# Tanoak root biomass from basal area (best AICc model, Table 2)

Root biomass equation for Notholithocarpus densiflorus, United States, from Namm & Berrill 2020. 12 trees, DBH 1.9–52.4 cm. Listed on Tree Allometrics, a free library of tree allometric equations, each quoted from the source that published it.

## Equation

As printed in Namm & Berrill 2020 (Table 2, last row (lowest AICc)):

> ln (Belowground biomass) = 6.683 + 0.8149( ln BA )

Cite: https://treeallometry.org/equations/namm-2020-bgb-ba/#equation

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

```
Root biomass = exp(6.683 + 0.8149 * ln(0.000078539816 * D^2))
```

Inputs: D = Diameter at breast height (1.3 m) (cm).
The source's own form: exp(6.683 + 0.8149 * ln(0.000078539816 * DBH^2)), with DBH in cm; output in kg.
Cite: https://treeallometry.org/equations/namm-2020-bgb-ba/#canonical

## What it covers

- Output: Root biomass, kg
- Taxon: Notholithocarpus densiflorus (species), family Fagaceae; broadleaf
- Where: L.W. Schatz Demonstration Tree Farm, Humboldt County, California. Cite: https://treeallometry.org/equations/namm-2020-bgb-ba/#where
- Biomes: temperate
- Stand: mixed
- Trees measured: 12. Cite: https://treeallometry.org/equations/namm-2020-bgb-ba/#n_trees
- DBH range: 1.9–52.4 cm. Cite: https://treeallometry.org/equations/namm-2020-bgb-ba/#dbh
- Height range: 2.7–21.1 m. Cite: https://treeallometry.org/equations/namm-2020-bgb-ba/#height
- R²: 0.9425. Cite: https://treeallometry.org/equations/namm-2020-bgb-ba/#r2
- Method: linear mixed model on ln scale (block random effect), excavated root systems. Cite: https://treeallometry.org/equations/namm-2020-bgb-ba/#method
- Verification: read in the original source
- Last checked: 2026-11-02. Cite: https://treeallometry.org/equations/namm-2020-bgb-ba/#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

Namm, B. H., & Berrill, J.-P. (2020). How do tree- and stand-level factors influence belowground biomass and carbon storage in tanoak (Notholithocarpus densiflorus)? The Forestry Chronicle, 96(1), 50–60.

- DOI: https://doi.org/10.5558/tfc2020-007
- Access: open access
- Copy we read: https://pubs.cif-ifc.org/doi/pdf/10.5558/tfc2020-007
- Every equation from this source: https://treeallometry.org/sources/namm-2020/
- Cite: https://treeallometry.org/equations/namm-2020-bgb-ba/#source

## The facts, in the source's words

**Equation** (Table 2, last row (lowest AICc)):

> ln (Belowground biomass) = 6.683 + 0.8149( ln BA )

Cite: https://treeallometry.org/equations/namm-2020-bgb-ba/#equation

**Trees measured** (Table 2 caption):

> n = 12 trees

Cite: https://treeallometry.org/equations/namm-2020-bgb-ba/#quote-fit-n-trees

**Smallest DBH** (Results, p. 53):

> the dbh of individual stems were between 1.9 cm and 52.4 cm

Cite: https://treeallometry.org/equations/namm-2020-bgb-ba/#quote-fit-dbh-min-cm

**h min m** (Results, p. 53):

> Tree heights ranged from 2.7 m to 21.1 m

Cite: https://treeallometry.org/equations/namm-2020-bgb-ba/#quote-fit-h-min-m

**R²** (Table 2, R2 adj. of the best-AICc model):

> 0.9425

Cite: https://treeallometry.org/equations/namm-2020-bgb-ba/#quote-fit-r2

**Our note:** The paper's predictor is total stem basal area BA (m2, summed over all stems of a multi-stemmed tanoak). Here BA is written as pi/4 * (DBH/100)^2, so D is the dbh of a single stem; for multi-stemmed trees use the summed basal area instead. Output is belowground biomass excluding stump, in kg. r2 is the adjusted R2 as printed. The paper does not state a back-transformation correction factor, so none is applied. Other candidate models (with crown position, SDI, height) and the root:shoot models (arcsine transform, coefficients not legible in the text layer) were not added.

## 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 = 31.1 | 98 | 97.8 | Value printed in the paper: Results, p. 53: tanoak with average tree BA of 0.076 m2 (single-stemmed dbh 31.1 cm) expected to store 98 kg belowground (rounded in paper) |
| D = 15 | 29.8 | 29.8 | Computed from the printed form: computed from the published form (coefficients as printed) |
| D = 45 | 179 | 179 | Computed from the printed form: computed from the published form (coefficients as printed) |

Cite: https://treeallometry.org/equations/namm-2020-bgb-ba/#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: Namm, B. H., & Berrill, J.-P. (2020). How do tree- and stand-level factors influence belowground biomass and carbon storage in tanoak (Notholithocarpus densiflorus)? The Forestry Chronicle, 96(1), 50–60. https://doi.org/10.5558/tfc2020-007

Cite this page for the record and checks: Tree Allometrics (Restoration Scope), "Tanoak root biomass from basal area (best AICc model, Table 2)", checked 2026-11-02, https://treeallometry.org/equations/namm-2020-bgb-ba/. 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/namm-2020-bgb-ba.json
Report a problem: email info@restorationscope.com with the equation id (namm-2020-bgb-ba) and where the right value appears.