Learning about Northland Native forest regeneration

Large areas of the lower canopy in the forest conservation area have been devastated due to grazing from goats, pigs possums and rats.

This page focuses on the regeneration of plants in the forest around the lodge

All of our Native forests have been impacted by man and other introduced species so

understanding Native forest regeneration is important.

As more land is retired and additional pest control is applied, managing regenerating forests successfully, will play a large part of conservation.

The forest around the Lodge has been logged, burnt, grazed by cattle and attacked by introduced pests. Different areas of the forest are at different stages of regeneration. This provides a great opportunity to study the regeneration of a native forest. It is easy to see and study  the different stages and how they relate to each other.

The aim is for students

• to recognize the various stages of native forest regeneration
• understand what is required to allow a forest to regenerate

Regeneration is how a forest heals itself

A forest is a living organism and like all living things it needs to have a way of recovering from harmful incidents.

Like our bodies (for example when you scrape skin off your knee) the forest goes through a succession of stages until it is back to its normal state.

The Tangihua Forest surrounding the Tangihua lions lodge has been modified by Europeans  and introduced pests. Large areas of the canopy and under canopy have been destroyed or altered.

The group who made 450 bait stations for our pest control program.

The first step for a regenerating forest is often conservation.

The first step for most of our forests are conservation strategies which will significantly reduce or stop the damage inflicted by introduced animals.

In most of our native forests the damage is caused by introduced animals. Even if they are not the initial cause these animals will prevent the forest from naturally regenerating.

Introduced pests not only prevent regrowth but by grazing some species and not others, they decide which species will establish successfully and which will not.
Although goats, pigs and possums are the biggest problem, rats and mice cause considerable damage by eating the seeds which would normally stay in the soil ready for an event.

Areas of bush with heavy infestations of pests are often very open at ground level with no mid canopy. This can be seen on the nature trail where there are a lot of older trees and many young plants up to a metre high. The trees which should have been in between were killed off.

For more information about our conservation projects

How forest plants regenerate to form a stable bush habitat

Native forests regenerate over successive stages where each plant community improves the conditions for the next.

These stages occur in a predictable manner. One group of plants will establish, over time they are replaced by another group until a final stage is reached and you have a stable, mature forest. This is called plant succession.

Each individual forest regenerative stage is called a seral community

Typical examples of this succession and seral communities in the northland forests are.

1. First of all light-demanding pioneer or primary species such as grasses, ferns and sedges establish
2. They are closely followed by  hardy  shrubs. Manuka
3. They are followed by taller longer lived colonisers. Kanuka
4. Taller emergent species can then establish. lancewood, Rewrewa
5. Under these trees only the more shade tolerant canopy species such as kauri, Rimu, can survive.
6. Eventually, the colonising species are replaced by tree ferns, climbing and perching plants and a climax forest is reached. The cycle continues as trees fall through decay, wind, flood or fire.

Many plants are adapted to just one phase of a forest succession. They suit either the pioneer phase, the climax stage, or somewhere in between

6ft 3 man standing beside a mature Kauri in unlogged section of the Tangihua ranges.

Plant succession in New Zealand native bush

As a succession proceeds, some plant and soil trends are fairly universal.

The soil changes: As the process progresses  more organic matter is deposited from plants, resulting in more soil which is richer in nutrients. This means more and other types of plants are able to establish.

Plants change:

• From species that regularly produce many small, light seeds, to those that produce a few large seeds, or occasionally produce many seeds.
• Plant height increases.
• Plant density and variety increases.
• Species with short life cycles, are replaced with long-lived trees
• Shade-intolerant species are replaced to those that tolerate shade

As the plants change so do the animals that live in the forest.  As the stages progress you will find a far wider range of plant and animal species.

In the climax stage, although there is still constant change due to plant growth, storms, fire and other influences, the forest will have matured with many big trees. The forest will remain very similar and stable for 100s if not 1,000s of years.

This is the stage the Tangihua forest was at before Maori discovered New Zealand. A fully functional forest  with large numbers of mature trees providing habitats for a wide range of animals and other plant species.

Tutu can be seen growing on the steep banks on the lodge road.

A variety of factors will decide which plants will become established.

Different plants do better in different habitats, The factors effecting the habitat in the Tangihua ranges are:

• light availability  – some plants can establish in shade others cannot tolerate to much light.
• Soil type and availability  – soil depth for anchoring and nutrients are an important factor
• Altitude  – Different species grow at different altitudes
• Soil moisture  – some prefer wet areas others can only survive on well drained slopes
• Plants seeds  available at the time either from local trees or stored in the ground.
• Grazing, some plants intolerant to grazing by introduced species will not be able to establish
• Nitrogen.  All living things need nitrogen to grow and where there is no top soil or organic soil,  there is little nitrogen. Some native plants can fix nitrogen, one of these is Tutu. Tutu will become established  and over time, the dead leaves and roots of will mix into the soil creating a nutritious top soil complete with nitrogen. As the nitrogen content increases other plants are able to grow there too. Kowhia also fixes nitrogen and can establish rocky ridges with little soil which is why they are so common in the Tangihua’s.

As the forest gradually grows back, broadleaved trees may dominate for 200–500 years – These trees will have established at the same time as some conifers such as Kauri. The conifers Kauri, Kaihikea, Totara, Rimu will live 500- 2000 years and tower above the forest. As the Broadleaved species fall over more conifer seedlings will germinate.  Eventually the conifers will dominate and the forest will become known by its biggest most common trees e.g the Tangihua forest is a Kauri forest

An example of this is the confidence course where a large bushy Totara and other trees were removed. Four years latter there is a dense regrowth from shrub type plants.

Gap-phase regeneration

This occurs when there is a disturbance to an existing forest, for example when a fire or storm leaves an opening in the forest, a slip or just a large tree falling

In this case the first plants back were the grasses and now Manuka, Mingimingi, Kanuka and other bushy shrubs or stage two plants.

In older mature forests Conifer (Kauri, Kaihikea, Totara, Rimu) regeneration is stimulated by such a disturbance. Seedling and sapling growth of many species is prolific, and one or more species grows up filling the opening. They will compete amongst their own and other species for domination until the strongest survives. In order to do this they tend to grow straight and tall where in situations where this is more room they are much bushier. An example of this is Totara trees on the nature trail nand Totara on open farm land .

The regeneration of a forest does not only apply to the plants.

The lack of birds is very apparent in the Tangihua’s,  less noticeable are the other species, snails, invertebrates, fish etc. This has an impact on the forests ability to regenerate.

Many of our plant species will not survive unless they are pollinated. This is carried out by insects, mammals and birds, for example Bees, Bats and Tui. The seeds then need to be spread, which often done by birds such as wood pigeons.

In all cases these animal species require a suitable habitat. Open country and species that  germinate in open land  cannot provide food and habitat for the birds that are required for a stage three regenerating forest.

Important food sources for example Epyphites such as crimson rata which flower in may, june provide food for insects and birds in early winter when food is scarce. These plants must have mature forest in order to exist.

This is why the remaining patches of mature forest are so important.

As described these other species play a vital role in a healthy forest and must be able to regenerate as well.

The issues all forest species are

• loss of habitat
• Predation
• Disease

The loss of habitat in the forest has, to a certain extent, been addressed, predation and grazing are the main issues. Once the predators, ranging from grazing animals to carnivores are under control the forest will recover.

New diseases are also looming as a threat, Kauri dieback, Myrtle Rust, and require monitoring and dealt with.

Introduction to the Regenerating Native Forest at the lodge

The Tangihua forest is a Regenerating Native Forest. The forest surrounding the Tangihua lions lodge has been modified by Europeans  and introduced pests. Large areas of the canopy and under canopy have been destroyed or altered making it easy to see and study the different regenerative stages and how they relate to each other.

At this stage the forest is regenerating but animals such as pigs, goats possums, rats, and mice still have a significant negative impact.

The conservation program.

It is apparent that the fate of the ecosystem in the Tangihua Ranges depends on putting in place conservation strategies which will significantly reduce or stop the damage inflicted by introduced pests. The forest, if this is done will regenerate or we can  successfully reintroduced and established locally extinct species of animals.

DOC does not have enough funding to conserve the Tangihua forest, it is up to the community and others to  step up.

The Tangihua lions lodge has set up the following

• Tangihua Community Pest Control Area  click here for more information 
• Conservation on DOC land  click here for more information
  
• Conservation trap lines for schools click here for more information

Teaching resources for regeneration

We have

1. Open spaces that are kept mown and tidy for campers and other human habitation. This is similar to a farmed paddock, burnt over area or city park
2. Clearings that are turned over by pigs and browsed by goats. The struggle for plants to regenerate against introduced pest is very obvious here.
3. Areas where stage one is occurring eg Bracken fern, sedges and young Manuka – around the confidence course and by some tracks and camping site with toilets
4. Areas where the bush has come back but is still grazed and only plants which goats, possums and pigs find unpalatable survive.
5. Regenerating bush a lower level coming away as well, nature trail.
6. Bush which was never cut or burnt but has felt the effects of grazing predation from introduced species.
7. Massive Kauri stumps and heads slowly breaking or being broken down

Mixed in with this is the natural variety in the forest which is created by altitude, soil type, soil moisture and gradient.

Regeneration Steps

The Tangihua Forest surrounding the lodge was heavily logged in the early 1900s. The easier country was then burnt and developed for farming. The steeper country remained in its original state.

The land surrounding the lodge was eventually sold to the government by the then owners (Smiths) who moved down stream to better country.

This land was then leased for grazing until 1970. It was not heavily stocked but fires, cattle, pigs and goats kept the clearings open. A heavy infestation of goats also prevented the under canopy of the standing forest from regenerating. Many of the goats were removed in the 1980s goat boom or hunted out, but some remain.

At this stage the forest is regenerating but animals such as pigs goats possums, rats, mice and wasps still have a significant impact.

Examples of Native forest regeneration Stages

Manuka growing at the camp site amongst grasses and some bracken fern. This area is regulatory cleared for camping. The area surrounding the camping spot has not been cleared so regularly hence dense manurka and further back Kanuka.

The first plants in a cleared area are called pioneer plants. They arrive either by wind, birds  or are residual seeds which can survive fire or remain under ground for long periods with out germinating.  These plants can germinate in the open and grow quickly. This is usually grass and weeds such as thistles and other introduced species. A native pioneer species is Bracken fern which will establish with or just after the grass.

They are often followed by Manuka. Manuka seedlings germinate prolifically, thousands to a square metre. These compete intensely for nutrients, water and light.

Over time most mānuka seedlings and saplings will die, until just one tree dominates every few square metres. The manuka will grow to 5 or 6m and  provides a thick shady cover. Underneath this other native plants get started.

Manuka will die off after about 30 years. Often Kanuka will establish with the Manuka and will grow taller and survive upto 150 years. Kanuka will be part of stage two and three becoming the dominate species until replaced by confers and broad leaved trees.

Trees which establish earlyunder kanuka are Rewarewa, Nikau, Kowhai, Lancewood, Cabbage trees.

Third and fourth stage forest composing of mature shrubs with young mature forest type trees growing through. Taken from the lookout on entrance road

Later to establish are the taller emergent species like Rewarewa, Rimu, Totara, Matai and Kahikatea. Under these trees only the more shade tolerant canopy species such as Kauri, Tawa, Kohekohe, Hinau and Kamahi can survive.
Eventually, the colonising species are replaced by tree ferns, climbing and perching plants and a climax forest is reached. The cycle continues as trees fall through decay or wind, flood or fire.

Other Regeneration examples which can be observed

Lodge road

All along the lodge road you will see examples of regeneration. From the gate to the bush edge you have grasses and plants such as manuka, Gorse, and blackberry.  On the bush edge there are other trees such as  Lancewood, cabbage trees, and Totara. All these trees are unpalatable to stock and so can withstand grazing pressure.

Inside the forest where grazing is not an issue but lack of light is we have different species. Beside the road is grass and weeds which regenerate after regular spraying. Further in are ferns, punga,  pitosporums, manuka. On banks with limited top soil are plants which fix nitrogen such as Tutu.

Around the lodge are Manuka, Rewarewa, Kowhai

Nature trail

This is an area where we have identified a wide range of plants and are developing teaching resources for teachers. See  Nature trail identifying Northlands native plants

This area was logged and then cleared for grazing. It  has become established longer but been effected by grazing from goats pigs possums and cattle.

Regenerating on logs and stumps

When the kauri trees were cut down only the good timber was taken out with the stumps and the heads (where on mature trees the straight trunk ends and the branches occur) left.

These have become habitats for a wide range of plant and animal species.

There are many examples of this on the Nature trail. These trees were cut about a century ago in the 1920s

References

it is very apparent that specific information has been shared online between many organisations. Attributing to the initial  source is impossible. As much as possible we use our own photos but this will take time and for extinct birds that is not possible. We have used the following websites as sources for our information

• Te Ara The Encyclopaedia of New Zealand
• Wikipedia
• DOC website.
• T.E.R:R.A.I.N Taranaki Educational Resource: Research Analysis and Information Network