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National survey of indigenous plantations for carbon accounting

Project Status: Completed

50 year old totara plantation at Holt Forest Trust at Waikoau, Hawkes Bay. Photo credit: Michael Bergin

50 year old totara plantation at Holt Forest Trust at Waikoau, Hawkes Bay. Photo credit: Michael Bergin

Tāne’s Tree Trust (TTT) completed a nationwide survey of significant plantings of native trees and shrubs in 2012. The history and growth performance of these stands are used to increase the reliability of growth models and carbon sequestration estimates of key native tree and shrub species.

More than 120 landowners and managing agencies have responded to a questionnaire requesting information about planted stands of indigenous trees and shrubs.

Most stands have been inspected and Permanent Sample Plots (PSPs) or growth plots established. Stand management information and growth data including stem density, stem diameter, tree height and tree form is being collated.

Background

Preliminary calculations indicate that at least 80 million seedlings of indigenous timber trees have been planted throughout New Zealand over the past 150 years to meet a wide range of purposes. Planting programmes involving hundreds of thousands of seedlings of many indigenous species were initiated by the Lands Department before 1900 and continued with the NZ Forest Service into the 1980s.

Most local authorities have planted indigenous trees in parks and gardens during the past century, and many of these well-maintained stands exist today. Interest in the planting of indigenous timber species by private individuals and public organisations has also intensified over the last couple of decades.

A survey covering some of the native tree plantations was undertaken by the Forest Research Institute (FRI) in the mid-1980s. Nearly 30 years on, TTT has completed a new nationwide survey of significant plantings including re-measurement of some of those covered by the earlier FRI survey. Many new plantings were located and included in this more recent survey and included assessment of a range of native shrub species often used as nurse cover and established before or at the same time as the tree species to provide early shelter and improve stem form.

The TTT indigenous plantation survey was funded for three years by the Ministry of Agriculture and Forestry’s Sustainable Farming Fund and TTT with support from Scion’s Diverse Species Programme as part of the Future Forests Research (FFR) Diversified Species Programme. Considerable inkind support was provided by members of TTT, the NZ Farm Forestry Association, the NZ Institute of Forestry, local authorities, numerous environmental trusts, landowners, and the Department of Conservation.

Methods

The survey involved both the re-measurement of plots from key plantations included in the earlier survey, and the location and measurement of additional suitable plantations of native trees. The survey also included a selection of revegetation sites planted with native shrub species. The aim was to obtain growth data and stand management information for developing and refining growth and carbon models for native trees and shrubs.

In larger stands, Permanent Sample Plots (PSPs) were established within representative areas of known age and management history. PSPs were established following the methods of Ellis and Hayes (1997) using circular or square plots up to 400 m2. From 1-6 plots were established at each site depending on the range of species and ages and extent of the stand. In smaller stands, inventory growth plots were established.

Age of stands since planting was determined from stand records and landowners. Stand stocking was calculated based on the number of trees within bounded plots or estimated in inventory plots using a sample of intra-tree distances.

Diameter at breast height (DBH, measured 1.4 m above ground level) was measured for tree species. Due to multiple leaders and heavy branching from near ground level, root collar diameter (RCD, diameter measured 10 cm above ground level) were usually taken for shrub and small tree species. However, DBH was measured in some older stands of small tree species.

Data from the new survey was combined with data from both the earlier plantation survey to form a comprehensive native tree and shrub database known as the Tāne’s Tree Trust Indigenous Plantation Database.

Results

Location of planted stands of native trees and shrubs assessed nationwide by Tāne’s Tree Trust.Location of planted stands of native trees and shrubs assessed nationwide by Tāne’s Tree Trust.Over 120 planted stands of native trees and shrubs were inspected nationwide and assessed for growth (Figure 1). Almost 10,000 planted trees and shrubs were measured during the survey comprising 4000 conifers, 2000 hardwood trees and 3000 shrub hardwoods with an age range of 3-110 years. Most stands assessed were less than 50 years of age. Stand density averaged 1900 stems/ha for trees and 3500 stems/ha for shrubs and small trees reflecting the high proportion of relative young plantations established.

Over 60 different native tree and shrub species were encountered during the survey. Of the more than 10,000 trees and shrubs assessed during the survey, 6600 were conifers, 800 beeches, 900 other hardwood trees, and 2200 shrubs and small trees.

The major conifers planted are totara, rimu, kauri and kahikatea, and of the beeches, red beech and black beech are most common. Of the remaining hardwood trees, there are relatively high numbers of puriri followed by karaka on a limited number of sites. Shrub and small trees often planted included karamu, ti kouka, manuka, kanuka, houhere, kohuhu, tarata, manatu and whauwhaupaku.

Detailed species-specific models of height, diameter and volume growth, as well as carbon sequestration for planted natives have been developed from this survey and are provided in Section 10 of the Tāne’s Tree Trust Technical Handbook. See the Outputs section below.

Outputs

Seven technical articles have been completed for the TTT Handbook Section 10 including one on carbon sequestration and two case studies:

  1. Nationwide survey of planted native trees
  2. Performance of planted native conifer trees
  3. Performance of planted native hardwood trees
  4. Performance of planted native shrubs
  5. Carbon sequestration by planted native trees and shrubs
  6. A decade of planting by the Kauri 2000 Trust
  7. Establishing a native production forest, Rewanui Forest Park, Wairarapa

Refer to the Publications page for PDFs of these articles.

Contacts for this project

  • Dr David Bergin, Tāne’s Tree Trust: Enable JavaScript to view protected content.
  • Michael Bergin, Environmental Restoration Ltd: Enable JavaScript to view protected content.