淮北平原典型砂姜黑土优先流形成机理研究

Soil preferential flow, a fast translocation, non-equilibrium form of water movement in heterogeneous soils, has significant effects on rainfall infiltration, moisture distribution, and hydrological and ecological process. At the pedon scale, the function-structure separation model which commonly used can’t explain the evolution law of preferential flow path, and how preferential flow path affect the preferential flow. The lime concretion black soil (LCBS) is characterized by the cracks in the surface soil and lime concretion in the lower one. Under the alternating wet and dry conditions, the formation of preferential flow would be markly different between the surface soil and the lower one. In order to reveal relationship between the morphological characteristics and formation mechanism of preferential flow path, with the typical LCBS in the Huaibei Plain taken as to experimental object, the dye tracer and hydraulic monitoring in weighed lysimeter will be employed. Based on the assumption that the degree of preferential flow is associated with the zonal distribution of preferential flow path, preferential flow type will be identified by its structural characteristics firstly. The relationship between preferential flow type and preferential flow degree in different soil layers will be analyzed as follow, which can verify the coupling effect of “structure-function” parameters. Lastly, the relationship between the preferential flow and the acting factors such as rainfall and irrigation will be established, following with quantitatively assessment of the motivaing factors of the preferential flow. Through this research in LCBS, the process of rainfall infiltration and soil moisture infiltration will be cognized fatherly, which will provide a theoretical basis for precise management of water and fertilizer in LCBS area.

优先流是非均质土壤中快速、非平衡的水分运动形式，影响降雨入渗、土壤水分分布、水文及生态过程。在土体单元尺度下，“结构~功能”分离是优先流形成机理研究的常见模式，该模式尚不能回答优先流演变规律、优先路径如何影响优先流程度等科学问题。砂姜黑土土体结构呈层状分布，干湿交替条件下，表层土壤的裂隙、下层土壤的砂姜状结核以不同机制激发优先流的形成。基于优先流程度与优先路径层状分布相关联的科学假设，以淮北平原典型砂姜黑土为研究对象，统筹大田染色示踪、大型蒸渗仪等实验手段；以反映优先路径的优先流类型识别为基础，建立优先流类型的分层结构；解析不同土层中优先流类型~优先流程度关系，识别优先路径对优先流程度的作用机制；构建优先流程度与降雨、灌溉等激发因子的关系，定量评估优先流程度及影响因子。通过砂姜黑土优先流形成机理研究，深化土壤水分入渗的过程认识，为砂姜黑土区水肥精准化管理提供理论依据。

优先流是非均质土壤中普遍存在的一种土壤水分运动形式。砂姜黑土具有典型的非均质土壤，干缩湿涨特性造成受旱时易发育裂隙，并且在土层中分布有钙质结核砂姜。.本研究以淮北平原典型砂姜黑土为研究对象，提出基于染色示踪实验形态学解析的优先流类型识别、基于大型蒸渗仪水力观测实验的优先流程度定量评估方法，开展了砂姜黑土水力参数测定、原位入渗、大型原状土柱染色示踪、大型蒸渗仪水力穿透等实验研究，揭示了砂姜黑土分层土壤优先流机理，评估了砂姜黑土分层土壤优先流类型与优先流程度的定量关系，初步回答了砂姜黑土优先流程度和激发因子的响应关系。.本研究结果表明：（1）砂姜黑土初渗率高达140~180mm/h，由于砂姜黑土裂隙、垂向纹理发育，砂姜黑土初渗率较之黄潮土（砂土）高。（2）砂姜黑土不同层位土壤质地均为粉质粘土，但各层位土壤容重、颗粒集配、土壤水分特征曲线差异性较大。（3）初始条件为田间持水量的砂姜黑土土体，在自然风干条件2-3天后，土壤表层即发育有细纹状的裂隙，随着时间推移，细纹装裂隙宽度、网络密度加大，且向深层土体延伸，深层土体以大裂隙为主，细纹状裂隙基本无发育。降雨初期以裂隙为形态的优先路径是深层渗漏的主要通道。在初始条件、环境条件相同情况下，砂姜黑土耕作层土壤裂隙的发育速度较之深层土壤的要快。（4）在湿润条件下，砂姜黑土耕作层优先流基本不发育，水流均匀性较好；在达到田间持水量时，耕作层土壤开始发育细裂隙，形成一些优先流通道，裂隙连通度不高；随着土壤含水率进一步下降，裂隙网络向深层展布，裂隙发育的最大深度达到0.5m。（5）土体表层水力穿透曲线的非对称性程度要比深层土壤的要高。.本研究构建了砂姜黑土分层位土壤水力参数数据库、时域反射仪类土壤水分传感器响应关系曲线，研发了土壤不均匀渗漏监测装置、分层淋溶装置、土壤水分传感器标定方法及设备，初步揭示了砂姜黑土优先流形成机理等研究成果，对农田水文实验研究、区域水循环研究具有推动作用。