在大西洋西北岸的美国部分地区,由于冻土造成的较低渗透率是影响径流、土壤侵蚀和淤积的主要原因。我们在1984年秋季,冬季和土壤解冻后的春季进行了渗透试验,试验仪器主要是人工模拟降雨机和土壤渗透测定仪,在三种耕作处理,即高茬、松土茬和夏季休闲后新播种冬小麦的耕地上进行土壤渗透试验,测出了土壤渗透曲线。在上冻以后测量冻土的渗透率,要求渗透到预定深度。松土茬处理后非冻土土壤最终渗透率是最大的,冬小麦耕地的最终渗透率最低。在秋季、春季测量松土茬,高茬处理的冻土渗透率都是较低的,而在土壤上冻后的冬小麦耕地里测量。则根本没有渗透。 在大西洋西北岸的美国西部山区的冬季,土壤冻结会影响径流和土壤侵蚀。这些地区四季变化很明显,冬季寒冷、潮湿,有的地区还干燥,夏季炎热。冬季降雨强度很低,通常小于4mm/h。下雪也不太大。每年冬天土壤冻结以后都会出现几次融化现象,一般每天都是在地表面几毫米深度范围内出现冻结——融化现象。特别是在未加保护的耕地中更为明显。有关资料表明冻结——融化循环是降低土壤表面抗剪强度,增加土壤可蚀性的一个重要因子。 上冻后土壤结构和上冻期间土壤含水量都会影响冻土渗透率。水分含量较低的冻土上冻后变成颗粒状,对入渗产生较轻微影响。相反冻土水分 In parts of the United States on the northwestern Atlantic, the lower permeability due to frozen soils is the main cause of runoff, soil erosion and siltation. We conducted infiltration tests in the autumn of 1984, in the spring and in the spring after thawing of the soils. The test instruments were mainly artificial simulated rainfall machines and soil infiltration testers. After three kinds of tillage treatments, that is, high-stubble, loose stubble and summer after-break Soil infiltration test was conducted on the sown fields of winter wheat and the soil infiltration curve was measured. The permafrost permeability is measured after freezing, requiring penetration to a predetermined depth. The ultimate permeability of soil after non-permafrost treatment is the largest, the final permeability of winter wheat is the lowest. In the autumn and spring, loose soil was measured, while permafrost treated with high-stubble soil had a lower permeability and was measured in winter wheat fields frozen on soil. There is no penetration at all. In the winter months in the western part of the Atlantic on the northwestern Atlantic, soil freezing can affect runoff and soil erosion. The seasonal changes in these areas are obvious, the winter cold and humid, and some areas are also dry, summer hot. Winter rainfall intensity is very low, usually less than 4mm / h. Snow is not too big. There are several thawing events that occur after freezing the soil each winter, and freezing-thawing occurs at a depth of a few millimeters every day on the ground. Especially in unprotected arable land is more obvious. Relevant data show that freeze-thaw cycles are an important factor in reducing soil surface shear strength and increasing soil erodibility. The structure of the soil after freezing and the soil moisture during the freezing will affect the permafrost permeability. Frozen permafrost with lower moisture content becomes pelletized after freezing, which has a slight influence on infiltration. In contrast to frozen soil moisture