Characterization of a substrate-induced respiration method for measuring fungal, bacterial and total microbial biomass on plant residues

• Published in: Agriculture, ecosystems & environment ecosystems & environment, 1991-02, Vol.34 (1), p.65-73
• Main Authors: Beare, M.H., Neely, C.L., Coleman, D.C., Hargrove, W.L.
• Format: Article
• Language: English
• Subjects: biomass; measurement; methodology; microorganisms; plant residues; respiration; soil bacteria; soil fungi
• ISSN: 0167-8809; 1873-2305
• DOI: 10.1016/0167-8809(91)90094-E

A substrate-induced respiration (SIR) method is described to measure the contributions of fungi and bacteria to total glucose-induced microbial respiration on plant residues of differing composition. Relationships between fungal, bacterial and total SIR and biomass were used to develop regression equations for predicting microbial biomass C from measures of SIR. Total SIR rates (100–2000 μg CO 2-C g −1 h −1) and biomass-specific SIR rates (64–72 ng CO 2-C h −1 μg −1 biomass C) from plant residues were considerably greater than those calculated from the literature for soils. Results of longer term decomposition studies indicate that the C:N ratios of plant residues through time account for the greatest amount of the variation in total SIR. Annual decomposition rate constants ( k) for plant residues were positively correlated ( r 2=0.99) to overall mean estimates of total SIR. The plant residue SIR method has advantages over conventional direct count methods because it distinguishes a physiologically active component of the microbial biomass. Furthermore, it allows separation of fungal and bacterial components that may aid in understanding microbial controls on plant residue decomposition.