GCubeR – Implementation

Function	Method	Outputs	Inputs	Main formula (generic form)	Notes / Context
Converting module
`c150_c130()`	Convert `c150` to `c130` or Convert `c130` to `c150`	`c150` `c130`	`c130` `c150`	`c130=a⋅c150+b` `c150=(c130-b)/a`	The function computes `c150` or `c130` depending on data availabity
`add_c130_dbh()`	Add or compute `c130` and `dbh`	`c130` `dbh`	`dbh` `c130`	`dbh = c130 / π` `c130 = dbh · π`	Auto-fills missing `c130` or `dbh`.
General & widely applicable volume models
`dagnelie_vc22_1()`	Dagnelie single entry	`vc22`	`c130`	`vc22 = a + b·c130 + c·c130² + d·c130³`	Simplest Dagnelie taper model, relies only on circumference.
`dagnelie_vc22_1g()`	Dagnelie graduaded	`vc22`	`c130` `hdom`	`vc22 = a + b·c130 + c·c130² + d·c130³ + e·hdom + f·c130²·hdom`	Improves accuracy in pure, even-aged stands by adding dominant height.
`dagnelie_vc22_2()`	Dagnelie 2 entry	`vc22`	`c130` `htot`	`vc22 = a + b·c130 + c·c130² + d·c130³ + e·htot + f·c130²·htot`	Most precise Dagnelie model; recommended mainly for high-value trees due to height measurement cost.
`dagnelie_br()`	Dagnelie – Branch volume	`vbr`	`c130`	`vbr = a + b·c130 + c·c130² + d·c130³`	Estimates branch volume from circumference only.
`vallet_vta()`	Vallet - Volume above ground	`vta`	`c130` `htot`	`form = (a + b·c130 + c·c130/htot)·(1 + d·c130²)` `vta = form · (π / 40000) · c130² · htot`	Explicitly models stem form factor; primarily for French species.
`vallet_vc22()`	Vallet merchantising volume	`vc22`	`dbh` `htot`	`vc22 = a·htot/dbh + (b + c·dbh)·π·dbh²·htot / 40000`	Geometrically adjusted; species-specific coefficients reflecting stem structure.
Context-specific methods
`algan_vta_vc22()`	Algan - volume computer(2006)	`vta` `vc22`	`dbh` `htot`	`vta = 0.40 · (dbh/100)² · htot` `vc22 = 0.33 · (dbh/100)² · htot`	Simplified geometric estimator; mainly used in France for Abies alba.
`bouvard_vta()`	Bouvard - Volume above ground	`vta`	`dbh` `htot`	`vta = 0.50 · (dbh/100)² · htot`	Specific to oaks (Quercus sp.), especially in coppice-with-standards regimes.
`rondeux_vc22_vtot()`	Rondeux / Pauwels et al. (2022)	`vtot` `vc22`	`c130` `htot`	`vtot = a · c130² · htot` `vc22 = a + b · c130² · htot`	Wallonia-specific; calibrated for larch (Larix sp.) in small-circumference trees (first thinnings).
Biomass / carbon computer
`biomass_calc()` – CNPF pathway	CNPF / France Valley	`bag` `bbg` `btot` `carbon` `CO₂`	`vc22`	`bag = vc22 · feb · density` `bbg = exp(−a + b·ln(bag) + c)` `btot = bag + bbg` `C = 0.475 · btot`	`feb = 1.30` (conifers) `feb = 1.56` (broadleaves) carbon and CO₂ derived from total biomass.
`biomass_calc()` – Vallet pathway	Follow Vallet et al. (2006)	`bag` `bbg` `btot` `carbon` `CO₂`	`vallet_vta`	`bag = vta · density` `bbg = exp(−a + b·ln(bag) + c)` `btot = bag + bbg`	Used when `vallet_vta` is available root biomass is implicitly included.
Plot module
`plot_by_class()`	Plot histogram by class of `c130`	`vc22` `vta` `btot`			Class width can be adjusted by the breaks input in the function