Tree Allometrics

Knightia excelsa / Root biomass

Knightia excelsa, NZ, belowground biomass from RCD (Table 3)

Root biomassKnightia excelsa · ProteaceaeNew ZealandplantationRead from the original paper
Photo of Knightia excelsa
© Jacqui Geux · CC BY · iNaturalist
Equation

As printed (Table 3, Total below-ground biomass, Knightia excelsa)

y = 21.3e0.05x

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

Root biomass = 0.0213 * exp(0.5 * DRC)
DRC
Root collar / stem base diameter, cm

Open-spaced juvenile plants (2-year-old containerised plants on-grown for 3 years, sampled up to 5 years). The tables are headed 'at age 5 years' but the appendix figures show points from all harvest years, and the paper gives no n or RCD range for these fits, so none is recorded. x is root collar diameter in mm; biomass in g and height in m (units inferred from Table 2 and Appendix 1 means, which the equations reproduce; the paper does not print units beside the equations). r² for exponential fits is a pseudo r².

Source
0.758
R² · Table 3, Total below-ground biomass, Knightia excelsa, r² column
R²
0.758
Method
nonlinear least squares, exponential (y = a e^(bx))
Where
Taruheru River terrace, Gisborne, New Zealand
Last checked
2026-11-02
Calculate
0.0579
Root biomass (kg)
0.0272
Carbon (kg), ×0.47
0.0998
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
DRC = 20.05790.0579Computed from the printed form
hand-computed from the published form (RCD in mm, mass in g, converted)
DRC = 60.4280.428Computed from the printed form
hand-computed from the published form (RCD in mm, mass in g, converted)
DRC = 1538.538.5Computed from the printed form
hand-computed from the published form (RCD in mm, mass in g, converted)

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