# BGB Model 1 (DBH, H, WD), peat swamp forest Sarawak

Root biomass equation for Mixed tree species, tropical peat swamp forest, Malaysia, from Monda et al. 2015. 32 trees, DBH 5.2–110.8 cm. Listed on Tree Allometrics, a free library of tree allometric equations, each quoted from the source that published it.

## Equation

As printed in Monda et al. 2015 (Models section, p. 15):

> Model 1: ln(DW)＝a＋b ln(DBH)＋c ln(H)＋d ln(WD)

Cite: https://treeallometry.org/equations/monda-2015-bgb-m1/#equation

In this library's units, ready to compute (root biomass in kg):

```
Root biomass = 1.1334 * exp(-4.0218 + 2.2177 * ln(D) + 0.5784 * ln(H) + 1.1541 * ln(rho))
```

Inputs: D = Diameter at breast height (1.3 m) (cm); H = Total tree height (m); rho = Wood density (oven-dry mass / green volume) (g/cm³).
The source's own form: 1.1334 * exp(-4.0218 + 2.2177 * ln(DBH) + 0.5784 * ln(H) + 1.1541 * ln(WD)), with DBH in cm, H in m, WD in g/cm3; output in kg.
Cite: https://treeallometry.org/equations/monda-2015-bgb-m1/#canonical

## What it covers

- Output: Root biomass, kg
- Taxon: Mixed tree species, tropical peat swamp forest (mixed species); broadleaf
- Where: Logged-over peat swamp forest, Sarawak (Alan Batu and other sites, PC1-PC3). Cite: https://treeallometry.org/equations/monda-2015-bgb-m1/#where
- Biomes: tropical
- Stand: natural
- Trees measured: 32. Cite: https://treeallometry.org/equations/monda-2015-bgb-m1/#n_trees
- DBH range: 5.2–110.8 cm. Cite: https://treeallometry.org/equations/monda-2015-bgb-m1/#dbh
- Correction factor: 1.1334 (applied). Cite: https://treeallometry.org/equations/monda-2015-bgb-m1/#cf
- Method: log-log regression of dry weight on ln-transformed predictors, back-transformed and multiplied by the correction factor CF = exp(RSE²/2). Cite: https://treeallometry.org/equations/monda-2015-bgb-m1/#method
- Verification: read in the original source
- Last checked: 2026-11-02. Cite: https://treeallometry.org/equations/monda-2015-bgb-m1/#checked_at

A missing fit statistic is one the source doesn't state, or that we haven't recorded; it is never estimated. Outside the stated DBH range or region, the equation is an extrapolation.

## Source

Monda, Y., Kiyono, Y., Melling, L., Damian, C., & Chaddy, A. (2015). Allometric equations considering the influence of hollow trees: A case study for tropical peat swamp forest in Sarawak. TROPICS, 24(1), 11-22.

- DOI: https://doi.org/10.3759/tropics.24.11
- Access: open access
- Copy we read: https://www.jstage.jst.go.jp/article/tropics/24/1/24_11/_pdf
- Every equation from this source: https://treeallometry.org/sources/monda-2015/
- Cite: https://treeallometry.org/equations/monda-2015-bgb-m1/#source

## The facts, in the source's words

**Equation** (Models section, p. 15):

> Model 1: ln(DW)＝a＋b ln(DBH)＋c ln(H)＋d ln(WD)

Cite: https://treeallometry.org/equations/monda-2015-bgb-m1/#equation

**Equation** (Table 5, Belowground biomass, p. 19 (columns a, b, c, d, e, adjusted R2, CF, AIC, FI)):

> Model 1 −4.0218 2.2177 *** 0.5784 ns 1.1541 ns 0.9521 1.1334 52.25 0.02437

Cite: https://treeallometry.org/equations/monda-2015-bgb-m1/#quote-expression

**Trees measured** (Table 5):

> Belowground biomass (n＝32)

Cite: https://treeallometry.org/equations/monda-2015-bgb-m1/#quote-fit-n-trees

**Largest DBH** (Discussion, p. 20):

> BGB data for trees ranging in DBH from 5.2 to 110.8 cm

Cite: https://treeallometry.org/equations/monda-2015-bgb-m1/#quote-fit-dbh-max-cm

**Our note:** Coefficients a-e as printed in Table 5; the e term enters with a minus sign per the model definitions. WD is wood density in Mg m-3, numerically equal to g/cm3. Back-transformed result multiplied by the printed CF. Adjusted R2 0.9521 is not entered as r2. DW is dry mass (kg) of the whole above- or belowground part; hollow cavity volume was measured separately and the models are fitted to the measured biomass of hollow trees.

## Checks this equation passes

On every build, the library's form and the source's own form (in its units) must both give these values within 1%.

| Inputs | Expected | We get | From |
| --- | --- | --- | --- |
| D = 10, H = 12, rho = 0.5 | 6.34 | 6.34 | Computed from the printed form: computed from the published form (coefficients and CF as printed) |
| D = 30, H = 22, rho = 0.6 | 127 | 127 | Computed from the printed form: computed from the published form (coefficients and CF as printed) |
| D = 60, H = 30, rho = 0.55 | 639.5 | 639.5 | Computed from the printed form: computed from the published form (coefficients and CF as printed) |

Cite: https://treeallometry.org/equations/monda-2015-bgb-m1/#checks

The calculator on the page shows carbon as biomass × 0.47 (IPCC 2006 Guidelines, Vol. 4, Ch. 4, Table 4.3) and CO₂e as carbon × 44/12.

## How to cite

Cite the source for the equation: Monda, Y., Kiyono, Y., Melling, L., Damian, C., & Chaddy, A. (2015). Allometric equations considering the influence of hollow trees: A case study for tropical peat swamp forest in Sarawak. TROPICS, 24(1), 11-22. https://doi.org/10.3759/tropics.24.11

Cite this page for the record and checks: Tree Allometrics (Restoration Scope), "BGB Model 1 (DBH, H, WD), peat swamp forest Sarawak", checked 2026-11-02, https://treeallometry.org/equations/monda-2015-bgb-m1/. Data CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Quotes are the authors' words.

Data for this equation: https://treeallometry.org/data/equations/monda-2015-bgb-m1.json
Report a problem: email info@restorationscope.com with the equation id (monda-2015-bgb-m1) and where the right value appears.