Regulators of heterotrophic microbial potentials in wetland soils

Potential rates of aerobic respiration, denitrification, sulfate reduction and methanogenesis were investigated in 10 different wetland soils with a wide range of biogeochemical characteristics, with the objective of determining relationships between process rates and soil properties. Electron acceptor amendments to methanogenic soils caused gradual (1-13 d) to immediate transitions in electron flow from methanogenesis to alternate electron accepters. Rates of organic C mineralization ranged between 0.2 and 34 mu mol C g(-1) d(-1) and averaged three times faster with O-2 as compared to alternate electron accepters. There was no significant difference between rates of organic C mineralization (CO2 + CH4 production) under denitrifying, sulfate-reducing and methanogenic conditions, indicating that soil organic carbon availability was similar under the different anaerobic conditions. Rates of electron acceptor consumption ranged between 1 and 107 mu mol g(-1) d-1 for O-2, 0.5 and 9.3 mu mol g(-1) d(-1) for NO3-, 0.1 and 11.1 mu mol g(-1) d(-1) for SO42- and 0.1 and 6.2 mu mol g(-1) d(-1) for CO2. Heterotrophic potentials in wetland soils were strongly correlated with inorganic N and several available C indices (total, dissolved and microbial C), but not with pH or dissolved nutrients (P, Ca2+, Mg2+, Fe(II)). Microbial activity-soil property relationships determined in this study may be useful for predicting the fate of pollutants that are influenced by microbial oxidation-reduction reactions in different types of wetland soils. (C) 1999 Elsevier Science Ltd. All rights reserved.