冻融作用对典型黑土土壤风蚀的影响

东北黑土区农田晚春冻融作用通过改变土壤物理性质而对风蚀作用有重要影响。基于室内冻融模拟试验与风洞试验,分析了东北典型黑土区前期冻融作用对土壤风蚀的影响。试验处理包括3个土壤含水量(16.5%,24.8%,33.0%)、3个风速(9,12,15 m/s)、1次冻融循环。试验过程是先将装有不同含水量土壤的试验土槽进行冻融循环模拟,然后将冻融后的土壤在室温下自然风干(至其土壤含水量为6.0%～7.0%)后进行风洞试验。结果表明:前期土壤冻融作用显著增加了风蚀量和输沙量,试验条件下前期土壤冻融作用使风蚀强度增加23.5%～404.2%,使平均输沙率增加59.1%～305.3%,其增加幅度受土壤含水量和风速影响。同时有、无前期冻融作用处理下,风蚀强度和风蚀输沙率皆随风速的增加而显著增加,且风蚀强度随风速的变化遵循幂函数关系。在冻融作用下,不同土壤冻结含水量下土壤风蚀强度和输沙率的增幅排序皆为16.5%33.0%24.8%。风蚀输沙率随地表高度的增加呈指数递减,风蚀输沙主要集中在距地表40 cm的范围内,且冻融作用使风蚀输沙高度增加。

Effects of Freeze-thaw on Wind Erosion in the Typical Mollisol Region

Freeze-thaw has an important effect on wind erosion by changing soil physical properties in the agricultural field of Chinese Mollisol region in late spring. The research analyzed the effects of previous freeze-thaw on wind erosion in agricultural fields based on simulated freeze-thaw and wind tunnel experiments. The experimental treatments included three initial soil moisture contents (16.5%, 24.8% and 33.0%), three wind speeds (9, 12 and 15 m/s), one freeze-thaw cycle, and non previous freeze-thaw experimental treatment was taken as a control. During the experiment, the soil box filled by tested soil samples with different initial moisture contents was firstly placed in the refrigerator to simulate freezing and thawing effect, and then it was air-dried in room temperature until its soil moisture content was approximately 6.0% to 7.0%. Late on, the soil box was placed into the wind tunnel to simulate soil loss by different wind speeds, respectively. The results showed that previous soil freeze-thaw significantly increased wind erosion rate and sediment delivery rate. At the experimental conditions, wind erosion intensity increased by 23.5%~404.2% (P<0.05), and the average sediment delivery rate increased by 59.1%~305.3% (P<0.05), compared with the control treatment; and both increments were related to initial soil moisture content and wind speed. Meanwhile, the wind erosion and sediment delivery rates increased significantly with an increase of wind speed with/without previous soil freeze-thaw action, and the wind erosion intensity followed the power function with increasing of wind velocity. For the previous soil freeze-thaw treatment, the order of increments of wind erosion and sediment delivery rates under three initial soil moisture contents was 16.5% > 33.0% > 24.8%. Moreover, the sediment delivery rate decreased exponentially with an increase of surface height, the wind erosion material was mainly concentrated in the range of 40 cm above the surface; and the previous soil freeze-thaw action increased the sediment delivery height.