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''Agathis australis'', commonly known by its
Māori Māori or Maori can refer to: Relating to the Māori people * Māori people of New Zealand, or members of that group * Māori language, the language of the Māori people of New Zealand * Māori culture * Cook Islanders, the Māori people of the C ...
name kauri (), is a coniferous tree in the family ''
Araucariaceae Araucariaceae – also known as araucarians – is an extremely ancient family of coniferous trees. The family achieved its maximum diversity during the Jurassic and Cretaceous periods and the early Cenozoic, when it was distributed almost worldw ...
'', found north of 38°S in the northern regions of New Zealand's
North Island The North Island, also officially named Te Ika-a-Māui, is one of the two main islands of New Zealand, separated from the larger but much less populous South Island by the Cook Strait. The island's area is , making it the world's 14th-largest ...
. 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 novel soil interaction and regeneration pattern it can compete with faster growing
angiosperm Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...
s. 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 is the number of different species represented in an ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the abundances of the species or their relative ab ...
than those found further south. Kauri even act as a
foundation species In ecology, the foundation species are species that have a strong role in structuring a community. A foundation species can occupy any trophic level in a food web (i.e., they can be primary producers, herbivores or predators). The term was coined ...
that modify the soil under their canopy to create unique plant communities.


Taxonomy

Scottish botanist
David Don David Don (21 December 1799 – 15 December 1841) was a Scottish botanist. Biography David Don was born on 21 December 1799 at Doo Hillock, Forfar, Angus, Scotland to Caroline Clementina Stuart, and her husband George Don of Forfar. His olde ...
described the species as ''Dammara australis''. ''Agathis'' is derived from
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
and means 'ball of twine', a reference to the shape of the male cones, which are also known by the botanical term stroboli.Gledhill, David (2008). "The Names of Plants". Cambridge University Press. (hardback), (paperback). pp 39, 62 ''Australis'' means 'southern'.


Description

The young plant grows straight upwards and has the form of a narrow cone with branches going out along the length of the trunk. However, as it gains in height, the lowest branches are shed, preventing
vine A vine (Latin ''vīnea'' "grapevine", "vineyard", from ''vīnum'' "wine") is any plant with a growth habit of trailing or scandent (that is, climbing) stems, lianas or runners. The word ''vine'' can also refer to such stems or runners themselv ...
s from climbing. By maturity, the top branches form an imposing crown that stands out over all other native trees, dominating the
forest canopy In biology, the canopy is the aboveground portion of a plant cropping or crop, formed by the collection of individual plant crowns. In forest ecology, canopy also refers to the upper layer or habitat zone, formed by mature tree crowns an ...
. 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 A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...
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 A conifer cone (in formal botanical usage: strobilus, plural strobili) is a seed-bearing organ on gymnosperm plants. It is usually woody, ovoid to globular, including scales and bracts arranged around a central axis, especially in conifers an ...
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 A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiospe ...
s, which are then dispersed by the wind. A single tree produces both male and female seed cones. Fertilisation of the seeds occurs by
pollination Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds ...
, 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 The Hauraki Gulf / Tīkapa Moana is a coastal feature of the North Island of New Zealand. It has an area of 4000 km2,Waihou River The Waihou River is located in the northern North Island of New Zealand. Its former name, Thames River, was bestowed by Captain James Cook in November 1769, when he explored of the river from the mouth. An older Māori name was "Wai Kahou Roun ...
(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 is a large V-shaped bay on the eastern coast of the Coromandel Peninsula on the North Island of New Zealand. It was named by the English navigator Captain James Cook during his exploratory expeditions. It was first named ''Te-Whangan ...
, 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. 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 Crown land (sometimes spelled crownland), also known as royal domain, is a territorial area belonging to the monarch, who personifies the Crown. It is the equivalent of an entailed estate and passes with the monarchy, being inseparable from it. ...
ranger, Henry Wilson, in 1860. It was on a spur of Mt Tutamoe about 30 km south of
Waipoua Forest Waipoua Forest is a forest, on the west coast of the Northland Region of New Zealand's North Island. It preserves some of the best examples of kauri forest remaining in New Zealand. It is notable for having two of the largest living kauri t ...
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 or Tāne may refer to: People * Tane Ikai (1879–1995), a Japanese supercentenarian * Tané Matsukata (1918–1989), founder of Nishimachi International School in Azabu, Tokyo * Tané McClure (born 1958), an American singer and actress * Tan ...
'' and its clean bole larger than that of
Te Matua Ngahere Te Matua Ngahere is a giant kauri (''Agathis australis'') coniferous tree in the Waipoua Forest of Northland Region, New Zealand. The tree's Māori name means "Father of the Forest". Although not as massive or tall as its neighbour Tāne Mahuta, ...
, 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. 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. 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. By combining
tree ring Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed. As well as dating them, this can give data for dendroclimatology, the study of climate and atmos ...
samples from living kauri, wooden buildings, and preserved swamp wood, a dendrochronology has been created which reaches back 4,500 years, the longest tree ring record of past
climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
in the southern hemisphere. One 1700 year old swamp wood kauri that dates to approximately 42,000 years ago contains fine-scale carbon-14 fluctuations in its rings that may be reflective of the most recent magnetic field flip of the earth.


Root structure and soil interaction

One of the defining aspects of the kauri tree's unique
ecological niche In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of resources and competitors (for ...
is its relationship with the soil below. Much like
podocarp Podocarpaceae is a large family of mainly Southern Hemisphere conifers, known in English as podocarps, comprising about 156 species of evergreen trees and shrubs.James E. Eckenwalder. 2009. ''Conifers of the World''. Portland, Oregon: Timber Pr ...
s, it feeds in the organic litter near the surface of the soil through fine
root hair Root hair, or absorbent hairs, are outgrowths of epidermal cells, specialized cells at the tip of a plant root. They are lateral extensions of a single cell and are only rarely branched. They are found in the region of maturation, of the root. Root ...
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 or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is e ...
. On the other hand,
broadleaf tree A broad-leaved, broad-leaf, or broadleaf tree is any tree within the diverse botanical group of angiosperms that has flat leaves and produces seeds inside of fruits. It is one of two general types of trees, the other being a conifer, a tree with n ...
s such as māhoe derive a good fraction of their nutrition in the deeper mineral layer of the soil. Although its feeding 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 to prevent a tree the size of a kauri from blowing over in storms and cyclones. The
litter Litter consists of waste products that have been discarded incorrectly, without consent, at an unsuitable location. Litter can also be used as a verb; to litter means to drop and leave objects, often man-made, such as aluminum cans, paper cups, ...
left by kauri is much more
acidic In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a ...
than most trees, and as it decays similarly acidic compounds are liberated. In a process known as
leaching Leaching is the loss or extraction of certain materials from a carrier into a liquid (usually, but not always a solvent). and may refer to: * Leaching (agriculture), the loss of water-soluble plant nutrients from the soil; or applying a small amou ...
, these acidic molecules pass through the soil layers with the help of rainfall, and release other nutrients trapped in
clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...
such as
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
and
phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...
. 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 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 Waxes are a diverse class of organic compounds that are lipophilic, malleable solids near ambient temperatures. They include higher alkanes and lipids, typically with melting points above about 40 °C (104 °F), melting to giv ...
es and
phenols In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of one or more hydroxyl groups (— O H) bonded directly to an aromatic hydrocarbon group. The simplest is phenol, . Phenolic compounds are ...
, most notably
tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' (from Anglo-Norman ''tanner'' ...
s, that are harmful to
microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
s. This results in a large buildup of litter around the base of a mature tree in which its own roots feed. As with most perennials, these feeding roots also house a symbiotic
fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
known as mycorrhiza 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.


Distribution


Local spatial distribution

In terms of local
topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sc ...
, 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 it the 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, at low elevations. This pattern is known as
niche partitioning In ecology, niche differentiation (also known as niche segregation, niche separation and niche partitioning) refers to the process by which competing species use the environment differently in a way that helps them to coexist. The competitive exclu ...
, and allows more than one species to occupy the same area. Those species which live alongside kauri include tawari, a montane broadleaf tree which is normally found in higher altitudes, where
nutrient cycling A nutrient cycle (or ecological recycling) is the movement and exchange of inorganic and organic matter back into the production of matter. Energy flow is a unidirectional and noncyclic pathway, whereas the movement of mineral nutrients is cycli ...
is naturally slow.


Changes over recent geological time

Kauri is found growing in its natural ecosystem north of 38°S
latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north pol ...
. Its southern limit stretches from the
Kawhia Harbour Kawhia Harbour (Maori: ''Kāwhia'') 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 southwe ...
in the west to the eastern
Kaimai Range The Kaimai Range (sometimes referred to as the ''Kaimai Ranges'') is a mountain range in the North Island of New Zealand. It is part of a series of ranges, with the Coromandel Range to the north and the Mamaku Ranges to the south. The Kaimai R ...
. However, its distribution has changed greatly over
geological time The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochron ...
because of
climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
. This is shown in the recent
Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...
epoch by its migration southwards after the peak of the last
ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gree ...
. During this time when frozen
ice sheet In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at La ...
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 (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon. The method was dev ...
is one technique used by scientists to uncover the history of the tree's distribution, with stump kauri from
peat Peat (), also known as turf (), is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. The peatland ecosystem covers and is the most efficien ...
swamps used for measurement. The coldest period in recent times occurred about 15,000 to 20,000 years ago, during which 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 may refer to: * Proxy or agent (law), a substitute authorized to act for another entity or a document which authorizes the agent so to act * Proxy (climate), a measured variable used to infer the value of a variable of interest in climate ...
for temperature changes during this period. While not present in modern days, the
Aupouri Peninsula The Aupouri Peninsula is a tombolo at the northern tip of the North Island of New Zealand. It projects between the Tasman Sea to the west and the Pacific Ocean to the east. It constitutes the northern part of the Far North District, incorpora ...
in the far north was a refuge for kauri, as large quantities of
kauri gum Kauri gum is resin from kauri trees (''Agathis australis''), which historically had several important industrial uses. It can also be used to make crafts such as jewellery. Kauri forests once covered much of the North Island of New Zealand, bef ...
were present in the soils. 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 Whangārei () is the northernmost city in New Zealand and the regional capital of Northland Region. It is part of the Whangarei District, Whangārei District, a local body created in 1989 from the former Whangārei City, Whangārei County and ...
, past
Dargaville Dargaville ( mi, Takiwira) is a town located in the North Island of New Zealand. It is situated on the bank of the Northern Wairoa River in the Kaipara District of the Northland region. The town is located 55 kilometres southwest of Whangāre ...
and as far south as
Waikato Waikato () is a Regions of New Zealand, local government region of the upper North Island of New Zealand. It covers the Waikato District, Waipa District, Matamata-Piako District, South Waikato District and Hamilton, New Zealand, Hamilton City ...
, attaining its peak distribution during the years 3000 BP to 2000 BP. 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 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 is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by wind. Pollinating agents can be animals such as insects, birds ...
and
seed dispersal In Spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant. Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, ...
, while many other native trees have their seeds carried large distances by frugivores (animals which eat fruit) such as the
kererū The kererū (''Hemiphaga novaeseelandiae'') or New Zealand pigeon is a species of pigeon native to New Zealand. Johann Friedrich Gmelin described the bird in 1789 as a large, conspicuous pigeon up to in length and in weight, with a white br ...
(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 are hardy species that are the first to colonize barren environments or previously biodiverse steady-state ecosystems that have been disrupted, such as by wildfire. Pioneer flora Some lichens grow on rocks without soil, so ...
, despite the fact that their long lifespan is characteristic of
K-selected In ecology, ''r''/''K'' selection theory relates to the selection of combinations of traits in an organism that trade off between quantity and quality of offspring. The focus on either an increased quantity of offspring at the expense of indivi ...
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

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
puriri ''Vitex lucens'', or pūriri, is an evergreen tree endemic to New Zealand. History Pūriri was first collected (by Europeans) at Tolaga Bay by Banks and Solander during Cook's first visit in 1769. The plant was excellently described by Soland ...
and
kohekohe Kohekohe (''Dysoxylum spectabile'') is a medium-sized tree in the Meliaceae family, native to New Zealand. It is found in lowland and coastal forests throughout most of the North Island and also occurs in the Marlborough Sounds in the north ...
that show far more
shade tolerance In ecology, shade tolerance is a plant's ability to tolerate low light levels. The term is also used in horticulture and landscaping, although in this context its use is sometimes imprecise, especially in labeling of plants for sale in commercial ...
. Unlike kauri, these broadleaf 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 relatively strong 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, these smaller trees are far less capable of regenerating. 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
seedling A seedling is a young 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 (embryonic root), the hypocotyl (embry ...
s 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
biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
tends to decrease during such times, as more biomass becomes concentrated in angiosperm species like
towai Towai ( mi, Tōwai) is a locality in the Northland Region of the North Island of New Zealand. New Zealand State Highway 1, State Highway 1 passes just to the east. Kawakawa, New Zealand, Kawakawa is 16 km northwest, and Whakapara is 17  ...
. 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 is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...
sediments (see
palynology Palynology is the "study of dust" (from grc-gre, παλύνω, palynō, "strew, sprinkle" and '' -logy'') or of "particles that are strewn". A classic palynologist analyses particulate samples collected from the air, from water, or from deposit ...
) have helped shed light on the life history 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. Studies show that kauri develop root grafts through which they share water and nutrients with neighbours of the same species.


Ethnobotany


Deforestation

Heavy
logging Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidding, on-site processing, and loading of trees or logs onto trucks or skeleton cars. Logging is the beginning of a supply chain ...
, 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. The British
Royal Navy The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against F ...
sent four vessels, HMS ''Coromandel'' (1821), ''HMS ''Dromedery'' (1821), (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. 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) per 100 superficial feet (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). 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) 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
tōtara ''Podocarpus totara'' (; from the Maori-language ; the spelling "totara" is also common in English) is a species of podocarp tree endemic to New Zealand. It grows throughout the North Island and northeastern South Island in lowland, montane a ...
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

Although today its use is far more restricted, in the past the size and strength of kauri
timber Lumber is wood that has been processed into dimensional lumber, including beams and planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, w ...
made it a popular
wood Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin th ...
for construction and
ship building Shipbuilding is the construction of ships and other floating vessels. It normally takes place in a specialized facility known as a shipyard. Shipbuilders, also called shipwrights, follow a specialized occupation that traces its roots to befor ...
, particularly for masts of sailing ships because of its parallel grain and the absence of branches for much of its height. Kauri crown and
stump Stump may refer to: * Stump (band), a band from Cork, Ireland and London, England * Stump (cricket), one of three small wooden posts which the fielding team attempt to hit with the ball *Stump (dog): Clussexx Three D Grinchy Glee (born 1998), 200 ...
wood was much appreciated for its beauty, and was sought after for ornamental wood panelling 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, bridge construction material, fences, moulds for metal forges, large rollers for the textile industry, railway sleepers and
cross bracing In construction, cross bracing is a system utilized to reinforce building structures in which diagonal supports intersect. Cross bracing is usually seen with two diagonal supports placed in an X-shaped manner. Under lateral force (such as wind or ...
for mines and tunnels. In the late 19th and early 20th centuries
Kauri gum Kauri gum is resin from kauri trees (''Agathis australis''), which historically had several important industrial uses. It can also be used to make crafts such as jewellery. Kauri forests once covered much of the North Island of New Zealand, bef ...
(semi-fossilised kauri
resin In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on natu ...
) 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 A carbon sink is anything, natural or otherwise, that accumulates and stores some carbon-containing chemical compound for an indefinite period and thereby removes carbon dioxide () from the atmosphere. Globally, the two most important carbon si ...
. 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 Carbon capture may refer to: * Carbon capture and utilization, where the captured carbon dioxide is used * Carbon sequestration, where the captured carbon dioxide is stored ** Carbon capture and storage, referring to carbon sequestration from point ...
is up to nearly 1000 tones per hectare. In this capacity, kauri are bettered only by mature ''
Eucalyptus regnans ''Eucalyptus'' () is a genus of over seven hundred species of flowering trees, shrubs or mallees in the myrtle family, Myrtaceae. Along with several other genera in the tribe Eucalypteae, including ''Corymbia'', they are commonly known as euc ...
'' forest, and are far higher than any tropical or boreal forest type yet recorded. 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 ''Pinus radiata'' ( syn. ''Pinus insignis''), the Monterey pine, insignis pine or radiata pine, is a species of pine native to the Central Coast of California and Mexico ( Guadalupe Island and Cedros island). It is an evergreen conifer in the ...
''.


Timber

;Technical specifications * Moisture content of dried wood: 12 per cent * Density of wood: 560 kg/m3 *
Tensile strength Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials t ...
: 88
MPa MPA or mPa may refer to: Academia Academic degrees * Master of Performing Arts * Master of Professional Accountancy * Master of Public Administration * Master of Public Affairs Schools * Mesa Preparatory Academy * Morgan Park Academy * Mou ...
*
Modulus of elasticity An elastic modulus (also known as modulus of elasticity) is the unit of measurement of an object's or substance's resistance to being deformed elastically (i.e., non-permanently) when a stress is applied to it. The elastic modulus of an object is ...
: 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. A considerable number of kauri have been found buried in
salt marsh A salt marsh or saltmarsh, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. It is domin ...
es, resulting from ancient natural changes such as volcanic eruptions, sea-level changes and floods. Such trees have been
radiocarbon dated Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon. The method was dev ...
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 stain Wood stain is a type of paint used to colour wood and consists of colourants dissolved and/or suspended in a 'vehicle' or solvent. Vehicle is the preferred term, as the contents of a stain may not be truly dissolved in the vehicle, but rather ...
s 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 Waipoua Forest is a forest, on the west coast of the Northland Region of New Zealand's North Island. It preserves some of the best examples of kauri forest remaining in New Zealand. It is notable for having two of the largest living kauri t ...
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 The Waitākere Ranges is a mountain range in New Zealand. Located in West Auckland between metropolitan Auckland and the Tasman Sea, the ranges and its foothills and coasts comprise some of public and private land. The area, traditionally kno ...
near Auckland, and Coromandel Forest Park on the
Coromandel Peninsula The Coromandel Peninsula ( mi, Te Tara-O-Te-Ika-A-Māui) on the North Island of New Zealand extends north from the western end of the Bay of Plenty, forming a natural barrier protecting the Hauraki Gulf and the Firth of Thames in the ...
. The importance of
Waipoua Forest Waipoua Forest is a forest, on the west coast of the Northland Region of New Zealand's North Island. It preserves some of the best examples of kauri forest remaining in New Zealand. It is notable for having two of the largest living kauri t ...
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 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 The Coromandel Peninsula ( mi, Te Tara-O-Te-Ika-A-Māui) on the North Island of New Zealand extends north from the western end of the Bay of Plenty, forming a natural barrier protecting the Hauraki Gulf and the Firth of Thames in the ...
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 Tāne Mahuta, also called "God of the Forest", is a giant kauri tree (''Agathis australis'') 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. It is the largest livin ...
'' and ''
Te Matua Ngahere Te Matua Ngahere is a giant kauri (''Agathis australis'') coniferous tree in the Waipoua Forest of Northland Region, New Zealand. The tree's Māori name means "Father of the Forest". Although not as massive or tall as its neighbour Tāne Mahuta, ...
'' in Waipoua Forest. These two trees have become tourist attractions because of their size and accessibility. Tane Mahuta, named after the
Māori Māori or Maori can refer to: Relating to the Māori people * Māori people of New Zealand, or members of that group * Māori language, the language of the Māori people of New Zealand * Māori culture * Cook Islanders, the Māori people of the C ...
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) 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).


Kauri dieback

Kauri dieback Kauri dieback is a forest dieback disease of the native kauri trees (''Agathis australis'') of New Zealand that is suspected to be caused by the oomycete ''Phytophthora agathidicida.'' Symptoms can include root rot and associated rot in a col ...
was observed in the Waitākere Ranges caused by ''
Phytophthora cinnamomi ''Phytophthora cinnamomi'' is a soil-borne water mould that produces an infection which causes a condition in plants variously called " root rot", "dieback", or (in certain ''Castanea'' species), "ink disease". The plant pathogen is one of the wo ...
'' in the 1950s, again on
Great Barrier Island Great Barrier Island ( mi, Aotea) lies in the outer Hauraki Gulf, New Zealand, north-east of central Auckland. With an area of it is the sixth-largest island of New Zealand and fourth-largest in the main chain. Its highest point, Mount Hobson ...
in 1972 linked to a different pathogen, ''
Phytophthora agathidicida ''Phytophthora'' (from Greek (''phytón''), "plant" and (), "destruction"; "the plant-destroyer") is a genus of plant-damaging oomycetes (water molds), whose member species are capable of causing enormous economic losses on crops worldwide, as ...
'' 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. ''Phytophthora agathidicida'' was identified as a new species in April 2008. Its closest known relative is '' Phytophthora katsurae''. The pathogen is believed to be spread on people's shoes or by mammals, particularly feral pigs.Borley, Craig.
Groups join forces to fight kauri-killer fungus
. ''New Zealand Herald''. October 18, 2008.
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,
Waikato Regional Council Waikato () is a local government region of the upper North Island of New Zealand. It covers the Waikato District, Waipa District, Matamata-Piako District, South Waikato District and Hamilton City, as well as Hauraki, Coromandel Peninsula ...
, and Bay of Plenty Regional Council. 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.Information on kauri dieback
/ref>


See also

* Gum-digger *
Forestry in New Zealand Forestry in New Zealand has a history starting with European settlement in the 19th century and is now an industry worth seven percent of annual revenue. Much of the original native forest cover was burnt off and logged, however forests have been e ...
*
Kauri Museum The Kauri Museum is in the west coast village of Matakohe, Northland, New Zealand. The museum, to the south of the Waipoua Forest, contains many exhibits that tell the story of the pioneering days when early European settlers in the area extract ...
*
List of superlative trees The world's superlative trees can be ranked by any factor. Records have been kept for trees with superlative height, trunk diameter or girth, canopy coverage, airspace volume, wood volume, estimated mass, and age. Tallest The heights of th ...
* Northland temperate kauri forest


References


Bibliography

* * *


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 New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

Masters thesis on growth and yield of NZ kauri
{{Taxonbar, from=Q955413 australis Trees of New Zealand Conservation dependent plants Kauri gum