Substrate utilisation profiles of microbial communities in peat are depth dependent and correlate with whole soil FTIR profiles

A multiple substrate induced respiration (SIR) assay, using 14C-labelled carbon sources, was used to evaluate community level physiological profiles (CLPP) of the microbial community in peat horizons of differing degrees of humification. The separation and grouping of the peat horizons by CLPP was similar to the pattern produced by analysis of the organic carbon chemistry of the peat horizons by Fourier Transform Infrared (FTIR) spectroscopy and therefore reflected the level of decomposition. Partial redundancy analysis showed that a large proportion (68.7%) of the variability in the CLPP data could be attributed to the ratio of polysaccharide to ‘carboxylate’ FTIR bands alone. The multiple substrate SIR technique may, therefore, be a powerful technique to further elucidate the influence of the microbial constituent of peat on the potential activity and patterns of cycling of labile carbon in peatlands.