Agathis australis, commonly known as the
kauri, is a
coniferousThe 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...
treeA tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
found north of 38°S in the northern districts of
New ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses , and numerous smaller islands, most notably Stewart Island/Rakiura and the Chatham Islands. The indigenous Māori named New Zealand Aotearoa, commonly translated as The Land of the Long White Cloud...
's North Island. It is the largest (by volume) but not tallest species of tree in New Zealand, standing up to 50m tall in the emergent layer above the forest's main canopy. The tree has smooth
barkBark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines and shrubs. Bark refers to all the tissues outside of the vascular cambium and is a nontechnical term. It overlays the wood and consists of the inner bark and the outer bark. The inner...
and small oval leaves. Other common names to distinguish
A. australis from other members of the
genusThe genus Agathis, commonly known as kauri or dammar, is a relatively small genus of 21 species of evergreen trees in the very ancient Araucariaceae family of conifers. While initially widespread during the Jurassic period they are now found only in small areas of the Southern Hemisphere...
are
southern kauri and
New Zealand kauri.
Though kauri are among the most ancient trees in the world, they have developed a unique niche in the forest. With their novel soil interaction and regeneration pattern they are able to 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, though kauri need not be the most abundant tree. In the warmer northern climate, kauri forests have a higher
species richnessSpecies richness is the number of different species in a given area. It is represented in equation form as .Typically, species richness is used in conservation studies to determine the sensitivity of ecosystems and their resident species. The actual number of species calculated alone is largely an...
than others found further south.
Description
Young plants grow straight upwards and have the form of a narrow cone with branches going out along the length of the
trunkIn botany, trunk refers to the main structural member 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...
. However, as they gain in height, the lowest branches are shed, preventing
epiphyteAn epiphyte is:Epiphyte is one of the subdivisions of the Raunkiær system. The term most commonly refers to higher plants, but epiphytic bacteria, fungi , algae, lichens, mosses, and ferns exist as well. The term epiphytic derives from the Greek epi- and phyton...
s from climbing. By maturity, the top branches form an imposing crown that stand out over all other native trees, dominating the heights of the forest.
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
leavesIn botany, a leaf is an above-ground plant organ specialized for photosynthesis. For this purpose, a leaf is typically flat and thin. There is continued debate about whether the flatness of leaves evolved to expose the chloroplasts to more light or to increase the absorption of carbon dioxide. In...
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 conesA 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
seedA seed , referred to as a kernel in some plants, 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. While the reproduction of kauri seed cones takes place between male and female seed cones of the same tree,
fertilisationFertilisation , is the fusion of gametes to produce a new organism. In animals, the process involves a sperm fusing with an ovum, which eventually leads to the development of an embryo...
of the seeds occurs by
pollinationPollination is the process by which pollen is transferred in plants, thereby enabling fertilization and sexual reproduction. Pollen grains, which contain 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.
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).
Size
Agathis australis can attain heights of 40 to 50 metres and trunk diameters big enough to rival Californian
SequoiasSequoiadendron giganteum is the sole 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 Metasequoia glyptostroboides Sequoiadendron...
at over 5 meters. The largest kauris do not attain as much height or girth at ground level but contain more timber in their cylindrical trunks than a comparable Sequoia with its tapering stem.
The largest specimen of which there is any known record grew on the mountains at the head of the Tararu Creek that falls into the
Hauraki GulfThe 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 Coromandel Peninsula, and the Hauraki Plains. Hauraki is Māori for North Wind.-Gulf:...
just north of the mouth of the
Waihou Riverthumb|The Waihou River as it passes [[Paeroa]]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). This tree was known as The Great Ghost. Local Thames Historian Alastair Isdale noted this 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, ercury Bay], known as "Father of the Forests" was measured in the early 1840s to be 22 metres in circumference and 24 metres to the first branches. It is thought that this tree was felled around 1870.
Another huge tree, Kairaru, had a girth of 20.1 meters and a columnular trunk free of branches for 30.5 meters as measured by a Crown Lands Ranger, Henry Wilson, in 1860. It was on a spur of Mt Tutamoe about 30km south of Waipoua forest near Kaihau. It was destroyed some years later in the 1880's or 90's after a series of huge fires swept the area.
Other trees far larger than living kauri have been noted in other areas also. Near the Billygoat Track above the Kauaeranga Valley near Thames, there are records of stumps up to 6 metres in diameter. Relocating these, if they still exist, would provide a tangible link to a lost past.
Given that over 90% 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 1970's. These were Toronui, in Waipoua forest. Its diameter was larger than that of Tane Mahuta and its clean bowl larger than that of Te Matua Ngahere, and by forestry measurements of the time was the largest standing. Another tree, Kopi, in Omahuta Forest near the standing Hokianga Kauri, fell in 1973. It was the 3rd largest in the country at that time with a height of 56.39 m (185') and a diameter of 4.19 m (13.75'). Like many very old kauri both trees were partly hollow, a characteristic shared by some very large old sequoias.
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 concluded 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.
Experts agree that because of the variation in growth rate it is not possible to accurately assess the age of a standing tree from its diameter alone.
Trees can normally live longer than 600 years. Probably many individuals exceed 1000 years, but there is no conclusive evidence that trees can exceed 2000 years in age. (Ahmed & Ogden 1987)
Root structure and soil interaction
One of the defining aspects of this tree's unique
nicheIn 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 school if the members of these schools utilize significantly different...
is its relationship with the
soilSoil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics. It is composed of particles of broken rock that have been altered by chemical and...
below. Much like podocarps, it feeds in the organic litter near the surface of the soil through fine
root hairA root hair is a tubular outgrowth of root epidermal cells of vascular plants. They are found only in the region of maturation of the root. Root hairs are a specialized form of rhizoid....
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
decompositionDecomposition is the process by which tissues of a dead organism break down into simpler forms of matter. The process is essential for new growth and development of living organisms because it recycles the finite matter that occupies physical space in the biome. Bodies of living organisms begin to...
. On the other hand, broadleaf trees such as
MāhoeMahoe 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
nutritionNutrition is the provision, to cells and organisms, of the materials necessary to support life. Many common health problems can be prevented or alleviated with a healthy diet....
in the deeper
mineralA mineral is a naturally occurring solid formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. A rock, by comparison, is an aggregate of minerals and/or mineraloids, and need not have a specific...
layer of the soil. Although its
rootIn vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...
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 avoid blowing over, especially during
stormA storm is any disturbed state of an astronomical body's atmosphere, especially affecting its surface, and strongly implying severe weather...
s and
cycloneIn meteorology, a cyclone is an area of closed, circular fluid motion rotating in the same direction as the Earth. This is usually characterized by inward spiraling winds that rotate counter clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere of the Earth.Large-scale...
s.
The
litterPlant litter is dead plant material, such as leaves, bark, 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 the environment...
left by kauri is much more acidic than most trees, and as it decays similarly acidic compounds are liberated. In a process known as
leachingIn general, leaching is the extraction of certain materials from a carrier into a liquid . Specifically, it may refer to:*Leaching *Leaching *Leaching **Dump leaching...
, these acidic molecules pass through the soil layers with the help of
rainRain is liquid precipitation, as opposed to other kinds of precipitation such as snow, hail and sleet. On Earth, it is the condensation of atmospheric water vapor into drops heavy enough to fall, often making it to the surface...
fall, and release other nutrients trapped in
clayClay is a naturally occurring material composed primarily of fine-grained minerals, which show plasticity through a variable range of water content, and which can be hardened when dried and/or fired...
such as
nitrogenNitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere.Many industrially important...
and
phosphorusPhosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus is commonly found in inorganic phosphate rocks. Elemental phosphorus exists in two major forms - white phosphorus and red phosphorus...
. 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
competesInterspecific competition, in ecology, is a form of competition in which individuals of different species vie for the different resource in an ecosystem...
with other species for space.
Leaf litter and other decaying parts of a kauri decompose much slower than most other species. Besides its acidity, the plant also bears substances such as
waxWax refers to beeswax or another substance with similar properties. The traditional meaning, beeswax, refers to a substance secreted by bees and used by them in constructing their honeycombs...
es and
phenolPhenol, also known as carbolic acid, is a toxic, white crystalline solid. Its chemical formula is C6H5OH and its structure is that of a hydroxyl group bonded to a phenyl ring, making it an aromatic compound.-Phenols:...
s that are harmful to
microorganismA microorganism or microbe is an organism that is microscopic...
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
mycorrhizaA mycorrhiza is a symbiotic association between a fungus and the roots of a plant. In a mycorrhizal association, the fungus may colonize the roots of a host plant, either intracellularly or extracellularly...
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
lineagesThe evolution of plants occurred through increasing levels of complexity, from the earliest algal mats, through bryophytes, lycopods, ferns and gymnosperms to the complex angiosperms of today...
.
Local spatial distribution
In terms of local
topographyTopography 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
hillA hill is a landform that extends above the surrounding terrain, in a limited area. Hills often have a distinct summit, although in areas with scarp/dip topography a hill may refer to a particular section of scarp slope without a well-defined summit A hill is a landform that extends above the...
s 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, kauri trees are 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
taraireTaraire, 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
tawariTawari is an angiosperm tree, the single member of the New Zealand's only endemic vascular plant family. It is only found in the North Island, between Waitomo and Kaitaia. It is used to make honey.-References:*...
, a montane broadleaf tree which is normally found in higher altitudes, where nutrient cycling is naturally slow.
Changes over geological time
Kauri is presently found north of 38°S
latitudeLatitude, usually denoted by the Greek letter phi gives the location of a place on Earth north or south of the equator. Lines of Latitude are the imaginary horizontal lines shown running east-to-west on maps that run either north or south of the equator...
, its southern limit stretching from
Kawhia HarbourKawhia 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 RangesThe Kaimai Range is a mountain range in the North Island of New Zealand. It can be seen as a continuation southwards of the hills of the Coromandel Peninsula, and separates the Waikato in the west from the Bay of Plenty in the east...
.
However, its distribution has changed greatly over geological time due to the phenomenon of
climate changeClimate change is a change in the statistical distribution of weather over periods of time that range from decades to millions of years. It can be a change in the average weather or a change in the distribution of weather events around an average...
. This is exemplified in the recent
HoloceneThe Holocene is a geological epoch which began approximately 11 700 years ago . According to traditional geological thinking, the Holocene continues to the present. The Holocene is part of the Neogene and Quaternary periods. Its name comes from the Greek words and , meaning "entirely...
epoch by migration southwards following the peak of the last
Ice AgeThe general term "ice age" or, more precisely, "glacial age" denotes a geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in an expansion of continental ice sheets, polar ice sheets and alpine glaciers. Within a long-term ice age, individual...
. During this time when frozen
ice sheetAn ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² . The only current ice sheets are in Antarctica and Greenland; during the last glacial period at Last Glacial Maximum the Laurentide ice sheet covered much of Canada and North America, the...
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 datingRadiocarbon dating, or carbon dating, is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to determine the age of carbonaceous materials up to about 60,000 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 this tree's distribution, with stump kauri from
peatPeat is an accumulation of partially decayed vegetation matter. Peat forms in wetlandbogs, moors, muskegs, pocosins, mires, and peat swamp forests...
swampA swamp is a wetland featuring temporary or permanent inundation of large areas of land by shallow bodies of water. A swamp generally has a substantial number of hammocks, or dry-land protrusions, covered by aquatic vegetation, or vegetation that tolerates periodical inundation. The two main types...
s being used for measurement. The coldest period in recent time occurred very roughly 15-20,000 years ago, and during this time kauri was apparently confined north of Kaitaia, which itself is not far from the northern most point of the North Island, North Cape. Much like
kumaraKumara may refer to:* Kumara, New Zealand, a town* The Four Kumaras, sages from the Hindu tradition* Murugan, a Hindu deity also known as Kumara* Sweet potato, called kūmara in New Zealand...
s grown in New Zealand, kauri requires a mean temperature of 17°C or more for the majority of the year. Kauri's retreat can in fact be used as a
proxyIn climate research, a proxy variable is something that is probably not in itself of any great interest, but from which a variable of interest can be obtained...
for temperature changes during this period.
It remains unclear whether kauri recolonized 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
WhangareiTe Hihi to airport|-| bgcolor="#FFCCBB" | Territorial
Authority| bgcolor="#FFEEDD" | Name || Whangarei District Council|-| bgcolor="#FFCCBB" | Regional
Council| bgcolor="#FFEEDD" | Name || Northland Regional Council|-|}...
, past
DargavilleDargaville 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
WaikatoWaikato is a Region of New Zealand. With coasts on the western and north-eastern sides of the North Island, it stretches from Lake Taupo and northern King Country in the south, north to the Coromandel Peninsula. It is bounded by Auckland on the north, Bay of Plenty on the east, Hawke's Bay on...
, attaining its peak distribution during the years 3000-2000
BPBefore 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 1 January 1950 as the arbitrary origin of the age scale...
. There is some suggestion it has receded somewhat since then, which may indicate temperatures have declined slightly since this time. During the peak of its movement southwards, it was traveling as fast as 200 metres per year. Regardless of where it originated from, its spread southward 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 as its means of both
pollinationPollination is the process by which pollen is transferred in plants, thereby enabling fertilization and sexual reproduction. Pollen grains, which contain 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 dispersalSeed 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...
, whereas many other natives may have their seeds carried large distances by
frugivoreA frugivore is a fruit eater. It can be any type of herbivore, omnivore or carnivore where fruit is a preferred food type. Frugivory is a very common diet choice. For example, 20% of herbivorous mammals could be sub-classed as frugivore/herbivore if such a classification existed in science...
s (animals which eat
fruitThe term fruit has different meanings dependent on context, and the term is not synonymous in food preparation and biology. Fruits are the means by which flowering plants disseminate seeds, and the presence of seeds indicates that a structure is most likely a fruit, though not all seeds come from...
) such as the
kererūThe kererū or New Zealand Pigeon 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 rapidly reach a stage at which they can produce seeds, taking only 50 years or so before giving rise to their own offspring. This trait makes them somewhat like a
pioneer speciesPioneer species are species which colonize previously uncolonized land, usually leading to ecological succession. Since uncolonized land may have thin, poor quality soils with few nutrients, pioneer species are often hearty plants with adaptations such as long roots, root nodes containing...
, 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
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 is much more
lightLight is electromagnetic radiation, particularly radiation of a wavelength that is visible to the human eye ....
demanding and requires larger gaps to regenerate, whereas broadleaf trees such as
puririPuriri is an evergreen tree endemic to New Zealand. -History:...
and
kohekoheKohekohe 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 toleranceIn 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
disturbanceIn ecology, a disturbance is a temporary change in average environmental conditions that causes a pronounced change in an ecosystem. Outside disturbance forces often act quickly and with great effect, sometimes resulting in the removal of large amounts of biomass...
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
windWind is the flow of air or other gases that compose an atmosphere . On Earth, wind consists of the bulk movement of air...
and
frostFrost is the solid deposition of water vapor from saturated air. It is formed when solid surfaces are cooled to below the dew point of the adjacent air. Frost crystals' size differ depending on time and water vapor available. Frost is also usually translucent in appearance. There are many types of...
s. Kauri reside in 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.
Due to this special regeneration niche, kauri trees can live over a thousand years, whereas most other trees experience
senescenceSenescence refers to the biological changes which take place in organisms as they age. It encompasses all of the biological processes of a living organism's approaching an advanced age...
long before this time. This extraordinary age is simply a reflection of how long this species must wait in order for there to be a disturbance large enough to favour its regeneration. The nature of this large disturbance also means that kauri trees regenerate
en mass, resulting in a
cohort or generation of trees of similar ages forming after each disturbance. Kauri in a given area are hence likely to be of similar age. Due to the nature of their regeneration, 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 be an indication that an area is prone to disturbances. Kauri
seedlingthumb|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 rateMortality rate is a measure of the number of deaths in some population, scaled to the size of that population, per unit time. Mortality rate is typically expressed in units of deaths per 1000 individuals per year; thus, a mortality rate of 9.5 in a population of 100,000 would mean 950 deaths per...
s 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 disturbances kauri tends to lose ground to broadleaf competitors which are more capable of establishing themselves in shaded environments. In the complete absence of disturbance, kauri tends to become more rare as it is excluded by its competitors.
BiomassBiomass, a renewable energy source, is biological material derived from living, or recently living organisms, such as wood, waste, and alcohol fuels. Biomass is commonly plant matter grown to generate electricity or produce heat. For example, forest residues , yard clippings and wood chips may be...
of kauri tends to decrease during such times, as more biomass becomes concentrated in angiosperm species like towai. Kauri trees also tend to become more randomly distributed in terms of their age, with each tree dying at a different point in time, and regeneration gaps being 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 are impossible to observe in the lifetime of a human, research into current patterns of distribution, behavior of species in experimental conditions, and study of
pollenPollen 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 between the stamens to the pistil of flowering plants or from the male cone to the...
sediments (see
palynologyPalynology 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 historyThe term life history has been given many meanings in several scientific fields. It can refer to a variety of methods and techniques that are used for conducting qualitative interviews, especially in the fields of sociology and anthropology.-Biology:...
of kauri.
Kauri seeds may be taken from mature cones generally in late March. Each scale on the cone (see picture) is home to one winged seed, a leaf litter brown in colour, approx 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 2-3 days of commencing, so it is best to watch for the first signs and then harvest the seeds for immediate generation.
Deforestation
Heavy
loggingDeforestation is the clearance of naturally occurring forests by the processes of logging and/or burning of trees in a forested area. There are several reasons deforestation occurs: trees or derived charcoal can be sold as a commodity and used by humans, while cleared land is used as pasture,...
which began around 1820 and continued for a century has considerably decreased the number of kauri trees in New Zealand. It has been estimated that before European colonisation, 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 km², comprising some 47 forests which were depleted of their best kauri. By 1900, less than 10% of the original kauri had survived. It is estimated that today, there is 4% of uncut forest left in small pockets.
Estimates are that around half of the timber had been accidentally or willfully burnt. More than half of the remainder had been exported to Australia, Britain, and other countries, while the balance was used locally for building houses and ships.
Much of the timber was sold for a return sufficient only to cover wages and expenses, plus reasonable interest on the capital employed in the industry. From 1871 to 1895 the receipts indicate a rate of about 8 shillings (around NZD$20 in 2003)
http://www.eastonbh.ac.nz/?p=515 per 100
superficial feetThe board-foot is a specialized unit of volume for measuring 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.Board-foot is abbreviated FBM...
(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 one sale in 1908 more than 5,000 standing kauris, totalling about 20,000,000 superficial feet (47,000 m³), were sold for less than two pounds per tree (two pounds in 1908 equates to around NZD$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 (NZD$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 1960's. 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 1/5 of the forest by area, and 1/4 by volume of timber) was essentially complete (as of the early 1990's 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 Labor 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 totora and other popdocarps 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 their use is far more restricted, in the past the size and strength of kauri
timberTimber may refer to:*Lumber, i.e. wood materials* Timber, Oregon, an unincorporated community in the U.S. state of Oregon* Timber , a 1984 arcade game by Bally Midway* An alternative spelling for Timbre...
made it a popular
woodWood is an organic material; in the strict sense wood is produced as secondary xylem in the stems of trees . In a living tree it transfers water and nutrients to the leaves and other growing tissues, and has a support function, enabling woody plants to reach large sizes or to stand up for themselves...
for construction and ship building, particularly for
mastsThe mast of a sailing ship 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 due to its parallel grain and the absence of branches extending 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 panellingPanelling 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. Though not as highly prized, the light colour of kauri trunk wood made it also well-suited for more utilitarian
furnitureFurniture is the mass noun for the movable objects intended to support various human activities such as seating and sleeping in beds, to hold objects at a convenient height for work using horizontal surfaces above the ground, or to store things...
construction, as well as for use in the fabrication of
cisternA cistern is a receptacle for holding liquids, usually water. Often cisterns are built to catch and store rainwater...
s, barrels,
bridgeA bridge is a structure built to span a valley, road, body of water, or other physical obstacle, for the purpose of providing passage over the obstacle. Designs of bridges vary depending on the function of the bridge and the nature of the terrain where the bridge is constructed.-History:The first...
s construction material,
fenceA fence is a freestanding structure designed to restrict or prevent movement across a boundary. It is generally distinguished from a wall by the lightness of its construction: a wall is usually restricted to such barriers made from solid brick or concrete, blocking vision as well as passage .Fences...
s, moulds for metal forges, large rollers for the
textile industryThe textile industry is a term used for industries primarily concerned with the design or manufacture of clothing as well as the distribution and use of textiles.-Cotton stage:...
,
railroad tieA railroad tie, cross tie, or railway sleeper is a rectangular object used as a base for railroad tracks. Sleepers are members generally laid transverse to the rails, on which the rails are supported and fixed, to transfer the loads from rails to the ballast and subgrade, and to hold the rails to...
s and braces for mines and tunnels, among many others.
In the late nineteenth and early twentieth centuries
kauri gumKauri forests once covered most of the upper North Island of New Zealand; the change of climate, geological activity and the impact of Maori and European settlers had led to much deforestation, with some areas reverting to sand dunes, scrub or swamp, but these ancient kauri fields continued to...
(semi-fossilised kauri
resinResin is a hydrocarbon secretion of many plants, particularly coniferous trees. It is valued for its chemical constituents and uses, such as varnishes and adhesives, as an important source of raw materials for organic synthesis, or for incense and perfume. Fossilized resins are the source of amber...
) was a valuable commodity, particularly for
varnishVarnish is a transparent, hard, protective finish or film primarily used in wood finishing but also for other materials. Varnish is traditionally a combination of a drying oil, a resin, and a thinner or solvent. Varnish finishes are usually glossy but may be designed to produce satin or semi-gloss...
, and was the focus of a considerable
industryKauri forests once covered most of the upper North Island of New Zealand; the change of climate, geological activity and the impact of Maori and European settlers had led to much deforestation, with some areas reverting to sand dunes, scrub or swamp, but these ancient kauri fields continued to...
at the time.
Timber
Technical specifications
- Moisture content of dried wood: 12%
- Density of wood: 560 kg/m³
- Tensile strength
Tensile strength is indicated by the maxima of a stress-strain curve and, in general, indicates when necking will occur. As it is an intensive property, its value does not depend on the size of the test specimen...
: 88 MPaThe pascal is the SI derived unit of pressure, stress, Young's modulus and tensile strength. It is a measure of force per unit area, defined as one newton per square metre...
- Modulus of elasticity
In solid mechanics, Young's modulus is a measure of the stiffness of an isotropic elastic material. It is also known as the Young modulus, modulus of elasticity, elastic modulus or tensile modulus...
: 9.1 GPa
- After felled kauri wood dries to a 12% moisture content, the tangential contraction is 4.1% and the radial contraction is 2.3%
A considerable number of kauri have been found buried in what are today salt marshes, resulting from ancient natural changes such as
volcanic eruptionsVolcanic Eruptions is the name of Crispin Glover's film production company. It has released two films to date, What Is It? and its sequel, It is Fine! EVERYTHING IS FINE . Its current plans include releasing the final film in the trilogy titled It Is Mine. It is unknown when It Is Mine will be...
,
sea levelMean sea level is the average height of the ocean's surface ; used as a standard in reckoning land elevation.- Measurement :...
changes and floods. Such trees have been
radiocarbon datedRadiocarbon dating, or carbon dating, is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to determine the age of carbonaceous materials up to about 60,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present"...
to originating as far back as 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 in contact with the air, these parts display rapid deterioration.
The quality of the disinterred wood varies, and some is in surprisingly good shape, comparable to that of newly-felled kauri, although often lighter in colour. This aspect can be improved by the use of natural
dyesA 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...shellac, lacquer, varnish, polyurethane, etc...
, which provide brown dark and greenish tones that heighten the details of the grain. After a
drying processWood drying refers to reducing the moisture content of wood prior to its use.For some purposes wood is not dried at all . Often the wood needs to be in an equilibrium with the air outside or the air indoors .Wood is either air-dried or kiln-dried...
, such ancient kauri can still be made use of for furniture and other construction.
Conservation and kauri today
The small remaining pockets of kauri forest in New Zealand have survived in areas that were not subjected to burning by Māori settlers and were too inaccessible to European loggers. The largest area of mature kauri forest is
Waipoua ForestWaipoua 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....
in
NorthlandThe Northland Region , one of the 16 regions of New Zealand, is, as the name suggests, the northernmost of New Zealand's administrative regions. The main centre is the city of Whangarei.-Geography:...
. Mature and regenerating kauri can also be found in other National and Regional Parks such as Puketi and Omahuta Forests in Northland, the
Waitakere RangesThe Waitakere Ranges are a chain of hills 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 . The ranges and surrounding areas were traditionally known to local Māori as Te Wao Nui a Tiriwa...
near Auckland, and Coromandel Forest Park on the
Coromandel PeninsulaThe Coromandel Peninsula lies in the North Island of New Zealand. It is part of the Waikato region 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 from the Pacific Ocean to the...
.
The importance of
Waipoua ForestWaipoua 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....
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. Along with the Warawara to the North, it contains three quarters of New Zealand's remaining kauri.
In 1921 a philanthropic Cornishman named James Trounson sold to the Government for 40 thousand pounds, a large area adjacent to a few acres of crown land and said to contain at least four thousand kauris. From time to time Trounson had added further areas by way of gift, until what is known as Trounson Park comprised a total of 4 km².
The most famous specimens are
Tāne MahutaTāne 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 1250 and 2500 years old...
and
Te Matua NgahereTe Matua Ngahere is a giant kauri 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 much stouter, with a girth just over 16 metres . There is no proof of...
in Waipoua Forest. These two trees have become tourist attractions due to their size. Tane Mahuta, named after the
MāoriThe Māori are the indigenous Polynesian people of New Zealand . The group probably arrived in southwestern Polynesia in several waves at some time before 1300...
forest godIn 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 m (45.2 ft), a trunk height of 17.68 m (58.0 ft), a total height of 51.2 m (168 ft) and a total volume including the crown of 516.7 m³ (18,247 cu ft).
Te Matua Ngahere, which means 'Father of the Forest', is smaller but stouter than Tane Mahuta, with a girth (
circumferenceThe circumference is the distance around a closed curve. Circumference is a special perimeter.-Circumference of a circle:The circumference of a circle is the length around it....
) of 16.41 m (53.8 ft).
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 (though seedlings are frost tender), and small footprint. Despite this, like many native urban trees, it falls victim to "new owners" syndrome, so there are relatively few such trees in cities older than 40 years. The present National Government's forcing through changes to remove categorical protection for these trees in suburbia effective 2012, despite an overwhelming proportion of submissions in favor of the current law, threatens their continued existence. It also endangers many square kilometers of regenerating kauri forest surrounding the Waitakeres. Formerly protected, these areas have largely been sub-divided below 10 acres (4 hectares), so they too now loose all protection.
In the 1970s, kauri dieback caused by a
phytophthoraPhytophthora 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...
was discovered on
Great Barrier IslandGreat Barrier Island is a large island of New Zealand, situated to the north-east of central Auckland in the outer Hauraki Gulf...
. The disease, known as kauri collar rot, has since started 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 katsuraePhytophthora 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 other mammals, particularly feral pigs. A collaborative response team has been formed to work on the disease. The team includes MAF Biosecurity, DOC, ARC, Northland RC, 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.
Simple precautions all can take are: keep to defined tracks, clean footwear before and after entering kauri forest areas, stay away from kauri roots .
Ancient Kauri
The prehistoric Kauri forests that grew 50,000 years ago are preserved under the surface of the North Island of New Zealand, particularly in waterlogged soils. This wood is referred to as "
Ancient KauriAncient 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".
External links