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Age at which a reference growth curve's increment peaks

growth_reference_inflection.Rd

The inflection point of a sigmoid growth curve: the age of maximum annual increment, after which growth slows and the curve approaches its asymptote.

Usage

growth_reference_inflection(
  reference,
  method = c("inflection", "asymptote"),
  frac = 0.9,
  sources = c("SORTIE", "TIPSY", "VDYP"),
  smooth_window = 21L,
  default = 100
)

Arguments

reference

A data frame of reference observations, with columns source ("SORTIE", "TIPSY", "VDYP" or "Ground plots"), age and aboveground_c_mg_ha.

method

"inflection" or "asymptote".

frac

Numeric. Fraction of the curve maximum, for "asymptote".

sources

Character vector of reference sources to use, in order of preference; the first one present is used.

smooth_window

Integer. Width of the moving average over increments.

default

Numeric. Returned when no usable model reference exists.

Value

A single age.

Details

This is what defines "mature" for scoring purposes. A fixed age threshold cannot: the modelled species differ several-fold in longevity and in how fast they get there, so age 100 is past the inflection for a fast, short-lived species and well before it for a slow, long-lived one. Deriving the threshold from each species' own reference curve keeps the prioritized window in the same place on every curve – the part where the trajectory is settling toward the level it will hold.

The increment is smoothed before the maximum is taken, because SORTIE curves are individual-tree simulations and their year-to-year increments are noisy enough for the raw argmax to land almost anywhere.

Two definitions are available. "inflection" is the age of peak increment itself, the point at which growth stops accelerating. "asymptote" is the age at which the curve first reaches frac of its maximum, which sits later and isolates the landing region more tightly – an inflection-based window can start very early for a fast species (age 18 for lodgepole pine) and so still carries much of the rapid-growth phase.

See also

Other growth calibration helpers: extract_landscape_cohort_structures(), growth_add_objective(), growth_auto_window(), growth_best_candidates(), growth_bin_observations(), growth_calibration_design(), growth_calibration_partition(), growth_calibration_work_root(), growth_climatic_distance(), growth_climatic_weight(), growth_expand_over_pseudo_species(), growth_factorial_ratio_grid(), growth_fitting_windows(), growth_identifiability(), growth_inflation_factor(), growth_mortality_onset_frac(), growth_plot_palette(), growth_pseudo_species_name(), growth_reference_curves(), growth_score_fit(), growth_scoring_for(), growth_smooth_observations(), growth_structure_cell_curves(), growth_structure_cohort_table(), growth_structure_design(), growth_structure_summary(), growth_window_for(), plot_growth_calibration(), plot_growth_candidate(), plot_growth_factorial_sensitivity(), plot_growth_structures(), read_growth_scoring(), read_landscape_cohort_structures(), scale_linetype_growth_reference(), write_growth_review_bundle()