# Pittosporum crassifolium (Massey University): AGB from D and H (Table 7)

Aboveground biomass equation for Pittosporum crassifolium, New Zealand, from Wangui et al. 2026. 5 trees. Listed on Tree Allometrics, a free library of tree allometric equations, each quoted from the source that published it.

## Equation

As printed in Wangui et al. 2026 (Table 7):

> P. crassifolium Massey University ln(AGB) =ln (a)+b×ln(D)+c×ln(H) -3.65*** 3.93** -2.40* … CF 1.00

Cite: https://treeallometry.org/equations/wangui-2026-agb-pittosporum-crassifolium-massey-d-h/#equation

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

```
Aboveground biomass = 1.0 * exp(-3.65 + 3.93 * ln(DRC) + -2.4 * ln(H))
```

Inputs: DRC = Root collar / stem base diameter (cm); H = Total tree height (m).
The source's own form: 1.0 * exp(-3.65 + 3.93 * ln(D) + -2.4 * ln(H)), with D in cm, H in m; output in kg.
Cite: https://treeallometry.org/equations/wangui-2026-agb-pittosporum-crassifolium-massey-d-h/#canonical

## What it covers

- Output: Aboveground biomass, kg
- Taxon: Pittosporum crassifolium (species), family Pittosporaceae; shrub
- Where: Massey University natural reserves and Dairy4 farm trial site. Cite: https://treeallometry.org/equations/wangui-2026-agb-pittosporum-crassifolium-massey-d-h/#where
- Biomes: temperate
- Stand: mixed
- Trees measured: 5. Cite: https://treeallometry.org/equations/wangui-2026-agb-pittosporum-crassifolium-massey-d-h/#n_trees
- Correction factor: 1 (applied). Cite: https://treeallometry.org/equations/wangui-2026-agb-pittosporum-crassifolium-massey-d-h/#cf
- Method: OLS regression on natural logarithms (power form), back-transformed with correction factor CF = exp(RSE^2/2). Cite: https://treeallometry.org/equations/wangui-2026-agb-pittosporum-crassifolium-massey-d-h/#method
- Verification: read in the original source
- Last checked: 2026-11-02. Cite: https://treeallometry.org/equations/wangui-2026-agb-pittosporum-crassifolium-massey-d-h/#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

Wangui, J. C., Pain, S. J., Kenyon, P. R., Tozer, P. R., & Millner, J. P. (2026). Biomass and carbon estimation for three browsable native shrubs in New Zealand. New Zealand Journal of Forestry Science, 56, 16.

- DOI: https://doi.org/10.33494/nzjfs562026x567x
- Access: open access
- Copy we read: https://nzjforestryscience.nz/index.php/nzjfs/article/download/567/153
- Every equation from this source: https://treeallometry.org/sources/wangui-2026/
- Cite: https://treeallometry.org/equations/wangui-2026-agb-pittosporum-crassifolium-massey-d-h/#source

## The facts, in the source's words

**Equation** (Table 7):

> P. crassifolium Massey University ln(AGB) =ln (a)+b×ln(D)+c×ln(H) -3.65*** 3.93** -2.40* … CF 1.00

Cite: https://treeallometry.org/equations/wangui-2026-agb-pittosporum-crassifolium-massey-d-h/#equation

**Correction factor** (Methods, Equation 2; Table 7):

> CF = e(RSE²/2)  Equation 2; Table 7 CF column 1.0

Cite: https://treeallometry.org/equations/wangui-2026-agb-pittosporum-crassifolium-massey-d-h/#quote-fit-cf

**Our note:** AGB is the sum of stem, branch and foliage dry biomass of the shrub. Natural log. D is the basal stem diameter over bark about 10 cm above ground (multi-stemmed shrubs: square root of the sum of stem diameters), mapped to DRC; H is total height in m. Table 7 reports adjusted R2 = 0.996 and RMSE = 0.038 (not used as r2 or rse). Shrubs had basal diameter up to 10 cm (mean D 3.4 to 3.8 cm by species, Table 4); the paper prints no D range for these models. The CF column is the factor the paper applies to back-transformed predictions.

## 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 |
| --- | --- | --- | --- |
| DRC = 2, H = 1 | 0.396 | 0.396 | Computed from the printed form: computed from the published form (a is ln(a), CF applied, coefficients as printed) |
| DRC = 4, H = 2 | 1.14 | 1.14 | Computed from the printed form: computed from the published form (a is ln(a), CF applied, coefficients as printed) |
| DRC = 8, H = 3 | 6.59 | 6.59 | Computed from the printed form: computed from the published form (a is ln(a), CF applied, coefficients as printed) |

Cite: https://treeallometry.org/equations/wangui-2026-agb-pittosporum-crassifolium-massey-d-h/#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: Wangui, J. C., Pain, S. J., Kenyon, P. R., Tozer, P. R., & Millner, J. P. (2026). Biomass and carbon estimation for three browsable native shrubs in New Zealand. New Zealand Journal of Forestry Science, 56, 16. https://doi.org/10.33494/nzjfs562026x567x

Cite this page for the record and checks: Tree Allometrics (Restoration Scope), "Pittosporum crassifolium (Massey University): AGB from D and H (Table 7)", checked 2026-11-02, https://treeallometry.org/equations/wangui-2026-agb-pittosporum-crassifolium-massey-d-h/. 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/wangui-2026-agb-pittosporum-crassifolium-massey-d-h.json
Report a problem: email info@restorationscope.com with the equation id (wangui-2026-agb-pittosporum-crassifolium-massey-d-h) and where the right value appears.