Rapid effects of windfall on soil microbial activity and substrate utilization patterns in the forest belt in the Tatra Mountains

Abstract

The aim of the study was to compare the activity, functional diversity, and community-level physiological profiles of soil microorganisms in light of soil physical and chemical properties in areas where a forest was damaged by hurricane-force winds and in untouched spruce forests of the lower montane belt of the Tatra Mountains (the Carpathians). Foehn winds caused a huge windfall in December 2013. The studied valley was strongly affected by windthrow, but in some places, patches of mature forest did survive. In the studied windthrow area, the first stage of secondary succession can now be observed. Sampling sites were selected in places where the soil was not mechanically disturbed. Soil samples were taken from the organic O and humus A soil horizons and basic soil properties were measured, as were the microbial parameters. Overall microbial activity was determined via the soil respiration rate (R), whereas the microbial biomass was determined via the substrate-induced respiration rate (SIR). Bacterial and fungal catabolic activity, functional diversity (H′), and community-level physiological profiles (CLPP) were determined using Biolog® ECO and FF plates, respectively. Research has shown that 21 months following the studied windthrow, in Hypereutric Skeletic Cambisols developed on calcareous parent material, changes have occurred in some soil properties: soil field moisture in O and A horizons has increased, DOC concentration in O horizons has decreased, and the C/N ratio in A horizons has decreased. The effect of the windthrow episode on overall biological activity was observed in soil A horizons, where overall microbial respiration and SIR biomass decreased. In both O and A horizons, the ratio of bacterial and fungal functional activity (AUCbact/fungi) increased as a result of a fungal AUC decrease. Significant differences in substrate utilization by bacteria occurred between forest-covered soils and windthrow soils in O horizons, where the share of polymer-utilized bacteria activity increased. Rapid effects of windfall on soil microbial parameters expressed mostly in decrease overall microbial activity caused by breakdown in fungal activity. However, those differences are more pronounced in A than in O horizons. In spite of changes in those differences, windthrow did not produce a significant effect on the functional diversity index of microorganisms found in the studied soils.