Moderate effects of tree species identity on soil microbial communities and soil chemical properties in a common garden experiment

Abstract

Knowledge about the effects of tree species on soil physicochemical and microbial properties is crucial for sustainable forest management. The evaluation of these effects in common garden experiments may be advantageous compared to natural conditions due to the reduction of confounding factors such as differences in topography, microclimate, the age of the tree stand, the admixture of other tree species or soil type. In this study, we assessed the effects of 14 tree species grown for nearly 50 years in monospecific plots in the Siemianice Experimental Forest in Poland on soil microbial community assessed by phospholipid fatty acid (PLFA) analysis, namely total, bacterial (G+, G−) and fungal biomass, fungi/bacteria ratio, G+/G− ratio, and microbial community structure, as well as on soil chemical properties, namely pH, organic C, total Ca, K, Mg, N, P, exchangeable Ca, K, Mg, N-NH4, N-NO3, S-SO4, and C/N ratio. Species richness (species number) and cover of undergrowth vegetation were also assessed. We found only moderate effects of tree species identity on soil. Significant differences were found in fungal biomass, fungi/bacteria ratio, and microbial community structure, with the highest fungal biomass under Betula pendula and Quercus rubra. Among chemical parameters, significant differences were observed in soil pH and base cations concentrations. The highest values of these parameters were under Acer pseudoplatanus, A. platanoides, and Tilia cordata. Total microbial, bacterial (G−), fungal biomass, and fungi/bacteria ratio were significantly higher under broadleaf than under coniferous species, while for G+/G− ratio the opposite was observed. Tree species with arbuscular mycorrhiza did not generally differ in their effects on soil microbial biomass from those with ectomycorrhiza. Total microbial and G+ bacterial biomass correlated positively with soil elements, mainly base cations, C, and N, while very few correlations were found between soil chemical properties and G− bacteria and fungi. Species richness and cover of undergrowth vegetation were not related to any of soil microbial properties. The lack of correlations between soil element contents, undergrowth vegetation, and some microbial groups may suggest that these microorganisms are primarily influenced by other soil/litter properties, for example secondary metabolite concentrations.