agb.ind {CTFS} | R Documentation

## Computes Above Growth Biomass for Individual Tree

### Description

This function is called from `biomass`. This is the core function that uses the wood specific gravity data file and the coefficients from the model in Chave, J. et.al. to compute the above ground biomass for each tree and multiple stem. This package contains only wood specific gravity values from species found at the CTFS site, BCI. For access to the full data set of wood specific gravity, contact J. Chave at: chave@cict.fr

### Usage

    agb.ind(dbh, wsg.vct, forest = forest)
    agb.mult(census, multfile, wsgfile, forest = forest)
    getwsg.vct(census, wsgfile, by.col = "wsg")

### Arguments

`dbh` | dbh in mm of tree, determined through logic and parameters of `biomass`
`wsg.vct` | wood specific gravity for all species
`forest` | forest type which determines which set of coefficients are used for calculation
`census` | name dataframe of a census
`multfile` | name of dataframe with dbh measurements of secondary stems of census. Tree tag numbers can appear multiple times in this file if there is more than two stems for a tree.
`wsgfile` | name of the dataframe that contains wood density values for selected species. See `tst.ctfs.wsg`
`by.col` | column name of the wood specific gravity values in `tst.ctfs.wsg.Rdata`, usually “wsg”

### Details

These functions are only used internally but can, with the correct parameter values, be used directly. `agb.ind` is the core function with the coefficients for the estimation of above ground biomass. `agb.mult` calls `agb.ind` to compute the sum of the above ground biomass of all secondary stems of the same individual tree as defined by `tag`.

The current set of coefficients used are given below anda are taken from Table 4, II.3 and II.4. `forest = NULL` is the same as “all types” as described in Chave, J. et.al.

AGB = p * exp(aprime + b*lndbh + c*lndbh^2 + d*lndbh^3)

p = wood specific gravity for species

aprime = (a*RSE^2) / 2

Forest | a | b | c | d | RSE
NULL | -1.589 | 2.284 | 0.129 | -0.0197 | 0.377
wet | -1.302 | 1.98 | 0.207 | -0.0281 | 0.356
moist | -1.562 | 2.148 | 0.207 | -0.0281 | 0.356
dry | -0.730 | 7.784 | 0.207 | -0.0281 | 0.356

`getwsg.vct` matches the species name to the wood specific gravity for that species in `wsg.ctfs.RData`.

### Value

Returns a number, `AGB`, the above ground biomass for the dbh submitted.

### See Also

`CTFS.biomass`

[Package CTFS version 1.00 Index]