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半干旱区复垦煤矿不同土地利用类型对土壤结构和水力学特性的影响

Effects of different land use types on soil structure and hydraulic characteristics of reclaimed coal mines in semi-arid areas

  • 摘要: 为探究半干旱区复垦煤矿土壤的水分特征,使复垦矿区土地得到更好的利用,选取复垦矿区还田、还草、还林、自然恢复等4种土地利用方式后的耕地、草地、林地、裸地等4种土地利用类型的土地,对土壤基本物理性质、水分特征曲线、非饱和导水率、水分扩散率进行研究。结果表明:复垦矿区内土壤为砂壤,林地孔隙度、含水量最高,容重和黏粒含量最低,耕地有机质含量最高,裸地有机质含量最低。裸地砂粒含量相对较高,耕地、草地、林地粉粒含量较高,可见通过还田、还草、还林这3种土地利用方式能改善矿区土壤的机械组成。Van-Genuchten (V-G)模型能够较好地拟合矿区土壤水分特征曲线,决定系数R2均大于0.99,土壤毛管重力水随水吸力增加显著下降,在2.5 kPa之前的吸力段持水能力呈现为耕地>草地>裸地>林地,随吸力增大,林地持水能力表现优于其他地类;释水过程主要出现在0~4.8 kPa吸力段,耕地释水能力最好,林地最差。土壤孔隙度与非饱和导水率呈现显著正相关,4种地类非饱和导水率林地>裸地>耕地>草地,林地的土壤结构性最好。土壤体积含水率与水分扩散率均符合D(θ)=Aexp()的经验公式并呈指数曲线变化(A为当含水量为零时的土壤水分扩散能力;B为水分扩散率随含水量的变化速率),水分扩散率D(θ)随土壤体积含水率θ呈指数递增,决定系数R2均大于0.92,林地潜在传输水分的能力最好,裸地水分扩散率随含水率变化最快。研究结果可为半干旱区复垦煤矿的土地利用和生态修复提供理论及数据支持。

     

    Abstract: In order to explore the water characteristics of soil in reclaimed coal mines in semi-arid areas and make better use of the land in reclaimed mining areas, the basic physical properties, water characteristic curves, unsaturated water conductivity and water diffusion rate of the reclaimed mining areas were selected for four types of land use after the four land use modes of reclaimed mining areas: farmland, grassland, forest land and bare land. The results showed that the soil in the reclaimed mining area was sandy soil, with the highest porosity and water content of forest land, the lowest bulk density and clay content, the highest organic matter content in cultivated land and the lowest organic matter content in bare land. The content of sand grain in bare land is relatively high, and the powder content of cultivated land, grassland and forest land is relatively high, indicating that the mechanical composition of soil in mining area can be improved by three land use methods: returning land, grassland and forest. The Van-Genuchten (V-G) model could fit the soil moisture characteristic curve in the mining area well, the coefficient of determination R2 was greater than 0.99, the gravity water of the soil capillary decreased significantly with the increase of water suction, and the water holding capacity in the suction section before 2.5 kPa was shown as cultivated land > grassland > bare land > forest land, and with the increase of suction, the water holding capacity of forest land was better than that of other land types. The water release process mainly appeared in the 0−4.8 kPa suction section, and the cultivated land had the best water release capacity and the worst forest land. Soil porosity and unsaturated water conductivity were significantly positively correlated, and the soil structure of four types of unsaturated water conductivity was the best in forest land > bare land > arable land > grassland. The soil volume moisture content and water diffusion rate conformed to the empirical formula of D(θ)=Aexp() and changed exponentially, and the water diffusivity D(θ) increased exponentially with the soil volume moisture content θ, and R2 was greater than 0.92, and the potential water transport capacity of forest land was the best, and the water diffusion rate of bare land changed the fastest with moisture content. The research results provide theoretical and data support for land use and ecological restoration of reclaimed coal mines in semi-arid areas.

     

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