摘要
陡坡土壤分离机制明显区别于缓坡,为揭示坡度对土壤分离能力的影响,采用放水冲刷的试验方法,分析黄壤坡面土壤分离能力的坡度效应。结果表明:1)表征能量指标的水流功率是描述土壤分离能力的最佳参数,表征力学指标的径流剪切力次之,水深和达西阻力系数的表现最差。2)基于WEPP土壤分离能力的计算方程,土壤可蚀性和临界径流剪切力对坡度的响应较为敏感,并非定值。3)利用径流剪切力和水流功率幂函数关系来表征土壤分离能力都存在明显的坡度效应。径流剪切力的系数a_(1)随坡度的增加由二次函数先增大后减小转变为指数减小的趋势,坡度在17.63%时达到最大值;指数b_(1)随坡度的增加呈先减小后增大的二次函数关系,坡度在26.71%时达到最小值。水流功率的系数a_(2)随坡度的增加呈幂函数减小的趋势;指数b_(2)则呈现先减小后增大的二次函数关系,在坡度为28.10%时指数b_(2)达到最小值。因此,缓坡的研究结果不能直接推广到陡坡上,揭示土壤分离能力存在的坡度效应和阈值。
[Background]Soil detachment is the initial phase of soil erosion.Quantifying soil detachment capacity is crucial to establish the process-based soil erosion model.There is obvious difference in soil detachment mechanisms between gentle slope and steep slope,but the mechanism of slope effect is still unclear.Thus,the objective of this study is to reveal the slope effect of soil detachment capacity.[Methods]The soil samples from abandoned cropland on yellow soil slope in the upper and middle Yangtze River were selected as research object.The effect of hydrodynamic parameters(i.e.,flow rate,flow depth,flow velocity,Darcy-Weisbach resistance coefficient,flow shear stress,stream power,unit stream power and unit energy of water-carrying section and so on)on soil detachment capacity were analyzed by Pearson correlation analysis and regression analysis under different slope gradients(1.75%-48.77%)and flow rates(0.21-2.63 L/s).[Results]1)The stream power,which represented the flow energy,was the best parameter to describe the soil detachment capacity,followed by the flow shear stress associated with forces.However,the water depth and Darcy-Weisbach resistance coefficient were the worst to describe the soil detachment capacity.2)Based on the calculation equation of soil detachment capacity of WEPP,the response of soil erodibility and critical shear stress to slope was relatively sensitive and not constant value.The soil erodibility decreased firstly and then increased as the slope gradient increased,and the critical shear stress changed from power function to linear function as the slope gradient increased.This result showed that the constant values of soil erodibility and critical shear stress for previous studies can be extended to different slopes has great limitations.3)There was obvious slope effect in using the power function of flow shear stress or stream power to characterize soil detachment capacity.The coefficient a_(1)of flow shear stress changed from increased firstly and then decreased as a quadratic function to decreased as an exponential function with increasing slope gradient,and the maximum value reached at 17.63%of slope.The exponent b_(1)of flow shear stress showed a quadratic function relationship,which decreased firstly and then increased with the increase of slope gradient,and the slope reached the minimum value at 26.71%of slope.However,the coefficient a_(2)of stream power decreased as a power function with increasing slope gradient.The exponent b_(2)of stream power decreased firstly and then increased as a quadratic function,and it reached the minimum value when the slope was 28.10%.[Conclusions]This study illustrated that the results of gentle slopes cannot be directly generalized to steep slopes and reveal the slope effects and its thresholds of soil detachment capacity.The results of the study provide new insights into understanding soil detachment mechanism.
作者
王馨月
王彬
王云琦
安昕
王小平
王晨沣
WANG Xinyue;WANG Bin;WANG Yunqi;AN Xin;WANG Xiaoping;WANG Chenfeng(College of Natural Resources and Environment,Northwest A&F University,712100,Yangling,Shaanxi,China;Three-Gorges Reservoir Area(Chongqing)Forest Ecosystem Research Station,School of Soil and Water Conservation,Beijing Forestry University,100083,Beijing,China;Three-Gorges Reservoir Area(Chongqing)Forest Ecosystem Research Station,Ministry of Education,School of Soil and Water Conservation,Beijing Forestry University,100083,Beijing,China)
出处
《中国水土保持科学》
CSCD
北大核心
2023年第3期9-16,共8页
Science of Soil and Water Conservation
基金
国家自然科学基金“耦合植被作用的黄土高原次降雨坡面侵蚀动力学过程与机制”(42207396)
中央高校基本科研业务费专项资金“坡面侵蚀输沙过程中植被的阻控效应与机制”(2452022034)
重庆市科技兴林项目“重庆防护林林分结构质量精准提升技术研究”(渝林科研2020-10)
关键词
土壤分离
径流剪切力
水流功率
坡度效应
黄壤
soil detachment
flow shear stress
stream power
slope effect
yellow soil
