Characteristics of soil saturated hydraulic conductivity and its influencing factors of typical plantations in South Subtropical Zone

  Objective  The changing characteristics and influencing factors of soil saturated hydraulic conductivity in typical plantations were analyzed in South Subtropical Zone, the soil moisture movement law in the soil was studied, which provides basic scientific theoretical support for further study of soil moisture movement law in plantations in this area.

  Method  Taking the soils of Pinus massoniana, Cunninghamia lanceolata, Eucalyptus urophylla × E. grandis, Mytilaria laosensis and Castanopsis hystrix located in the state-owned Gaofeng Forest Farm of Guangxi Zhuang Autonomous Region of southern China as the research objects, the soil saturated hydraulic conductivity (K_s) of plantations was determined by the constant water head method, and mathematical analysis methods such as correlation analysis and grey correlation analysis were used to explore the characteristics and influencing factors of soil saturated hydraulic conductivity of plantation soils in South Subtropical Zone.

  Result  (1) The average saturated hydraulic conductivity of Cunninghamia lanceolata and Pinus massoniana was relatively higher, and the average saturated hydraulic conductivity of Eucalyptus urophylla × E. grandis was the lowest. The soil saturated hydraulic conductivity and soil depth of different plantations had the changing rule of decreasing first and then increasing, in which the saturated hydraulic conductivity of the surface soils was significantly higher than that of deep soils. (2) Correlation analysis result showed that content of organic matter, water stable aggregate content greater than 0.2 mm, total porosity, non-capillary porosity, capillary porosity, saturated water content and content of clay were positively correlated with soil saturated hydraulic conductivity, while soil density was significantly negatively correlated with soil saturated hydraulic conductivity. (3) Grey correlation analysis result showed that content of organic matter, water stable aggregate content greater than 0.2 mm, soil density, total porosity, saturated water content, non-capillary porosity and capillary porosity were important factors, content of sand, content of silt and content of clay were the secondary important factors.

  Conclusion  In comparison to Castanopsis hystrix, Eucalyptus urophylla × E. grandis and Mytilaria laosensis, Cunninghamia lanceolata and Pinus massoniana can significantly increase soil saturated hydraulic conductivity, delay the generation of surface runoff and reduce incidence of soil erosion. Scientific management measures should be paid more attention to effectively improve soil water carrying capacity and water storage capacity.