Equations / Aboveground biomass
Understorey AGB from D30 and height
As printed (Data analysis, p. 3)
In this library's units, ready to compute (kg)
Aboveground biomass = exp(-3.215 + 0.09 + 1.665 * ln(D30) + 0.958 * ln(H))D30- Stem diameter at 30 cm, cm
H- Total tree height, m
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). The back-transform adds the paper’s CF column (0.09, = RSE²/2, an additive term on the log scale) to the intercept, as its Data analysis says the CF was used to correct the log-transformation bias. 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.
doi:10.1590/0102-33062020abb0475 · Open access · copy we read
lnM= a + b × ln(D) + c × ln(H) 1023 -3.215*** 1.665*** 0.958*** 0.192 0.423 0.935 1149 0.09 2.45
H: tree height; ρ: wood density; C: crown diameter; N: sample size; a, b, c and d are the model’s fitted parameters
AGB and several measurement variables (diameter, height, crown diameter, and wood density) were measured on 1023 understorey stems belonging to 184 species
The diameter was measured at 30 cm aboveground level
The correction factor (CF) calculated by the formula CF= RSE²/2 (5)
- Trees measured
- 1,023
- Height range
- 0.86–15.55 m
- Residual SE
- 0.423
- Method
- log-log regression, lnM = a + b ln(X1) + ...
- Where
- Semi-deciduous rainforest, East region, Cameroon
- Last checked
- 2026-11-03
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, H = 4 | 1.03 | 1.03 | Computed from the printed form computed with python3 from the published form (CF added to the intercept) |
| D30 = 8, H = 9 | 11.5 | 11.5 | Computed from the printed form computed with python3 from the published form (CF added to the intercept) |
Related
- Understorey AGB from D30 and wood density · Yonkeu Ntonmen et al. 2022 · D30 + Wood density
- 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 wood density · 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