Agathis australis
Agathis australis | |
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Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Gymnospermae |
Division: | Pinophyta |
Class: | Pinopsida |
Order: | Araucariales
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Family: | Araucariaceae |
Genus: | Agathis |
Species: | A. australis
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Binomial name | |
Agathis australis | |
Natural range of A. australis | |
Synonyms[2] | |
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Agathis australis, commonly known by its
It is the largest (by volume) but not tallest species of tree in New Zealand, standing up to 50 m tall in the emergent layer above the forest's main canopy. The tree has smooth bark and small narrow leaves. Other common names to distinguish A. australis from other members of Agathis are southern kauri and New Zealand kauri.
With its
Etymology
The Māori name is descended from Proto-Polynesian *kauquli, Samoan ebony or Diospyros samoensis.[5]
Taxonomy
Scottish botanist David Don described the species as Dammara australis.
Agathis is derived from Greek and means 'ball of twine', a reference to the shape of the male cones, which are also known by the botanical term strobili.[6]
Australis means 'southern'.[6]
Description
The young plant grows straight upwards and has the form of a narrow cone with branches going out along the length of the
The flaking bark of the kauri tree defends it from parasitic plants, and accumulates around the base of the trunk. On large trees it may pile up to a height of 2 m or more.[7] The kauri has a habit of forming small clumps or patches scattered through mixed forests.[8]
Kauri leaves are 3 to 7 cm long and 1 cm broad, tough and leathery in texture, with no midrib; they are arranged in opposite pairs or whorls of three on the stem. The seed cones are globose, 5 to 7 cm diameter, and mature 18 to 20 months after pollination; the seed cones disintegrate at maturity to release winged seeds, which are then dispersed by the wind. A single tree produces both male and female seed cones. Fertilisation of the seeds occurs by pollination, which may be driven by the same or another tree's pollen.
Size
Agathis australis can attain heights of 40 to 50 metres and trunk diameters big enough to rival Californian sequoias at over 5 metres. The largest kauri trees did not attain as much height or girth at ground level but contain more timber in their cylindrical trunks than comparable Sequoias with their tapering stems.
The largest recorded specimen was known as The Great Ghost and grew in the mountains at the head of the Tararu Creek, which drains into the Hauraki Gulf just north of the mouth of the Waihou River (Thames). Thames Historian Alastair Isdale says the tree was 8.54 metres in diameter, and 26.83 metres in girth. It was consumed by fire c.1890.[9]
A kauri tree at Mill Creek, Mercury Bay, known as Father of the Forests was measured in the early 1840s as 22 metres in circumference and 24 metres to the first branches. It was recorded as being killed by lightning in that period.[10]
Another huge tree, Kairaru, had a girth of 20.1 metres and a columnar trunk free of branches for 30.5 metres as measured by a Crown Lands ranger, Henry Wilson, in 1860. It was on a spur of Mt Tutamoe about 30 km south of Waipoua Forest near Kaihau. It was destroyed in the 1880s or 1890s when a series of huge fires swept the area.[11][12]
Other trees far larger than living kauri have been noted in other areas. Rumors of stumps up to 6 metres are sometimes suggested in areas such as the Billygoat Track above the Kauaeranga Valley near Thames.[13] However, there is no good evidence for these (e.g., a documented measurement or a photograph with a person for scale).
Given that over 90 per cent of the area of kauri forest standing before 1000AD was destroyed by about 1900, it is not surprising that recent records are of smaller, but still very large trees. Two large kauri fell during tropical storms in the 1970s. One of these was Toronui, in Waipoua Forest. Its diameter was larger than that of Tāne Mahuta and its clean bole larger than that of Te Matua Ngahere, and by forestry measurements was the largest standing. Another tree, Kopi, in Omahuta Forest near the standing Hokianga kauri, was the third largest with a height of 56.39 metres (185') and a diameter of 4.19 metres (13.75'). It fell in 1973. Like many ancient kauri both trees were partly hollow.
Growth rate and age
In general over the lifetime of the tree the growth rate tends to increase, reach a maximum, then decline.[14] A 1987 study measured mean annual diameter increments ranging from 1.5 to 4.6 mm per year with an overall average of 2.3 mm per year. This is equivalent to 8.7 annual rings per centimetre of core, said to be half the commonly quoted figure for growth rate. The same study found only a weak relationship between age and diameter. The growth of kauri in planted and second-growth natural forests has been reviewed and compared during the development of growth and yield models for the species. Kauri in planted forests were found to have up to 12 times the volume productivity than those in natural stands at the same age.[15]
Individuals in the same 10 cm diameter class may vary in age by 300 years, and the largest individual on any particular site is often not the oldest.
Root structure and soil interaction
Much like
The
Leaf litter and other decaying parts of a kauri decompose much more slowly than those of most other species. Besides its acidity, the plant also bears substances such as
Distribution
Local spatial distribution
In terms of local
Changes over recent geological time
Kauri is found growing in its natural ecosystem north of 38°S latitude. Its southern limit stretches from the Kawhia Harbour in the west to the eastern Kaimai Range.[22] However, its distribution has changed greatly over
It remains unclear whether kauri recolonised the North Island from a single refuge in the far north or from scattered pockets of isolated stands that managed to survive despite climatic conditions. It spread south through Whangārei, past Dargaville and as far south as Waikato, attaining its peak distribution during the years 3000 BP to 2000 BP.[22] There is some suggestion that it has receded somewhat since then, which may indicate temperatures have declined slightly. During the peak of its movement southwards, it was travelling as fast as 200 metres per year.[22] Its southward spread seems relatively rapid for a tree that can take a millennium to reach complete maturity. This can be explained by its life history pattern.
Kauri relies on wind for
Regeneration and life history
Just as the niche of kauri is differentiated through its interactions with the soil, it also has a separate regeneration 'strategy' compared to its broadleaf neighbours. The relationship is very similar to the podocarp-broadleaf forests further south. Kauri demand much more light and require larger gaps to regenerate than such broadleaf trees as
When there is a disturbance severe enough to favour their regeneration, kauri trees regenerate en masse, producing a generation of trees of similar age after each disturbance. The distribution of kauri allows researchers to deduce when and where disturbances have occurred, and how large they may have been; the presence of abundant kauri may indicate that an area is prone to disturbance. Kauri seedlings can still occur in areas with low light but mortality rates increase for such seedlings, and those that survive self-thinning and grow to sapling stage tend to be found in higher light environments.
During periods with less disturbance kauri tends to lose ground to broadleaf competitors which can better tolerate shaded environments. In the complete absence of disturbance, kauri tends to become rare as it is excluded by its competitors. Kauri
Kauri seeds may generally be taken from mature cones in late March. Each scale on a cone contains a single winged seed approximately 5 mm by 8 mm and attached to a thin wing perhaps half as large again. The cone is fully open and dispersed within only two to three days of starting.
Studies show that kauri develop root grafts through which they share water and nutrients with neighbours of the same species.[24][25]
Ethnobotany
Deforestation
Heavy logging, which began around 1820 and continued for a century, has considerably decreased the number of kauri trees.[26] It has been estimated that before 1840, the kauri forests of northern New Zealand occupied at least 12,000 square kilometres. The British Royal Navy sent four vessels, HMS Coromandel (1821), HMS Dromedary (1821), HMS Buffalo (1840), and HMS Tortoise (1841) to gather kauri-wood spars.
By 1900, less than 10 per cent of the original kauri survived. By the 1950s this area had decreased to about 1,400 square kilometres in 47 forests depleted of their best kauri. It is estimated that today, there is 4 per cent of uncut forest left in small pockets.[27]
Estimates are that around half of the timber was accidentally or deliberately burnt. More than half of the remainder had been exported to Australia, Britain, and other countries, while the balance was used locally to build houses and ships. Much of the timber was sold for a return sufficient only to cover wages and expenses. From 1871 to 1895 the receipts indicate a rate of about 8 shillings (around NZ$20 in 2003)[28] per 100 superficial feet (34 shillings/m3).[29]
The Government continued to sell large areas of kauri forests to sawmillers who, under no restrictions, took the most effective and economical steps to secure the timber, resulting in much waste and destruction. At a sale in 1908 more than 5,000 standing kauri trees, totalling about 20,000,000 superficial feet (47,000 m3), were sold for less than £2 per tree (£2 in 1908 equates to around NZ$100 in 2003).[28][30] It is said that in 1890 the royalty on standing timber fell in some cases to as low as twopence (NZ$0.45 in 2003)[28] per 100 superficial feet (8 pence/m3), though the expense of cutting and removing it to the mills was typically great due to the difficult terrain where they were located.[31]
Probably the most controversial kauri logging decision in the last century was that of the National Government to initiate clear fell logging of the Warawara state forest (North of the Hokianga) in the late 1960s. This created a national outcry as this forest contains the second largest volume of kauri after the Waipoua forest and was until that time, essentially unlogged (Adams, 1980). The plan also involved considerable cost, requiring a long road to be driven up a steep high plateau into the heart of the protected area. Because the stands of kauri were dense, the ecological destruction in the affected plateau area (approximately a fifth of the forest by area, and a quarter by volume of timber) was essentially complete (as of the early 1990s most of the affected area contained a thick covering of native grasses with little or no kauri regeneration). Logging was stopped in fulfillment of an election pledge by the Labour Government of 1972. When the National Party was reelected in 1975, the ban on kauri logging in the Warawara remained in place, but was soon replaced by policies encouraging the logging of giant
Uses
Although today its use is far more restricted, in the past the size and strength of kauri
In the late 19th and early 20th centuries Kauri gum (semi-fossilised kauri resin) was a valuable commodity, particularly for varnish, spurring the development of a gum-digger industry.
Today, the kauri is being considered as a long-term carbon sink. This is because estimates of the total carbon content in living above ground biomass and dead biomass of mature kauri forest are the second highest of any forest type recorded anywhere in the world. The estimated total carbon capture is up to nearly 1000 tonnes per hectare. In this capacity, kauri are bettered only by mature Eucalyptus regnans forest, and are far higher than any tropical or boreal forest type yet recorded.[32] It is also conjectured that the process of carbon capture does not reach equilibrium, which along with no need of direct maintenance, makes kauri forests a potentially attractive alternative to short rotation forestry options such as Pinus radiata.
Timber
- Technical specifications
- Moisture content of dried wood: 12 per cent
- Density of wood: 560 kg/m3
- Tensile strength: 88 MPa
- Modulus of elasticity: 9.1 GPa
- After felled kauri wood dries to a 12 per cent moisture content, the tangential contraction is 4.1 per cent and the radial contraction is 2.3 per cent.
Kauri is considered a first rate timber. The whiter sapwood is generally slightly lighter in weight. Kauri is not highly resistant to rot and when used in boatbuilding must be protected from the elements with paint, varnish or epoxy to avoid rot. Its popularity with boatbuilders is due to its very long, clear lengths, its relatively light weight and its beautiful sheen when oiled or varnished. Kauri wood planes and saws easily. Its wood holds screws and nails very well and does not readily split, crack, or warp. Kauri wood darkens with age to a richer golden brown colour. Very little New Zealand kauri is now sold, and the most commonly available kauri in New Zealand is Fiji kauri, which is very similar in appearance but lighter in weight.
Swamp kauri
Prehistoric kauri forests have been preserved in waterlogged soils as swamp kauri.[33] A considerable number of kauri have been found buried in salt marshes, resulting from ancient natural changes such as volcanic eruptions, sea-level changes and floods. Such trees have been radiocarbon dated to 50,000 years ago or older. The bark and the seed cones of the trees often survive together with the trunk, although when excavated and exposed to the air, these parts undergo rapid deterioration. The quality of the disinterred wood varies. Some is in good shape, comparable to that of newly felled kauri, although often lighter in colour. The colour can be improved by the use of natural wood stains to heighten the details of the grain. After a drying process, such ancient kauri can be used for furniture, but not for construction.
Conservation
The small remaining pockets of kauri forest in New Zealand have survived in areas that were not subjected to burning by Māori and were too inaccessible for European loggers. The largest area of mature kauri forest is Waipoua Forest in Northland. Mature and regenerating kauri can also be found in other National and Regional Parks such as Puketi and Omahuta Forests in Northland, the Waitākere Ranges near Auckland, and Coromandel Forest Park[34] on the Coromandel Peninsula.
The importance of Waipoua Forest in relation to the kauri was that it remained the only kauri forest retaining its former virgin condition, and that it was extensive enough to give reasonable promise of permanent survival. On 2 July 1952 an area of over 80 km2 of Waipoua was proclaimed a forest sanctuary after a petition to the Government.[35] The zoologist William Roy McGregor was one of the driving forces in this movement, writing an 80-page illustrated pamphlet on the subject, which proved an effective manifesto for conservation.[36] Along with the Warawara to the North, Waipoua Forest contains three quarters of New Zealand's remaining kauri. Kauri Grove on the Coromandel Peninsula is another area with a remaining cluster of kauri, and includes the Siamese Kauri, two trees with a conjoined lower trunk.
In 1921 a philanthropic Cornishman named James Trounson sold to the Government for £40,000, a large area adjacent to a few acres of Crown land and said to contain at least 4,000 kauri trees. From time to time Trounson gifted additional land, until what is known as Trounson Park comprised a total of 4 km2.
The most famous specimens are Tāne Mahuta and Te Matua Ngahere in Waipoua Forest. These two trees have become tourist attractions because of their size and accessibility. Tane Mahuta, named after the Māori forest god, is the biggest existing kauri with a girth of 13.77 metres (45.2 feet), a trunk height of 17.68 metres (58.0 feet), a total height of 51.2 metres (168 feet)[37] and a total volume including the crown of 516.7 cubic metres (18,250 cubic feet).[38] Te Matua Ngahere, which means 'Father of the Forest', is smaller but stouter than Tane Mahuta, with a girth (circumference) of 16.41 m (53.8 ft). Important note: all the measurements above were taken in 1971.[39]
Kauri is common as a specimen tree in parks and gardens throughout New Zealand, prized for the distinctive look of young trees, its low maintenance once established (although seedlings are frost tender).[citation needed]
Kauri dieback
Kauri dieback was observed in the Waitākere Ranges caused by Phytophthora cinnamomi in the 1950s,[40] again on Great Barrier Island in 1972 linked to a different pathogen, Phytophthora agathidicida[41] and subsequently spread to kauri forest on the mainland. The disease, known as kauri dieback or kauri collar rot, is believed to be over 300 years old and causes yellowing leaves, thinning canopy, dead branches, lesions that bleed resin, and tree death.[42]
Phytophthora agathidicida was identified as a new species in April 2008. Its closest known relative is
See also
- Gum-digger
- Forestry in New Zealand
- Kauri Museum
- List of superlative trees
- Northland temperate kauri forest
References
- ^ "NZTCS".
- ^ "Agathis australis".
- ^ Conservation —, Department of (20 March 2016). "Protecting our kauri forests". Conservation blog. Retrieved 27 May 2021.
- ISSN 1442-9993.
- ^ "Kauri". Te Māra Reo: The Language Garden. Benton Family Trust. 2022.
- ^ ISBN 9780521685535(paperback). pp 39, 62
- ^ Reed, p.60
- ^ Reed, p.74
- ^ "Giant Kauri Trees". Tararu Valley Sanctuary. Archived from the original on 23 December 2007. Retrieved 2 November 2007.
- ^ Reed, p.89-92
- ^ "Mammoths of the Forest". Forestry Insights. 2005. Archived from the original on 7 September 2009. Retrieved 15 July 2009.
- New Zealand Forest Serviceand available online through Google Books.
- ^ "New Zealand Ecology: Kauri". TerraNature Trust. 2004. Retrieved 15 July 2009.
- ^ Reed p.62
- .
- ^ doi:10.1080/0028825x.1987.10410068. Archived from the original(PDF) on 7 December 2011. Retrieved 9 October 2010.
- ^ Reed p.61-63
- ^ Gross, Rachel. "Fellowship of the Tree Rings". National Geographic. Archived from the original on 23 April 2013. Retrieved 23 April 2013.
- ^ Voosen, Paul. "Ancient kauri trees capture last collapse of Earth's magnetic field". Science. Retrieved 6 September 2021.
- ^ Verkaik, Eric; Gardner, R.O.; Braakhekke, W.G. (2007). "Site conditions affect seedling distribution below and outside the crown of kauri trees (Agathis australis)" (PDF). New Zealand Journal of Ecology. 31 (1): 13–21. Retrieved 20 June 2007.
- S2CID 23420808.
- ^ JSTOR 2845704.
- ISBN 0-908608-39-X.
- PMID 31353168.
- ^ Mayes, Kelly (25 July 2019). "Trees share water to keep this dying stump alive". Science.
- ^ King p.125
- ^ "Home". Archived from the original on 21 June 2008. Retrieved 3 February 2007.
- ^ a b c "What Was a Pound Worth? | Brian Easton". Eastonbh.ac.nz. 2 March 2004. Retrieved 28 March 2015.
- ^ Reed p.74-75
- ^ Reed p.267
- ^ Reed p.79
- PMID 19553199.
- ^ Adams p.114
- ^ Johansen (of Pauanui), Doug (June 1978). "Coromandel Forest Park". Ohinemuri Regional History Journal (22). Archived from the original on 10 February 2013. Retrieved 6 January 2013.
- ^ Reed p.268-269
- ^ "McGregor, William Roy 1894–1977 Zoologist, university lecturer". New Zealand Government. Retrieved 8 December 2010.
- ^ "Tane Mahuta Track". Department of Conservation. Archived from the original on 13 May 2007. Retrieved 29 March 2007.
- ^ "Agathis australis". The Gymnosperm Database. Retrieved 3 November 2010.
- ^ New Zealand Forest Service, Forest Research Institute, Mensuration Report No. 16 1971 (unpublished).
- .
- S2CID 82446164.
- ^ Gregory, Angela. "Waitakere kauri in danger". New Zealand Herald. July 12, 2008.
- ^ "Kauri dieback: What is Phytophthora taxon Agathis? Archived 27 September 2012 at the Wayback Machine". Auckland Council. 29 September 2008.
- ^ "Kauri dieback: how you can help Archived October 14, 2008, at the Wayback Machine". Auckland Council.
- ^ Borley, Craig. "Groups join forces to fight kauri-killer fungus". New Zealand Herald. October 18, 2008.
- ^ Information on kauri dieback
Bibliography
- ISBN 978-0-14-301867-4.
- ISBN 978-0-589-00732-4.
- Adams, J.G. (1980). Kauri: A King Among Kings. Wilson & Horton Group Publication. ISBN 978-0-86864-080-8.
External links
- Agathis australis description The Gymnosperm Database
- Agathis australis collection at Museum of New Zealand Te Papa Tongarewa
- Kauri forest in Te Ara - the Encyclopedia of New Zealand
- Kauri at the New Zealand Department of Conservation
- Keep Kauri Standing - Kauri dieback information
- Kauri Gum entry from the 1966 Encyclopaedia of New Zealand
- Masters thesis on growth and yield of NZ kauri