Soil hydrological function at different vegetation restoration stages in purple soil slopelands in Hengyang

Soil hydrological functions at different vegetation restoration stages in purple soil slopelands in Hengyang were explored by using spatial series in replace of temporal series. The results showed significant increases (P < 0.05) in soil water storage capacity and permeability from bare-land (CK) to grassland stage (Ⅰ), bushwood and grassland stage (Ⅱ), bushwood (Ⅲ) and to arbor and bushwood stage (Ⅳ). The orders of initial and stable infiltration rates were respectively arbor and bushwood stage (IV) (1 347.09 mm·h^-1 and 338.00 mm·h^-1) > bushwood stage (III) (876.98 mm·h^-1 and 323.30 mm·h^-1) > bushwood and grassland stage (II) (834.99 mm·h^-1 and 320.64 mm·h^-1) > grassland stage (I) (729.09 mm·h^-1 and 306.18 mm·h^-1) > bare-land stage (CK) (412.43 mm·h^-1 and 122.98 mm·h^-1). The fitness of Horton infiltration model derived for soil infiltration at each stage was strong (R² ≥ 0.765), and the model was highly applicable. Soil infiltration capability was greatly affected by soil physio-chemical properties and root system. Fine roots (≤ 1 mm in diameter) was effective in improving soil physio-chemical properties, and soil infiltration capability increased with increasing density of the fine roots. Principal component analysis (PCA) showed that from bare-land stage to grassland stage, bushwood and grassland stage, bushwood stage to arbor and bushwood stage, hydrological properties significantly increased (P < 0.05). The order of comprehensive hydrological function was arbor and bushwood stage (IV) (57.45) > bushwood stage (III) (48.54) > bushwood and grassland stage (II) (40.68) > grassland stage (36.81) (I) > bare-land stage (CK) (31.43). The study enriched and broadened vegetation ecology and ecological restoration in the area. It also provided the critical basis for vegetation restoration and reconstruction of ecosystem in purple soil slopelands in Hengyang.