,as well as inappropriate and intensive land use,soil erosion is a serious problem.Inappropriate land use is the main factor that has caused soil erosion in this area.Guizhou,in southwestern China,covers an area of 17.6×10~4 km~2 and is located in the center of southwestern China's karst mountains,with about 73% of the total area covered with typical karst landscapes.Soil erosion and the resultant rocky desertification,termed cancer of the earth in karst areas,has been a key obstacle to sustainable development.Using GIS/RS technology and the RUSLE model,we analyzed the temporal and spatial characteristics of land use change and simulated soil erosion under different land use patterns in order to explore the relationship between land use and soil erosion over the past 30 years in the Maotiao River watershed of Guizhou Province.The results show that there was an obvious change in land use in the study area.During 1973～1990,paddy field,shrubland and shrub-grassland decreased,while dry farmland,forestland,water bodies,and built-up land and bare rock increased.During 1990～2002,paddy field,forestland,shrubland,shrub-grassland,water bodies,and built-up land notably increased,while dry farmland and bare rock decreased sharply.At the same time,the annual soil erosion modulus increased to 35.08 t/(hm~(2)·a) in 1990 from 30.88 t/(hm~(2)·a)in 1973 and then decreased to 28.16 t/(hm~(2)·a) in 2002.Dry farmland and shrub-grassland are the key land use types to target for soil erosion control in the study area.Therefore,the effective measures for controlling soil erosion in the watershed includes policies which require afforestation of all farmland with a slope gradient above 25°,as well as bare mountains.These results confirm the findings of previous studies and provide useful information for decision-makers and planners to take appropriate land management measures.This study also demonstrates that the RUSLE-GIS model is a useful tool for the quantitative and spatial evaluation of soil erosion at a watershed scale.