Soil Enzyme Activity as a Functional Indicator of Biodiversity in Silvopasture Systems

Silvopasture systems, integrating woody components, permanent grasslands, and grazing animals, create spatial habitat diversity that can influence soil biological functioning. Soil enzyme activity, related to microbial metabolism and carbon, nitrogen, and phosphorus transformations, can serve as a functional indicator of changes in soil biodiversity. However, it does not replace direct assessment of the composition or taxonomic richness of soil organisms. The aim of this study was to assess the impact of soil use in silvopasture systems on the physicochemical properties and enzymatic activity of soil. The study included soils used as pasture, permanent grassland, and forest. Samples were collected from the 0–20 and 20–40 cm layers. Soil pH, total organic carbon (TOC) and total nitrogen (TN) contents, as well as dehydrogenase, acid and alkaline phosphatase, and urease activity were determined. The land use method significantly influenced soil pH, TOC and TN contents, and dehydrogenase and phosphatase activity. The highest mean TOC and TN contents were found in the permanent grassland soil—47.72 and 6.12 g·kg⁻¹, respectively—while the lowest were found in the forest soil: 16.40 and 2.81 g·kg⁻¹. The lowest mean dehydrogenase activity was recorded in pasture (4.64 mg TPF·kg⁻¹·24 h⁻¹), while in forest soil it was 18.39 mg TPF·kg⁻¹·24 h⁻¹, and in permanent grassland soil it was 16.53 mg TPF·kg⁻¹·24 h⁻¹. However, in the 0–20 cm layer, the highest dehydrogenase activity was found in permanent grassland (21.72 mg TPF·kg⁻¹·24 h⁻¹). Permanent grassland was also characterized by the highest mean acid (204.12 mmol PNP·kg⁻¹·h⁻¹) and alkaline (204.88 mmol PNP·kg⁻¹·h⁻¹) phosphatase activity. No significant effect of land use on urease activity was demonstrated. The results indicate that land use variation within a silvopasture system influences the biological functioning of the soil and the enzymatic potential of microbial communities. The higher activity of selected enzymes in the soils of permanent grassland and forest, compared to the studied pasture, may indicate more favorable conditions for the functional component of soil biodiversity. However, enzyme activity should be interpreted as an indirect indicator of functional biodiversity, preferably supplemented in the future with direct analyses of microbial diversity.