Biochemical properties and biodegradation of dissolved organic matter from soils

摘要

Various biologically mediated processes are involved in the turnover of dissolved organic matter (DOM) in soil; however, relatively little is known about the dynamics of either the microbial community or the individual classes of organic molecules during the decomposition of DOM. We examined the net loss of DOC, the mineralisation of C to CO and the degradation of DOC from six different soils by soil microorganisms. We also quantified the changes in the concentrations of protein, carbohydrate and amino acid C during microbial biodegradation. Over a 70-day incubation period at 20pC, the mineralisation of DOC to CO was described by a double exponential model with a labile pool (half-life, 3-8 days) and a stable pool (half-life, 0.4-6 years). However, in nearly all cases, the mass loss of DOC exceeded the C released as CO with significant deviations from the double exponential model. Comparison of mass DOC loss, CO production and microbial cell counts, determined by epifluorescence microscopy, showed that a proportion of the lost DOC mass could be accounted for by microbial assimilation. Carbohydrate and protein C concentrations fluctuated throughout the incubation with a net change of between 3 to 13 and -30 to 22.4% initial DOC, respectively. No amino acid C was detected during the incubation period (level of detection, 0.01 mg C lp#).