# AGB Model 4 (DBH, WD and [ln(DBH)]²), peat swamp forest Sarawak

Aboveground biomass equation for Mixed tree species, tropical peat swamp forest, Malaysia, from Monda et al. 2015. 41 trees, DBH 5.2–97 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 4: ln(DW)＝a＋b ln(DBH)＋d ln(WD)−e [ln(DBH)]2

Cite: https://treeallometry.org/equations/monda-2015-agb-m4/#equation

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

```
Aboveground biomass = 1.0452 * exp(-3.1574 + 3.7215 * ln(D) + 0.4931 * ln(rho) - 0.2618 * ln(D)^2)
```

Inputs: D = Diameter at breast height (1.3 m) (cm); rho = Wood density (oven-dry mass / green volume) (g/cm³).
The source's own form: 1.0452 * exp(-3.1574 + 3.7215 * ln(DBH) + 0.4931 * ln(WD) - 0.2618 * ln(DBH)^2), with DBH in cm, WD in g/cm3; output in kg.
Cite: https://treeallometry.org/equations/monda-2015-agb-m4/#canonical

## What it covers

- Output: Aboveground 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-agb-m4/#where
- Biomes: tropical
- Stand: natural
- Trees measured: 41. Cite: https://treeallometry.org/equations/monda-2015-agb-m4/#n_trees
- DBH range: 5.2–97 cm. Cite: https://treeallometry.org/equations/monda-2015-agb-m4/#dbh
- Correction factor: 1.0452 (applied). Cite: https://treeallometry.org/equations/monda-2015-agb-m4/#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-agb-m4/#method
- Verification: read in the original source
- Last checked: 2026-11-02. Cite: https://treeallometry.org/equations/monda-2015-agb-m4/#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-agb-m4/#source

## The facts, in the source's words

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

> Model 4: ln(DW)＝a＋b ln(DBH)＋d ln(WD)−e [ln(DBH)]2

Cite: https://treeallometry.org/equations/monda-2015-agb-m4/#equation

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

> Model 4 −3.1574 3.7215 *** 0.4931 ns 0.2618 ** 0.9699 1.0452 22.74 0.00303

Cite: https://treeallometry.org/equations/monda-2015-agb-m4/#quote-expression

**Trees measured** (Table 5):

> Aboveground biomass (n＝41)

Cite: https://treeallometry.org/equations/monda-2015-agb-m4/#quote-fit-n-trees

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

> AGB data were obtained for trees ranging in DBH from 5.2 to 97.0 cm

Cite: https://treeallometry.org/equations/monda-2015-agb-m4/#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 0.9699 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, rho = 0.5 | 41.5 | 41.5 | Computed from the printed form: computed from the published form (coefficients and CF as printed) |
| D = 30, rho = 0.6 | 525 | 525 | Computed from the printed form: computed from the published form (coefficients and CF as printed) |
| D = 60, rho = 0.55 | 1,703 | 1,703 | Computed from the printed form: computed from the published form (coefficients and CF as printed) |

Cite: https://treeallometry.org/equations/monda-2015-agb-m4/#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), "AGB Model 4 (DBH, WD and [ln(DBH)]²), peat swamp forest Sarawak", checked 2026-11-02, https://treeallometry.org/equations/monda-2015-agb-m4/. 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-agb-m4.json
Report a problem: email info@restorationscope.com with the equation id (monda-2015-agb-m4) and where the right value appears.