基于Cs-137示踪的西江流域典型丘陵坡地土壤侵蚀研究

Assessment of Soil Erosion on the Typical Hilly Upland of Xijiang River Basin Based on Cs-137 Tracer Method

为快速、有效评估西江流域丘陵山地中长期土壤侵蚀状况,初步掌握区域土壤侵蚀与沉积规律,定量化西江流域土壤侵蚀强度,采用放射性核素Cs-137示踪方法,结合相关土壤侵蚀定量估算模型,探讨了西江流域梧州段典型丘陵山地人工林坡地和坡耕地的土壤侵蚀状况。结果表明,研究区Cs-137背景值为968.19Bq/m^2,Cs-137含量在坡面土壤中随土壤深度增加而递减,呈较好的线性关系。人工林地与坡耕地坡面土壤均呈侵蚀现象,人工林谷底表现为堆积现象。人工林地与坡耕地坡面土壤的侵蚀强度表现为上坡>中坡>下坡。人工林坡面年均土壤侵蚀模数为3 889t/(km^2·a),坡耕地坡面年均土壤侵蚀模数为4 257t/(km^2·a),坡耕地侵蚀模数大于人工林坡地,二者均为土壤中度侵蚀。在西江流域土地开发过程中,要加强对丘陵山地土壤的利用规划,防止过度开发;同时,要营造有效的水土保持措施,减少土壤侵蚀的形成,促进区域经济和环境的可持续发展。

The aim of this study was to find a new way to quickly and effectively evaluate middle-long term soil erosion status of hilly area in Xijiang river basin and quantify regional soil erosion and deposition.Based on Cs-137 tracer method and some relative soil erosion models,soil erosion status of artificial forest slope land and cultivated slope land in Wuzhou hills within Xijiang river basin were discussed.The results showed that background value of Cs-137 in study site was 968.19Bq/m^2.The content of Cs-137 in the soil profiles on hilly slope gradually decreased along with the increase of soil depth,which showed significantly positive linear correlation.Both of soils distributed on surface of the artificial forest land and cultivated land of hilly slope presented an erosion trend,whereas those on the bottom of artificial forest slope land demonstrated an accumulated trend.The soil erosion intensities on the slope of artificial forest and cultivated land were described as：upslope〉midstslope〉downslope.According to statistical analysis,the annual soil erosion modulus of artificial forest slope land and cultivated slope land were 3 889t/（km^2·a）and 4 257t/（km^2·a）,respectively.Cultivated land presented more severe erosion than artificial forest,both belonging to middle-grade soil erosion level.Therefore,in the process of land use in hilly area of XiJiang river basin,it is necessary to strengthen the plan of slope land use,and prevent the excessive land exploration.Meanwhile,it is essential to adopt some effective measures of soil and water conservation and reduce soil erosion so as to improve the sustainable development of economy and environment in the region.