Agathis australis
Encyclopedia
Pinophyta
The conifers, division Pinophyta, also known as division Coniferophyta or Coniferae, are one of 13 or 14 division level taxa within the Kingdom Plantae. Pinophytes are gymnosperms. They are cone-bearing seed plants with vascular tissue; all extant conifers are woody plants, the great majority being...
tree found north of 38°S in the northern districts of New Zealand's North Island. 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 the genus
Agathis
The genus Agathis, commonly known as kauri or dammar, is a relatively small genus of 21 species of evergreen tree. The genus is part of the ancient Araucariaceae family of conifers, a group once widespread during the Jurassic period, but now largely restricted to the Southern Hemisphere except for...
are southern kauri and New Zealand kauri.
Kauri forests are among the most ancient in the world. The antecedents of the kauri appeared during the Jurassic period (between 190 and 135 million years ago). Although the kauri is among the most ancient trees in the world, it has developed a unique niche in the forest. With its novel soil interaction and regeneration pattern it can compete with the more recently evolved and faster growing angiosperms. Because it is such a conspicuous species, forest containing kauri is generally known as kauri forest, although kauri need not be the most abundant tree. In the warmer northern climate, kauri forests have a higher species richness
Species richness
Species richness is the number of different species in a given area. It is represented in equation form as S.Species richness is the fundamental unit in which to assess the homogeneity of an environment. Typically, species richness is used in conservation studies to determine the sensitivity of...
than those found further south.
Description
Trunk (botany)
In botany, trunk refers to the main wooden axis of a tree that supports the branches and is supported by and directly attached to the roots. The trunk is covered by the bark, which is an important diagnostic feature in tree identification, and which often differs markedly from the bottom of the...
. However, as it gains in height, the lowest branches are shed, preventing vine
Vine
A vine in the narrowest sense is the grapevine , but more generally it can refer to any plant with a growth habit of trailing or scandent, that is to say climbing, stems or runners...
s from climbing. By maturity, the top branches form an imposing crown that stands out over all other native trees, dominating the forest canopy.
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. The kauri has a habit of forming small clumps or patches scattered through mixed forests.
Kauri leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
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
Conifer cone
A cone is an organ on plants in the division Pinophyta that contains the reproductive structures. The familiar woody cone is the female cone, which produces seeds. The male cones, which produce pollen, are usually herbaceous and much less conspicuous even at full maturity...
are globose, 5 to 7 cm diameter, and mature 18 to 20 months after pollination; the seed cones disintegrate at maturity to release winged seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
s, which are then dispersed by the wind. A single tree produces both male and female seed cones. Fertilisation
Fertilisation
Fertilisation is the fusion of gametes to produce a new organism. In animals, the process involves the fusion of an ovum with a sperm, which eventually leads to the development of an embryo...
of the seeds occurs by pollination
Pollination
Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...
, 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 sequoiaSequoiadendron
Sequoiadendron giganteum is the sole living species in the genus Sequoiadendron, and one of three species of coniferous trees known as redwoods, classified in the family Cupressaceae in the subfamily Sequoioideae, together with Sequoia sempervirens and...
s 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
Hauraki Gulf
The Hauraki Gulf is a coastal feature of the North Island of New Zealand. It has a total area of 4000 km², and lies between the Auckland Region, the Hauraki Plains, the Coromandel Peninsula and Great Barrier Island...
just north of the mouth of the Waihou River
Waihou River
thumb|The Waihou River near [[Putaruru]]The Waihou River is located in the northern North Island of New Zealand. Its former name, Thames River, was bestowed by Captain James Cook....
(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.
A kauri tree at Mill Creek, Mercury Bay
Mercury Bay
Mercury Bay is a large V-shaped bay on the eastern coast of the Coromandel Peninsula on the North Island of New Zealand. This bay was named by the English navigator Captain James Cook during his exploratory expeditions. By the Māori it was named Te-Whanganui-o-Hei, the great bay of Hei.On November...
, 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 is was recorded as being killed by lightning in that period.
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
Waipoua Forest
Waipoua Forest preserves some of the best examples of kauri forest remaining in New Zealand. It is notable for having two of the largest living kauri trees, Tane Mahuta and Te Matua Ngahere.The forest was declared a sanctuary in 1952....
near Kaihau. It was destroyed in the 1880s or 1890s when a series of huge fires swept the area.
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. 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 Tane Mahuta
Tane Mahuta
Tāne Mahuta is a giant kauri tree in the Waipoua Forest of Northland Region, New Zealand. Its age is unknown but is estimated to be between 1,250 and 2,500 years old. It is the largest kauri known to stand today...
and its clean bole larger than that of Te Matua Ngahere
Te Matua Ngahere
Te Matua Ngahere is a giant kauri coniferous tree in the Waipoua Forest of Northland Region, New Zealand. The tree's Maori name means "Father of the Forest". Although not as massive or tall as its neighbour Tāne Mahuta, Te Matua Ngahere is stouter, with a girth just over...
, 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. 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.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. Trees can normally live longer than 600 years. Many individuals probably exceed 1000 years, but there is no conclusive evidence that trees can exceed 2000 years in age.
Root structure and soil interaction
One of the defining aspects of the kauri trees's unique ecological nicheEcological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...
is its relationship with the soil below. Much like podocarps, it feeds in the organic litter near the surface of the soil through fine root hair
Root hair
A root hair, the rhizoid of a vascular plant, is a tubular outgrowth of a trichoblast, a hair-forming cell on the epidermis of a plant root. That is, root hairs are lateral extensions of a single cell and only rarely branched, thus invisible to the naked eye. They are found only in the region of...
s. This layer of the soil is composed of organic matter derived from falling leaves and branches as well as dead trees, and is constantly undergoing decomposition
Decomposition
Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death...
. On the other hand, broadleaf trees such as māhoe
Mahoe
Mahoe may refer to:Alaalahua , a species of tree in the soapberry family that is endemic to Hawaii*Melicytus ramiflorus, a species of tree in the violet family that is endemic to New Zealand...
derive a good fraction of their nutrition in the deeper mineral layer of the soil. Although its root system is very shallow, it also has several downwardly directed peg roots which anchor it firmly in the soil. Such a solid foundation is necessary for a tree the size of a kauri to prevent it blowing over in storms and cyclones.
The litter
Plant litter
Plant litter, leaf litter or tree litter is dead plant material, such as leaves, bark, needles, and twigs, that has fallen to the ground. Litter provides habitat for small animals, fungi, and plants, and the material may be used to construct nests. As litter decomposes, nutrients are released to...
left by kauri is much more acidic than most trees, and as it decays similarly acidic compounds are liberated. In a process known as leaching
Leaching (pedology)
In pedology, leaching is the loss of mineral and organic solutes due to percolation. It is a mechanism of soil formation. It is distinct from the soil forming process of eluviation, which is the loss of mineral and organic colloids. Leached and elluviated materials tend to be lost from topsoil and...
, these acidic molecules pass through the soil layers with the help of rainfall, and release other nutrients trapped in clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
such as nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
and phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
. This leaves these important nutrients unavailable to other trees, as they are washed down into deeper layers. This process is known as podsolization, and changes the soil colour to a dull grey. For a single tree, this leaves an area of leached soil beneath known as a cup podsol. This leaching process is important for kauri's survival as it competes
Interspecific competition
Interspecific competition, in ecology, is a form of competition in which individuals of different species compete for the same resource in an ecosystem...
with other species for space.
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 wax
Wax
thumb|right|[[Cetyl palmitate]], a typical wax ester.Wax refers to a class of chemical compounds that are plastic near ambient temperatures. Characteristically, they melt above 45 °C to give a low viscosity liquid. Waxes are insoluble in water but soluble in organic, nonpolar solvents...
es and phenol
Natural phenol
Natural phenols, bioavailable phenols, plant phenolics, low molecular weight phenols or phenoloids are a class of natural products. They are small molecules containing one or more phenolic group. These molecules are smaller in size than polyphenols, containing less than 12 phenolic groups...
s that are harmful to microorganism
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...
s. This results in a large buildup of litter around the base of a mature tree in which its own roots feed. These feeding roots also house a symbiotic fungi known as mycorrhiza
Mycorrhiza
A mycorrhiza is a symbiotic association between a fungus and the roots of a vascular plant....
which increase the plant's efficiency in taking up nutrients. In this mutualistic relationship, the fungus derives its own nutrition from the roots. In its interactions with the soil, kauri is thus able to starve its competitors of much needed nutrients and compete with much younger lineages
Evolutionary history of plants
The evolution of plants has resulted in increasing levels of complexity, from the earliest algal mats, through bryophytes, lycopods, ferns to the complex gymnosperms and angiosperms of today...
.
Local spatial distribution
Topography
Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...
, kauri is far from randomly dispersed. As mentioned above, kauri relies on depriving its competitors of nutrition in order to survive. However, one important consideration not discussed thus far is the slope of the land. Water on hills flows downward by the action of gravity, taking with in nutrients in the soil. This results in a gradient from nutrient poor soil at the top of slopes to nutrient rich soils below. As nutrients leached are replaced by aqueous nitrates and phosphates from above, the kauri tree is less able to inhibit the growth of strong competitors such as angiosperms. In contrast, the leaching process is only enhanced on higher elevation. In Waipoua Forest this is reflected in higher abundances of kauri on ridge crests, and greater concentrations of its main competitors, such as taraire
Taraire
Taraire, Beilschmiedia tarairi, is a tree of the Lauraceae family, endemic to the North Island of New Zealand. It is a common canopy tree in lowland forests north of Auckland, often growing in association with kauri , pōhutukawa , tawapou , and with pūriri on basalt rocks and soils...
are found at low elevations. This pattern is known as niche partitioning, and allows more than one species to occupy the same area. Those species which live alongside kauri include tawari
Tawari
Ixerba brexioides, commonly known as Tawari, is an angiosperm tree. Until 2009 it was the single member of New Zealand's only endemic vascular plant family of Ixerbaceae. It is now placed with the New Caledonian Strasburgiaceae....
, a montane broadleaf tree which is normally found in higher altitudes, where nutrient cycling is naturally slow.
Changes over recent geological time
Kauri is naturally found north of 38°S latitude. Its southern limit stretches from the Kawhia HarbourKawhia Harbour
Kawhia Harbour is one of three large natural inlets in the Tasman Sea coast of the Waikato region of New Zealand's North Island. It is located to the south of Raglan Harbour, Ruapuke and Aotea Harbour, 40 kilometres southwest of Hamilton...
in the west to the eastern Kaimai Range.
However, its distribution has changed greatly over geological time because of climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
. This is shown in the recent Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
epoch by its migration southwards after the peak of the last ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
. During this time when frozen ice sheet
Ice sheet
An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² , thus also known as continental glacier...
s covered much of the world's continents, kauri was able to survive only in isolated pockets, its main refuge being in the very far north. Radiocarbon dating
Radiocarbon dating
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
is one technique used by scientists to uncover the history of the tree's distribution, with stump kauri from peat
Peat
Peat is an accumulation of partially decayed vegetation matter or histosol. Peat forms in wetland bogs, moors, muskegs, pocosins, mires, and peat swamp forests. Peat is harvested as an important source of fuel in certain parts of the world...
swamps used for measurement. The coldest period in recent times occurred about 15,000 to 20,000 years ago, when time kauri was apparently confined north of Kaitaia, near the northernmost point of the North Island, North Cape. Kauri requires a mean temperature of 17°C or more for most of the year. The tree's retreat can be used as a proxy
Proxy (climate)
In the study of past climates is known as paleoclimatology, climate proxies are preserved physical characteristics of the past that stand in for direct measurements , to enable scientists to reconstruct the climatic conditions that prevailed during much of the Earth's history...
for temperature changes during this period.
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 Whangarei
Whangarei
Whangarei, pronounced , is the northernmost city in New Zealand and the regional capital of Northland Region. Although commonly classified as a city, it is officially part of the Whangarei District, administered by the Whangarei District Council a local body created in 1989 to administer both the...
, past Dargaville
Dargaville
Dargaville is a town in the North Island of New Zealand. It is situated on the bank of the Northern Wairoa River in the Northland region. The town is located 55 kilometres southwest of Whangarei....
and as far south as Waikato
Waikato
The Waikato Region is a local government region of the upper North Island of New Zealand. It covers the Waikato, Hauraki, Coromandel Peninsula, the northern King Country, much of the Taupo District, and parts of Rotorua District...
, attaining its peak distribution during the years 3000 BP
Before Present
Before Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...
to 2000 BP. There is some suggestion it has receded somewhat since then, which may indicate temperatures have declined slightly. During the peak of its movement southwards, it was traveling as fast as 200 metres per year. 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 pollination
Pollination
Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...
and seed dispersal
Seed dispersal
Seed dispersal is the movement or transport of seeds away from the parent plant. Plants have limited mobility and consequently rely upon a variety of dispersal vectors to transport their propagules, including both abiotic and biotic vectors. Seeds can be dispersed away from the parent plant...
, while many other natives have their seeds carried large distances by frugivore
Frugivore
A frugivore is a fruit eater. It can be any type of herbivore or omnivore where fruit is a preferred food type. Because approximately 20% of all mammalian herbivores also eat fruit, frugivory is considered to be common among mammals. Since frugivores eat a lot of fruit they are highly dependent...
s (animals which eat fruit) such as the kererū
Kereru
The New Zealand Pigeon or kererū is a bird endemic to New Zealand. Māori call it Kererū in most of the country but kūkupa and kūkū in some parts of the North Island, particularly in Northland...
, a native pigeon. However, kauri trees can produce seeds while relatively young, taking only 50 years or so before giving rise to their own offspring. This trait makes them somewhat like a pioneer species
Pioneer species
Pioneer species are species which colonize previously uncolonized land, usually leading to ecological succession. They are the first organisms to start the chain of events leading to a livable biosphere or ecosystem...
, despite the fact that their long lifespan is characteristic of R-selected species. In good conditions, where access to water and sunlight are above average, diameters in excess of 15 centimetres and seed production can occur inside 15 years.
Regeneration and life history
Puriri
Puriri is an evergreen tree endemic to New Zealand. -History:...
and kohekohe
Kohekohe
Kohekohe is a medium-sized tree native to New Zealand. It is found in lowland and coastal forests throughout most of North Island and also occurs in the Marlborough Sounds in the north of the South Island. Mature trees grow up to 15m in height, with a trunk up to a metre in diameter...
show far more shade tolerance
Shade tolerance
In ecology, shade tolerance is a plant's abilities to tolerate low light levels. The term is also used in horticulture and landscaping, although in this context its use is sometimes sloppy, especially with respect to labeling of plants for sale in nurseries....
. These species can regenerate in areas where lower levels of light reach ground level, for example from a single branch falling off. Kauri trees must therefore remain alive long enough for a large disturbance to occur, allowing them sufficient light to regenerate. In areas where large amounts of forest are destroyed, such as by logging, kauri seedlings are able to regenerate much more easily due not only to increased sunlight, but their stronger resistance to wind and frosts. Kauri occupy the emergent layer of the forest, where they are exposed to the effects of the weather; however, the smaller trees that dominate the main canopy are sheltered both by the emergent trees above and by each other. Left in open areas without protection they are far less capable of regenerating.
When there is a disturbance severe enough to favour its regeneration, kauri trees regenerate en masse, producing a generation of trees of similar age after each disturbance. The distribution of kauri allows researchers to predict 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 seedling
Seedling
thumb|Monocot and dicot seedlingsA seedling is a young plant sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed. A typical young seedling consists of three main parts: the radicle , the hypocotyl , and the cotyledons...
s still occur in areas with low light, of course, but mortality rates for such seedlings are much higher, 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 biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
tends to decrease during such times, as more biomass becomes concentrated in angiosperm species like towai
Weinmannia silvicola
Weinmannia silvicola, known as Tōwai or Tawhero, a medium-sized tree of the family Cunoniaceae, is a very common tree in the north of the North Island of New Zealand, occurring in forest and forest margins from North Cape south to the Waitakere Ranges west of Auckland...
. Kauri trees also tend to become more randomly distributed in age, with each tree dying at a different point in time, and regeneration gaps becoming rare and sporadic. Over thousands of years these varying regeneration strategies produce a tug of war effect where kauri retreats uphill during periods of calm, then takes over lower areas briefly during mass disturbances. Although such trends cannot be observed in a human lifetime, research into current patterns of distribution, behavior of species in experimental conditions, and study of pollen
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
sediments (see palynology
Palynology
Palynology is the science that studies contemporary and fossil palynomorphs, including pollen, spores, orbicules, dinoflagellate cysts, acritarchs, chitinozoans and scolecodonts, together with particulate organic matter and kerogen found in sedimentary rocks and sediments...
) have helped shed light on the life history
Biological life cycle
A life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...
of 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.
Deforestation
Heavy loggingDeforestation
Deforestation is the removal of a forest or stand of trees where the land is thereafter converted to a nonforest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use....
which began around 1820 and continued for a century has considerably decreased the number of kauri trees. It has been estimated that before 1840, the kauri forests of northern New Zealand occupied at least 12,000 square kilometres. By the 1950s this area had decreased to about 1,400 square kilometres in 47 forests depleted of their best kauri. By 1900, less than 10 per cent of the original kauri survived. It is estimated that today, there is 4 per cent of uncut forest left in small pockets.
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)http://www.eastonbh.ac.nz/?p=515 per 100 superficial feet
Board foot
The board-foot is a specialized unit of measure for the volume of lumber in the United States and Canada. It is the volume of a one-foot length of a board one foot wide and one inch thick....
(34 shillings/m³).
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)http://www.eastonbh.ac.nz/?p=515. 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)http://www.eastonbh.ac.nz/?p=515 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.
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 totara and other podocarps in the central North Island. The outcry over the Warawara was an important stepping stone towards the legal protection of the small percentage of remaining virgin kauri-podocarp forest in New Zealand's Government-owned forests.
Uses
Timber
Timber may refer to:* Timber, a term common in the United Kingdom and Australia for wood materials * Timber, Oregon, an unincorporated community in the U.S...
made it a popular wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
for construction and ship building, particularly for masts
Mast (sailing)
The mast of a sailing vessel is a tall, vertical, or near vertical, spar, or arrangement of spars, which supports the sails. Large ships have several masts, with the size and configuration depending on the style of ship...
of sailing ships because of its parallel grain and the absence of branches for much of its height. Kauri is also a superb timber for building the hulls and decks of boats because of its resistance to rot. Kauri crown and stump wood was much appreciated for its beauty, and was sought after for ornamental wood panelling
Panelling
Panelling is a wall covering constructed from rigid or semi-rigid components. These are traditionally interlocking wood, but could be plastic or other materials....
as well as high-end furniture. Although not as highly prized, the light colour of kauri trunk wood made it also well-suited for more utilitarian furniture construction, as well as for use in the fabrication of cisterns, barrels, bridges construction material, fences, moulds for metal forges, large rollers for the textile industry, railway sleepers
Railroad tie
A railroad tie/railway tie , or railway sleeper is a rectangular item used to support the rails in railroad tracks...
and braces for mines and tunnels.
In the late nineteenth and early twentieth centuries kauri gum
Gum-digger
Kauri gum, a fossilized resin detracted from kauri trees, is used for chewing or tattooing, and often is made into jewellery. The gum comes from kauri trees found in Agathis australis forests. The trees once covered much of the New Zealand North Island, before Māori and European settlers caused...
(semi-fossilised kauri resin
Resin
Resin in the most specific use of the term is a hydrocarbon secretion of many plants, particularly coniferous trees. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials...
) was a valuable commodity, particularly for varnish, and was the focus of a considerable industry
Gum-digger
Kauri gum, a fossilized resin detracted from kauri trees, is used for chewing or tattooing, and often is made into jewellery. The gum comes from kauri trees found in Agathis australis forests. The trees once covered much of the New Zealand North Island, before Māori and European settlers caused...
.
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 tones per hectare. In this capacity they are bettered only by mature Eucalyptus regnans
Eucalyptus regnans
Eucalyptus regnans, known variously by the common names Mountain Ash, Victorian Ash, Swamp Gum, Tasmanian Oak or Stringy Gum, is a species of Eucalyptus native to southeastern Australia, in Tasmania and Victoria...
forest, and are far higher than any tropical or boreal forest type yet recorded (see Keith et al. 2009, PNAS, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2701447/ ). 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 Pinus radiata forests, for example.
Timber
Technical specifications- Moisture content of dried wood: 12 per cent
- Density of wood: 560 kg/m³
- Tensile strengthTensile strengthUltimate tensile strength , often shortened to tensile strength or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract...
: 88 MPaPascal (unit)The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre... - Modulus of elasticityYoung's modulusYoung's modulus is a measure of the stiffness of an elastic material and is a quantity used to characterize materials. It is defined as the ratio of the uniaxial stress over the uniaxial strain in the range of stress in which Hooke's Law holds. In solid mechanics, the slope of the stress-strain...
: 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.
Swamp kauri
Prehistoric kauri forests are sometimes preserved in waterlogged soils. This wood is referred to as ancient kauriAncient Kauri
Ancient Kauri or Swamp Kauri refers to prehistoric Kauri forests, buried and preserved in peat up to 50,000 years ago in New Zealand's North Island....
or swamp kauri. A considerable number of kauri have been found buried in salt marsh
Salt marsh
A salt marsh is an environment in the upper coastal intertidal zone between land and salt water or brackish water, it is dominated by dense stands of halophytic plants such as herbs, grasses, or low shrubs. These plants are terrestrial in origin and are essential to the stability of the salt marsh...
es, resulting from ancient natural changes such as volcanic eruptions, sea-level changes and floods. Such trees have been radiocarbon dated
Radiocarbon dating
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
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 surprisingly 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 stain
Wood stain
A wood stain consists of a colorant suspended or dissolved in a 'vehicle' or solvent. The suspension agent can be water, alcohol, petroleum distillate, or the actual finishing agent...
s to heighten the details of the grain. After a drying process
Wood drying
Wood drying reduces the moisture content of wood before its use.There are two main reasons for drying wood:...
, such ancient kauri can still used for furniture and other construction.
Conservation and kauri today
Waipoua Forest
Waipoua Forest preserves some of the best examples of kauri forest remaining in New Zealand. It is notable for having two of the largest living kauri trees, Tane Mahuta and Te Matua Ngahere.The forest was declared a sanctuary in 1952....
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 Waitakere Ranges
Waitakere Ranges
The Waitakere Ranges are a chain of hills in the Auckland metropolitan area, generally running approximately 25 km from north to south, 25 km west of central Auckland, New Zealand. The maximum elevation within the ranges is 474 m...
near Auckland, and Coromandel Forest Park on the Coromandel Peninsula
Coromandel Peninsula
The Coromandel Peninsula lies in the North Island of New Zealand. It is part of the Waikato Region and Thames-Coromandel District and extends 85 kilometres north from the western end of the Bay of Plenty, forming a natural barrier to protect the Hauraki Gulf and the Firth of Thames in the west...
.
The importance of Waipoua Forest
Waipoua Forest
Waipoua Forest preserves some of the best examples of kauri forest remaining in New Zealand. It is notable for having two of the largest living kauri trees, Tane Mahuta and Te Matua Ngahere.The forest was declared a sanctuary in 1952....
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.
The zoologist William Roy McGregor
William Roy McGregor
William Roy McGregor was a New Zealand zoologist and conservationist who was successful in halting forestry in the Waipoua forest and establishing the forest as a protected sanctuary.-Academic career:...
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.
Along with the Warawara to the North, Waipoua Forest contains three quarters of New Zealand's remaining kauri. Kauri Grove on the Coromandel Peninsula
Coromandel Peninsula
The Coromandel Peninsula lies in the North Island of New Zealand. It is part of the Waikato Region and Thames-Coromandel District and extends 85 kilometres north from the western end of the Bay of Plenty, forming a natural barrier to protect the Hauraki Gulf and the Firth of Thames in the west...
is another area with a remaining cluster of kauri, and includes the Siamese Kauri
Siamese Kauri
The Siamese Kauri is a kauri tree growing in Kauri Grove, about 10 kilometres south of Coromandel township in the north-east of the North Island of New Zealand. The tree gains its name from the conjoined lower trunk that the two trees share. It grows in the Kauri Grove, one of the few remaining...
, 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
Tane Mahuta
Tāne Mahuta is a giant kauri tree in the Waipoua Forest of Northland Region, New Zealand. Its age is unknown but is estimated to be between 1,250 and 2,500 years old. It is the largest kauri known to stand today...
and Te Matua Ngahere
Te Matua Ngahere
Te Matua Ngahere is a giant kauri coniferous tree in the Waipoua Forest of Northland Region, New Zealand. The tree's Maori name means "Father of the Forest". Although not as massive or tall as its neighbour Tāne Mahuta, Te Matua Ngahere is stouter, with a girth just over...
in Waipoua Forest. These two trees have become tourist attractions because of their size and accessibility. Tane Mahuta, named after the Māori
Maori culture
Māori culture is the culture of the Māori of New Zealand, an Eastern Polynesian people, and forms a distinctive part of New Zealand culture. Within the Māori community, and to a lesser extent throughout New Zealand as a whole, the word Māoritanga is often used as an approximate synonym for Māori...
forest god
Tane
In Māori mythology, Tāne is the god of forests and of birds, and the son of Ranginui and Papatuanuku, the sky father and the earth mother, who lie in a tight embrace...
, 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) and a total volume including the crown of 516.7 cubic metres (18,247 cubic feet). 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.
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).
In the 1970s, kauri dieback caused by a phytophthora
Phytophthora
Phytophthora is a genus of plant-damaging Oomycetes , whose member species are capable of causing enormous economic losses on crops worldwide, as well as environmental damage in natural ecosystems. The genus was first described by Heinrich Anton de Bary in 1875...
was discovered on Great Barrier Island
Great Barrier Island
Great Barrier Island is a large island of New Zealand, situated to the north-east of central Auckland in the outer Hauraki Gulf. With an area of it is the fourth-largest island of New Zealand's main chain of islands, with its highest point, Mount Hobson, rising...
. The disease, known as kauri collar rot, has begun spreading through kauri forests on the mainland. The disease causes yellowing leaves, thinning canopy, dead branches, lesions that bleed resin and tree death. It is caused by Phytophthora taxon Agathis (PTA) which was identified as a new species in April 2008. Its closest known relative is Phytophthora katsurae
Phytophthora katsurae
Phytophthora katsurae is a plant pathogen. It was first isolated from chestnut trees in Japan. It has also been reported from Taiwan, Papua New Guinea, Australia and Korea.- External links :* *...
. The phytophthora is believed to be spread on people's shoes or by mammals, particularly feral pigs. A collaborative response team has been formed to work on the disease. The team includes MAF Biosecurity, the Conservation Department, Auckland and Northland regional councils, Environment Waikato, and Environment BOP. The team is charged with assessing the risk, determining methods and their feasibility to limit the spread, collecting more information (e.g. how widespread), and ensuring a coordinated response. The Department of Conservation has issued guidelines to prevent the spread of the disease, including keeping to defined tracks, cleaning footwear before and after entering kauri forest areas, and staying away from kauri roots.
External links
- Kauri Gum entry from the 1966 Encyclopaedia of New ZealandNew ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
- Agathis australis description The Gymnosperm Database
- Agathis australis collection at Museum of New Zealand Te Papa TongarewaMuseum of New Zealand Te Papa TongarewaThe Museum of New Zealand Te Papa Tongarewa is the national museum and art gallery of New Zealand, located in Wellington. It is branded and commonly known as Te Papa and Our Place; "Te Papa Tongarewa" is broadly translatable as "the place of treasures of this land".The museum's principles...
- Kauri forest in Te Ara - the Encyclopedia of New Zealand
- Kauri at the New Zealand Department of Conservation