Land Use Change And The Effects Of Soil Conservation In Daning River Watershed

Land is the most fundamental natural resources about human survival. Since the 1990 s, with the contradictions between human and environmental resources have become increasingly prominent, LUCC research has became the forefront of the Geography, and the study on land use change has further strengthened. Soil erosion would cause destruction and degradation of land resources and land functions, and may trigger a series of environmental problems which threatening the social environment. Due to the high hazards caused by soil erosion, soil erosion has been the key study in soil and water conservation research, and people are more and more concerned about soil erosion monitoring and forecasting. In recent decades, GIS technology are developing rapidly, the mechanism of soil erosion has been deepening, the use of GIS technology to build a lot of soil erosion model for the study of soil erosion is of great importance.This paper taking Daning River Watershed as study area, taking GIS as a platform to establish the Daning River land use database, analyzes the land use change in 1988-2010, then discusses the impact of land use change on the landscape pattern. Meanwhile, apply the USLE soil erosion model to quantitative analysis the actual soil erosion in Daning River watershed, then combining In VEST model to calculate the potential soil erosion, and evaluate the soil conservation service, discuss the relationship between soil conservation and slope, elevation, lithology and land use patterns, the results shows that:（1） Analysis the relationship between land-use data（1988, 1999, 2010） and its elevation, slope and lithology in Daning River watershed, the results show that during 1988 to 2010, the land use pattern changes a lot, mainly shows the increase of dry land and construction land, and the decrease of shrubbery which embodied in low altitude（<800 m）, low grade（<25 °） under mudstone sandstone area. Landscape diversity index, fragmentation index and evenness index decreases with the increasing of elevation, and the landscape diversity index decreases with the increasing of slope, the landscape diversity index continue to rise in all lithology regions. Statistics the landscape diversity index in different land use types, the results show that the change in land use type has a greater impact on the landscape diversity.（2） Based on USLE model, evaluate the actual soil erosion of Daning River watershed, the results show that the average soil erosion modulus in 1988,1999 and 2010 was 1030.35 t /（km2.a）, 954.95 t /（km2.a） and 878.49 t /（km2.a） in Daning River watershed, respectively. According to the soil erosion intensity criteria issued by Ministry of Water Resources, the actual erosion in Daning River Watershed was mainly mild erosion. Overlay analysis the correlation of soil erosion and slope, elevation and lithologic, we found soil erosion occurs mainly in the region of 8 ° or more in Daning River Watershed which should be designated as the focus of regional soil and water conservation work. As to the elevation, soil erosion mainly occur under 1200 m areas, and the soil erosion modulus was biggest in 300-500 m, soil erosion is obvious in the limestone areas.（3） Combined with In VEST model, calculated the results of potential soil erosion of average soil erosion modulus is 3740.84 t ? km-2 ? a^-1 in Daning River Watershed. According to the grading standards of soil erosion intensity, the soil erosion in Daning River is moderate erosion. The soil conservation functions gradually increased in 1988-2010. Analyze the changes of soil conservation under different soil slope, elevation and lithologies, the results showed the soil conservation maintained a minimum amount of 15-20 ° areas, while better at 35 ° and above areas. In elevation, soil conservation amount the biggest band in 1500-2000 m, which is the largest percentage areas. From the perspective of lithological, limestone hold the largest percentage area. This was mainly because the Daning River Watershed is dominated by limestone, and the limestone retaining a lower amount, only second to the mudstone.（4） Overlay analysis of soil conservation function under different land use types, descending sort the remaining amount of the average soil, water> shrubbery> forest land> construction land> grassland> dry land> paddy field. On the total amount in terms of soil conservation, bush, forest and dry land constitute the body of ecosystem conservation function in Daning River Watershed, combined with the actual situation of Daning River Watershed, soil and water conservation measures was suggested after taking the overall efficiency of the economic, environmental and social prerequisite into account.