The establishment of a secondary forest in a degraded pasture to improve hydraulic properties of the soil

The recovery of soil hydraulic properties after the conversion of pasture areas into forests is still poorly studied. The aim of this research was to evaluate the effect the vegetation has on the hydraulic properties of soil, as well as the physical and chemical properties of the soil in pasture and secondary forest areas, located in a hill with east and west sun exposed faces. The study was carried out in two 15-year-old secondary forest areas and two pasture areas. Undeforrned soil samples were collected in the upper third of each slope using steel rings at depths of 0-10 cm, for laboratory analyses of the physical properties and the saturated hydraulic conductivity of the soil. Additional samples were collected to evaluate the total organic carbon, the carbon storage and the chemical characteristics of the soil. A tension infiltrometer was used to determine the hydraulic properties and the contribution of the macropores to the infiltration of water into the soil. The use of a unmanned aerial vehicle helped to identify the soil cover at different locations and different faces of sun exposure. Secondary forests showed the higher values of macroporosity, soil water infiltration, and carbon storage than pasture areas. Macropores had greatest contribution to soil water infiltration in the secondary forests, whereas the mesopores and micropores had greatest effect in the pasture areas. The high content of organic matter found in the forests resulted in soils with better chemical quality. The saturated hydraulic conductivity and the carbon storage of the soil were smaller in the western forest than eastern forest. These results indicate that in order to increase water flow and water quality it is required to encourage the use of vegetative practices such as silvopastoral systems in pastures and the revegetation of the upper third of the hills.