北方生态脆弱区土壤侵蚀敏感性空间分异

榆林是我国北方农牧交错带典型的生态脆弱区,土壤侵蚀严重制约着榆林地区人类生存和社会经济的可持续发展。以通用土壤流失方程为理论基础,选取自然因素(包括降雨、地形和土壤因子)和人为参数(包括生物措施、农业措施和社会经济措施因子)构建评估指标体系。在完成单因子敏感性评价的基础上,利用GIS空间叠加分析功能,对榆林市土壤侵蚀敏感性空间分异特征进行了综合研究。结果表明:研究区土壤侵蚀敏感性以中敏感为主,低敏感和高敏感次之,不敏感仅有零星分布。空间上土壤侵蚀敏感性程度呈南部黄土沟壑区向北部风沙草滩区递减趋势,高敏感区主要集中在靖边、定边两县南端,东部黄河沿岸以及南六县的部分地区。修正后的土壤侵蚀敏感性评价结果与前人研究的土壤侵蚀分布规律趋于一致,充分说明人类活动对土壤侵蚀也产生了极大影响。因此,急需转变不合理的土地利用方式,加强水土流失治理和植被恢复,针对不同敏感区实施分区管理,有效控制研究区能源开发建设对土壤侵蚀潜在发生的影响程度。

Spatial Differentiation of Soil Erosion Sensitivity in Ecologically Vulnerable Areas

Yulin City,which is located in the transition zone sandwiched between Mu Us Desert and Plateau hilly-gully region,is not only a typical ecologically vulnerable area in agro-pastoral transitional zone of North China,but also a key ecological function protection area with soil conservation and sand fixation in China.Affected by aeolian landform,arid climate,sparse vegetation and high-strength land use during recent years,soil erosion has become the main ecological disaster in Yulin.Soil erosion seriously restricts human survival and socio-economy sustainable development of the region.So many scholars have paid much attention to the soil erosion problems in the study area.Based on the Universal Soil Loss Equation theory and GIS spatial analysis function,three natural factors (precipitation,terrain and soil factors) affecting soil erosion,and other three artificial parameters (biological measures,agricultural measures and socio-economic measures factors) were collected as the evaluation indexes to make the assessment equations.Then assessment of each factor was produced and an integrated soil erosion sensitivity evaluation was examined by using GIS.Furthermore,distribution characteristics and spatial difference of sensitivity of soil erosion in the study area were also analyzed.The sensitivity of the influences was classified into four degrees.The result demonstrates that moderate sensitive is the main type of soil sensitivities in the Yulin,followed by slight sensitive and strong sensitive distribute,and the area proportion with non-sensitivity is very small.Based on the overall distribution patterns,the general trend of soil erosion sensitivity descends from the southern loess hilly-gully areas to the northern sandy marsh areas.The strong soil erosion sensitivities mainly distribute in the south of Jingbian and Dingbian Counties,the Yellow River coast area in the eastern and the part areas of six counties in the south.The evaluation results of improved soil erosion sensitivities equation were found to be consistent with the previous studies for Yulin.It fully illustrates that biological measures,agricultural measures and socio-economic measures also have the great impacts on soil erosion and human activities are the inducement of soil erosion.Especially two indicators,population density and unit land area GDP introduce into assessment could reflect the impact on soil erosion by human activities more accuracy.Therefore,irrational land use should be changed,water and soil loss prevention should be strengthened and cured urgently,and partition management for different sensitive areas should be implemented so as to prevent soil erosion aggravation.Strong sensitivity area should be delimited as the priority area for soil erosion prevention and ecological restore.While moderate sensitivity is mainly located in the area of active social and economic activities,excessive and frequent human activities causing surface environmental damage to new disaster must be avoided.Light and non-sensitivity area mainly distribute in the northern sand mars areas with the flat terrain and the abundant irrigated agriculture.Therefore,prevention awareness should be strengthened and unreasonable construction causing soil erosion should be restricted.Because light and non-sensitivity just existe in the form of relativity,irrational human activities will bring a series of ecological problems.