Ground vegetation, forest floor and mineral topsoil in a clear-cutting and reforested Scots pine stands of different ages: a case study

Scots pine (Pinus sylvestris L.) is a dominant tree species on nutrient-poor sandy soils in the Baltic region's hemiboreal forests. A final clear-cut in commercial stands is a common practice. However, the maintenance of relatively stable vegetation indices and ecological processes throughout the rotation promote new scientific and social debates. Overall, clear-cuttings disturb forest functions for a certain period, i.e., phytocenoses with forest-based species composition, biodiversity, and vegetation cover. Soil organic carbon (SOC) and nutrients can also be affected. As key indices, ground vegetation, SOC and main nutrients in the forest floor and in 40-cm topsoil layer were analysed in the clear-cuttings (not reforested) and in reforested 10-, 30-, and 101-year-old Scots pine stands in 2020. The results show an increase in species richness at the beginning of stand formation up to 30 years after clear-cutting; species typical of a mature forest occurred relatively quickly post-harvest. The mean mass of forest floor vegetation was negatively related to the richness of ground vegetation species. Forest floor pH consequently decreased with stand age. Higher SOC levels were in the mature stand. In the mineral topsoil layers, total SOC and total nitrogen were in the upper 10-cm layer in the 30-year-old stand. A post-harvest peak in mineral N concentration was observed and other nutrients, especially mobile P2O5, K2O, Ca2+ and Mg2+, increased the clear-cuttings and in the 10-year-old stand compared to the mature stand.