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Soil Microbial Respiration at Different Water Potentials and Temperatures: Theory and Mathematical Modeling
Author(s) -
Grant R. F.,
Rochette P.
Publication year - 1994
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1994.03615995005800060015x
Subject(s) - porosity , soil science , respiration , arrhenius equation , environmental science , substrate (aquarium) , soil water , chemistry , environmental chemistry , ecology , biology , botany , activation energy , organic chemistry
If ecosystem simulation models are to be used to study changes in C distribution under proposed changes in climate, then they must represent the effects of soil physical conditions upon microbial activity. Hypotheses for the effects of soil water content (θ) and temperature ( T s ) on microbial oxidation rates were formulated into mathematical algorithms as part of the ecosys modelling program. Access to organic substrates by heterotrophic microbial populations was represented from competitive enzyme kinetics, which were presumed to be sensitive to θ. Access to O 2 by obligately aerobic or facultatively anaerobic microbial populations was represented from O 2 diffusion gradients and active uptake rates controlled by θ and T s . Sensitivity to T s of substrate hydrolysis and oxidation by heterotrophic microbial populations was modelled from an Arrhenius function. Rates of simulated respiration were tested against rates measured under laboratory and field conditions at different θ and T s . Simulated CO 2 fluxes were largest when θ = 0.6 to 0.7 of total porosity and declined to <0.2 of their largest values when θ declined to 0.2 or rose above 0.9 of total porosity. The sensitivity of simulated CO 2 fluxes to θ was consistent with that measured during laboratory incubations, except in the range of 0.65 to 0.80 of total porosity, where sensitivity of measured fluxes was greater than that simulated. When θ was >0.8 of total porosity, simulated respiratory quotients rose above 1.0 to values consistent with those recorded elsewhere at high θ. Model hypotheses allowed simulated CO 2 evolution rates to reproduce those reported from wheat residue during a 30‐d incubation at T s from 0 to 20°C and ψ s from −0.033 to −5.0 MPa. These hypotheses also allowed simulated changes in CO 2 evolution rates attributed to changes in T s and θ to reproduce those measured in the field during 60 d under barley.