Generic land-use soil-cover curve for the RothC/HSOC cover factor.

Monthly vegetated soil-cover fraction (0 bare, 1 fully covered) by land-use class, driving the plant-cover term of the RothC and HSOC decomposition modifier (soc_rate_modifier_rothc, where the cover factor is 0.6 + 0.4 * (1 - soil_cover): covered soil decomposes more slowly than bare soil). build_carbon_balance attaches these values to each cell-month before reducing the monthly climate drivers to an annual modifier, so cropland (a seasonal crop canopy with a bare fallow period) mineralizes soil carbon differently from grassland and natural land (perennial cover). The curve is keyed on the signed month offset from the cell-year's warmest (peak-canopy) month rather than the calendar month, so the same generic curve aligns to the growing season in either hemisphere from the temperature seasonality alone.

For cropland the fractions follow the FAO-56 crop growth-stage canopy development of a generic 150-day annual field crop (the FAO-56 maize-grain template, 30/40/50/30 days for the initial, development, mid-season and late-season stages): a low establishment cover during the initial stage (about 10 percent ground cover), rising through the development stage to an effective full canopy at mid-season (the peak, offset 0), then declining through late-season senescence, with the remaining fallow/off-season months at a low bare-soil cover. Grassland and natural land carry a sustained high perennial cover in every month (no bare fallow period), following the RothC convention that permanent vegetation is treated as covered year-round.

Usage

soc_soil_cover_curve

Format

A tibble with columns:

land_use

Land-use class: "cropland", "grassland" or "natural" (matched case-insensitively; a class absent from the table, such as "urban", is treated as bare soil).

months_from_peak

Signed month offset from the warmest month of the cell-year (integer -5 to 6; 0 is the peak-canopy mid-season month).

soil_cover

Vegetated soil-cover fraction for that class and month offset (0 bare, 1 fully covered).

Source

Crop canopy development stages and their durations follow the FAO-56 crop coefficient framework: Allen, R. G., Pereira, L. S., Raes, D. & Smith, M. (1998). Crop evapotranspiration: Guidelines for computing crop water requirements (FAO Irrigation and Drainage Paper 56). Food and Agriculture Organization of the United Nations, Rome (Chapter 6 and Table 11: initial stage to about 10 percent ground cover, development to effective full cover, full canopy at mid-season, senescence in late-season; generic 150-day annual-crop template). The binary covered-versus-bare cover convention it feeds is that of the RothC model: Coleman, K. & Jenkinson, D. S. (1996). RothC-26.3: a model for the turnover of carbon in soil. doi:10.1007/978-3-642-61094-3_17 (the soil cover rate-modifying factor slows decomposition when growing plants are present). The perennial grassland/natural cover and the fallow-period bare-soil value are generic modelling assumptions, not a per-crop observational survey.

Examples

soc_soil_cover_curve
#> # A tibble: 36 × 3
#>    land_use months_from_peak soil_cover
#>    <chr>               <int>      <dbl>
#>  1 cropland               -5       0.05
#>  2 cropland               -4       0.05
#>  3 cropland               -3       0.05
#>  4 cropland               -2       0.15
#>  5 cropland               -1       0.55
#>  6 cropland                0       0.95
#>  7 cropland                1       0.75
#>  8 cropland                2       0.3 
#>  9 cropland                3       0.05
#> 10 cropland                4       0.05
#> # ℹ 26 more rows