Tree Allometrics

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Albizia zygia stem biomass from Dbh

Stem biomassAlbizia zygiaBeninnaturalRead from the original paper
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Equation

As printed (Eq. 3 and 5, p. 7; Table 4 (Model structure: ln(X) = x0 + x1ln(Dbh)), p. 10)

A. zygia –2.63*** (0.17) 2.60*** (0.05) 98.92 23 0.03 26

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

Stem biomass = exp(-2.63 + 2.6 * ln(D) + 0.03)
D
Diameter at breast height (1.3 m), cm

Stem biomass only (stem = height to crown base); the authors say to multiply by a biomass expansion factor (IPCC 2006) to get aboveground biomass. Coefficients are printed to 2 decimals, so predictions are only as precise as that. σ²/2 is the paper's printed bias-correction term, added inside the exponent (Eq. 5); it is printed rounded to 2 decimals. Recommended-to-capture subset: species-specific Dbh-only biomass models for six species; the paper prefers species-specific models over the generic one.

Source
Albizia zygia 28 168 2.5–65.5
Trees measured · Table 1, p. 5 (number of sample trees)
Albizia zygia 28 168 2.5–65.5
Smallest DBH · Table 1, p. 5 (Dbh range, cm)
Trees measured
28
DBH range
2.5–65.5 cm
Method
ln-ln linear regression, back-transformed with exp(σ²/2) (printed σ²/2 is rounded to 2 decimals)
Where
Lama forest reserve, southern Benin (semi-deciduous forest)
Last checked
2026-11-02
Calculate
179.3
Stem biomass (kg)
84.26
Carbon (kg), ×0.47
308.9
CO₂e (kg), ×44/12
Fitted DBH range02004006008001,0001,200510152025303540DBH (cm)Stem biomass (kg)Stem biomass

Shaded: the DBH range the model was fitted on. Other inputs held at the values above.

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
D = 20179.3179.3Computed from the printed form
computed from the published form (coefficients as printed to 2 decimals)
D = 401,0871,087Computed from the printed form
computed from the published form (coefficients as printed to 2 decimals)

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