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Southern beech forest

by  Joanna Orwin

In 1850 a Dutch botanist recognised that beech trees in the southern hemisphere were different from those in the north. He named them Nothofagus, meaning false beech. Southern beech trees can be found on slopes around much of New Zealand; their inaccessibility means that many forests are still intact.


Southern beeches

The European botanists who first described plants in the southern hemisphere often named them after similar-looking northern hemisphere plants. New Zealand’s beech trees were first thought to resemble birches. Later they were described as true beech (Fagus). In 1850 a Dutch botanist recognised that southern-hemisphere beeches were distinct from northern species and named them Nothofagus, meaning false beech.

The term southern beech refers to beech species native to countries south of the equator – New Zealand, Australia, New Caledonia, New Guinea and South America.

Forest profile

New Zealand has two main types of native forest: conifer–broadleaf forest (including kauri forest) and beech forest. Most conifer–broadleaf forest grows at low altitudes, so has been logged and cleared for farming. Beech forest usually grows in hilly or mountainous areas, so has been left.

Pure beech forest now comprises almost half (about 3 million hectares) of New Zealand’s remaining native forest. Forests of beech and other tree species make up one quarter (about 1.3 million hectares).

Beech trees are found in 80–90% of native forest in the South Island, but in only 40% in the North Island. They do not grow naturally on Stewart Island.

Beech forest is typically less complex than other types of native forest:

  • There are few other species in the canopy layer.
  • There is a sparse, open understorey mostly made up of young beeches.
  • There are few epiphytes (perching plants) or climbers.

New Zealand beeches

New Zealand has four beech species and one subspecies. All are evergreen, broadleaf trees. Most New Zealand trees and shrubs are pollinated by insects or birds, or have their seeds dispersed by birds, but beech’s dry, nut-like seeds are spread by the wind. All except silver beech will form hybrids wherever they grow together.

Red beech

Red beech (Nothofagus fusca) is the largest beech species in New Zealand. Trees average 24–30 metres in height, with trunks 1.4–2.0 metres in diameter. When mature they have massive crowns, large flanges at the base of the trunk, and root buttresses. Of all the beeches, red beech is least resistant to unfavourable conditions. It grows on warm, lower- to mid-slopes, and deep, fertile, well-drained soils.

Hard beech

Hard beech (Nothofagus truncata) can grow as tall as red beech, but its trunk is more slender, at 0.6–1.2 metres in diameter. These trees develop basal flanges and buttressed roots. A low-altitude species, hard beech grows further north than other species, and is less tolerant of low temperatures. It can grow in poorer and more drought-prone soils than red beeches.

A good year

In mast years – years of exceptional flowering and seeding – the male flowers of mountain and black beech colour the entire forest canopy red. Masting may be a reproductive strategy, producing more seeds than can be eaten by birds and insects, or it may be a response to warm weather the previous summer.

Mountain beech

Mountain beech (Nothofagus solandri var. cliffortioides) is the smallest New Zealand beech, reaching 12–15 metres high, with a trunk diameter of 0.5–0.75 metres. It grows at higher altitudes (from about 700 metres above sea level up to the treeline), on drier sites, and tolerates poorer drainage and soils than other beeches. Mountain beech on exposed or elevated sites sometimes grows as hummocks only 45 centimetres high. Snow drifts and avalanches can make its trunks grow horizontally for several metres before turning upright.

Black beech

Black beech (Nothofagus solandri var. solandri) usually reaches 20–25 metres in height, with a trunk diameter similar to that of hard beech. Its trunks do not usually form flanges or buttresses. Black beech grows in poor and drought-prone soils.

Silver beech

Silver beech (Nothofagus menziesii) stands up to 20–25 metres high and has a trunk diameter of 0.6–1.5 metres. Its trunks can form heavy buttresses. Silver beech grows at similar altitudes to mountain beech, but needs wetter conditions and does not tolerate poor drainage or infertile soils. Like mountain beech, silver beech can grow as hummocks at high altitude, and can develop partly horizontal trunks in deep snow.


Distribution

At low altitudes on warm, moist, fertile sites, mixed conifer–broadleaf forest dominates. At higher altitudes, where the weather is colder and wetter, growing seasons are shorter and soils are less fertile, beech forest replaces mixed conifer–broadleaf forest.

Similarly, as latitude increases, beech forest gradually replaces the mixed conifer–broadleaf forest.

Pure beech forest

Pure beech forests, made up of a single beech species, grow where conditions best suit a particular species. There are large areas of mountain beech forest on the eastern mountains, particularly in the South Island. Silver beech forest dominates the wetter, western mountains, and grows from sea level to the treeline in Southland and Fiordland.

Pure forests of other beech species have a more limited distribution. Black beech forms lowland to mountain forests on eastern slopes from Canterbury to the East Cape, and is the only beech in the Taranaki region. Red beech forests grow in deeper, more fertile soils, and at lower altitudes than other beech forests.

Beech mixtures

Forests may be made up of a mixture of beech species. All four of New Zealand’s beeches grow together in the north-west South Island and on the East Cape mountains. Red and silver beech co-exist on mid-slopes in the north-west of the South Island. Forests of silver and mountain beech are also common.

Beeches form forests with other broadleaf trees and conifers. For example, there is hard beech–kauri forest in Auckland and the Coromandel Peninsula, beech–tawa forest in the central North Island, and beech–rātā–kāmahi forest in the western South Island. Hard beech grows with other broadleaf species and conifers (such as rimu) in the North Island and in the north-west South Island.

Beech gaps

Some areas have suitable climates and soils, but lack beech forest. There is a large region free of beeches in central Westland, and beech does not grow on Stewart Island. Other 'gaps' are Mt Taranaki (Mt Egmont), in the northern Tararua and southern Ruahine ranges (known as the Manawatū gap), and central Canterbury.

These gaps may have been created when glaciation or volcanic activity destroyed forests. The beech gap in central Canterbury may have been caused by drought. In the past, all forest in the area was destroyed by fire – naturally caused or lit by early Māori. The beeches then failed to regenerate because the climate was unsuitable or there was competition from other plants. Beech is particularly slow to spread because its seeds are dispersed by wind or water, and its seedlings' roots have to establish a relationship with specialised fungi to survive.


Ecology

Response to disturbances

Earthquakes, landslides, gales, fire, snowstorms and drought can kill stands of trees. These leave gaps in the forest that trigger dynamic responses.

Small gaps are covered by nearby tree crowns, but larger gaps will be filled by beech seedlings. Dense patches of shade-tolerant seedlings establish themselves after mast years (when there are large numbers of flowers and seeds), but their growth is restricted. The seedlings can persist in the understorey for decades. When large trees die, extra light and nutrients become available, and the seedlings can grow into trees.

In forests of mixed beech, or beech with other trees, responses to gaps can be complex. For example, in mountain–silver beech forest, faster-growing mountain beech seedlings initially fill new gaps, but the more shade-tolerant, longer-lived silver beech gradually takes over. The forest patchwork continually changes, but in the long term the relative proportion of species is maintained.

Beech-eating insects

Many leaf-eating insects live in beech canopies. Among the most important are caterpillars of the moth Proteodes carnifex. They periodically defoliate thousands of hectares of mountain beech forest in outbreaks that last several years.

Insects can increase the damage caused by natural disasters and weather. Wood-boring pinhole beetles (Platypus) are attracted to moist, dead wood in damaged forests. They carry the Sporothrix fungus, which kills trees and prompts a new cycle of pinhole beetle invasion.

Increase in predators

In mast years, when large numbers of male beech flowers fall, caterpillars have plenty to eat and their numbers increase. Seed- and insect-eating birds also have a good breeding season. But rats and mice also prosper, competing with the birds for food. With more rodents come more stoats, which eat the rodents and then prey on the birds. This cycle may have caused the decline in kākā (parrot) numbers, and the near-extinction of mohua (yellowheads) and kākāriki (orange-fronted parakeets).

An ark for birds

In 2003 the New Zealand government launched Operation Ark, where 11 key areas of South Island beech forest were monitored to identify a possible plague of rats or mice after mast years. Once the rodents were trapped and poisoned, the cycle that leads to the death of native birds was broken.

Honeydew and wasps

Beech forests in the South Island are infested with sooty beech scale insects (Ultracoelostoma), which produce sugary honeydew, an important food for native insects and nectar-feeding birds such as tūī, bellbirds and kākā. For five months each year, introduced wasps eat at least 90% of the honeydew. They also prey on insects, spiders and other invertebrates, further reducing the food of native animals.


Beech timber

Native hardwoods such as beech and tawa are harder to saw and season than native and exotic softwoods, so they have never figured prominently in New Zealand’s timber industry. In the early days of European settlement, native softwoods such as kauri, rimu, mataī, tōtara and kahikatea satisfied the nation’s demand for timber. Since the 1950s, wood from exotic conifer plantations (mostly pine and some Douglas fir) has been readily available.

Wood use

New Zealand beeches are medium-density hardwoods with a straight grain and a fine, even texture. Their timbers are excellent for furniture and interior decoration.

Black beech

Black beech timber is red-grey, strong and durable. It has a high silica content and blunts saw teeth. Milling of black beech began in Canterbury in the second half of the 19th century and continued until the First World War. There were limited native softwoods in the area, so beech was used for house frames and weatherboards, piles, fence posts, bridges and firewood. By 1915 most of Canterbury’s lowland beech had been milled and the land it grew on converted to pasture. Black beech has not been commercially logged since.

Mountain beech

Mountain beech wood looks similar to black beech, but is not durable. It is also relatively inaccessible, and because it protects upper river catchments, mountain beech is rarely milled.

Hard beech

Hard beech timber is light yellow-brown, durable, and has a high silica content. It has been sparsely milled in the past as it is abrasive to saws and tools. It was usually used for wharves, mine props, and general building on farms.

Red beech

The red-brown wood of red beech is attractive, strong and durable, but can warp during seasoning. In the past it was used for railway sleepers, bridges, wharves, fence posts and mine props. Since the 1970s high-grade red beech has been used for furniture, flooring and decorative interior finishes.

Silver beech

Since the 1920s silver beech has provided the bulk of beech timber, much of it from Southland and Westland. It is light pink, strong and pliable, although it does not last well in exposed situations. It is easily worked and has been put to many uses, including furniture, bentwood work, car and coach bodies, flooring, interior finishes, dowels, tool handles and brush backs.


Uses and management

Beech forests are used for recreation, commercial hunting, sphagnum-moss harvesting, beekeeping (using honeydew) and tourist ventures. Because beeches grow on slopes, they help reduce erosion and minimise the effects of flash floods.

Although beech species are resilient, forests are threatened by over-use and introduced animal pests.

Sustainable timber production

In the early 20th century beech forest was recognised as a potential sustainable, high-quality timber resource. Since then, foresters have proposed a number of management schemes, but because of low timber prices and conservation groups’ opposition to logging native trees, there has been no large-scale, sustainable beech forestry.

Logging on public land

In the 1970s and 1980s, logging of publicly owned beech forests in Westland and Nelson was opposed by conservationists. In 1986, conservation groups, the West Coast timber industry and the New Zealand government entered into an agreement known as the West Coast Accord. This allowed for the sustainable management of 130,000 hectares of beech forest to provide chipwood and sawlogs. The government stopped the scheme in 1999. A year later beech logging on public lands stopped when all West Coast native forest became conservation land.

Logging on private land

In Southland, pristine beech–rimu forest on Māori-owned SILNA land (granted under the South Island Landless Natives Act 1906) was at risk of being logged until 1996 legislation protected this Waitutu block as if it were a national park. The agreement gave the land owners alternative cutting rights of 11,582 hectares of state-owned beech forest in western Southland already being managed for production. As nominally private forests, they are now managed according to the Forests Amendment Act 1993. This operation was awarded Smart Wood/Forest Stewardship Council certification in 2004 – possibly the first managed Australasian native forest to achieve this stringent international environmental accreditation.

Life’s a beech

Two of the Department of Conservation’s six ‘mainland islands’ are beech forest. At Lake Rotoiti in Nelson Lakes National Park, pest control is helping to restore honeydew and protect kākā and other nectar-feeding birds. Birds no longer living in the area, such as kiwi, have been re-introduced. At the Hurunui River, North Canterbury, conservation staff are working to protect and replenish yellowheads and orange-fronted parakeets.

Beech forestry today

Today’s small but potentially valuable native forest industry is based on timber logged from private land under strict conditions that seek to balance commercial use and intrinsic natural value. Production of beech timber on private land has declined steadily from nearly 12,000 cubic metres in 2002 to about 6,750 cubic metres in 2005. Most of this comes from Southland, the rest from small operations in Nelson and Marlborough and on the West Coast.


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How to cite this page: Joanna Orwin, 'Southern beech forest', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/en/southern-beech-forest/print (accessed 22 January 2018)

Story by Joanna Orwin, published 24 Sep 2007