Guidelines for native revegetation plantings
These guidelines will assist applicants in preparing proposals for native revegetation planting covering:
•pre-planting site assessment
•planting plan assessment
•annual monitoring programme.
1.Pre-planting assessment guide:
To ensure the survival of revegetation planting and indigenous biodiversity, it is important that the appropriate plants are selected for the site. There are two aspects to selecting appropriate plants:
a.sourcing from the ecological district i.e. eco-sourcing:
New Zealand has been divided into ecological districts based on the underlying geology, landforms, and soils which affect the plant species found within an area. Within theses ecological districts the same plant species often have slight variations, which are adapted to the specific conditions of the area. To retain these variations and in essence the genetic diversity, it is important plants sourced in the specific ecological district are used
b.appropriate plants for the locality of the planting:
i.slope i.e. steepness affects the species which will survive
ii.characteristics of the soil i.e. certain species do not grow well in certain soils
iii.wind i.e. certain species are not wind tolerant
iv.aspect i.e. direction the slope faces, as this affects the dryness of a slope
v.degree of shading. Certain species are light intolerant, i.e. secondary succession plants such as nikau and ferns. Others cannot survive in low light conditions, i.e. primary succession plants such as manuka and kanuka
vi.distance from the coast. Many plants are not tolerant to salt spray and struggle to survive in coastal environments
vii.wetness of the site. Many plants either do not grow in wet conditions, such as kauri, or only grow in wet soil conditions, such as kaihikatea
viii.viii. frost zones as certain species are frost intolerant
To ensure appropriate plant species are selected, the council expects an assessment by a suitably qualified and experienced person, with the following information to be provided with each application:
ix.ecological district of the site
x.characteristics of the soil i.e. clay, silt, loam
xi.soil drainage
xii.topography and aspect of the area to be planted
xiii.exposure of the site to wind, frost, sunlight and salt spray
xiv.extent of existing bush or native vegetation on the site and its species composition
xv.distance from established bush if there is none on the site and its condition.
Points (xiv) and (xv) above will help the council determine which plants would grow naturally on the site and, therefore, they should be in the planting plan assessment.
Where an applicant proposes to defer planting requirements under rules 12A.13.2.4, 12A.13.2.8 or 12A.13.2.9, it is important that the production forest and its harvest be managed as to facilitate native revegetation planting and minimise any adverse effects of production forestry on any naturally occurring native revegetation.
c.management of planting where planting requirements are deferred in areas of existing production forest within a riparian management or slopes constraints area. Native species may naturally regenerate as an understorey beneath existing production forestry. To encourage this process, the pre-planting assessment must include a management plan detailing methods for:
i.optimising the development of a naturally regenerating native understorey
ii.harvesting the production forest in a way which minimises loss and damage to the naturally regenerating native understorey
iii.minimising the loss of and damage to any naturally regenerating native vegetation with in-stream habitats or in areas
iv.adjacent to the riparian or slopes constraints areas
v.managing and minimising weeds and pests
vi.excluding livestock.
2.Planting plan assessment:
To help the council establishg whether a planting proposal is adequate, this asessment must be produced by a suitably qualified and experienced person and contain the following:
•purpose of the planting, including hill country erosion control, stream bank erosion, habitat control, habitat restoration, ecological corridor creation, buffer planting to protect the edges of existing bush, water quality enhancement
•location and extent of planting on a plan
•site preparation for planting, including stock-proof fencing of areas, weed and animal pest control
•site planting, including species to be planted, size of plants and where they are to be planted, density of planting, sourcing of plants and fertilisers
•maintenance of planting, including fertiliser, releasing plants, animal and plant pest control, and mulching.
The reasons for the detail required in the planting plan assessment are discussed below:
a.site preparation:
Many of the areas to be replanted have relatively harsh growing conditions because of animal pests, stock and weeds and grasses which compete with the new plants. Therefore, it is important to minimise these effects by:
i.identifying and removing weeds.
Weeds compete with native plants by reducing moisture and nutrients available. Because the weeds are usually better able to do this than many natives, especially in open and exposed situations, they need to be removed manually or with sprays before planting. Continual management is needed after planting to ensure the site is not re-infested. It is also important to close the canopy closure as soon as possible after planting, as most weed species do not survive in shady conditions.
Kikuyu is one species which competes vigorously with native plants, suppressing growth by releasing a chemical into the soil, which reduces root growth. It must be removed from the site of the planting hole for each plant and cleared regularly from the site so that new plantings are not strangled. Canopy closure is the best mechanism in the long-term control of kikuyu, as it is shade intolerant.
Mulching can be an effective means of suppressing weed growth in the initial phases of revegetation, reducing the need for weed control (see section on maintenance planting in this appendix).
ii.animal pest control:
Browsers, such as possums, feral goats and feral deer are a large threat to native plantings. They must be controlled and eliminated to levels where the plantings are not severely affected. possums must be eradicated using bait stations, trapping or shooting. In the case of feral deer and goats, fences are required or the animals eradicated.
After the planting is established, animal pest control must continue to ensure the long-term survival of the plants and also undergrowth to generate
iii.stock control:
Stock can cause a huge amount of damage to native planting through browsing or trampling and that area must have a stockproof fence. The fence must be maintained in the long-term to prevent keep stock out, allow for undergrowth regeneration, and allow a diversity of species to establish.
b.site planting:
i.canopy closure and planting spacing
After planting, the canopy must be closed as quickly as possible because:
•many weeds, and kikuyu, are more easily suppressed and controlled, as they tend to be shade intolerant
•summer water stress is greatly reduced
•frost intensity is greatly reduced or eliminated
•problems caused by wind are reduced i.e. wind and cold
•a closed canopy is more likely to attracted seed eating birds that increases the number of seeds deposited on the floor beneath the trees.
All of the above results in greater species diversity, especially for sensitive plants which require shade and conditions free of extreme conditions such as wind and frost.
To acheive rapid canopy closure, the native plants should be planted at a minimum density of 1.4m centres i.e 5100 stems/ha.
ii.size of plants:
The size of plants affects their ability to survive when planted out. Very small plants are less likely to survive, as their root system is not well established. Very large plants are also less likely to survive because of the physical conditions of most revegetation sites, including wind and salt exposure, extremes of conditions, drought and damp conditions. Larger plants take longer to establish extensive root systems to anchor them and to provide nutrients for growth, often resulting in their being toppled over by wind or damaged. Based on these constraints, the most appropriate sizes for planting out are considered to be root trainers, PB3/4 or PB2 and PB5.
iii.fertiliser:
The decision to apply fertiliser, what type and in what quantity, will vary depending on the site.
Fertiliser can proactively assist native plants to establish, grow quickly and close the canopy, especially in coastal environments or where they are planted into kikuyu. However, too much fertiliser can be toxic to native plants and lead to poor growth.
In many cases the ground will already be quite fertile and support good growth. While many areas of native revegetation have been fertilised in the past for pasture growth, this is not appropriate for native tree establishment as these fertilisers tended to be nitrogen-based. Trees require trace elements, minerals and phosphorous-based fertilisers.
Certain environments will be adversely affected by fertiliser, such as waterways and riparian areas, and there may be good reason to avoid applying fertiliser to adopting a cautious approach. Conservative applications uses slow- release tablets in each planting hole, allowing soil to act as a natural filter. A cautious approach which considers timing is required where fertiliser is to be a side dressing. Application should coincide with growth spurts during spring and autumn to maximise nutrient uptake and prevent nutrient enrichment of receiving water bodies.
iv.time of planting:
The timing of the planting is important. Late autumn and winter i.e. late April to September, are the best months as most native plants are adapted to moist conditions and watering is required at the time of planting. Rainfall is the best means of ensuring adequate watering as it encourages the development of deep roots. Hand or surface watering can encourage the development of surface roots, resulting in the plants being more adversely affected in low rainfall periods. However, the disadvantage of planting in winter is the exposure to frost, particularly on level, exposed sites in inland areas. In these areas, hardier pioneer species should be used to provide shelter before planting more sensitive species. Mulching greatly increases the chances of survival as it helps retain soil moisture by reducing evapotranspiration (see section on mulching in this appendix.
c.maintenance planting:
i.mulching:
This involves spreading permeable material around newly planted trees to:
•protect the roots
•reduce moisture loss from the soil
•insulate the soil, thus stabilising soil temperatures
•suppress weed growth.
Mulches can be either organic e.g. straw, sawdust, bark chip, wood shavings, compost, grass, leaves, or synthetic e.g. wet paper/cardboard, and tar paper.
Mulching greatly increases the chances of survival for plants on dry, open, exposed sites.
The disadvantages of mulch is that it can:
•introduce plant diseases or insect pests to the site
•introduce weed species
•prevent water from reaching the roots, making it important to wet the soil before applying mulch
•increase costs.
Certain mulches, such as sawdust and bark chip, can be toxic to plants and they must be well rotted down.
Mulches comprising compost and grass clippings should be treated with caution. Unless temperatures high enough to ‘cook’ the seeds have been reached, it has the potential to introduce unwanted weed species to the area. Cheap mulches should be treated with caution, as they tend to rob the soil of nitrogen, stunting adjacent plant growth unless compensated for with fertiliser application.
ii.weed control and animal control:
This involves ongoing plant and animal pest control to ensure the survival of the planting (see the section onsite preparation above).
iii.monitoring programme
Monitoring must be done for five years, as it takes between 3-5 years before native replantings are well established and their certainty of survival is assured. The following needs to be monitored:
•survival rates. Council requires a 90 per cent survival rate which is thought appropriate in ensuring the replanting will become ecologically viable
•size of plants. This is an indication of the health of the plantings. The greater the growth, the healthier the planting and therefore the more likely a planting is to survive
•Canopy closure. If planting is healthy, canopy closure should occur at year three, although it can take to year five if site conditions are particularly harsh. This is an important indication of the health of the planting.
iv.plants that do not survive should be replaced to avoid creatings which could allow weeds to enter the planting and to ensure there is an adequate canopy cover in the long-term.
Reference
Evans, B. 1983. Revegetation Manual: Using New Zealand Native Plants. Produced for the Queen Elizabeth National Trust II.