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Soil C decomposition and temperature The way forward Key issues from a modelling perspective. Göran Ågren Department of Ecology Swedish University of Agricultural Sciences. Litter input I ( q , t ). Respiration = (1/ e -1) P. DECOMPOSERS. NLOM. P / e. P ( q’ , t ). r C ( q , t ).
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Soil C decomposition andtemperatureThe way forwardKey issues from a modellingperspective GöranÅgren Department of Ecology Swedish University of Agricultural Sciences
Litter input I(q,t) Respiration = (1/e-1)P DECOMPOSERS NLOM P/e P(q’,t) rC(q,t) rB(q’,t) D(q’,q) q Quality, q Quality, q’ µ(q,t)rB(q,t) • P Decomposer growth rate • e Decomposer efficiency • D(q,q’) Dispersion • µ Decomposer mortality
Litter input I(q,t) Respiration = (1/e-1)P DECOMPOSERS NLOM P/e P(q’,t) rC(q,t) rB(q’,t) • P Decomposer growth rate D(q’,q) This is normally the only function that is assumed to depend on temperature q Quality, q How rapidly can decomposers use substrate, Arrhenius? Quality, q’ µ(q,t)rB(q,t) Do they use different qualities with different rates depending on quality? How rapidly is substrate becoming accessible? Does this depend upon quality?
Thornley JHM, Cannell MGR. 2001. Soil carbon storage response to temperature: an hypothesis. Annals of Botany 87:591-598. Is mineral associated the same as protected? Regulatory Gate Hypothesis, Kemmit et al. 2008
Litter input I(q,t) Respiration = (1/e-1)P DECOMPOSERS NLOM P/e P(q’,t) rC(q,t) rB(q’,t) D(q’,q) • e Decomposer efficiency q Quality, q Quality, q’ µ(q,t)rB(q,t) Does it depend upon temperature?
Litter input I(q,t) Respiration = (1/e-1)P DECOMPOSERS NLOM P/e P(q’,t) rC(q,t) rB(q’,t) D(q’,q) • D(q,q’) Dispersion q It is likely that decomposers’ chemical composition depends on temperature? Differences in membrane structure Differences in community composition Quality, q Quality, q’ µ(q,t)rB(q,t) Time scale issue: If temperature responses depend upon changes in species composition, how rapidly does the composition respond?
Litter input I(q,t) Respiration = (1/e-1)P DECOMPOSERS NLOM P/e P(q’,t) rC(q,t) rB(q’,t) • µ Decomposer mortality D(q’,q) q Probably of less importance as decomposer turnover anyhow is rapid compared to that of NLOM Quality, q Quality, q’ µ(q,t)rB(q,t)
Does it matter? • P Decomposer growth rate (u0q0b, b) • e Decomposer efficiency (e0) • D(q,q’) Dispersion (h) Steady state carbon as a function of parameter values u0q0b e0 h b
Litter input I(q,t) What is measured Respiration = (1/e-1)P DECOMPOSERS NLOM P/e P(q’,t) rC(q,t) rB(q’,t) D(q’,q) q Quality, q Quality, q’ µ(q,t)rB(q,t) Mike: ”Are we even studying the right universe?” ”Maybe, but we seem to only be scratching the surface”