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Read natural-land soil cover from an LPJmL run.

Source: R/lpjml_natural_cover.R
read_lpjml_natural_cover.Rd

Per-cell, per-year vegetated cover of the natural stand, from LPJmL's foliar projective cover (fpc.nc). Band 1 of that file is the natural stand FRACTION – how much of the cell is natural – and bands 2 to 15 are the fourteen natural PFTs' projective cover WITHIN that stand. The cover of natural land is therefore the sum of bands 2 to 15, capped at 1, and never band 1, which is an area share and a different quantity.

Supply the result as data$natural_cover to build_carbon_balance() to replace soc_soil_cover_curve's constant 0.85 for the natural class.

Usage

read_lpjml_natural_cover(
  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

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.

example

If TRUE, return a small fixture instead of reading a run. Defaults to FALSE.

Value

A tibble with lon, lat, year, natural_stand_frac and natural_cover (both fractions in 0-1).

Why it matters where it does

The constant is close on the global mean – measured cover runs 0.858 in 1901 to 0.884 in 2023 – and wrong in the distribution: the median natural cell is fully covered at 1.000 while the 5th percentile is bare at roughly zero. The RothC plant-retainment term is 0.6 + 0.4 * (1 - cover), so a near-bare cell moves from 0.66 to 1.00, decomposes half again as fast, and loses about a third of its equilibrium carbon. Those arid cells are exactly where the model sits furthest from observation. The effect on the global mean is about 1.8%; per cell it spans 0.66 to 1.10 times.

Managed grassland has no FPC band – fpc.nc covers the natural stand only – so it necessarily stays on the curve.

Examples

read_lpjml_natural_cover(example = TRUE)
#> # A tibble: 2 × 5
#>     lon   lat  year natural_stand_frac natural_cover
#>   <dbl> <dbl> <int>              <dbl>         <dbl>
#> 1 -0.25  5.25  2010               0.98          0.99
#> 2 12.2  18.8   2010               0.95          0.04