三峡库区不同土地利用背景下的土壤侵蚀时空变化及其分布规律

Spatial and temporal variation of soil erosion under different land uses in the Three Gorges Reservoir Region

土壤侵蚀是影响三峡库区土壤养分流失、河道淤积等一系列生态环境问题的重要原因,本文基于GIS技术,采用通用土壤流失方程,对三峡库区1990、1995、2000、2005和2010年的土壤侵蚀进行计算,并对研究区1990—2010年不同土地利用背景下土壤侵蚀强度的时空变化和分布规律进行定量分析。结果表明:1990—2010年,三峡库区平均土壤侵蚀模数与土壤侵蚀量呈减少的趋势,多年平均土壤侵蚀量为18 356.450 7万t,属于中度侵蚀;从空间上看,研究区微度、轻度侵蚀等级分布面积最广。在同一年分内,6种不同土地利用下土壤侵蚀模数依次为:旱地>草地>林地>未利用地>水田>建设用地;不同土地利用下的土壤侵蚀差异显著,不同土地利用对土壤侵蚀的贡献率相差很大;各土地利用类型中,微度侵蚀的面积逐渐增加,中度侵蚀及以上侵蚀等级的侵蚀面积,都不同程度的向低等级转移;随着退耕还林还草及大量农村劳动力的外出,库区的土壤侵蚀总体上呈现转好的趋势,但是局部地区的治理工作仍需加强。

[ Background ] Soil erosion is an important cause of soil nutrient loss, river channel sedimentation and many other ecological environment problems in the Three Gorges Reservoir Region. And severe soil loss in the Three Gorges Reservoir Region is in a widespread. [ Methods] Taking the Reservoir Region as the study area, based on Geographical Information System, the Revised Universal Soil Loss Equation（RUSLE） was used to calculate the soil erosion of the five years, 1990, 1995, 2000, 2005 and 2010, in the Three Gorges Reservoir Region. ANOVA was used to analyze the significant impact on soil erosion in different land use. In addition, quantitative analysis was used to investigate the temporal and spatial variation of soil erosion intensity from 1990 to 2010; then the spatial distribution rules and spatial temporal characteristic of soil erosion under the different types of land use were studied.And all of above aimed to provide the supports for the sustainable development of the Three Gorges Reservoir Region. [ Results ] During the period of 1990--2010, the value of average soil erosion modulus and the amount of soil erosion in the Three Gorges Reservoir Region were generally in a decreasing trend with the amount of 183. 564 507 million tons, and it was graded as medium eroded area, in 2005 there was a certain degree of rebound with 19 282.74 million tons. From space, the slight and light erosion were the most widely distributed grades of soil erosion in this study area. The annual modulus of soil erosion of six different land use types in the same year was as： dry farmland 〉 grassland 〉 forestland 〉 unused land 〉 paddy field 〉 construction land; one-way ANOVA revealed the soil erosion under different land use patterns, with a very significant difference, and there was solid difference in contribution rate of soil erosion by different kinds of land uses. The area of slight erosion in all 6 land use types gradually increased. Concurrently, erosion areas in moderate- and highererosion level transferred to the lower level at varying degree. [ Conclusions] These above findings demonstrate that with returning farmland into forest and grass as well as large transferring of rural labor, the soil erosion in the Three Gorges Reservoir Region shows an improving trend as a whole, but the governance work in some parts of the Region still needs to be strengthened. The result of this study will be helpful to establish the quantitative relationship between land use and soil erosion, and also helpful in the adjustment of land use type in the future.