# Betula pendula stem in bark biomass vs DBH (Eq. 4), forest-swamp, Middle Urals

Stem biomass equation for Betula pendula, Russia, from Petrova et al. 2026. 18 trees, DBH 1.1–17.1 cm. Listed on Tree Allometrics, a free library of tree allometric equations, each quoted from the source that published it.

## Equation

As printed in Petrova et al. 2026 (Eq. (4) and Table 4, p. 126):

> lnPi = a0 + a1lnD (4); lnPst: a0 = –1,9888, a1 = 2,1307

Cite: https://treeallometry.org/equations/petrova-2026-birch-st/#equation

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

```
Stem biomass = exp(-1.9888 + 2.1307 * ln(D))
```

Inputs: D = Diameter at breast height (1.3 m) (cm).
The source's own form: exp(-1.9888 + 2.1307 * ln(D)), with D in cm; output in kg.
Cite: https://treeallometry.org/equations/petrova-2026-birch-st/#canonical

## What it covers

- Output: Stem biomass, kg
- Taxon: Betula pendula (species), family Betulaceae; broadleaf
- Where: Forest-swamp system by Lake Isetskoe, Sverdlovsk Oblast, Middle Urals. Cite: https://treeallometry.org/equations/petrova-2026-birch-st/#where
- Biomes: boreal
- Stand: natural
- Trees measured: 18. Cite: https://treeallometry.org/equations/petrova-2026-birch-st/#n_trees
- DBH range: 1.1–17.1 cm. Cite: https://treeallometry.org/equations/petrova-2026-birch-st/#dbh
- Height range: 2.1–14.5 m. Cite: https://treeallometry.org/equations/petrova-2026-birch-st/#height
- Residual SE: 0.349. Cite: https://treeallometry.org/equations/petrova-2026-birch-st/#rse
- Method: log-log regression (OLS on natural logs); Baskerville correction included in the intercept. Cite: https://treeallometry.org/equations/petrova-2026-birch-st/#method
- Verification: read in the original source
- Last checked: 2026-11-01. Cite: https://treeallometry.org/equations/petrova-2026-birch-st/#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

Petrova, I.V., Plukha, N.I., Usoltsev, V.A., et al. (2026). Aboveground biomass and its allometric models for the main and under storeys of the forest-swamp system in the Middle Urals. Forests of Russia and economy in them, 3(98), 118–134.

- DOI: https://doi.org/10.51318/fret.2026.98.3.012
- Access: open access
- Copy we read: https://usfeu.ru/media/filer_public/46/8f/468f8f54-0a39-4ff0-a7a5-0c995daa8d5b/12_petrova_i_dr_nadzemnaia_biomassa_i_ee2.pdf
- Every equation from this source: https://treeallometry.org/sources/petrova-2026/
- Cite: https://treeallometry.org/equations/petrova-2026-birch-st/#source

## The facts, in the source's words

**Equation** (Eq. (4) and Table 4, p. 126):

> lnPi = a0 + a1lnD (4); lnPst: a0 = –1,9888, a1 = 2,1307

Cite: https://treeallometry.org/equations/petrova-2026-birch-st/#equation

**Trees measured** (Abstract (RU)):

> 18 и 12 деревьев соответственно березы и сосны

Cite: https://treeallometry.org/equations/petrova-2026-birch-st/#quote-fit-n-trees

**Our note:** The Baskerville log-correction is already in the printed intercept a0 (Table 4 footnote), so no separate factor. adjusted R2 reported: 0.947 (not used as r2). Pa excludes dead branches (reported separately as Pmort); the contract cannot express that exclusion. Only the 4 main fractions (stem in bark, branches, foliage, total) are added; bark and dead-branch fits omitted. 18 birch and 12 pine trees from 4 plots in one forest-swamp system.

## 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 = 5 | 4.22 | 4.22 | Computed from the printed form: hand-computed from the published form (Table 4 coefficients) |
| D = 10 | 18.5 | 18.5 | Computed from the printed form: hand-computed from the published form (Table 4 coefficients) |
| D = 15 | 43.9 | 43.9 | Computed from the printed form: hand-computed from the published form (Table 4 coefficients) |

Cite: https://treeallometry.org/equations/petrova-2026-birch-st/#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: Petrova, I.V., Plukha, N.I., Usoltsev, V.A., et al. (2026). Aboveground biomass and its allometric models for the main and under storeys of the forest-swamp system in the Middle Urals. Forests of Russia and economy in them, 3(98), 118–134. https://doi.org/10.51318/fret.2026.98.3.012

Cite this page for the record and checks: Tree Allometrics (Restoration Scope), "Betula pendula stem in bark biomass vs DBH (Eq. 4), forest-swamp, Middle Urals", checked 2026-11-01, https://treeallometry.org/equations/petrova-2026-birch-st/. 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/petrova-2026-birch-st.json
Report a problem: email info@restorationscope.com with the equation id (petrova-2026-birch-st) and where the right value appears.