GCubeR (version 0.1.3)

vallet_vta: Calculate Total Aboveground Volume (VTA) Vallet Method

Description

Computes the total aboveground volume (VTA) for trees based on the circumference at 1.30m (c130) and total height (htot) using the Vallet form factor method.

Usage

vallet_vta(data, na_action = c("error", "omit"), output = NULL)

Value

The resulting data frame (same as the printed data) with the new columns and vallet_vta (Total Aboveground Volume in m3)..

Arguments

data

A data frame containing tree measurements. Must include the columns: species_code (in uppercase Latin format), c130 (circumference at 1.30m, in cm), and htot (total height, in m).

na_action

How to handle missing input values. "error" (default) stops if core required values are explicitly NA. "omit" removes rows with missing core data. Note: Model constraint violation (c130 < 45 cm) and unknown species are always handled by setting VTA and Form Factor to NA, preserving input values.

output

Optional file path (string). If provided, the resulting data frame will be written to this file using semicolon (;) as a delimiter. NA values are written as empty strings (""). Defaults to NULL.

Supported species

The Vallet VTA method is currently implemented for the following species (via their species_code):

• "PICEA_ABIES"

• "QUERCUS_ROBUR"

• "FAGUS_SYLVATICA"

• "PINUS_SYLVESTRIS"

• "PINUS_PINASTER"

• "ABIES_ALBA"

• "PSEUDOTSUGA_MENZIESII"

Details

The model is only valid for trees with a circumference at 1.30m (c130) of at least 45 cm. For non-compliant trees or unknown species, results are set to NA.

The Form Factor (form) is calculated as: $$form = (a + b \cdot c_{130} + c \cdot \frac{\sqrt{c_{130}}}{h_{tot}}) \cdot \left(1 + \frac{d}{c_{130}^2}\right)$$

The Total Aboveground Volume (VTA) is then: $$VTA = form \cdot \frac{1}{\pi \cdot 40000} \cdot c_{130}^2 \cdot h_{tot}$$

Coefficients a, b, c, d are loaded from the vallet_vta.csv file.

Examples

data_test <- data.frame(
  species_code = c("PICEA_ABIES", "FAGUS_SYLVATICA", "UNKNOWN_SPECIES", "QUERCUS_ROBUR"),
  c130 = c(60, 80, 50, 40), 
  htot = c(25, 18, 20, 22)
)

results_console <- vallet_vta(data_test)