陕北地区退耕还林还草工程土壤保护效应的时空特征

Spatiotemporal patterns of soil protection effect of the Grain for Green Project in northern Shaanxi

以中国退耕还林生态工程重点区域陕北地区作为研究区,基于耕地遥感监测数据集,分析了陕北地区2000-2013年耕地的时空变化特征;基于梯田空间分布,对RUSLE模型进行改进,模拟生成陕北地区土壤侵蚀模数栅格数据并进行精度验证;最后结合耕地变化数据集对陕北地区退耕还林(草)地及未退耕地的土壤侵蚀变化特征进行对比分析,以明确工程对全区土壤侵蚀变化的影响。结果表明,2000-2010年,陕北退耕农田内部侵蚀模数减少了22.70 t/hm^2,是退耕农田区2000年土壤侵蚀模数的47.08%。同期,陕北地区未退耕农田侵蚀模数减少了10.99 t/hm^2,占未退耕农田区域2000年土壤侵蚀模数的28.60%。从陕北全区的角度看,各种土地利用类型2000-2010年土壤侵蚀模数平均减少了14.51 t/hm^2,占2000年全区土壤侵蚀模数的41.87%。由此可见,退耕还林还草工程可以有效减少土壤侵蚀模数,达到土壤保护的作用。其中,由耕地转为林草所导致的侵蚀减少最为显著,对土壤保护的贡献作用最大。但是,2010年以后(2010-2013年)为退耕还林还草巩固时期,因此该阶段陕北地区土壤侵蚀模数和土壤侵蚀量变化较前10年显著降低。

The study took northern Shaanxi,a key region of Grain for Green Project,as the research area.We firstly analyzed the spatiotemporal patterns of cropland during 2000-2013 using the remotely sensed time series cropland.The RUSLE model was improved by taking terraced fields as a parameter,and then the soil erosion modulus(SEM)was simulated using the calibrated model.Finally,the impacts of the Grain for Green Project on the soil erosion were assessed by comparing SEM changes in shifted and unshifted cropland.The results indicated that,the SEM across the areas of'Grain for Green'decreased by 22.70 t/hm^2 from^2000 to 2010,accounting for 47.08%of that from the returned cropland in 2000.In the same period,the SEM from the unreturned cropland decreased by 10.99 t/hm^2,accounting for28.60%of that from the unreturned land in 2000.For the whole study area,the SEM of different land use types averagely decreased by 14.51 t/hm^2,which is 41.87%of the SEM in northern Shaanxi in 2000.We concluded that'Grain for Green'could effectively reduce the SEM in northern Shaanxi and made the most contribution to soil protection.The Grain for Green Project entered a consolidation period after 2000(during 2010-2013 in this study),and changes of the SEM during this period were thus relatively low.