Soil microbial functional activity is governed by a combination of tree species composition and soil properties in temperate forests

Abstract

Soil microbial community function is influenced, among other factors, by the chemical composition of C substrates, which in turn is dependent on the overlying tree species and the soil environmental conditions. The aim of this study was to examine how different dominant forest species and soil properties are related to soil microbial community level physiological profiles (CLPPs) in temperate forests. Forest floor properties and physico-chemical properties of the topsoil (0–30cm) and the subsoil (30–60cm) were studied in National Forest Inventory (NFI) plots differing in the dominant tree species (Quercus robur L., Fagus sylvatica L., Quercus ilex L. and Pinus radiata D. Don) but affected by similar climatic conditions. Soil microbial functional activity was assessed by the MicroResp analytical system. The only forest floor properties that differed significantly under different tree species were the concentrations of Ca, Mg and K. The forest floor of oak plots was characterized by higher concentrations of Mg and K, and the forest floor in holm oak plots by higher concentrations of Ca than in the other stands. Holm oak plots were also characterized by significantly higher concentrations of topsoil organic matter, nitrogen, phosphorus and potassium than beech, oak and pine, as well as a higher cation exchange capacity. Substrate C respiration was always higher for carboxylic acids than other substrates and the activity of soil microbial communities was higher under beech and holm oak than under oak and pine. The Mantel partial test and forward stepwise regression revealed that the soil microbial activity in the topsoil was mainly related to the topsoil N concentration. Most of the variation in CLPP in the subsoil was related to the concentration of Ca and pH in the subsoil. In conclusion, the soil microbial functional activity was related to both forest species and soil properties