基于GIS的农业土壤侵蚀分级和退耕还林决策--以川西干旱河谷地区为例

为定量研究川西干旱河谷的土壤侵蚀和土壤侵蚀的时空变异，指导退耕还林时序决策，本文综合考虑川西干旱河谷的地形、气候的特点和农业土壤特征，分析了计算通用土壤流失方程USLE因子指标的方法，利用地理信息技术建立生态环境本底数据库并进行了土壤侵蚀定量分级。根据土壤侵蚀的定量分级结果，分析了如何结合土壤侵蚀分级结果进行退耕还林(草)时序决策，认为应当优先考虑河流两侧土壤肥力条件差和土壤侵蚀严重的需退耕的坡耕地，这样，既避免了这些坡耕地造成的水土流失，也将土壤肥力好的耕地留下来为农业生产服务。此方法适应川藏边境及其三江之源地区地形因素复杂的土壤侵蚀的计算，GIS支持下的土壤侵蚀定量分级对于退耕还林时序决策具有指导意义。

Grading Agriculture Soil Loss Amount Integrated GIS and USLE:A Case of the Dry Valley Region in Western Sichuan Province

In order to quantitate the grade of agriculture soil loss amount and soil erosion volume spatio-temporal variation, as well as to guide the process of the reforestation(afforestation or agroforestry) in the dry valley region of western Sichuan province in China, the paper analyzed how to calculate K, S,L,C and P factors of USLE and how to build the ecology elements database by the support of geographical information system on the base of considering terrain, climate and characters of agricultural soil. What's more, how to grade the soil loss amount was introduced in detail by the methodology integrating USLE and GIS. The methods used in the paper can adapt to the variation terrain of the dry valley region in western Sichuan province. Believed the reforestation was a long-term engineering, the paper set up a new theory named temporal decision of reforest farmland according to the grading of the soil loss amount and the others conditions of reforested farmland. The theory considered not only the economic situation of the rural farmer but also the order of nature in the present reforestation. It conduces to program feasible plan in reforestation.