Equations / Root biomass
Root biomass from basal area at breast height, Piliostigma thonningii
© Robert Taylor · CC BY · iNaturalistAs printed (Table 2, BA1.3 row, Piliostigma thonningii, p. 7)
In this library's units, ready to compute (kg)
Root biomass = 519.6 * (0.7853982 * (D/100)^2)^0.75D- Diameter at breast height (1.3 m), cm
Not one of the authors' best models (they recommend basal area at 0.2 m, BA0.2, which has no canonical diameter variable here, and BA×H terms); this is the breast-height-only fit from Table 2, included because it can be used with DBH. Paper input is basal area at 1.3 m in m2; here BA1.3 is computed from DBH as pi*D^2/4 (0.7853982*(D/100)^2) in both forms. Fit dbh range is the printed C1.3 min and max divided by pi (circumference at 1.3 m, Table 1). BGB is stump plus coarse roots (roots over 5 mm for the non-protected species) from excavation, oven-dry. Table 2 prints a and b to 1 or 2 decimals. No correction factor is stated. Only the BA1.3-only models are included: the paper's height columns are labelled cm while the coefficients only make sense with H in metres, so the BA×H and H models are left out. For forked trees the paper's C1.3 is the quadratic sum of stem circumferences (Eq. 1, p. 4), so D here is the equivalent diameter sqrt(ΣDi²).
doi:10.14214/sf.1631 · Open access · copy we read
BGB = a × BA1.3b + ε
basal area (m2) at 1.3 m above ground level (BA1.3)
Piliostigma thonningii 30 26.5±1.7 12 40 15.7±1.4 6 30
- Trees measured
- 30
- DBH range
- 1.91–9.55 cm
- R²
- 0.58
- Method
- nonlinear regression, BGB = a × BA1.3^b
- Where
- Tiogo and Laba state forests, Burkina Faso (north Sudanian savanna-woodland)
- Last checked
- 2026-11-01
Outside the data this model was fitted on: DBH above the fitted 9.55 cm. Results may be unreliable.
Shaded: the DBH range the model was fitted on. Other inputs held at the values above.
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 = 10 | 13.7 | 13.7 | Computed from the printed form computed from the published form with BA1.3 = pi*D^2/4 in m2 |
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