Impacts of intercropping tea trees under forest on soil water infiltration in the northern of Dabie Mountains

Soil water infiltration, a hydrological process, can be significantly dominated by land use types (vegetation cover). There is also some impact on the formation and distribution of slope runoff, soil moisture regulation, water conservation, and soil conservation. This study aims to investigate the impact of slope economic forest development on soil water infiltration, in order to determine the main influencing factors on the soil water infiltration. Field surveys and visits were carried out as well. Four cultivation modes were selected from Jinzhai County, Anhui Province, including Castanea Mollissima forest, Castanea Mollissima with tea interplanting, Camellia Oleifera forest, and Camellia Oleifera with tea interplanting, with Miscellaneous Wood forest as the control. Indoor experiments were then combined with field investigations. A systematic analysis was implemented to explore the main influencing factors of soil water infiltration, including the soil bulk density (BD), porosity, soil mechanical composition, soil organic matter (SOM), soil aggregate structure, and soil water infiltration characteristics (Initial infiltration rate, steady infiltration rate, average infiltration rate) under different cultivation modes. Meanwhile, four models were selected to evaluate their applicability under different cultivation modes, including Philip, Kostiakov, Kostiakov-Lewis, and Horton. The results showed: 1) The soil water infiltration significantly decreased after the cultivation of slope economic forests into Castanea Mollissima forest, Castanea Mollissima with tea interplanting, Camellia Oleifera forest and Camellia Oleifera with tea interplanting. The average infiltration rate (AIR), initial infiltration rate (IIR), and stable infiltration rate (SIR) decreased by 46.14% to 64.88%, 39.60% to 58.97%, and 49.88% to 72.84%, respectively. The initial infiltration rate and stable infiltration rate were ranked in the descending order as follows: Miscellaneous Wood forest, Castanea Mollissima with tea interplanting, Camellia Oleifera with tea interplanting, Castanea Mollissima forest, Camellia Oleifera forest; There was no significant difference in the average infiltration rate between Castanea Mollissima with tea interplanting and Camellia Oleifera with tea interplanting (P>0.05). 2) Miscellaneous Wood forests shared the higher soil porosity, soil organic matter, clay content, mean weight diameter (MWD), and geometric mean diameter (GMD), indicating large aggregate content, higher soil stability, and lower bulk density and fractal dimension (D), compared with Castanea Mollissima forest, Castanea Mollissima with tea interplanting, Camellia Oleifera forest, and Camellia Oleifera with tea interplanting; 3) The initial, average, and stable infiltration rate were significantly negatively correlated with the soil bulk density, sand content, mechanical stable aggregate 1-2 mm, mechanical stable aggregate 0.5-1 mm, water stable aggregates 1-2 mm, and water stable aggregates 0.5-1 mm (P<0.05). There was a significant positive correlation with the soil organic matter, capillary porosity (CP), non-capillary porosity (NCP), total porosity (TP), powder particles, clay particles, mechanical stable aggregate>5 mm, 0.25-0.5 mm, MWD, GMD, D, water stable aggregates>5 mm, 2-5 mm, 0.25-0.5 mm, MWD, GMD, and D. The path analysis showed that the mechanical stable aggregate>5 mm, water stability aggregate MWD, and mechanical stable aggregate MWD were the main influencing factors on soil water infiltration, while the mechanical stable aggregate>5 mm was the main influencing factor. 3) The goodness of fit of the infiltration was ranked in descending order as follows: Kostiakov model > Philip model > Horton model > Kostiakov-Lewis model, according to the coefficient of determination R², RRMSE, CRM, and CE. The Kostiakov model was the most suitable to describe the actual situation of soil infiltration in the northern Dabie Mountains. The findings can also provide a strong reference for the cultivation modes