Simulate soil organic carbon with the Century five-pool model.

Annual Century trajectory integrated with deSolve::lsoda. Carbon flows through structural and metabolic litter and active, slow and passive soil organic matter pools, with texture-dependent rates and inter-pool transfer fractions.

Usage

calculate_soc_century(
  initial_soc_mgc_ha,
  c_input_mgc_ha_yr,
  years,
  clay_pct = NA,
  climate_modifier = 1,
  silt_pct = NA
)

Source

Parton, W. J. et al. (1987). doi:10.2136/sssaj1987.03615995005100050015x ; SoilR implementation: Sierra, C. A. et al. (2012). doi:10.5194/gmd-5-1045-2012 .

Arguments

initial_soc_mgc_ha

Initial soil organic carbon stock (Mg C per ha).

c_input_mgc_ha_yr

Annual carbon input (Mg C per ha per year).

years

Number of years to simulate.

clay_pct

Soil clay content (percent).

climate_modifier

Annual climate rate modifier (dimensionless), scaling every pool decomposition rate.

silt_pct

Soil silt content (percent). NA, the default, falls back to soc_turnover_params' century,defaults,silt_pct, which is SoilR's function-signature default of 45 rather than a measurement. Both of Century's texture terms are functions of clay PLUS silt – the active-pool multiplier fTxtr = 1 - 0.75 * (clay + silt) and its respired fraction Es = 0.85 - 0.68 * (clay + silt) – so silt is as load-bearing as clay. HWSD's share-weighted global mean is 28.2%, not 45%.

Value

A tibble with one row per year: year, str, met, act, slw, pas and soc_total.

Examples

calculate_soc_century(
  initial_soc_mgc_ha = 50,
  c_input_mgc_ha_yr = 2,
  years = 5,
  clay_pct = 20
)
#> # A tibble: 6 × 7
#>    year   str    met   act   slw   pas soc_total
#>   <dbl> <dbl>  <dbl> <dbl> <dbl> <dbl>     <dbl>
#> 1     0  0    0      2.5    20    27.5      50  
#> 2     1  1.06 0.0143 0.584  18.7  27.4      47.8
#> 3     2  1.42 0.0143 0.528  16.8  27.4      46.2
#> 4     3  1.53 0.0143 0.503  15.4  27.3      44.7
#> 5     4  1.58 0.0143 0.478  14.1  27.2      43.4
#> 6     5  1.59 0.0143 0.455  13.1  27.1      42.2