| The Loess Plateau in north Shaanxi Province is located in the center of the loess plateau in China, it's not only the most typical loess area in China, but also is typical soil erosion sensitive and fragile environment area in China. Aimed at the main ecological environment problems (soil and water loss) to evaluate in studied region, and drawn the range of red line of soil erosion sensitivity in accordance with the local geography, it can provide scientific basis for the ecological red line and eco-environment management in studied region.This paper based on GIS technology and Universal Soil Loss Equation (USLE), and considering regional background of the Loess Plateau in north Shaanxi Province, this paper selects 6 factors-rainfall erosion force, soil erodibility, slope length and slope gradient, gully density, farmland slope and land use/cover type, and divides the influence of each factor upon the water and soil loss sensitivity of Loess Plateau in north Shaanxi Province into 5 levels-insensitive, slightly sensitive, moderately sensitive, highly sensitive and extremely sensitive. This paper gets the spatial distribution map of the water and soil loss sensitivity of Loess Plateau in north Shaanxi Province through the overlay analysis, conducts the evaluation and analysis on the potential risks of water and soil loss of the Loess Plateau in north Shaanxi Province, and finally draws the red line region of water and soil loss sensitivity of the Loess Plateau in north Shaanxi Province. This paper mainly draws the following conclusions:(1) In the spatial distribution, water and soil loss sensitivity of the studied region takes 37°N as the boundary. Area in the north of 37°N has the obvious strip-map spatial distribution characteristic, with water and soil loss sensitivity level from west to east in 45°N direction of insensitive, slightly sensitive, moderately sensitive and extremely sensitive in turn. For the area in the south of 37°N, except that Ziwuling Mountain, Huanglong Mountain and other regions are slightly sensitive, water and soil loss sensitivity level of other regions has the obvious regional characteristic, with sensitivity level from north to south of moderately sensitive, extremely sensitive and highly sensitive in turn.(2) Among the area of water and soil loss at each sensitivity level in the studied region, total area of water and soil loss at the insensitive and slightly sensitive level is 36300 km2, accounting for 43.12% of the total area of the studied region, and mainly distributed in the windy and sandy area in the north of area along the Great Wall as well as Ziwuling Mountain, Huanglong Mountain and other mountains with higher vegetation coverage. Area of water and soil loss at the moderately level is 18000 km2, accounting for 21.45% of the total area, and mainly distributed in the south of 6 counties and cities in the northern margin of studied region. Area of water and soil loss at the highly sensitive and extremely sensitive level is 29800 km2, accounting for 35.43% of the total area, and mainly distributed in the loess hilly and gully region in the middle of the studied region, earth-rock mountains along the Yellow River in the northeast and loess broken and gully region in the north.(3) Potential risk of water and soil loss of the studied region is moderate, with SEPDI value of 3.70. All cities are mainly highly sensitive and extremely sensitive, and potential risk of water and soil loss of Yan'an, Tongchuan and Yulin is relieved in turn. Among various land-use types, the potential risk of water and soil loss of farmland is the highest. Among various slope grades, the potential risk of water and soil loss of slope zone with slope gradient between 25° and 35° is the highest.(4) The area of water and soil loss red line region in the studied region is 5854.11 km2, accounting for 6.97% of the total area of the studied region, and mainly distributed in the loess hilly-gully region in the middle of the studied region. The area of water and soil loss red line region of Zhidan, Wuqi, Ansai, Dingbian, Baota District, Yanchuan, Qingjian and other counties and districts is larger, accounting for 61.92% of the total area of water and soil loss red line region in the studied region and 4.32% of the total area of the studied region.This paper can provide the important basis for the prevention and control of water and soil loss in the studied region, reasonable development and utilization of land resources and establishment of local environmental protection policy based on the comprehensive assessment on the water and soil loss sensitivity of Loess Plateau in north Shaanxi Province. |
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