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土地利用类型对内蒙古盐碱地土壤大孔隙特征的影响

Effects of land use types on the macropore characteristics of saline-alkali soil in Inner Mongolia Region of China

  • 摘要: 为探究内蒙盐碱地不同土地利用类型下土壤大孔隙特征及其差异,结合CT扫描和图像处理技术对稻田、葵花地、盐荒地的土壤大孔隙结构进行三维重建和参数量化表征。结果表明,稻田以短小密集孔隙为主,葵花地及盐荒地以长粗稀疏孔隙交错为主。土壤孔隙度随土层深度的增加而减小,土壤孔隙主要集中在3.8~15cm土层,该土层孔隙度变化范围为7.59×10−3~24.83×10−3 mm3/mm3,稻田土壤总孔隙数、孔隙总表面积、孔隙总长度、分形维数整体上高于葵花地和盐荒地。葵花地土壤大孔隙连通性优于稻田及盐荒地,其分支节点密度高达2.87个/cm3;从等效水力半径来看,盐荒地、葵花地、稻田的水力传输能力依次减弱。土壤孔隙复杂程度与孔隙总表面积、孔隙度、孔隙总体积、孔隙总长度、总孔隙数相关性较高,相关系数变化范围为0.84~0.97。不同土地利用类型影响了盐碱地土壤孔隙结构特征及复杂程度,该研究有助于完善对盐碱地土壤孔隙结构的认识,可为土壤水盐运移理论研究及盐碱地改良提供基础支撑。

     

    Abstract: Macropore structures can directly influence the hydraulic properties and solute transport in saline-alkaline soil, particularly in the stability and complexity. It is very crucial to explore the pore structure and its characteristic parameters for the better quality of the arable land. Therefore, this study aims to quantitatively analyze the structural parameters of the soil pores under different land-use types. Computed tomography and AVIZO image processing were used for the three-dimensional reconstruction and visualization of the soil pore structures in the paddy, sunflower field, and saline Wasteland. The results indicated that the paddy fields were characterized primarily by small and compact pores, indicating a relatively simple pore structure. In contrast, the sunflower field and saline wasteland shared sparse, large, and interconnected pores, indicating the more complex structures of the soil pore. Furthermore, the vertical extent of the soil pores in the sunflower field was lower than that in the saline wastelands. The total number of the macropore, total macropore volume, total macropore surface area, and macropore length in the paddy field were all higher than those in the sunflower field and saline wasteland. The porosity of all three land-use types decreased with the increasing soil depth, which was primarily concentrated in the 3.8~15 cm surface layer. The porosity of the 3.8~15 cm layer was 2.58 to 5.95 times that of the 15~38.6 cm layer. Across the 3.8~38.6 cm soil layer, the paddy field exhibited the highest macroporosity of9.82×10³-9.90×10³ mm³/mm³,, while the saline wasteland shared the widest macroporosity range of 6.07×10³-10.33×10³ mm³/mm³. The greater fractal dimension (1.93~1.94) and tortuosity (1.5~1.19) were observed in the paddy field, compared with the sunflower field and saline wasteland. The connectivity of the soil macroporosity in the sunflower field was superior to that in the paddy field and saline wasteland, with a branching node density of 2.05 number/cm³. The number of segments also reached up to 8472. The equivalent hydraulic radius of the saline wasteland reached up to 1.37 mm. Furthermore, spatial heterogeneity was observed in the soil structural parameters among the samples of the same land-use type. The complexity of the soil pores was highly correlated with the total pore surface area, porosity, total volume, total length, and total number of pores, with correlation coefficients ranging from 0.84 to 0.97. Different land use types significantly dominated the pore structure of the saline soil. These findings can also provide valuable insights to explore the effects of the soil pore structure on the soil water and salt transport in the saline-alkali land.

     

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