Impacts of Subtropical Forest Type Conversion on Soil Hydrophysical Characteristics

［Objective］ In order to investigate the effects of forest type conversion on the hydrophysical characteristics of forest soils. ［Methods］ The effects of forest type conversion on soil porosity, permeability, and matric potential, using subtropical natural evergreen broad-leaved forests and the secondary forests were compared, Castanopsis carlesii artificial forests, and Cunninghamia lanceolata artificial forests derived from them as research subjects. ［Results］ 1) After forest type conversion, total soil porosity in the lower soil layer of secondary forests significantly increased by 5.43% compared to natural forests. Soil matric potential also significantly increased in C. lanceolata artificial forests during the dry season by 5.01 kPa compared to natural forests. However, the variation of soil permeability in different forest types was not significant. 2) In the 0~40 cm soil layer of the four forest types, soil particles were mainly dominated by sand particles, but only clay particles and silt particles showed a significant correlation with total soil porosity, and soil particle composition was not the controlling factor for soil water-holding indicators under forest type conversion. 3) The main controlling factors for soil water-holding indicators were soil bulk density and soil moisture, with significant correlations between soil bulk density and each water-holding indicator, while forest conversion leaded to changes in soil bulk density and soil moisture, thereby causing changes in soil water-holding performance. ［Conclusion］ Forest type conversion has a significant impact on the hydrophysical parameters of subtropical region soils, with the conversion from natural forests to secondary forests being beneficial for water conservation or soil retention, and conversion to C. lanceolata artificial forests requiring soil amelioration measures to optimize their water retention and permeability. The results can provide a theoretical basis and data support for sustainable management of subtropical forests and water conservation.