|其他摘要||As the world's biggest environmental problem, water and soil loss has been a general big concern. As the foundation of the survival and development of northwest region of China, the protection of water and soil resources is imminent. Due to its unique characteristics, especially arable temperature and rainfall, the valley of Yili River Valley has become an important agricultural and animal husbandry production base in Xinjiang and even in the whole northwest region. In recent years, with the development of social economy, it faces a lot of problems, such as increasing population, the attenuation of forest resources, grassland degradation, vegetation reduction, serious soil erosion, etc., which seriously restrict the economic and social development of the region. It is imperative to explore the characteristics of soil and water loss in Yili Valley and reduce soil erosion. Based on the universal soil loss equation (USLE) and spatial analysis functions in ArcGIS, this study evaluated the temporal and spatial characteristics of soil erosion sensitivity according to selected factors (i.e. precipitation, vegetation cover, soil, slope, slope length) in the valley, with the factors of precipitation and vegetation being discriminated in different seasons.
The results show that in the study area, the soil erosion was most sensitive in spring, followed by autumn, while it was only slightly sensitive in summer and in the whole year. The total area of soil erosion with high sensitivity had a significant seasonal difference. It was largest in spring (32.3% of the total area), while only 6.1% in summer, and slightly less in autumn than in summer. Spatially, soil erosion area of low sensitivity was mainly distributed in plain area of the valley, while the area of medium and high sensitivity was mainly in the steep field, and in mountain area with elevation above 1500 m and slope about 20°. Furthermore, the influence of vegetation factor on soil erosion was greater than that of precipitation factor.
Take west valley hillside where human disturbance seriously as the study area, this work studied the soil erosion intensity in different land use types and different slope ranges and results show: the soil erosion in the study area showed different distributions for different slope range. In the range of 0-15 degree, soil erosion is increasing with the increase of slope, and the change is very obvious. When the slope range is above 15 degree, the soil erosion is more serious, but the distribution pattern of soil erosion intensity is not as obvious as the increase of slope gradient. Between different land use patterns, soil erosion intensities are different. The cultivated land and construction land are mainly minor erosion, the soil erosion intensity of forest land and grassland was mainly concentrated in the light range and the intensity of soil erosion was relatively large. Through the analysis soil erosion rates for landuse types in 1995 and 2005, 2013, it can be found that the region soil erosion rates are higher, including woodland, grassland, unused land soil erosion rate is higher than 60%, cultivated land and construction with soil erosion rate is higher than 20%.
Then, the study area was divided into subbasins to study the dynamic relationship between soil erosion intensity distribution and the above factors at the subbasin scale using statistical analysis. The investigation showed that the soil erosion intensity in valley hillside region presented an increase from 1995 to 2005 and then a decrease to 2013. Slope was the most critical factor affecting the distribution of erosion intensity, and its impact is stable. Its contribution rate fell from 46.6% in 1995 to 45% in 2005, and rose to 47.1% in 2013. The vegetation cover factor after the slope factor effect on soil erosion intensity, its impact on the volatility of the fell, its contribution rate fell from 31.3% in 1995 to 30.2% in 2013.With the development of soil and water resources in this area, the influence of land use factors will continue to rise, and its contribution rate rose from 8.2% in 1995 to 13.9% in 2013. The contribution rate of rainfall erosion factor fell from 13.9% in 1995 to 8.8% in 2013. As the precipitation increases, the influence of rainfall erosion factor will continue to rise. Effects of natural factors on soil erosion are hard to change, so it is suggested that adjustment and optimization of land use structure should still be made in this area for the control of soil erosion.|