Soil microbial community response to variation in vegetation and abiotic environment in a temperate old-growth forest

• Changes of soil microbiota in relation to abiotic and biotic environment in a forest reserve are shown.
• Mutual links between the above- and belowground components of a forest ecosystem exist.
• Beta diversity of microorganisms is higher in an old growth than in a commercial stand.
• Microclimate affects soil microorganisms less than the availability of organic material.
• Soil microbiota prefers a diverse ground-layer vegetation rather than a diverse tree layer.

Changes of soil microbial community caused by the heterogeneity of abiotic and biotic environment were studied in the reserve Dobroč, Slovakia. Data on vegetation, microclimate, soil properties and microbial activity were collected on two linear transects crossing both the core of the reserve and the buffer zone.In contrast to expectations, the variation of most environmental variables was comparable or even higher in the buffer zone than in the old-growth forest. Beta diversity was much higher in the natural forest, which coincided with differentiation patterns of trees and understory plants.Mantel correlations between microbial community indicators and environmental variables showed that soil chemistry and vegetation diversity were the most important determinants of microbial activity. Redundance analysis of microbial data identified potassium content, plant richness and influence of fir as the drivers of functional group composition. Inconsistency of correlations of microbial community characteristics with environmental variables indicates that different processes associated with the demography and functions of microbiota are driven by different environmental factors. Amount and variety of substrates available for decomposition seems to influence microbial community more than microclimate.