# Chinese fir root biomass (compatible total-biomass system)

Root biomass equation for Cunninghamia lanceolata, China, from Du et al. 2026. 74 trees. Listed on Tree Allometrics, a free library of tree allometric equations, each quoted from the source that published it.

## Equation

As printed in Du et al. 2026 (Table 8, Eq. 29-31):

> Broot = 0.024760 (D 2 H) 0.774387 (31)

Cite: https://treeallometry.org/equations/du-2026-fir-root/#equation

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

```
Root biomass = 0.024760 * (D^2 * H)^0.774387
```

Inputs: D = Diameter at breast height (1.3 m) (cm); H = Total tree height (m).
The source's own form: 0.024760 * (D^2 * H)^0.774387, with D in cm, H in m; output in kg.
Cite: https://treeallometry.org/equations/du-2026-fir-root/#canonical

## What it covers

- Output: Root biomass, kg
- Taxon: Cunninghamia lanceolata (species), family Cupressaceae; conifer
- Where: Hunan Province (14 prefecture-level cities and autonomous prefectures). Cite: https://treeallometry.org/equations/du-2026-fir-root/#where
- Biomes: subtropical
- Stand: mixed
- Trees measured: 74. Cite: https://treeallometry.org/equations/du-2026-fir-root/#n_trees
- R²: 0.7734. Cite: https://treeallometry.org/equations/du-2026-fir-root/#r2
- Method: weighted nonlinear least squares. Cite: https://treeallometry.org/equations/du-2026-fir-root/#method
- Verification: read in the original source
- Last checked: 2026-11-02. Cite: https://treeallometry.org/equations/du-2026-fir-root/#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

Du, Z., Liu, Z., Wang, J., Zou, Z., He, W., Zeng, W., Meng, J., & Chen, Z. (2026). Development of Compatible Biomass Models for Chinese Fir, Poplar, and Oak in Hunan Province. Forests, 17(7), 770.

- DOI: https://doi.org/10.3390/f17070770
- Access: open access
- Copy we read: https://www.mdpi.com/1999-4907/17/7/770/pdf?version=1782822414
- Every equation from this source: https://treeallometry.org/sources/du-2026/
- Cite: https://treeallometry.org/equations/du-2026-fir-root/#source

## The facts, in the source's words

**Trees measured** (Table 1):

> Chinese fir 154 (74) (Total Samples (Root Samples))

Cite: https://treeallometry.org/equations/du-2026-fir-root/#quote-fit-n-trees

**Equation** (Table 8, Eq. 29-31):

> Broot = 0.024760 (D 2 H) 0.774387 (31)

Cite: https://treeallometry.org/equations/du-2026-fir-root/#equation

**R²** (Table 11, row (22) * (root model evaluated on the trees with measured root samples)):

> (22) * 0.7734 7.98 0.45 3.68 29.31 90.96

Cite: https://treeallometry.org/equations/du-2026-fir-root/#quote-fit-r2

**Our note:** Final root model of the compatible system, fitted on trees with root samples (n from Table 1). Compatible total-biomass system (aboveground fitted independently, total and root fitted jointly by simultaneous estimation; weighted nonlinear least squares). Total = aboveground + root. The paper lists the sample as stratified random felled trees across eight diameter classes (4-32 cm) from 2022-2023; the reported minimum and maximum DBH and height are for all sampled trees of the species (Table 1). Root biomass was measured on a subset only (whole-root excavation: root collar, coarse roots, fine roots), so root and total fit ranges are not given beyond the full sample. No back-transform factor (nonlinear fit). The paper also gives aboveground-component (stem, crown, wood, bark, branch, foliage) systems (Tables 17-39), not added here. R² is the evaluation row marked * (the 74 trees with measured roots, matching n_trees; the paper's Discussion cites these starred values as the root-model R²); the unstarred row (0.8762) is evaluated over all sampled trees, most of which have no measured roots.

## 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, H = 9 | 4.8 | 4.8 | Computed from the printed form: hand-computed from the published form |
| D = 30, H = 20 | 48.9 | 48.9 | Computed from the printed form: hand-computed from the published form |

Cite: https://treeallometry.org/equations/du-2026-fir-root/#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: Du, Z., Liu, Z., Wang, J., Zou, Z., He, W., Zeng, W., Meng, J., & Chen, Z. (2026). Development of Compatible Biomass Models for Chinese Fir, Poplar, and Oak in Hunan Province. Forests, 17(7), 770. https://doi.org/10.3390/f17070770

Cite this page for the record and checks: Tree Allometrics (Restoration Scope), "Chinese fir root biomass (compatible total-biomass system)", checked 2026-11-02, https://treeallometry.org/equations/du-2026-fir-root/. 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/du-2026-fir-root.json
Report a problem: email info@restorationscope.com with the equation id (du-2026-fir-root) and where the right value appears.