Permanent Sample Plots

One of the fundamental elements of a breeding programme is to establish and regularly measure permanent sample plots (PSPs) within trial plantings. NZDFI now has over 600 PSPs throughout its trial network.

NZDFI’s earliest demonstration trials were planted with 11 species, but from 2018 onwards this was reduced to six species and included comparative genetic seedlots and clones.

A comprehensive measurement programme overseen by Ruth McConnochie was completed in 2021-22, thanks to Specialty Wood Products Research Partnership (SWP) funding. Ruth’s overall objective was ‘to analyse and report on the performance of NZDFI species across varying environmental conditions and compare the long-term adaptability and productivity of each species’.  

Data from all PSPs - i.e. across poor to top-performing sites - has been validated and stratified. The next step is to use statistical analyses to assess species x site performance, identify and review failed sites and species, and produce a list of plots for on-going measurement. Ultimately the analysis will identify winners and losers and provide recommendations on what to plant where, equally, what NOT to plant.

Table 1: 2018 Demonstration Trial - NZ Redwood Company, Paparoa near Taumaranui. An example of a site level analysis using the data collected for trials planted with the NZ Redwood Company in September 2018. These PSPs were measured in January 2022 when the trees were 3.4 years old.

Species Class Age (years) Survival % DBH_All   (mm) DBH_Top 25% (mm) Height_All    (m) Height_Top 25% (m) MAIH_All (m) MAIH_Top 25% (m)
E. bos PFS 3.4 90.3 43.9 63.8 4.8 6.6 1.4 1.9
E. bos NFS 3.4 76.7 41.7 69.4 4.7 7.0 1.4 2.1
E. glob SSS 3.4 90.3 104.9 126.7 7.9 9.3 2.3 2.7
E. glob PFS 3.4 84.0 94.0 119.6 7.2 8.8 2.1 2.6
E. macr SSS 3.4 88.0 69.3 91.0 6.1 7.4 1.8 2.2
E. quad NFS 3.4 88.3 61.6 100.3 5.5 7.3 1.6 2.1

NZDFI's seed source classification system

The ‘Class’ column in the table relates to the class of germplasm in the planted material. A seed source classification system is a practical tool to document the stages of tree improvement and assist with predicting plantation value. Seed is sourced in a variety of ways and each can have a different level of adaptation, and genetic composition.

In a breeding programme seed is obtained initially from locations that match the environmental conditions of where the seeds are collected (source) and the site where the seedlings are to be planted (with reference to altitude, rainfall, temperature and soil characteristics). This first step of domestication and selection from native forests are at a population level.

These early collections should represent a broad genetic base (genetic diversity) to allow selection and reduce the risk of inbreeding in future generations. These populations can be segregated at a provenance level if there are distinct differences in the growth habit or other desired traits.

To maximise the improvement of heritable traits, germplasm is managed at a family level to allow control of outcrossing and inbreeding. The resulting genetic gain is deployed in different stages of the breeding programme.

A system to identify the origin of seed or vegetative propagules to reflect genetic value and document genetic gain has been developed for NZDFI.

General criteria for germplasm source classification

The aim is to provide a simple, clearly defined classification system.

  • Classes represent major differences
  • Classes reflect a distinct step in genetic improvement.
  • Classes distinguish propagule types – seedling versus clonal
  • A descriptive code constructed that can be use for maps, databases, marketing material etc

List of Germplasm Classes

Class No. Code Description
1. NFS Native Forest Stand Naturally occurring populations of trees in a forest where the target species has a reasonable density that will allow out-crossing.
2. PFS Provenance Collection Seed collected from a distinct geographical region of native forest.
3. SSS Seedling Seed Stand Unpedigreed planted stand. Seed collected from phenotypically selected mother trees.
4. SSO Seedling Seed Orchard Pedigreed. Within and between family selection. Each family should ideally be represented by approximately the same quantity of seed.
5. CSO Clonal Seed Orchard Pedigreed. Established from clonal material produced by graft or cutting
6. CCS Clonal cuttings Pedigreed. Tree stocks produced by cuttings from select clones.
Genetic value increases from Class no. 1-6

Early PSP data analysis

Earlier PSP measurements were completed in the summers of 2013-14  and and 2015-16 and were reported below. Since then, PSPs at each of these sites will have been re-measured at least once.

NZDFI PSP MeasurementProgramme 2015-16 (pdf)

Initial analyses are already showing some interesting results. Example analyses of survival and comparative height/growth data from two of our trial sites are available below:

1. Saggers trial, Marlborough

This demonstration trial was established in 2011, and has been measured twice.

Aerial photo of Saggers plot layout (pdf)

Saggers survival, height and growth analyses  (pdf)

2. Lake Taupo Forest Trust trial site

This demonstration trial is on a pine cut-over site, was established in 2014, and was measured for the first time in summer 2015-16.

GIS-based trial site analysis (jpeg)

Survival and height growth analyses (pdf)