Read litterfall by land-use class from an LPJmL run. — read_lpjml

Per-cell, per-year carbon returned to the soil as litter, split by the stand that shed it. Litterfall is what physically enters the soil; net primary production is not, because it also contains the increment that stays in living biomass. On this run natural litterfall is 0.84 times natural NPP at the median cell and 0.68 in aggregate, the shortfall being biomass accumulation, fire, and the conversion pulse.

Usage

read_lpjml_litterfall(
  class = c("nv", "agr", "mgrass", "luc", "total"),
  run_dir = NULL,
  years = NULL,
  first_year = NULL,
  example = FALSE
)

Source

Schaphoff, S. et al. (2018). LPJmL4 - a dynamic global vegetation model with managed land - Part 1: Model description. Geoscientific Model Development, 11, 1343-1375. doi:10.5194/gmd-11-1343-2018 .

Arguments

class: Which stand's litterfall to read: "nv" (standing natural vegetation), "agr" (crop stands), "mgrass" (managed grassland), "luc" (the land-use conversion pulse) or "total".
run_dir: Path to the LPJmL run output directory. NULL (default) uses WHEP_LPJML_RUN_DIR.
years: Optional integer vector of calendar years to keep. NULL (default) keeps every year the file covers.
first_year: Calendar year of the file's first time step. NULL (default) reads it from the file's own time axis, which LPJmL stamps as "days since YYYY-M-D". Pass a value only to override a file that carries no reference date.
example: If TRUE, return a small fixture instead of reading a run. Defaults to FALSE.

Value

A tibble with lon, lat, year, class and litterfall_c_mgc_ha_yr.

Whole-cell densities

Every class is a density per square metre of GRIDCELL, not of its own stand: each accumulation site in LPJmL multiplies by stand->frac. To get the density a stand actually experiences, divide by that stand's area fraction – for "nv", natural_stand_frac from read_lpjml_natural_cover(). Mixing the two conventions understates a partly-natural cell's input by exactly its natural fraction.

The four classes sum to the total

nv + luc + agr + mgrass recovers total to float32 rounding, the remainder being set-aside grass. "luc" is the pulse released when land is converted, and it is large – 9.9% of all litterfall at 2010 against 1.3% for crop stands. It is booked to no destination: at landusechange.c the receiving stand is still natural when the pulse is credited, so apportioning it to the land that gained area is a decision for the caller, not a quantity LPJmL reports.

Examples

read_lpjml_litterfall(example = TRUE)
#> # A tibble: 2 × 5
#>     lon   lat  year class litterfall_c_mgc_ha_yr
#>   <dbl> <dbl> <int> <chr>                  <dbl>
#> 1 -0.25  5.25  2010 nv                      6.42
#> 2 12.2  18.8   2010 nv                      0.31