What is a Kauri Tree? - Home Stratosphere

What is a Kauri Tree?

Here is everything you need to know about the kauri tree, what it looks like, where it grows naturally, how it reproduces, how tall it grows, and its relationship with fungi.

This is a close look at the tall canopy of kauri trees.

Agathis Australis

So far in our series of 101 Types of Trees from around the world, we haven’t covered any trees that are native to New Zealand, and we figured that talking about the kauri tree would be a good place to start.

Kauri is the Maori name (indigenous Polynesian peoples) for the coniferous, evergreen trees that are part of the agathis species, and the Araucariaceae botanical family. Some other common names for the kauri tree (mostly for non-New Zealand natives) are the kauri pine, the southern kauri, and the New Zealand kauri.

This incredible tree may not be the tallest of all trees, but it is the largest by volume. They rival the girth of even the California redwood tree, with trunk diameters sometimes reaching 9 meters around. That is one giant kauri, an incredibly large tree.

The kauri forest is also one of the most ancient forests on the planet, and this fact has awarded the tree the nickname “the ancient kauri”. Scientific research has determined that kauri forests’ antecedents appeared in the Jurassic period, which occurred 135-190 million years ago. This means that the genetic makeup of the kauri tree is so robust that it could survive an extinction that destroyed almost everything alive.

The largest Kauri tree known on the planet was discovered by the historian Alastair Isdale, in 1890 who named it, The Great Ghost. This tree was found in the mountains near Tararu Creek and is said to have been 8.54 meters in diameter, and 26.83 meters in girth!

And if all of that wasn’t impressive enough, the average lifespan of this tree is anywhere between 600 to 1000 years old. Without further ado, we present to you the ancient kauri tree.

Related: Wollemi Pine Tree | Monkey Puzzle Tree

What do Kauri Trees Look Like?

Root System

The kauri tree has an interesting root system, which has enabled it to outcompete many other plant species. They possess 2 different root systems that contribute to their success. These are a deep peg root system, as well as a shallow and fine root system.

The peg root system grows directly down into the soil, and quite deep as well. These roots are necessary for the tree to stay upright and strong against wind and storm damage.

The shallow root system is designed specifically for nutrient uptake. These shallow roots are made up of thinner roots that are covered in fine root hairs. These hairs absorb water and nutrients through osmosis.

The relationship between kauri trees and soil is a unique and complex one, which we will expand on further in the section “How do Kauri Trees Interact with Soil?”

Dimensions

The kauri is a very large tree, with an average height between 40 and 50 meters high. These are sun-loving trees and they must be the emergent layer above the forest canopy.

Though they are not the tallest tree in the world, they do come very close to the redwood tree in terms of pure mass. The trunk diameter and overall girth of the kauri tree beat the redwood tree, and redwood trunks tend to taper off, where kauri trees are extremely thick all the way up to its length.

Growth Pattern

This is a close look at a giant kauri tree.

A young tree will begin its development with a very straight trunk and branches growing along the length of the trunk, eventually forming a narrow crown.

As the tree matures and grows, it develops more height and more girth. The diameter of the kauri trunk is said to increase in increments between 1-5 mm per year. This may not sound like a lot, but that is equivalent to 8 annual tree rings.

A mature kauri will shed its lower branches, not only to conserve energy until they have a coveted spot in the forest canopy but to help protect them against fire damage and from invasive vine climbing.

A fully developed tree will only have top branches with a completely bare trunk. They are a very imposing-looking tree, with a narrow crown, and an almost comically robust trunk.

Bark

This is a close look at the bark of a mature kauri tree.

The bark of a kauri tree grows in smooth flaking sheets. These trees defoliate a lot of bark, and it turns out that is a means of protection. Trees will flake away bark in such mass amounts that sometimes pile 2 meters high are created.

These accumulating piles defend the tree from parasitic plants, making the tree essentially untouchable.

Foliage

This is a close look at a tall mature giant kauri tree.

Kauri leaves are arranged in opposite pairs along a twig. They grow in whorls of 3 per stem. A kauri leaf is small and narrow, usually ranging between 3 and 7 cm long. They are leathery in texture and rather tough. Leaves are a bright green color, and persist on a tree for up to 15 years!

How do Kauri Trees Reproduce?

This is a close look at the cone of a kauri tree.

Cones

This ancient tree is monoecious, meaning that they possess both male cones and female cones. Fertilization occurs through wind pollination when a female cone (seed cone) receives pollen from a male cone (pollen cone) of the same tree or a different tree.

Seed cones (ovule producing – female characteristics) are small and circular with a strikingly bright green color. They are covered in large scales that protrude slightly from the body of the cone.

Pollen cones (pollen-producing – male characteristics) are larger, long, and narrow. They are a deep brown color at maturity.

Cones become mature 18-20 months after original pollination Over the season, a mature cone will disintegrate and release winged seeds. Seeds will usually mature in the March of the second year since pollination.

Sexual Maturity

Kauri trees usually become sexually mature and start producing seed crops between the ages of 20 and 40 years.

Where do Kauri Trees Grow?

This is a close look at the asphalt road that has kauri trees on the side.

The kauri tree is native to New Zealand, specifically north of the 38 degrees south latitude. They occur more popularly in the southern area of the Kawhia harbor, westward to the Kaimai range.

In these regions, kauri trees occupied a range spanning 7500 miles. Due to severe logging that range has been brought down to only 870 miles. By 1900 only 10% was left of their natural groves, and today only 4% is left.

Luckily kauri trees are now protected as a forest sanctuary, and the largest area is present in the northland New Zealand area of the Waipoua forests.

What are the Growing Conditions of Kauri Trees?

This is a close look at a field with a nursery for kauri trees.

Soil

Possibly one of the most interesting things about the kauri tree, is that they actually are able to modify the soil that they exist in. They create a custom soil biome through the decay of their own bark and foliage.

This soil richness is highly beneficial to the kauri tree but can be to the detriment of other plant and tree species. It is a very complex system, and we will discuss it further in the “How do Kauri Trees Interact with Soil?” in the next section.

Sun Exposure

Kauri trees are sun adoring trees, which is a large part of the reason why they grow to be so tall, and why they self-prune their own branches that don’t have as much access to sunlight.

Water

A large part of the way that kauri trees are such high competitors in the forest biome is their ability to alter soil content. One of the main factors necessary for this to occur is lots of rainfall. Again, we’ll expand on this further in the section directly below.

How do Kauri Trees Interact with Soil?

This is a close look at the base and trunk of a mature kauri tree.

Competitive Method

Kauris are ancient trees. They have developed evolutionary traits that have enabled them to survive for this long, regardless of severe climate changes and natural devastations. Particularly the way in which these trees interact with soil has allowed them to thrive.

They are a fierce competitor for other angiosperms (flowering plants), and by creating soil that is very rich for them, they are depriving other species of nutrients. This creates a very unique plant community, where essentially only the strong will survive.

  1. The kauri tree feeds on the decaying organic matter in the topsoil through its fine root hairs. This organic matter is made up of the tree’s own fallen leaves, branches, and other decaying plant matter.
  2. The decaying matter from the kauri tree is far more acidic than the matter of other trees and plants. This allows for similarly acidic compounds in the soil to be released.
  3. When there is heavy rainfall, these acidic molecules bleed through several layers of soil. Acidic molecules are able to release other nutrients that are trapped in the more packed clay soils deep in the earth, like phosphorus and nitrogen.
  4. All of this is occurring directly below that kauri tree. This process makes it so that those nutrients are no longer available to other trees and plants. This process is call podsolization, and it is a very unique competition method.

Kauri – Fungi Symbiotic Relationship

Apart from acidity, the litter from kauri trees is also high in tannins and phenols, which are harmful to other microorganisms. This means that parasitic insects and plants avoid the base of kauri trees entirely.

This is a close look at a kauri tree's bark with a small fern fungi growing on it.

This results in large piles of litter that accumulate around the tree, and the kauri tree feeds off of its own decaying matter.

This is a close look at a kauri tree's bark covered in moss and fungi.

A relationship develops between feeding roots, and the network of fungus roots called mycelium. This is a symbiotic relationship, where the mycelium increases the trees’ efficiency in taking up nutrients, and the fungi take some of the nutrients for themselves in reward.

Tree Positioning

This is a tall and mature kauri tree in the middle of the forest.

As we just mentioned, this soil modifying competition method is dependent on the flow of rainwater through the soil. This is an important detail when it comes to the positioning of the tree on the land.

This method won’t work if the tree exists on a slope or hillside, as the water will flow downwards instead of directly under the tree. For this reason, kauri trees are rarely found at low elevations and are grow most successfully on ridge crests.

How is Kauri Trees Used?

Wood

Since kauri trees are now an endangered species, they are no longer used for their wood. In the past, the tree was very valued because of its straight trunk and enormous size.

The quality of wood was used specifically for shipbuilding, construction, and ornamental furniture, and flooring.

Kauri Gum

In the 19th century, kauri resin was collected for the use of varnish. This semi fossilized kauri resin completely started the development of the gum digger industry.

Carbon Capture

This is a close look at a tall and mature kauri tree surrounded by foliage.

Kauri trees are incredible for their massive contribution to carbon capture. They are the second greatest above-ground biomass capable of capturing this amount of carbon, beat out only by eucalyptus forests. A mature kauri forest is capable of capturing 1000 tonnes of carbon per hectare of forest.

FAQs

What is a swamp kauri tree?

Swamp kauri timber is created from ancient kauri trees that have fallen and been preserved in peat swamps. Some of them have been preserved for 60,000 years! Swamp kauri is simply a term used for timber made from these mature kauri trees.

What is kauri dieback disease?

Kauri dieback disease was first observed by Waitakere rangers. This disease is caused by the pathogen phytophthora agathidicida, which is a close relative of the invasive species phytophthora katsurae.

It is said that this disease is over 300 years old. The infection causes yellowing leaves and an overall diminishing canopy. It eventually spreads into the branches and causes wounds that bleed resin.

It results in completely canopy death, and eventually tree death. This pathogen is spread by attaching to people’s shoes, who then step around the foot of kauri trees and spread the disease, or through the movement of feral pigs and other local mammals.

Can you cut down a kauri tree?

Since kauri trees are endangered, and also subject to damage by the kauri dieback disease, one must first consult The Kauri Protection Company to determine whether it is safe or allowed to cut down a kauri tree, along with the proper time of year and method to do so.

How tall do kauri trees grow?

The kauri is a very large tree, with an average height between 40 and 50 meters high. These are sun-loving trees and they must be the emergent layer above the forest canopy.

Though they are not the tallest tree in the world, they do come very close to the redwood tree in terms of pure mass. The trunk diameter and overall girth of the kauri tree beat the redwood tree, and redwood trunks tend to taper off, where kauri trees are extremely thick all the way up to its length.

How fast do kauri trees grow?

Kauri trees are medium growing, and will usually grow up to 12 inches annually. Its growth is usually measured in width, rather than height.

As the tree matures and grows, it develops more height and more girth. The diameter of the kauri trunk is said to increase in increments between 1-5 mm per year. This may not sound like a lot, but that is equivalent to 8 annual rings.

How long do kauri trees live?

The average lifespan of this tree is anywhere between 600 to 1000 years old. There are only a handful of known specimens to have exceeded 2000 years old.

Where is the largest living kauri tree in New Zealand?

The largest kauri specimen known on the planet was discovered by the historian Alastair Isdale in 1890, who named it The Great Ghost. This tree was found in the mountains near Tararu Creek and is said to have been 8.54 meters in diameter, and 26.83 meters in girth!

How do you identify a kauri tree?

The easiest way to identify a kauri tree is through its bark. The bark of a kauri tree grows in smooth flaking sheets and it is a light gray/brown color. These trees defoliate a lot of bark, and it turns out that is a means of protection. Trees will flake away bark in such mass amounts that sometimes pile 2 meters high are created.

Since kauris are so tall it may be difficult to identify them by their leaves, but kauri leaves are arranged in opposite pairs along a twig. They grow in whorls of 3 per stem. A kauri leaf is small and narrow, usually ranging between 3 and 7 cm long. They are leathery in texture and rather tough. Leaves are a bright green color, and persist on a tree for up to 15 years!

Are kauri trees native to New Zealand?

Kauri trees are both native and endemic to New Zealand. Endemic meaning that this species only occurs in this one place, and nowhere else.

Do kauri trees grow in the south island Coromandel Peninsula?

Kauri trees grow naturally in the northern North Island and on the Coromandel Peninsula lowland.

What is the scientific name for the kauri tree?

The scientific term for the kauri tree is Agathis australis.

How old is the oldest kauri tree?

In the Tane Mahuta forest of New Zealand, there is a kauri tree that is approximately 2000 years old with no signs of tapping out any time soon.

What is a kauri dam?

Kauri dams were created to help transport felled trees. Logs would be sent downriver and filtered through a kauri dam (dam made from kauri wood) and directed to different locations for further transportation.

What is a Queensland kauri?

Also part of the genus Agathis, the Queensland kauri, or Agathis robusta, is a coniferous evergreen tree that is a native tree to Papua New Guinea and Queensland, Australia. In comparison to the larger tree from New Zealand (Agathis australis), Queensland kauri is much shorter with different colored bark.

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