冻融对长白山暗棕色森林土大孔隙及大孔隙流的影响研究

Distribution feature of soil macropore is one of the key factors in soil water movement. How to control distribution feature of soil macropore accurately and clarify its influence on mechanism of soil moisture movement has always been considered to be hot issues in subject research, such as Soil Physics and Soil Water Dynamics. Currently the relevant researches are mainly concentrated on macropore distribution characteristics and migration regularity of preferential flow of different soil types. However, researches on characteristic diversification of macropore to freeze-thaw, and on impact machnismes to soil moisture movement caused by the diversification procedure are still in blank. Typical seasonal frozen soil of broadleaved Korean pine forest in Changbai Mountain, the main forest types in China northeast temperate humid climate, is selected to be the research object. This research takes advantage of the combination of field observations and laboratory simulation, and uses advanced observation techniques to study time dynamics of macropore diffusion feature in seasonal frozen soil and to clarify impact of macropore diffusion feature on soil moisture movement, and reveal diffusion characteristic as well as impact mechanisms on water movement caused by freeze-thaw. Through this study, redistribution mechanism of dark brown forest soil to precipitation will be understanded accurately. In addition, the theory basis of evaluating the function accurately of forest water conservation will be provided. Besides, Hydrology, Soil Physics and Soil Water Dynamics will be developed further due to this study.

土壤大孔隙分布特征，是土壤水分运动的关键因素之一。如何准确掌握土壤大孔隙分布特征，阐明其对土壤水分运动的影响机制，一直是土壤物理学、土壤水动力学等学科研究的热点问题。目前相关研究主要集中在不同土壤类型大孔隙分布特征及其优先流运移规律上，对冻融造成的大孔隙特征变化，以及这种变化过程对土壤水分运动的影响机理的研究上，尚属空白。本研究以我国东北中温带湿润气候区最主要的森林类型-长白山阔叶红松林的典型季节性冻土为研究对象，通过野外观测与实验室模拟相结合的方法，利用多种先进观测技术，研究季节性冻土大孔隙分布特征的时间变化过程，阐释大孔隙分布特征变化对一维土壤水分运动的影响，揭示冻融改变土壤孔隙分布特征及其对水分运动的影响机制，为准确掌握暗棕色森林土对降水的再分配作用机制，准确评价森林的水源涵养功能提供理论依据，发展水文学、土壤物理学与土壤水动力学。

通过对长白山阔叶红松林土壤的人工冷冻模拟实验，研究了不同含水率、不同质地、层深的土壤在冻结条件下的膨胀率。结果表明：膨胀率随含水率呈线性递增趋势，含水率30%、40%和50%的土壤冻结后的膨胀率分别是20%含水率土壤的2.3、3.7、4.3倍。土壤含水率每增加1%，土壤体积膨胀率增加0.3211‰。在土壤含水率为50%状态时，4种土质的冻胀率均值分别为：深灰色粘壤土31‰，浅灰色粉沙粘土23‰，浅灰色粘土11‰，暗棕色粘土8‰。冻胀率随土层纵深增加呈降幂递减趋势，表层土壤（0-30cm）的冻胀率占整个冻土层（约1.2m）冻胀率的50%以上。本项目在科研工作者共同努力下，获得较多的研究成果，完成情况良好。