土壤含水率对冻结风沙土风蚀速率的影响

Effect of soil moisture content on wind erosion rate of frozen aeolian sand

乌兰布和沙漠冬季土壤冻结,流动沙丘表层干沙风蚀后出现冻结裸斑,风沙输移环境发生改变。为研究冻结裸斑对风蚀的影响,探讨不同含水率冻结风沙土风蚀的差异,根据野外实际情况,试验设置5、7、8.5、10、12 m·s^(-1)风速梯度,设置土壤含水率(1%~6%)6个梯度,以自然状态下干沙(含水率0.13%)作为对照,开展冻结风沙土风蚀模拟风洞试验。结果表明:发生冻结时,含水率≤2%风沙土2 h内即可产生稳定冻结,而含水率≥3%风沙土则5~12 h产生稳定冻结。风沙土含水率相同时,冻结风沙土风蚀速率随着风速升高而增大,风蚀速率Q与风速V符合指数函数Q=ae^(bV)。风速相同时,随着土壤含水率升高,冻结风沙土风蚀速率减小;风蚀速率与冻结风沙土含水率w符合指数函数Q=ce^(dw)。三者关系式符合Q=0.367e^(0.849V-0.677w)(R^(2)=0.994),冻结风沙土风蚀速率较自然干沙风蚀速率减小40%~98%,冻结风沙土含水率>3%时,可以有效抑制风蚀。风速、含水率是影响冻结风沙土风蚀速率的主要因素。当未来气候趋向干暖化,可能导致乌兰布和沙漠冬季风蚀增强。

The soil in Wulanbuhe Desert area frozes in winter,and the dry sand on the surface of the flowing sand dunes exposes and is frozen after wind erosion,so the wind and sand movement environment changes.In this paper,the influence of freezing on the wind erosion process is analyzed,and the influence of freezing on the wind erosion process under different moisture conditions is explored.The wind speed gradients of 5,7,8.5,10,12 m·s^(-1)were set up,and 6 gradients of soil moisture content(1%-6%)were set,and non-frozen soil with low moisture content(CK,0.13%)as the control.It is found that a stable frozen layer can be formed within 2 hours on aeolian sand foundation with a water content of≤2%,while a stable frozen layer can be formed in 5-12 hours on a aeolian sand foundation with a water content of≥3%.Under the same water content condition,the erosion rate of aeolian sand after freezing increases with the increase of speed,and the wind erosion rate Q and wind speed V conformes to the index Q=ae^(bV).Under the same wind speed,the wind erosion rate of frozen aeolian sand decreases with the increase of soil moisture,and the wind erosion rate and the moisture content w of frozen aeoli-an sand soil correspond to the exponential function Q=ce^(dw).In general,the wind erosion rate of frozen aeolian sand soil is reduced by more than 40%compared with that of dry sand,and the relationship between wind ero-sion rate of frozen aeolian sand soil and wind speed and moisture content is consistent with Q=0.367e^(0.849V-0.677w)(R^(2)=0.994).The wind erosion rate of frozen aeolian sand is reduced by 40%-98%compared with that of CK,and the water content of frozen aeolian sand is more than 3%,which can effectively inhibit wind erosion.Wind speed and moisture content are the main factors affecting the erosion rate of frozen aeolian sand.In the case of fu-ture warming and drying,wind erosion in Wulanbuhe Desert may increase.