# Acacia mangium plantation, stem biomass from stump diameter (SB6)

Stem biomass equation for Acacia mangium, Bangladesh, from Das & Chowdhury 2026. 25 trees. Listed on Tree Allometrics, a free library of tree allometric equations, each quoted from the source that published it.

## Equation

As printed in Das & Chowdhury 2026 (Table 3, model SB6 (columns: β0, β1, RMSE, F, adjusted R2, AIC, average deviation, CF, DW)):

> SB6 Mangium −2.519*** 2.175*** 0.222 2882 0.9454 −30.69 18.308 1.0249 2.002

Cite: https://treeallometry.org/equations/das-2026-sb6-mangium/#equation

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

```
Stem biomass = 1.0249 * exp(-2.519 + 2.175 * ln(D30))
```

Inputs: D30 = Stem diameter at 30 cm (cm).
The source's own form: 1.0249 * exp(-2.519 + 2.175 * ln(dst)), with dst in cm; output in kg.
Cite: https://treeallometry.org/equations/das-2026-sb6-mangium/#canonical

## What it covers

- Output: Stem biomass, kg
- Taxon: Acacia mangium (species); broadleaf
- Where: Ten plantation sites, Sylhet Division, Bangladesh. Cite: https://treeallometry.org/equations/das-2026-sb6-mangium/#where
- Biomes: tropical
- Stand: plantation
- Trees measured: 25. Cite: https://treeallometry.org/equations/das-2026-sb6-mangium/#n_trees
- R²: 0.9454. Cite: https://treeallometry.org/equations/das-2026-sb6-mangium/#r2
- Correction factor: 1.0249 (applied). Cite: https://treeallometry.org/equations/das-2026-sb6-mangium/#cf
- Method: OLS on ln-transformed data (ln-ln), adjusted R2. Cite: https://treeallometry.org/equations/das-2026-sb6-mangium/#method
- Verification: read in the original source
- Last checked: 2026-11-02. Cite: https://treeallometry.org/equations/das-2026-sb6-mangium/#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

Das, N., Chowdhury, M.Q. (2026). Stump diameter is a robust predictor of biomass and carbon stocks in tropical Acacia plantations. Discover Forests, 2, 73.

- DOI: https://doi.org/10.1007/s44415-026-00137-1
- Access: open access
- Copy we read: https://link.springer.com/article/10.1007/s44415-026-00137-1
- Every equation from this source: https://treeallometry.org/sources/das-2026/
- Cite: https://treeallometry.org/equations/das-2026-sb6-mangium/#source

## The facts, in the source's words

**Equation** (Table 3, model SB6 (columns: β0, β1, RMSE, F, adjusted R2, AIC, average deviation, CF, DW)):

> SB6 Mangium −2.519*** 2.175*** 0.222 2882 0.9454 −30.69 18.308 1.0249 2.002

Cite: https://treeallometry.org/equations/das-2026-sb6-mangium/#equation

**Equation** (Section 3.3):

> The ln–ln stump-based model (SB6) was parsimonious and produced adjusted R2 values of 0.945–0.968 across species

Cite: https://treeallometry.org/equations/das-2026-sb6-mangium/#quote-expression

**Units** (Abstract):

> stump diameter (dst, measured at 30 cm above ground)

Cite: https://treeallometry.org/equations/das-2026-sb6-mangium/#quote-published-units

**Output** (Section 2.4):

> Biomass estimates refer specifically to stem biomass; branch, foliage, and root components were not included.

Cite: https://treeallometry.org/equations/das-2026-sb6-mangium/#quote-output

**Trees measured** (Section 2.2):

> Calibration models were developed using 75 destructively sampled trees (25 per species, covering small, medium and large diameter classes)

Cite: https://treeallometry.org/equations/das-2026-sb6-mangium/#quote-fit-n-trees

**method** (Section 2.5):

> All log transformations used natural logs (ln).

Cite: https://treeallometry.org/equations/das-2026-sb6-mangium/#quote-fit-method

**Our note:** Stem biomass only (bark included, oven-dry), so output is stem_biomass not agb. Form read as ln(SB) = β0 + β1 ln(dst) from the text calling SB6 the "ln–ln stump-based model"; the full model list is in a supplementary Table S1 that was not read. The Table 3 CF (1.0249) is applied in both forms. Table 3 caption says RMSE is in kg but the body values (about 0.2) are log-scale (CF 1.0193 matches exp(0.196²/2)), so the body is followed and rse is not stored. Table 3 gives no DBH range for the 25 calibration trees, so none is stored. Row label "Mangium" in Table 3 maps to this taxon.

## 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 |
| --- | --- | --- | --- |
| D30 = 30 | 135 | 135 | Computed from the printed form: hand-computed from the published form |
| D30 = 50 | 409 | 409 | Computed from the printed form: hand-computed from the published form |

Cite: https://treeallometry.org/equations/das-2026-sb6-mangium/#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: Das, N., Chowdhury, M.Q. (2026). Stump diameter is a robust predictor of biomass and carbon stocks in tropical Acacia plantations. Discover Forests, 2, 73. https://doi.org/10.1007/s44415-026-00137-1

Cite this page for the record and checks: Tree Allometrics (Restoration Scope), "Acacia mangium plantation, stem biomass from stump diameter (SB6)", checked 2026-11-02, https://treeallometry.org/equations/das-2026-sb6-mangium/. 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/das-2026-sb6-mangium.json
Report a problem: email info@restorationscope.com with the equation id (das-2026-sb6-mangium) and where the right value appears.