v_gri {ForestElementsR} | R Documentation |
Calculate Tree Volumes With the GRI Volume Equations (Franz et al. 1973)
Description
Merchantable standing tree volumes over bark calculated with the GRI volume equations developed by Friedrich Franz in 1971. These volume equations are standard in the German Federal State of Bavaria
Usage
v_gri(species_id, dbh_cm, height_m)
Arguments
species_id |
Vector of species id's following the tum_wwk_short
species coding. Ideally, these species_id's are provided as an
|
dbh_cm |
Vector of tree dbh values in cm (dbh = stem diameter at breast height, i.e. 1.3 m) |
height_m |
Vector of tree height values in m. While missing values in
|
Details
The abbreviation GRI stands for the German word "Großrauminventur" (large
area inventory). This forest inventory was conducted in 1971 by Friedrich
Franz and his team of the Chair for Forest Growth and Yield Science at the
Munich Ludwig-Maximilians-University
(Franz et al. 1973). The inventory covered
the whole federal state of Bavaria (~ 70,600 km²). The volume equations
implemented in this function were calibrated with the data of several ten
thousands of trees which were felled for that purpose during the
inventory. The volume equations are available for exactly the species
(groups) defined in the coding tum_wwk_short. If they are called with
another species coding supported by the package ForestElementsR,
v_gri
will attempt to convert them accordingly.
Value
A vector of merchantable standing tree wood volumes over bark in m³. "Merchantable" means only wood with a minimum diameter of 7 cm over bark is taken into account. Therefore, for small trees without any merchandable wood, the function will return 0 m³.
References
Franz F, Bachler B, Deckelmann E, Kennel R, Schmidt A, Wotschikowski U (1973). Bayerische Waldinventur 1970/71, Inventurabschnitt I: Großrauminventur Aufnahme- und Auswertungsverfahren, volume 11 of Forstliche Forschungsberichte München. Forstwissenschaftliche Fakultät der Universität München und Bayerische Forstliche Versuchs- und Forschungsanstalt.
Examples
# Find out the species codes that work with v_gri
fe_species_get_coding_table("tum_wwk_short") |>
dplyr::select(-genus, -species_no) |>
dplyr::distinct()
# Merchantable volume of a European beech with dbh = 30 cm,
# and height = 29 m
v_gri("5", 30, 29)
v_gri(5, 30, 29)
v_gri(as_fe_species_tum_wwk_short(5), 30, 29)
# Several trees (three species, three sizes)
species_id <- fe_species_tum_wwk_short(c(1, 1, 1, 3, 3, 3, 5, 5, 5))
dbh_cm <- c(12, 30, 55, 12, 30, 55, 12, 30, 55)
height_m <- c(14, 33, 39, 14, 33, 39, 14, 33, 39)
v_gri(species_id, dbh_cm, height_m)
# The same, but the species id's are now originally defined in the
# coding of the 2012 German national forest inventory
species_id <- fe_species_ger_nfi_2012(
c(10, 10, 10, 20, 20, 20, 100, 100, 100)
)
v_gri(species_id, dbh_cm, height_m)