Table 1. Microbial functional traits used in model analysis.
| Parameter | Description | Fast growers | Slow growers | Unit |
|---|---|---|---|---|
| Microbial cell composition and stoichiometry* | ||||
| FDOM | Fraction of cell biomass accounting for cell solubles (immediately available for uptake by other microbes on cell death, C:N=15) | 0.06 | 0.06 | |
| FCC | Fraction of cell biomass accounting for C-rich complex compounds, that is, cell wall compounds, lipids, starch (C:N=150) | 0.52 | 0.37 | |
| FNC | Fraction of cell biomass accounting for N-rich complex compounds, that is, proteins, DNA, RNA (C:N=5) | 0.42 | 0.57 | |
| MCN | Resulting biomass C:N | 9.03 | 12.22 | |
| Microbial cell size and turnover rates† | ||||
| Smax | Size at which a microbial cell divides and colonizes a neighbouring microsite | 10 | 100 | fmol C |
| Smin | Size at which a microbial cell dies from starving | 1 | 10 | fmol C |
| c | Maximum number of microbes in one microsite | 3 | 1 | |
| Microbial enzyme production | ||||
| Efr | Fraction of C uptake (after deduction of maintenance respiration) that is invested into enzyme production | |||
| Enzyme producers | 0.12 | 0.12 | ||
| Cheaters | 0, 0.02, 0.04 or 0.06 | 0, 0.02, 0.04 or 0.06 | ||
| EfPS:EfCR:EfNR | Ratio in which specific enzymes are produced for the degradation of plant material : C-rich microbial remains : N-rich microbial remains | |||
| Enzyme producers | 0.7:0.15:0.15 | 0.7:0.15:0.15 | ||
| Cheaters (when also producing enzymes) | 0.7:0.15:0.15 | 0.7:0.15:0.15 | ||
*Chemical composition of prokaryotic and eukaryotic (for example, yeast) cells are based on ref. 27.
†Microbial cell sizes are based on refs 51, 52, 53. Microbial turnover rates are indirectly linked to cell size, as maximum C and N uptake rates are linked to the cell surface-to-volume ratio (which is higher in smaller cells). Maximum uptake rates are thus dynamic (depending on actual cell size). In addition, microbial mortality rates are inversely linked to maximum cell size, assuming that larger species invest more into defensive structures. Resultant uptake rates depend on maximum uptake rates and local C and N availability. For more details and all other model parameters, see Supplementary Methods.