Afforestation of agricultural land affects soil structural stability and related preconditions to resist drought

Afforestation is important for the EU forest management strategy. Afforestation of abandoned and marginal arable land is a favourable non-agricultural land use option for climate change mitigation. It may prevent threats of drought or erosion e.g. by affecting the water balance in soil via increased structural stability. The structural stability control in afforested soil is related to i.a. organic matter content, nutrient content, soil reaction, planted tree species prosperity, and amelioration. A four-year field small-plot experiment on afforestation was carried out with Chernozem covered with deciduous (oak), coniferous (pine) or mixed planting, amended with 3 doses (no-application, 0.5 kg×m-2, and 1.5 kg×m-2) of alginite. In 2013 and 2016, soil reaction pHH2O, mean weight diameter (MWD), organic matter content (LOI) and total organic carbon (TOC) were determined and related to the soil structural stability to evaluate the soil precondition to sustain drought twice per vegetation period (spring and autumn). Afforestation significantly improved MWD compared to the field soil between 2013 and 2016 from 1.63 ± 0.04 mm to 1.85 ± 0.05 mm. Tree planting significantly neutralized the soil pHH2O, mixed planting appeared to improve LOI and TOC. Four-year afforestation led also to higher structural stability, less alkaline pH and deciduous tree-related increase in LOI, which may indicate better soil sustainability to drought.