Process | Element | Process description |
---|---|---|
Inputs: | ||
 Total deposition | \( {\mathrm{SO}}_4^{2-} \), \( {\mathrm{NO}}_3^{-} \), \( {\mathrm{NH}}_4^{+} \), | Inputs; total (wet and dry) deposition fluxes |
 | BC2+ a, Na+, K+ | Element- and vegetation-dependent filtering factorb |
 Upward seepage | \( {\mathrm{SO}}_4^{2-} \), \( {\mathrm{NO}}_3^{-} \), \( {\mathrm{NH}}_4^{+} \), | Inputs |
 | BC2+ a, Na+, K+ |  |
 Water Balance | – | Inputs: precipitation, upward seepage, evapotranspiration |
Rate-limited reactions: | ||
 Foliar uptake | \( {\mathrm{NH}}_4^{+} \) | Linear function of total deposition |
 Foliar exudation | BC2+ a, K+ | Equals foliar uptake |
 Litterfall | BC2+ a, K+, | Logistic growth |
 | \( {\mathrm{NH}}_4^{+} \), NO3 - |  |
 Root decay | BC2+ a, K+, | Linear function of litterfall |
 | \( {\mathrm{NH}}_4^{+} \), \( {\mathrm{NO}}_3^{-} \) |  |
 Mineralisation | BC2+ a, K+, | First-order reaction and a function of pH, mean spring water level (MSW) and C/N ratio of the litter |
 | \( {\mathrm{NH}}_4^{+} \), \( {\mathrm{NO}}_3^{-} \) |  |
 N immobilisation | \( {\mathrm{NH}}_4^{+} \), \( {\mathrm{NO}}_3^{-} \) | Proportional to N deposition and a function of the C/N ratio soil organic matter |
 Growth uptake | BC2+ a, K+, | Logistic growth |
 | \( {\mathrm{NH}}_4^{+} \), \( {\mathrm{NO}}_3^{-} \) |  |
 Nitrification | \( {\mathrm{NH}}_4^{+} \), \( {\mathrm{NO}}_3^{-} \) | Proportional to net \( {\mathrm{NH}}_4^{+} \) input and a function of pH, mean spring water level (MSW) and C/N ratio |
 Denitrification | \( {\mathrm{NO}}_3^{-} \) | Proportional to net NO3 − input and a function of pH, mean spring water level (MSW) and C/N ratio |
 Silicate weathering | Al3+, BC2+ a, Na+, K+ | Zero-order reaction |
Equilibrium reactions: | ||
 Dissociation/association | \( {\mathrm{HCO}}_3^{-} \) | CO2 equilibrium |
 Carbonate weathering | BC2+ a | Carbonate equilibrium |
 Al hydroxide weathering | Al3+ | Gibbsite equilibrium |
 Cation exchange | H+ b, Al3+, BC2+ a | Gaines–Thomas equations |
 Sulphate sorption | H+ b, \( {\mathrm{SO}}_4^{2-} \) | Langmuir equation |