# NE India mixed-forest AGB from DBH, power law (Model 1, second best)

Aboveground biomass equation for Dominant tree species of four NE Indian forest types, from Nath et al. 2019. 303 trees, DBH 10.1–90 cm. Listed on Tree Allometrics, a free library of tree allometric equations, each quoted from the source that published it.

## Equation

As printed in Nath et al. 2019 (Abstract):

> AGBest = 0.18D2.16 × 1.32

Cite: https://treeallometry.org/equations/nath-2019-model1/#equation

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

```
Aboveground biomass = 0.18 * D^2.16 * 1.32
```

Inputs: D = Diameter at breast height (1.3 m) (cm).
The source's own form: 0.18 * D^2.16 * 1.32, with D in cm; output in kg.
Cite: https://treeallometry.org/equations/nath-2019-model1/#canonical

## What it covers

- Output: Aboveground biomass, kg
- Taxon: Dominant tree species of four NE Indian forest types (mixed species); mixed
- Where: North East India (tropical semi-evergreen, tropical wet evergreen, sub-tropical broad leaved and sub-tropical pine forest). Cite: https://treeallometry.org/equations/nath-2019-model1/#where
- Biomes: tropical, subtropical, montane
- Stand: natural
- Trees measured: 303. Cite: https://treeallometry.org/equations/nath-2019-model1/#n_trees
- DBH range: 10.1–90 cm. Cite: https://treeallometry.org/equations/nath-2019-model1/#dbh
- R²: 0.705. Cite: https://treeallometry.org/equations/nath-2019-model1/#r2
- Correction factor: 1.32 (applied). Cite: https://treeallometry.org/equations/nath-2019-model1/#cf
- Method: Linear mixed model on log scale (forest type random effect), back-transformed with CF = exp(MSE/2). Cite: https://treeallometry.org/equations/nath-2019-model1/#method
- Verification: read in the original source
- Last checked: 2026-11-02. Cite: https://treeallometry.org/equations/nath-2019-model1/#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

Nath, A.J., Tiwari, B.K., Sileshi, G.W., et al. (2019). Allometric Models for Estimation of Forest Biomass in North East India. Forests, 10(2), 103.

- DOI: https://doi.org/10.3390/f10020103
- Access: open access
- Copy we read: https://www.mdpi.com/1999-4907/10/2/103/htm
- Every equation from this source: https://treeallometry.org/sources/nath-2019/
- Cite: https://treeallometry.org/equations/nath-2019-model1/#source

## The facts, in the source's words

**Equation** (Abstract):

> AGBest = 0.18D2.16 × 1.32

Cite: https://treeallometry.org/equations/nath-2019-model1/#equation

**Trees measured** (Section 2.2):

> Sample tree data (a total of 303 trees) were collected from four major forest types

Cite: https://treeallometry.org/equations/nath-2019-model1/#quote-fit-n-trees

**Smallest DBH** (Section 2.2):

> seven diameter classes were formed: 10.1–20 cm, 20.1–30 cm, 30.1–40 cm, 40.1–50 cm, 50.1–60 cm, 60.1–70 cm, and 70.1–90 cm

Cite: https://treeallometry.org/equations/nath-2019-model1/#quote-fit-dbh-min-cm

**Correction factor** (Section 2.3):

> Upon back transformation, each model was multiplied with a correction factor (CF) estimated from the residual variance or mean square error (MSE) using the formula CF = exp(MSE/2)

Cite: https://treeallometry.org/equations/nath-2019-model1/#quote-fit-cf

**Units** (Section 2.3):

> AGB is total above-ground biomass in kg dry matter tree−1, ... D is diameter at breast height in centimeters

Cite: https://treeallometry.org/equations/nath-2019-model1/#quote-published-units

**R²** (Table 2, Model 1 LME row (Adj R2 column)):

> 1 ... LME −1.73 (0.45) 2.16 (0.10) - 705 0.705 0.749

Cite: https://treeallometry.org/equations/nath-2019-model1/#quote-fit-r2

**Our note:** Coefficients as printed in the Abstract and Results (two decimals). Table 2 (LME, Model 1) prints ln(a) = −1.73 (SE 0.45) and b = 2.16 (SE 0.10); exp(−1.73) = 0.177, consistent with the printed 0.18, and the Model 1 residual variance 0.56 (Table 3) gives CF = exp(0.56/2) = 1.32. r2 is the adjusted R2 of the LME fit as printed in Table 2 (R2 = 1 − RVm/RVi for the mixed model). The 1.32 correction factor is part of the printed equation. Model 3 (0.32(D²Hδ)^0.75 × 1.34, the authors' best) was not added: the text gives wood density in kg m-3 but the printed form only gives plausible biomass with g/cm3, so the unit is unclear. DBH range is the sampling-class span, not a stated fitted range.

## 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 = 30 | 368 | 368 | Computed from the printed form: computed from the published form in the Abstract |

Cite: https://treeallometry.org/equations/nath-2019-model1/#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: Nath, A.J., Tiwari, B.K., Sileshi, G.W., et al. (2019). Allometric Models for Estimation of Forest Biomass in North East India. Forests, 10(2), 103. https://doi.org/10.3390/f10020103

Cite this page for the record and checks: Tree Allometrics (Restoration Scope), "NE India mixed-forest AGB from DBH, power law (Model 1, second best)", checked 2026-11-02, https://treeallometry.org/equations/nath-2019-model1/. 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/nath-2019-model1.json
Report a problem: email info@restorationscope.com with the equation id (nath-2019-model1) and where the right value appears.