# BGB Model 5 (DBH only), 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 5: ln(DW)＝a＋b ln(DBH)

Cite: https://treeallometry.org/equations/monda-2015-bgb-m5/#equation

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

```
Root biomass = 1.1373 * exp(-4.2149 + 2.6109 * ln(D))
```

Inputs: D = Diameter at breast height (1.3 m) (cm).
The source's own form: 1.1373 * exp(-4.2149 + 2.6109 * ln(DBH)), with DBH in cm; output in kg.
Cite: https://treeallometry.org/equations/monda-2015-bgb-m5/#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-m5/#where
- Biomes: tropical
- Stand: natural
- Trees measured: 32. Cite: https://treeallometry.org/equations/monda-2015-bgb-m5/#n_trees
- DBH range: 5.2–110.8 cm. Cite: https://treeallometry.org/equations/monda-2015-bgb-m5/#dbh
- Correction factor: 1.1373 (applied). Cite: https://treeallometry.org/equations/monda-2015-bgb-m5/#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-m5/#method
- Verification: read in the original source
- Last checked: 2026-11-02. Cite: https://treeallometry.org/equations/monda-2015-bgb-m5/#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-m5/#source

## The facts, in the source's words

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

> Model 5: ln(DW)＝a＋b ln(DBH)

Cite: https://treeallometry.org/equations/monda-2015-bgb-m5/#equation

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

> Model 5 −4.2149 2.6109 *** 0.9508 1.1373 51.31 0.02466

Cite: https://treeallometry.org/equations/monda-2015-bgb-m5/#quote-expression

**Trees measured** (Table 5):

> Belowground biomass (n＝32)

Cite: https://treeallometry.org/equations/monda-2015-bgb-m5/#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-m5/#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 0.9508 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 | 6.86 | 6.86 | Computed from the printed form: computed from the published form (coefficients and CF as printed) |
| D = 30 | 120.8 | 120.8 | Computed from the printed form: computed from the published form (coefficients and CF as printed) |
| D = 60 | 737.8 | 737.8 | Computed from the printed form: computed from the published form (coefficients and CF as printed) |

Cite: https://treeallometry.org/equations/monda-2015-bgb-m5/#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 5 (DBH only), peat swamp forest Sarawak", checked 2026-11-02, https://treeallometry.org/equations/monda-2015-bgb-m5/. 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-m5.json
Report a problem: email info@restorationscope.com with the equation id (monda-2015-bgb-m5) and where the right value appears.