东北黑土区冻融、风力、水力交互作用对坡面侵蚀的影响

多种外营力作用的复合侵蚀是东北黑土区坡耕地的主要侵蚀特征,但目前缺乏冻融、风力、水力之间相互作用对复合侵蚀影响的量化研究。基于此,采用室内冻融模拟、风洞试验和降雨模拟试验相结合的研究方法,分析了前期土壤冻融作用对土壤风蚀以及前期土壤冻融和风力叠加作用对后期坡面水蚀的影响。结果表明,前期土壤冻融作用显著增加了后期坡面的风蚀量(P<0.01),在9,15 m/s风速试验条件下,前期土壤冻融作用使土壤风蚀量分别增加1.02,1.44倍;也显著增加了距地表不同高度的风蚀输沙总量(P<0.01),在9,15 m/s风速下前期土壤冻融作用使风蚀输沙率分别增加1.71,1.04倍;前期土壤冻融作用对土壤风蚀的贡献率在2个试验风速下分别为100.0%和140.0%。前期土壤冻融与风蚀叠加作用明显增加了坡面水蚀量。其中,在3°和7°条件下,前期土壤冻融和风蚀叠加作用试验处理的坡面水蚀量较之无前期冻融也无风蚀作用的试验处理分别增加11.9%和20.6%;且在2个坡度条件下前期土壤冻融和风蚀叠加作用对坡面水蚀的贡献率分别为11.9%和20.6%。前期土壤冻融作用减弱了土壤抗侵蚀能力,其中土壤容重减小3.42%,<0.25 mm的风干团聚体增加14.1%,而>1.0 mm的风干团聚体减少15.1%;同时,前期风蚀作用使地表产生了凹痕和条纹等微地形,进一步增加坡面降雨侵蚀和径流侵蚀能力,从而导致前期冻融作用和风蚀共同作用增加坡面土壤侵蚀的严重性。研究结果可为黑土区多营力复合侵蚀防治提供重要科学依据。

An Experimental Study on Freeze-thaw, Wind and Water Agents Impacts on Hillslope Soil Erosion in Chinese Mollisol Region

Compound soil erosion caused by various external forces is the main erosion characteristic of sloping farmland in Chinese Mollisol region.However,there are few reports on the quantitative study of interaction between freeze-thaw,wind and water-hydraulic on compound soil erosion.Thus,indoor freeze-thaw simulation,wind tunnel test and indoor simulated rainfall experiments were conducted to analyze previous freeze-thaw,wind and water agents impacts on hillslope soil erosion in Chinese Mollisol region.A series of experiments were designed,including test without previous freeze-thaw action and only wind erosion(Ⅰ),previous freeze-thaw action first and late on wind erosion test(Ⅱ),only water erosion(without previous freeze-thaw action and without wind erosion test)(Ⅲ),previous freeze-thaw test first,then followed by wind erosion test,and late on water erosion test(Ⅳ),so as to distinguish the contribution of previous freeze-thaw action to wind erosion,and the contribution of previous freeze-thaw and wind superposition action to slope water erosion.The results showed that the previous freeze-thaw action significantly increased the wind erosion amount on the slope(P<0.01).At the wind speed of 9 m/s and 15 m/s,the previous freeze-thaw action increased the amount of wind erosion by 1.02 and 1.44 times,respectively.It also significantly increased the total amount of wind erosion sediment transport at different heights from the soil surface(P<0.01).Under the two wind speeds,the previous freeze-thaw action increased the wind erosion sediment transport rate by 1.71 and 1.04 times,respectively.And the contribution rate of previous freeze-thaw action to wind erosion was 100.0%and 140.0%respectively at the two test wind speeds.The previous freeze-thaw and wind superposition action obviously increased the amount of water erosion on the slope.Compared with the treatment without previous freeze-thaw and wind superposition action,the amount of water erosion on the slope of previous freeze-thaw and wind superposition action increased by 11.9%and 20.6%respectively under 3°and 7°degree.Under the two gradients,the contribution rate of previous freeze-thaw and wind superposition action to slope water erosion was 11.9%and 20.6%respectively.Previous freeze-thaw action weakened the soil erosion resistance,after previous freeze-thaw action,the soil bulk density decreased 3.42%,less than 0.25 mm of dry aggregate increased by 14.1%,greater than 1.0 mm of dry aggregate decreased by 15.1%;Meanwhile,the early stage of the wind erosion produced a dent in the earth's surface and stripe micro topography,further increase the slope rainfall erosion and runoff erosion ability,as a result,the previous freeze-thaw action and wind erosion increased the severity of sloping soil erosion.