The kauri family
The New Zealand kauri (Agathis australis) belongs to one of the world's oldest family of conifers, the Araucariaceae (ora-care-ree-a-see) family. This family includes trees like the Monkey Puzzle tree and the very rare Wollemi tree only discovered in Australia in 1994.
When the dinosaurs became extinct 66 million years ago, so too did all members of the Araucariaceae family in the northern hemisphere. The family now includes three genera all naturally growing in the Southern Hemisphere. One of these is known as Agathis. Agathis has 21 tree species that are found in forests from South-East Asia to the western Pacific. All the trees in the Agathis genus are generally known today as kauri.
- Family Araucariacea - Genus Agathis - Species australis
Where kauri grows
Kauri naturally grow in forests throughout northern New Zealand (north of Kawhia and just south of Tauranga). They are generally found from sea level to 700 metres. Fossil evidence shows that it once grew as far south as Invercargill.
Kauri are still found in more southerly locations but their ability to grow and thrive is reduced. The exact reasons for this is still open for debate.
There is no typical kauri forest. Kauri can grow by themselves or as dense stands. A kauri forest often includes many other tree species. Fully grown kauri trees stand above a canopy of smaller trees. They may be covered in lianes and epiphytes. Close to the ground are small trees and shrubs such as kauri grass, found only in a kauri forest.
A keystone species
A keystone species is a plant or animal that has a special and important role in the way an ecosystem works. All species in an ecosystem are somehow linked to one another - this is called interconnectedness. But without keystone species, the ecosystem would be very different or it may not even exist. A small number of keystone species can have a huge impact on the environment.
Kauri are a keystone species. Many plants and animals have evolved to live on and around kauri. For example, kauri trees create a type of soil (kauri podsol) in which only specialised plants can survive. These plant species could become extinct if enough kauri die.
There are many other plants and animals that thrive within kauri forests. So it’s not just the kauri trees themselves that need to be saved – it is a whole ecosystem.
What kauri looks like
Young kauri trees have a narrow pyramid shape like most conifers. The trees shed their lower branches when the tops reach the forest canopy. Mature kauri develop massive column-like trunks and spreading crowns. Large trees are held up by spreading lateral roots anchored with peg roots. Peg roots can reach five metres into the ground. The feeding roots form a fine surface mat within the litter mound that surrounds each tree.
The trunk of the full-grown kauri has greyish bark. It has a pattern caused by the bark flaking off, known as hammer-mark bark. Kauri gum seeps from the bark of mature trees to repair injury or decay.
Kauri tree leaves are oblong in shape and bronze when young. The leaves turn bright green as the tree grows.
The kauri is a conifer which means it produces cones - both male and female. Male cones are finger-shaped and fall once they have released their pollen in spring. Female cones are round and turn from green to brownish red as they mature. They ripen after three years of growth and release seeds that are dispersed by the wind.
A kauri’s height averages 30–40 metres. Trunks reach an average diameter of over one metre by 600–700 years of age. Trees can survive for 1,000 years or more. At this age their trunk diameter averages two metres. Trees older than 1,700 years have trunk diameters measuring over three metres. Kauri of this size are now rare.
The ages of the largest survivors like Tāne Mahuta (diameter over 4 metres) are not accurately known, but have been estimated at 1,500–2,000 years. Even bigger trees were known in the past, some with diameters of more than 7 metres.
When people first arrived in New Zealand over 1,000 years ago, kauri forests covered 1.2 million hectares. Only 7,455 hectares of mature kauri forest remains today. Stands of these trees are scattered in patches.