Cost-effective planting and reversion scenarios for establishing native forests - factsheets
Project Status: Current
For the One Billion Trees Programme to have maximum impact, a range of site-specific, low-cost planting and regeneration scenarios are urgently required for establishment of permanent native forest, especially for scaling up the establishment of native forestry across marginal, pastoral hill country. The overall objectives of this project are to:
- Promote reduced-cost, large-scale establishment scenarios for native forest; and
- Demonstrate proof of concept by profiling low-cost establishment scenarios in collaboration with project partners, including native plant nurseries and planters/landowners.
We will do this by producing a minimum of 12 factsheets and six establishment plan templates for landowners and community groups interested in establishing permanent native forest for multiple purposes.
A brief summary of each draft factsheet is provided below.
- Right species right place
An understanding of ecological requirements of each of the native tree species will allow matching each species to suitable sites that mimics natural regeneration and gives a natural appearance. This planting pattern is likely to give good survival and growth rates for most species.
There is considerable variation in the ecological requirements and site preferences for native species. Some require shelter in early years on open sites to improve growth while others tolerate specific site conditions such as greater moisture levels. Planting native species at random through an area is unlikely to match species to the most suitable sites and therefore will probably compromise overall performance.
Choice of species and planting patterns will also be influenced by the objectives of planting. Growth habit and performance of each species will influence which ones are most suited to specific objectives and whether management of part of the planting for timber production is feasible even if it may be a long-term option.
- Seed collection of natives
Species selection and seed collection are critical steps in the restoration process, and because seed availability can be limiting, it needs to be considered long before the actual time of sowing. In most instances, seed is collected by hand from appropriate plants—a slow process that limits the quantities of viable seed available for large-scale restoration programmes.
Seeds of New Zealand native species are regarded as inherently poor germinators. Although low viability may be responsible for this, there is increasing recent evidence that low germination in a range of native species may be because of seed dormancy, i.e., the failure of a viable seed to germinate despite being exposed to favourable environmental conditions.
- Nursery raised native seedlings - selecting the right stock
The use of strong, healthy planting stock is critical to the success of any planting programme. Seed must be collected from the best sources and nursery stock raised for the particular programme well ahead of the planting season. A variety of plant grades and container types is available. Experience in the evaluation of planting stock is described and other approaches used in operational-scale planting are discussed briefly. Most information is based on experience rather than on comparative experimental trials.
Factors that should be considered before planting include relative suitability of bare-rooted and container-grown stock; appropriate plant size and quality; and the type and size of containers.
- Controlling pest animals and livestock
Farm livestock, many animal pests including deer, goats, pigs, possums, hares and rabbits, and even some native birds such as the pukeko can cause extensive damage to existing native forest and scrub and newly planted areas of native trees and shrubs. Effort should be put into controlling those animals that pose a risk to newly planted natives prior to planting, and ongoing control is likely to be necessary until the planted trees are well established.
While the role of mammalian herbivores in primeval New Zealand was at least partly filled by the moa, most of New Zealand’s tree and shrub species are highly palatable to introduced grazing animals. In addition, under intensive agricultural systems, our soils and plants cannot cope with the trampling and waste from stock.
- Maintenance of planted natives
Weed control, often referred to as ‘releasing’, is essential with any planting project using natives. A nationwide survey of native tree plantations identified suppression by grasses and herbaceous weeds, ground ferns, and exotic scramblers and shrubs or brush weeds as the main cause of poor survival and slow growth. Many of our native trees and shrub species are relatively slow growing especially for the first year or two after planting. It is during this time that vigorous fast-growing exotic species can out-compete planted native seedlings for light, preventing growth and contributing to mortality.
Several factors need to be considered when undertaking weed control. These include the quality of site preparation done before planting, timing of weed control operations, site characteristics, and scale of planting and resources available to carry out maintenance.
There is increasing interest in landowners who have recently or are about to clear fell stands of radiata pine in replacing them with a permanent native forest. These are at all scales from small 1-2 ha blocks to substantial areas owned by iwi, some well over 1000 ha.
The options to convert clear-felled radiata stands, or indeed other exotic forests such as eucalypts, needs to be assessed on a site-specific basis as climate, site, soils, weed growth including wilding pines, and pest animals are all factors that will influence decisions.
This factsheet provides landowners with some of the issues to consider when contemplating converting a productive exotic stand that has been logged to natives.
- Monitoring success of planted and regenerating natives
Most native planting projects are focused on planting and few follow up with monitoring other than a cursory glance that hopefully most planted natives have survived and beaten the weeds. Planting trees is only the first step toward establishing new areas of native forest.
Monitoring early survival and growth of your plantings will provide you with valuable insights into what is working or not. It will help you schedule in timely weed and pest animal control and enable you to learn from any failures.
Councils and some community groups are very keen to see a more formal quantitative approach but few have the skills, resources or practical methods to undertake monitoring, so it is hardly ever carried out. This factsheet outlines the options for monitoring newly planted native forest. Natural regeneration is increasingly being promoted for large scale establishment of native forest and some insights into monitoring of natural regeneration are provided.
- Building resilient new native forest
Greenhouse gas emissions have significantly altered the composition of the atmosphere and subsequently changed the global climate. Deforestation has also had an impact as fewer trees mean less absorption of carbon dioxide. Also, forests influence the local climate, providing shade and the cooling effect of evapotranspiration, making the surrounding environment more mesic (i.e., higher levels of moisture).
In New Zealand, we need to identify methods to improve the survival of native tree plantings and naturally regenerating forest. Wildfires have always occurred, but predictions of increased fire risk associated with anthropogenic climate change means that massive wildfires, similar to what was experienced recently in the South Island, are likely to become more common in parts of New Zealand. Effectiveness of green firebreaks largely depends on the selection of suitable native plant species with low flammability.
- Long-term management of planted natives
Many native tree species show excellent potential for plantation management to produce timber. Woodlots of key native timber trees will give optimum growth as part of single or mixed-species plantations – if they are established on sites that suit the ecological characteristics of their species and they are managed appropriately.
Those planting native trees for multiple reasons are establishing a resource where future generations have the option to manage for extraction of high-quality, high-value specialty timber. Sustainable harvesting plans can be designed to ensure that the non-timber values of planted native forest will be preserved using continuous cover forestry principles, i.e., only a small proportion of the stand is harvested at a time to leave the high forest structure and associated environmental values intact.
The aim is to have the factsheet series available on the TTT website with links to websites of other stakeholders as requested.
This TTT project is jointly funded by the Te Uru Rākau’s 1BTs Partnership Fund, with co-funding from the TTTs research fund and the Our Forests Our Future programme supported by The Tindall Foundation, project partners including Pamu Farms (Landcorp), other landowners and community groups, and Trees That Count. We are also collaborating with the research providers Scion and Auckland University of Technology in the delivery of the latest information on best practice methods for establishing multiple-use native forestry as part of the government’s current One Billion Trees programme.