Equations / Aboveground biomass

Moist tropical zone AGB, quadratic (Eq. 3.2.3)

Aboveground biomassTropical broadleaf trees (mixed species)PantropicalnaturalRead from the original paper

Many species, no single photo

Equation

As printed (Eq. 3.2.3, Section 3.2.1 table)

Y = 42.69-12.800(D)+1.242(D2)

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

Aboveground biomass = 42.69 - 12.800 * D + 1.242 * D^2

D: Diameter at breast height (1.3 m), cm

A. J. R. Gillespie (pers. comm.) revision of the Brown et al. (1989) moist equation. The primer recommends this form for trees with dbh above about 160 cm because it behaves better there than Eq. 3.2.4. r2 is adjusted r². Note: the primer's worked stand-table example says it uses Eq. 3.2.3 but its per-tree values match Eq. 3.2.4. The primer does not say whether a log back-transform correction is included; none applied. Climatic zones per the primer: dry <1500 mm/yr rain with a dry season of several months; moist 1500–4000 mm/yr; wet >4000 mm/yr, lowland conditions only.

Source

Brown, S. (1997). Estimating Biomass and Biomass Change of Tropical Forests: a Primer. FAO Forestry Paper 134. Rome: Food and Agriculture Organization of the United Nations. ISBN 92-5-103955-0.

https://www.fao.org/4/w4095e/w4095e00.htm · Open access · copy we read

Y= biomass per tree in kg, D = dbh in cm, and BA = basal area in cm2

Units · Section 3.2.1, biomass regression equations table header

5-148 | 170 | 0,84

Trees measured · Eq. 3.2.3 row: range in dbh (cm), number of trees, adjusted r2

Trees measured: 170
DBH range: 5–148 cm
R²: 0.84
Where: Tropics, moist zone
Last checked: 2026-11-01

Calculate

DBH (cm)

776.5

Aboveground biomass (kg)

365

Carbon (kg), ×0.47

1,338

CO₂e (kg), ×44/12

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%.

Inputs	Expected	We get	From
D = 30	776.5	776.5	Computed from the printed form computed with python3 from the published form
D = 100	11,183	11,183	Computed from the printed form computed with python3 from the published form

Report a problem with this equation · JSON

Dry tropical zone AGB from DBH (Eq. 3.2.1) · Brown 1997 · DBH
Moist tropical zone AGB, power law (Eq. 3.2.4) · Brown 1997 · DBH
Wet tropical zone AGB, quadratic (Brown 1997 Eq. 3.2.5) · Brown & Iverson 1992 · DBH
Dry tropical zone AGB from DBH (Eq. 3.2.1) · same paper · Aboveground biomass
Moist tropical zone AGB, power law (Eq. 3.2.4) · same paper · Aboveground biomass
Tropical pines AGB from DBH (Eq. 3.1.8 / 3.2.8) · same paper · Aboveground biomass

Compare these curves

Moist tropical zone AGB, quadratic (Eq. 3.2.3)

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