【作者】 张蔚；

【导师】 蒋志荣；

【作者基本信息】 甘肃农业大学 ， 水土保持与荒漠化防治， 2008， 硕士

【摘要】 塑料薄膜覆盖是提高土壤地温,保持土壤墒情的有效措施,这是通过阻断水分流通,改变土壤对太阳辐射的吸收-反射比率和地表长波辐射系数,以调节地面吸热和蒸发条件,达到改善地层水分和热状况的方法。本文就该方法在位于深季节冻土区的祁连山林区的适应性问题,包括促进融化和提高土温的效果进行了初步的分析。(1)通过分析最新相关文献资料,总结不同坡向、不同坡度、不同下垫面形式等条件对冻土区土壤的水热状况的影响规律;(2)总结了根据气象学基本原理和太阳辐射原理从理论上计算土壤表面的直接太阳辐射强度;以及考虑海拔高度和纬度影响的不同坡向、坡度下的气温计算方法;(3)在以上工作的基础上,利用分析软件计算了裸地在年内的冻融过程特点,并和实测资料比较验证了方法可行性。然后根据祁连山林区的具体气象和地理参数,对覆盖影响下的冻融过程进行了模拟计算,发现覆盖能减小最大冻结深度,提前表层融化时间。更多还原

【Abstract】 Polyethylene mulch is an efficient method for raising soil temperature and maintaining soil moisture content, which has been widely used worldwide to improve the hydrothermal regime of soil and increase crop yield, as it eliminates evaporation by blocking moisture transfer and has a greenhouse effect on the underlying soil by changing the albedo of the ground surface and influencing the long wave radiation from the ground surface. Here we study the applicability of this method in the forest regions in the Qilianshan Mountain, including its ability to promote soil thawing and improve soil temperature.(1) Based on a thorough retrieval and systematic analysis of the related literature, the effects of different factors on the hydrothermal regime of soils are reviewed;(2) The method for calculating the net radiation on soil surface according to the basic principle s of meteorology and solar radiation theory, and that for calculating the air temperature at different latitude and elevation with various slopes are summarized(3) The annual freezing-thawing cycle from a bare soil surface is simulated using a commercial software with the appropriate climate and other factor values of the forest regions in the Qilianshan Mountain, and the results compared are with in situ data in the literature to prove applicability of the method and validity of coefficient values. Then, the thermal regime in the ground covered by Polyethylene mulch using the same simulation method and coefficient values, it is found that Polyethylene mulch can decrease the maximum frozen depth and accelerate the thawing from the frozen ground surface in spring.更多还原