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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