Changes in soil infiltration and water flow paths: Insights from subtropical forest succession sequence

Maintaining and improving the water conservation capacity of forest ecosystems is an important step in building regional ecological protection barrier. At present, there is a lack of knowledge about the patterns of soil water flow in different stages of forest succession. Therefore, this study quantified the change tendency of soil infiltration and water flow paths in subtropical different forest types, including pine forests (PF), mixed pine and broadleaf forests (MF) and monsoon evergreen broadleaf forests (BF), and analysed the effect of soil physical properties on hydraulic properties. Results showed that (1) both BF and MF were characterized by a smaller bulk density and the larger porosity than PF. (2) The saturated hydraulic conductivity of BF and MF was 2.1 times and 3.1 times higher than that of PF, respectively, showing that there were clear differences in the soil infiltrability resistance of the different forest types. The observed soil water exchange amount also showed that both BF and MF had higher water holding capacity than PF. (3) Macropore flow and lateral flow were the dominant preferential flow behaviors, but the degree of preferential flow did not evolve along succession sequence PF, MF and BF. The pattern of soil water flow was found to show obvious spatial variability, restricted by the joint influence of soil porosity, root systems and rocks. The above results suggest that soil infiltration improve with the sequence of forest succession, but that soil water flow patterns may be independent of forest succession due to the complex conditions of the soil. This study provided effective data information of forest soil hydrological antecedents.