Assessment of soil microbial communities involved in cellulose utilization at two contrasting Alpine forest sites

Soil microbial communities involved in 13C-labeled cellulose utilization from two contrasting (in terms of vegetation and climatic conditions) forest sites at different elevations were studied by using a laboratory microcosm experiment and a PLFA (phospholipid fatty acid)-SIP (stable isotope probing) approach considering the effects of incubation temperature (0, 10 and 20 °C) and time (1–4 weeks). The amounts of cellulose-13C assimilated by soil microorganisms and the composition of microbial communities utilizing cellulose were site-dependent. Total, bacterial and actinobacterial biomass incorporated higher amounts of 13C in soil from the deciduous forest site (at the lower elevation), while fungal biomass contained increased amounts of 13C in soil from the coniferous forest site (at the higher elevation). Increasing temperatures resulted in increased amounts of 13C assimilated by the different PLFA-based microbial groups, except fungi, and in significant changes in the community structure of cellulose utilizers. Fungi were better adapted to cold conditions than bacteria. Longer incubation times determined an increase in the amount of 13C incorporated into total and bacterial PLFAs but had no effect on the composition of labeled microbial communities.