Tree Allometrics

Pseudotsuga menziesii / Stem biomass

Douglas-fir bole biomass, simple SUR (D only)

Stem biomassPseudotsuga menziesii · PinaceaeUnited StatesmixedRead from the original paper
Photo of Pseudotsuga menziesii
© Danny Steaven · CC BY-SA · iNaturalist
Equation

As printed (Eqs. 2-5 (X1 = ln DBH) and Table 3, Simple SUR, Douglas-fir)

Bole = exp(a11 + a12*X1); a11 = -0.349, a12 = 1.925

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

Stem biomass = exp(-0.349 + 1.925 * ln(D))
D
Diameter at breast height (1.3 m), cm

Read from the author's accepted manuscript (draft, manuscript ID cjfr-2015-0256.R1), not the typeset article; values may differ from the final print. Fitted in original scale (nonlinear SUR), so no log back-transform correction. DBH in cm, biomass in kg (Eq. 2-5 text). Bole is stem wood; bark is reported as a separate component (not provided here as there is no matching output quantity). Extended SUR models using height and crown length are not included (crown length is not a canonical variable).

Source
22 Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco) and 33 lodgepole pine (Pinus contorta) trees
Trees measured · Materials and Methods, Data and Study Area
Trees measured
22
DBH range
19.3–114 cm
Method
seemingly unrelated regression (simple SUR), component equations constrained to sum to total, fitted in original scale
Where
Oregon, USA (several forests)
Last checked
2026-11-02
Calculate
225
Stem biomass (kg)
106
Carbon (kg), ×0.47
388
CO₂e (kg), ×44/12
Fitted DBH range02004006008001,000510152025303540DBH (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 = 20225225Computed from the printed form
computed from the published form (coefficients as printed)
D = 501,3151,315Computed from the printed form
computed from the published form (coefficients as printed)
D = 1004,9944,994Computed from the printed form
computed from the published form (coefficients as printed)

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