ForestElementsR (version 2.0.1)

age_d_gnfi3: Inverse Stem Diameter Growth Model of the 3rd German National Forest Inventory (2012)

Description

Inverse tree diameter growth model of the third German National Forest Inventory of 2012 bwi3_methods_2017ForestElementsR. Allows to estimate a tree's age at any dbh if its dbh is known at a given age.

Usage

age_d_gnfi3(species_id, dbh_cm, dbh_cm_known, age_yr_known)

Value

A single age value or vector of age values corresponding to dbh_cm

Arguments

species_id

Vector of species id's preferably following the ger_nfi_2012 species coding. Ideally, these species_id's are provided as a fe_species_ger_nfi_2012 object. See Details for how other species codings are handled.

dbh_cm

Single numeric value or vector of dbh (cm) for which the age is to be estimated

dbh_cm_known

Vector of known dbh (cm) values at age age_yr_known

age_yr_known

Vector of ages (years) for which the dbh d_cm_known is known

Details

Originally, the function was parameterized for species and species groups corresponding to the national forest inventory's species coding (fe_species_ger_nfi_2012). We have attributed in addition these the original parameters also to the species codings fe_species_tum_wwk_short, and fe_species_bavrn_state_short. When called with a given species coding, the function will try to use the "nearest" of these three alternatives. Fallback option is the attempt to use fe_species_tum_wwk_short.

References

See Also

Other growth functions: age_h_gnfi3(), d_age_gnfi3(), h_age_gnfi3()

Examples

  # A Norway spruce has a diameter of 17.5 cm at age 45. Estimate
  # its age at dbh 20.6 cm
  age_d_gnfi3(10, 20.6, 17.5, 45) # 10 is ger_nfi_2012 code for Norway spruce

  # Do the same backward in time, age at dbh 12.4 cm
  age_d_gnfi3(10, 12.4, 17.5, 45)

  # Apply for more than one tree, different species, same age
  d_known   <- c(23.1, 16.2, 35.2, 19.3, 21.8)
  d_age     <- c(27.0, 19.0, 40.8, 22.9, 25.8)
  species   <- as_fe_species_tum_wwk_short(c(3, 3, 3, 6, 6))
  age_d_gnfi3(
    species, dbh_cm = d_age, dbh_cm_known = d_known, age_yr_known = 40
  )