不同土壤水分条件对内蒙古荒漠草原地表风蚀影响的风洞模拟研究

Simulation of influence of soil moisture content on near-surface wind erosion in desert steppe of Inner Mongolia

内蒙古荒漠草原由于地表植被覆盖度低,土壤颗粒分散,极易发生土壤风蚀现象。土壤水分能够增强土壤抗侵蚀能力,但其影响程度目前尚不明确。基于此,文中以内蒙古苏尼特右旗选择短花针茅(Stipa breviflora Griseb.)荒漠草原原状土为研究对象,根据研究区风季的风速数据及测定的土壤质量含水量情况,设置1.5%、2.5%、3.5%三个水分梯度与10、13、17m/s三个风速梯度,开展了不同土壤含水量条件下的土壤起动风速,不同土壤含水量及风速交互作用下的土壤风蚀率、风沙流垂直分布的风洞模拟试验,以探究土壤含水量、风速及其交互作用对土壤风蚀特征的影响。结果表明:1)土壤含水量的增加能够增大起动风速,从而提高土壤抗风蚀能力,土壤含水量对风蚀率的作用随着风速的增大逐渐减小。2)低风速下土壤含水量的增加显著降低土壤风沙流沙物质含量,随着风速的增加,近地表风蚀输沙量比例逐渐升高。3)含水量通过与风速的交互作用起到降低风蚀的作用,但影响程度较低,研究区土壤含水量条件下的风速影响阈值为13m/s,风速超过13m/s,土壤含水量对于风蚀率的影响不明显。因此,风速是研究区土壤风蚀的主导因素,但在一定的风速范围内适当增加土壤含水量能够有效减少苏尼特右旗荒漠草原土壤风蚀。

Wind erosion is easy to occur in desert steppe of Inner Mongolia due to low vegetation coverage and dispersion of soil particles.Soil moisture can enhance soil erosion resistance,but its effect is not clear at present.Based on this,this study selected the undisturbed soil of desert Stipa breviflora Griseb.steppe in Sunite Right Banner of Inner Mongolia as the research object.According to the wind speed data and soil mass water content measured in the study area during the monsoon season,three water gradients of 1.5%,2.5%and 3.5%and three wind speed gradients of 10,13 and 17 m/s were set to carry out wind tunnel simulation tests of soil threshold wind velocity under different soil moisture content,soil wind erosion rate and vertical distribution of sand flow under the interaction of different soil moisture content and wind speed.The effects of soil moisture content,wind speed and their interaction on soil wind erosion were studied.The results show that:1)Increase of soil moisture content can increase threshold wind velocity,and thus improve the ability of soil to resist wind erosion.The effect of soil moisture content on wind erosion rate decreases with the increase of wind speed.2)At low wind speed,the increase of soil moisture content significantly reduces the content of aeolian sand,and the proportion of near-surface wind erosion sediment transport increases with the increase of wind speed.3)Water content can reduce wind erosion through the interaction between water content and wind speed,but the influence degree is low.In the study area,the influence threshold of wind speed under soil water content is 13 m/s,and the influence of soil water content on wind erosion rate is not obvious when wind speed exceeds 13 m/s.Therefore,wind speed is the dominant factor in soil wind erosion in the study area,but increasing soil moisture content appropriately within a certain range of wind speed can effectively reduce soil wind erosion in desert steppe.