Tree Allometrics

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Miombo Regional BGB from stump diameter

Root biomassMiombo woodland trees (mixed species)TanzanianaturalRead from the original paper
Many species, no single photo
Equation

As printed (Table 6, selected model (1))

Regional = a × (SD) b 0.1056 2.1035 623.5 154.01 46.5 -12.2 0.86

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

Root biomass = 0.1056 * D30^2.1035
D30
Stem diameter at 30 cm, cm

Stump diameter (SD) is measured over bark just below the felling cut, at least 30 cm above ground (higher when the stump is irregular), so it is mapped to D30 as the nearest canonical variable. Form Y = a × SD^b is the first (non-linear mixed-effects, nlme) model form; the paper selected it as best in every case shown here, and the printed Table row shows it. Manyara BGB is not included because the paper selected a different (quadratic) form there. The three model forms (1)-(3) are typeset equations; the form of (1) is read from the table row "= a × (SD) b". The fit used nlme with random effects; coefficients are the fixed effects as printed. Table 2 gives SD ranges, not DBH, so no dbh range is stored.

Source
SD is stump diameter (cm)
Units · Section 2.3.4
AGB and BGB models were developed from 127 and 57 sample trees, respectively
Trees measured · Abstract (volume: 114 trees)
Trees measured
57
R²
0.86
Method
non-linear mixed-effects regression (nlme), power model
Where
Miombo woodlands of Manyara, Lindi and Tabora, Tanzania
Last checked
2026-11-02
Calculate
135
Root biomass (kg)
63.5
Carbon (kg), ×0.47
233
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%.

InputsExpectedWe getFrom
D30 = 30135135Computed from the printed form
hand-computed from the published form
D30 = 60581581Computed from the printed form
hand-computed from the published form

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