Denoting the intensity of soil biochemical transition according to stand species composition

The aim of this study was to denote biochemical soil activity in pure Scots pine, Norway spruce, silver fir, European larch, European beech and oak stands as well as in mixed fir-pine, beech-pine and fir-beech forests growing on a fertile fresh mixed deciduous site. The field work was carried out in the following Forest Districts: Nowe Ramuki (Mazursko-Podlaska forest region), Płońsk, Jabłonna, Brzeziny Siedlce, Grójec (Mazowiecko-Podlaska forest region) and Skarżysko, Ostrowiec and Marcule (Małopolska forest region). In 2015–2017, sample plots were assigned and chemical as well as soil enzyme activity measurements were made in each forest stand. Samples were taken from the organic (O) and humus (A) layers and for both the acidity (in 1M KCl), content of nitrogen, carbon, sum of exchangeable alkaline cations and hydrolytic acidity were determined. The investigation of soil enzymes included the measurements of urease, asparginase, acid phosphatase and dehydrogenase activity. Coniferous trees, especially fir, spruce or larch, and mixed fir-beech and pine-beech stands were observed to have a very positive influence on the biochemical soil properties. The highest activity of dehydrogenase was observed in soils of spruce and mixed fir-beech stands, whereas it was lower in soils of beech and pine stands, and the lowest in oak stands. Oak stands were furthermore characterized by the lowest soil acidity, lowest concentration of alkaline cations, the lowest nitrogen and carbon content as well as the smallest C/N ratio. In overall, soil enzyme activity showed a significant correlation with chemical soil parameters