冻融条件下藻结皮对土壤分离能力的影响

Effects of Algal Crusts on Soil Detachment Capacity Under Freeze-Thaw Conditions

为探明生物结皮存在时,冻融条件下结皮盖度、坡度和流量对土壤分离能力的影响,以黄土高原北部东柳沟小流域的藻结皮为研究对象,采用室内模拟冻融和放水冲刷相结合的试验方法,利用正交设计和田口方法分析藻结皮盖度、坡度、流量和冻融对土壤分离能力的影响。结果表明:土壤分离能力最大时盖度、坡度和流量分别为10%、20 °和24 L/min,而冻融次数正交设计和田口方法中分别为10,1次。冻融条件下,随藻结皮盖度的增大土壤分离能力逐渐减小;随坡度和流量的增加土壤分离能力增大;正交设计中土壤分离能力随冻融次数的增减呈先减小后增大的趋势,而田口方法中则在试验条件下无明显变化规律。正交设计中坡度是影响土壤分离能力的主要因子,各因子对土壤分离能力的贡献率为坡度(15.08%)>盖度(14.38%)>流量(13.69%)>冻融(-13.23%);田口方法中藻结皮盖度是土壤分离能力的主要影响因子,且各因子对土壤分离能力的贡献率为盖度(30.41%)>坡度(25.32%)>流量(1.59%)>冻融(0.85%)。田口方法预测的土壤分离能力相对误差变化幅度小(CV=0.49),决定系数大(R2=0.961,p≤0.001),在一定的试验条件下能够用田口方法预测土壤分离能力。研究结果可为黄土高原北部的土壤侵蚀研究提供理论参考。

In order to explore the effects of biological crusts coverage, slope and flow rate on soil detachment capacity under freeze-thaw conditions when biological crusts existed, the algal crusts in the Dongliugou small watershed in the northern Loess Plateau were taken as the research object. A test method combining indoor freeze-thaw simulation and scour were carried out, and Taguchi method and Orthogonal design were used to analyze the effects of algal crust coverage, slope, flow and freeze-thaw on soil detachment capacity. The results showed that when the soil detachment capacity was the maximum, the crusts coverage, slope, flow was 10%, 20° and 24 L/min, respectively, while the number of freeze-thaw times was 1 and 10 in Taguchi method and Orthogonal design, respectively. Under freezing and thawing conditions, with the increasing of algal crust coverage, the soil detachment capacity gradually decreased. Soil detachment capacity increased with the increasing of slope and flow. In the orthogonal design, soil detachment capacity firstly decreased and then increased, but in the Taguchi method, the change of soil detachment capacity did not have had obvious law with the increasing of freeze-thaw times under the experimental conditions. Slope was the main factor affecting soil separation ability in the Orthogonal design, and the contribution rate of each factor was slope(15.08%)>coverage(14.38%)>flow(13.69%)>freeze-thaw(-13.23%). In Taguchi method, algal crust coverage was the main factor affecting soil detachment capacity, and the contribution rate of each factor followed the order of coverage(30.41%)>slope(25.32%)>flow(1.59%)>freeze-thaw(0.85%). The relative error of the soil separation ability predicted by the Taguchi method was small(CV=0.49), and the coefficient of determination was large(R~2=0.961>0.958, p≤0.001). Taguchi method could be used to predict soil detachment capacity under certain experimental conditions. The results could provide a theoretical reference for soil erosion research on the northern Loess Plateau.