Wednesday, August 4, 2010
Exhibit Hall A, David L Lawrence Convention Center
Background/Question/Methods Soil erosion is a natural geologic phenomenon but it can become a destructive process when it is accelerated by human activities, and cause a serious environmental and economic problem, such as depletion of soil fertility, degradation of soil structure, reduction of crop production, and increase of sediment in lake, river and reservoir. The unplanned land use change on agricultural lands in Three Gorge Reservoir region of China led to an accelerated erosion of soil in the area, which has raised a serious potential threat on environment health and reservoir security. The influence of land use change on water and soil losses was investigated at Houhe Watershed located in the Three Gorge Reservoir region, southwestern China. The aim of the research is to examine the relationships between land use changes, soil sediment yield and nitrogen and phosphate losses in the study area. Four different land use patterns: bare soil, economic forest, slope cultivated cropland, and terrace cultivated cropland were chosen in the project. Rainfall, surface runoff and soil erosion were monitored, and nitrogen (N) and phosphors (P) losses due to soil erosion were estimated in the four land use types.
Results/Conclusions The results of the study showed that surface runoff was positively correlated to the rainfall amount, but negatively related to vegetation cover in the four land use types. Soil erosion and the losses of N and P were found in an order in the four land use patterns: slope cultivated cropland > bare soil > economic forest > terrace cultivated cropland under the similar geographical and rainfall conditions. For instants, soil losses were 58.2, 35.6, 12.0 and 11.8 kg/ha in slope cultivated cropland, bare soil, economic forest, and terrace cultivated cropland, respectively in a 40 mm rainfall event. It meant that if the slop cultivated cropland was replaced by the terrace cultivated cropland, soil loss would be reduced by about 80% under a 40 mm rainfall event. The losses of N and P were decreased by about 87% in the terrace cultivated cropland pattern when compared the values found in the slope cultivated cropland pattern. Our results suggested that appropriate land use patterns and reasonable cultivation approach on agricultural land in the study area can efficiently prevent soil and nutrient losses from water erosion.
Results/Conclusions The results of the study showed that surface runoff was positively correlated to the rainfall amount, but negatively related to vegetation cover in the four land use types. Soil erosion and the losses of N and P were found in an order in the four land use patterns: slope cultivated cropland > bare soil > economic forest > terrace cultivated cropland under the similar geographical and rainfall conditions. For instants, soil losses were 58.2, 35.6, 12.0 and 11.8 kg/ha in slope cultivated cropland, bare soil, economic forest, and terrace cultivated cropland, respectively in a 40 mm rainfall event. It meant that if the slop cultivated cropland was replaced by the terrace cultivated cropland, soil loss would be reduced by about 80% under a 40 mm rainfall event. The losses of N and P were decreased by about 87% in the terrace cultivated cropland pattern when compared the values found in the slope cultivated cropland pattern. Our results suggested that appropriate land use patterns and reasonable cultivation approach on agricultural land in the study area can efficiently prevent soil and nutrient losses from water erosion.