# Lower wood density subgroup (CEI) AGB from dbh (Table 4)

Aboveground biomass equation for Conzattia multiflora, Euphorbia schlechtendalii and Ipomoea arborescens (CEI subgroup, lower wood density), Mexico, from Gómez et al. 2021. Listed on Tree Allometrics, a free library of tree allometric equations, each quoted from the source that published it.

**Its authors advise against it:** the source fits this equation and then says not to use it: "Thus, it is only possible to use a single equation for the species of the first subgroup, but not for those of the second or all species together (Table 4)." (Results, p. 8).

Fitted on Conzattia multiflora, Euphorbia schlechtendalii, Ipomoea arborescens.

## Equation

As printed in Gómez et al. 2021 (Eq. 2, p. 4):

> ln(Y) = ln(a) + b ln(X)

Cite: https://treeallometry.org/equations/gomez-2021-cei-group/#equation

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

```
Aboveground biomass = exp(-3.515 + 2.652 * ln(D))
```

Inputs: D = Diameter at breast height (1.3 m) (cm).
The source's own form: exp(-3.515 + 2.652 * ln(DBH)), with DBH in cm; output in kg.
Cite: https://treeallometry.org/equations/gomez-2021-cei-group/#canonical

## What it covers

- Output: Aboveground biomass, kg
- Taxon: Conzattia multiflora, Euphorbia schlechtendalii and Ipomoea arborescens (CEI subgroup, lower wood density) (mixed species); broadleaf
- Where: Sierra de Huautla Biosphere Reserve (Ejido El Limón), Morelos. Cite: https://treeallometry.org/equations/gomez-2021-cei-group/#where
- Biomes: tropical, dryland
- Stand: natural
- R²: 0.908. Cite: https://treeallometry.org/equations/gomez-2021-cei-group/#r2
- Method: Linear regression of ln(biomass) on ln(dbh). Cite: https://treeallometry.org/equations/gomez-2021-cei-group/#method
- Verification: read in the original source
- Last checked: 2026-11-02. Cite: https://treeallometry.org/equations/gomez-2021-cei-group/#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

Gómez, J.D., Etchevers, J.D., Campo, J., Monterroso, A.I., Paustian, K., Asensio, C. (2021). Allometric relationships to estimate aboveground biomass of species in a tropical dry forest of Central Mexico. Madera y Bosques, 27(4), e2742441.

- DOI: https://doi.org/10.21829/myb.2021.2742441
- Access: open access
- Copy we read: https://myb.ojs.inecol.mx/index.php/myb/article/download/2441/2274
- Every equation from this source: https://treeallometry.org/sources/gomez-2021/
- Cite: https://treeallometry.org/equations/gomez-2021-cei-group/#source

## The facts, in the source's words

**Equation** (Eq. 2, p. 4):

> ln(Y) = ln(a) + b ln(X)

Cite: https://treeallometry.org/equations/gomez-2021-cei-group/#equation

**Equation** (Table 4, p. 9):

> CEI: n 26; β0 -3.515; β1 2.652; R2 0.908

Cite: https://treeallometry.org/equations/gomez-2021-cei-group/#quote-expression

**R²** (Table 4, p. 9):

> R2 0.908

Cite: https://treeallometry.org/equations/gomez-2021-cei-group/#quote-fit-r2

**Output** (p. 4):

> Y is aboveground biomass (kg), X is dbh (cm)

Cite: https://treeallometry.org/equations/gomez-2021-cei-group/#quote-output

**Our note:** ln(Y) = b0 + b1 ln(DBH), natural log, no correction factor stated in the paper. Aboveground biomass includes foliage and small branches (trunk and crown sections were summed). The paper found the CEI parameters heterogeneous across species. n 26 counts branch units, so n_trees is left out.

## 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 | 13.3 | 13.3 | Computed from the printed form: computed from the printed coefficients |
| D = 20 | 83.9 | 83.9 | Computed from the printed form: computed from the printed coefficients |

Cite: https://treeallometry.org/equations/gomez-2021-cei-group/#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: Gómez, J.D., Etchevers, J.D., Campo, J., Monterroso, A.I., Paustian, K., Asensio, C. (2021). Allometric relationships to estimate aboveground biomass of species in a tropical dry forest of Central Mexico. Madera y Bosques, 27(4), e2742441. https://doi.org/10.21829/myb.2021.2742441

Cite this page for the record and checks: Tree Allometrics (Restoration Scope), "Lower wood density subgroup (CEI) AGB from dbh (Table 4)", checked 2026-11-02, https://treeallometry.org/equations/gomez-2021-cei-group/. 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/gomez-2021-cei-group.json
Report a problem: email info@restorationscope.com with the equation id (gomez-2021-cei-group) and where the right value appears.