Equations / Aboveground biomass

Understorey AGB from D30 and wood density

Aboveground biomassUnderstorey trees and saplings, 184 species (stems 1–10 cm diameter)CameroonnaturalRead from the original paper

Many species, no single photo

Equation

As printed (Table 2, block "All (1≤ diameter <10 cm)", p. 5)

lnM= a + b × ln(D) + c × ln(ρ) 1023 -2.144*** 2.505*** 1.164*** 0.184 0.419 0.936 1126 0.09 1.16

In this library's units, ready to compute (kg)

Aboveground biomass = exp(-2.144 + 2.505 * ln(D30) + 1.164 * ln(rho))

D30: Stem diameter at 30 cm, cm
rho: Wood density (oven-dry mass / green volume), g/cm³

Selected from Table 2/3 "All" (1 ≤ diameter < 10 cm, n = 1023) block; the paper also gives separate seedling (1-5 cm) and sapling (5-10 cm) fits and crown-diameter models (not included: crown diameter unit is ambiguous, Table 1 header says cm but values are 0.19-7.55). D is the stem diameter at 30 cm above ground (D30), not DBH, so no DBH range is stored; Table 1 gives D 1.00-9.99 cm and H 0.86-15.55 m for the whole data set. Wood density is the mean of base, trunk and branch samples (dry weight / fresh volume). Published as the plain exp() back-transform: the paper lists a CF column (= RSE²/2, an additive term on the log scale) but does not print the corrected equation, so no correction factor is applied or stored. Total AGB = trunk + branches + leaves (dry mass, oven-dried at 105/70 °C). Recommended by the authors: the models with more predictors fit better (Adj.R² up to 0.956 with four predictors); the D-only model is the simplest.

Source

Yonkeu Ntonmen, A. F., Zapfack, L., Djomo Chimi, C., et al. (2022). Complementary allometric model of understory tree biomass in the semi-deciduous rainforest of Cameroon. Acta Botanica Brasilica, 36, e2020abb0475.

doi:10.1590/0102-33062020abb0475 · Open access · copy we read

H: tree height; ρ: wood density; C: crown diameter; N: sample size; a, b, c and d are the model’s fitted parameters

Units · Table 3 note, p. 6

AGB and several measurement variables (diameter, height, crown diameter, and wood density) were measured on 1023 understorey stems belonging to 184 species

Trees measured · Data collection, p. 3

The diameter was measured at 30 cm aboveground level

Note · Data collection, p. 3

The correction factor (CF) calculated by the formula CF= RSE²/2 (5)

Note · Data analysis, p. 4

Trees measured: 1,023
Residual SE: 0.419
Method: log-log regression, lnM = a + b ln(X1) + ...
Where: Semi-deciduous rainforest, East region, Cameroon
Last checked: 2026-11-02

Calculate

D30 (cm)Wood density (g/cm³)

0.935

Aboveground biomass (kg)

0.44

Carbon (kg), ×0.47

1.61

CO₂e (kg), ×44/12

Checks this equation passes

On every build, the library's form and the paper's own form (in its units) must both give these values within 1%.

Inputs	Expected	We get	From
D30 = 3, rho = 0.56	0.935	0.935	Computed from the printed form computed with python3 from the published form (uncorrected, as printed)
D30 = 8, rho = 0.6	11.8	11.8	Computed from the printed form computed with python3 from the published form (uncorrected, as printed)

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Understorey AGB from D30 and height · Yonkeu Ntonmen et al. 2022 · D30 + Height
Understorey AGB from D30 (1-10 cm stems) · Yonkeu Ntonmen et al. 2022 · D30
Understorey AGB from D30²·H and wood density · Yonkeu Ntonmen et al. 2022 · D30 + Height + Wood density
Understorey AGB from D30 and height · same paper · Aboveground biomass
Understorey AGB from D30 (1-10 cm stems) · same paper · Aboveground biomass
Understorey AGB from D30²·H and wood density · same paper · Aboveground biomass
Understorey trunk biomass from D30, height and wood density · same paper · Stem biomass

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Understorey AGB from D30 and wood density

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