# Subtropical China AGB from D and wood density (Model I.4)

Aboveground biomass equation for 41 subtropical forest tree species (Fagus lucida, Castanea seguinii, Carpinus viminea and others), China, from Xu et al. 2015. 147 trees. Listed on Tree Allometrics, a free library of tree allometric equations, each quoted from the source that published it.

Fitted on Fagus lucida, Castanea seguinii, Carpinus viminea, and other species the source does not name here.

## Equation

As printed in Xu et al. 2015 (Recommended model when height is not available, p. 7 (Table 2, model I.4)):

> AGB = exp(−1.8226 + 2.4105ln(D) + 0.5781ln(WD))

Cite: https://treeallometry.org/equations/xu-2015-i4-dwd/#equation

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

```
Aboveground biomass = exp(-1.8226 + 2.4105 * ln(D) + 0.5781 * ln(rho))
```

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: exp(-1.8226 + 2.4105 * ln(D) + 0.5781 * ln(WD)), with D in cm, WD in g/cm3; output in kg.
Cite: https://treeallometry.org/equations/xu-2015-i4-dwd/#canonical

## What it covers

- Output: Aboveground biomass, kg
- Taxon: 41 subtropical forest tree species (Fagus lucida, Castanea seguinii, Carpinus viminea and others) (mixed species); mixed
- Where: Badagongshan National Nature Reserve, Hunan province. Cite: https://treeallometry.org/equations/xu-2015-i4-dwd/#where
- Biomes: subtropical, montane
- Stand: natural
- Trees measured: 147. Cite: https://treeallometry.org/equations/xu-2015-i4-dwd/#n_trees
- R²: 0.932. Cite: https://treeallometry.org/equations/xu-2015-i4-dwd/#r2
- Residual SE: 0.207. Cite: https://treeallometry.org/equations/xu-2015-i4-dwd/#rse
- Method: Bayesian log-log regression (MCMC). Cite: https://treeallometry.org/equations/xu-2015-i4-dwd/#method
- Verification: read in the original source
- Last checked: 2026-11-02. Cite: https://treeallometry.org/equations/xu-2015-i4-dwd/#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

Xu, Y., Zhang, J., Franklin, S. B., et al. (2015). Improving allometry models to estimate the above- and belowground biomass of subtropical forest, China. Ecosphere, 6(12), 289.

- DOI: https://doi.org/10.1890/es15-00198.1
- Access: open access
- Copy we read: https://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/ES15-00198.1
- Every equation from this source: https://treeallometry.org/sources/xu-2015/
- Cite: https://treeallometry.org/equations/xu-2015-i4-dwd/#source

## The facts, in the source's words

**Equation** (Recommended model when height is not available, p. 7 (Table 2, model I.4)):

> AGB = exp(−1.8226 + 2.4105ln(D) + 0.5781ln(WD))

Cite: https://treeallometry.org/equations/xu-2015-i4-dwd/#equation

**R²** (Table 3, model I.4 (R2 and RSE columns)):

> I.4  R² 0.932  RSE 0.207

Cite: https://treeallometry.org/equations/xu-2015-i4-dwd/#quote-fit-r2

**Trees measured** (Abstract):

> we harvested and weighted dry mass of 147 trees from 41 dominant species in subtropical forest

Cite: https://treeallometry.org/equations/xu-2015-i4-dwd/#quote-fit-n-trees

**Our note:** Log-log model fitted by Bayesian MCMC; no correction factor is stated, so none is applied. Natural log assumed from the paper's ln notation. Wood density WD is in g cm-3 (Table 2; the running text says g/m3). Whole-tree AGB includes branches, leaves and fruit. Recommended by the authors when height is not available. Coefficients are the more precise values printed in the recommended-model equation (Table 2 gives -1.823, 2.411, 0.578).

## 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 = 20, rho = 0.57 | 160 | 160 | Computed from the printed form: computed from the printed coefficients |
| D = 40, rho = 0.6 | 875 | 875 | Computed from the printed form: computed from the printed coefficients |

Cite: https://treeallometry.org/equations/xu-2015-i4-dwd/#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: Xu, Y., Zhang, J., Franklin, S. B., et al. (2015). Improving allometry models to estimate the above- and belowground biomass of subtropical forest, China. Ecosphere, 6(12), 289. https://doi.org/10.1890/es15-00198.1

Cite this page for the record and checks: Tree Allometrics (Restoration Scope), "Subtropical China AGB from D and wood density (Model I.4)", checked 2026-11-02, https://treeallometry.org/equations/xu-2015-i4-dwd/. 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/xu-2015-i4-dwd.json
Report a problem: email info@restorationscope.com with the equation id (xu-2015-i4-dwd) and where the right value appears.