The kauri is New Zealand's largest tree in volume of timber, and the largest in its' genus. The biggest living kauri, Tane Mahuta, has a 4.4m diameter trunk clear of branches up to 18m, reaches a height of 52m, and has been standing for over 2,000 years. Kauri exceeds all New Zealand trees in its antiquity. The genus Agathis evolved from the fossil Araucariacites australis that was present in Gondwana 230 million years ago. Kauri forest destruction is the saddest story of the country's natural history. Before rampant logging and burning to clear for pasture, kauri covered 1.6 million hectares in the northern half of the North Island. Just one primary forest of 7,000 ha remains in the Waipoua Forest, Northland. See more
The kahikatea is a large tree in the ancient podocarp group of conifers. It is New Zealand's tallest tree, reaching up to 60m. The trunk diameter is up to 1.5m in 600 year-old trees. Specimens that are hundreds of years older grow to 2.6m. It is mainly a lowland tree, forming pure stands that may exclude all other trees, or associating with pukatea and swamp maire in wetlands on alluvial terraces. Kahikatea is also found on steep country in podocarp-broadleaf forests at elevations up to 600m. It has suffered the most depletion of any native tree from wetland conversion to pasture, especially in the Waikato region, and forest clearing throughout the country. See more
With heights up to 35 metres, pukatea and tawa are New Zealand's tallest flowering trees. Pukatea is commonly found with kahikatea, and sometimes swamp maire in wetlands and on moist alluvial plains. It is unusual as the only New Zealand tree that forms thin plank buttresses in wet conditions, a base structure normally only on tropical trees. In swamps, pukatea grows breathing roots above ground called pnuematophores to obtain oxygen. It also features in moist conditions, often on stream banks from sea level to 600 m in conifer-broadleaf forests. Pukatea is widely dispersed throughout the North Island, but in the South Island is only near the coast in western Nelson and northern Marlborough. See more
NEW ZEALAND ECOLOGY
BIG CONIFER AND BROADLEAF TREES
Big trees characterise the distinctive appearance, biodiversity, antiquity, and feeling of the two main New Zealand native forest types - conifer-broadleaf, and southern beech. Eleven species grow to 30 metres or more, and another six get 25 m tall. Except for red and black beech, they are all part of conifer-broadleaf forests throughout the North Island and west coast of the South Island.
All of these large trees are only found in New Zealand. A long period of isolation from the rest of the world allowed a unique flora to evolve, with 80 percent of 2300 species of conifers, flowering plants and ferns endemic, and remarkable endemism in 35 genera.
Conifer-broadleaf forest has a rich diversity in five layers, with a ground layer of herbaceous plants and ferns, a layer of shrubs and small trees, a sub-canopy of medium sized trees such as tree ferns and nikau, a continuous canopy of broadleaf trees dominated by tawa or kamahi 20-25 m tall, and the emerging big trees at the top. The podocarps rimu, kahikatea, matai and totara; broadleaf rata, rewarewa and sometimes tawa; or kauri, all 30 to 40 m tall and some up to 60 m tower above it all. Five layers are untypical of temperate rainforest, and normally only occur in tropical locations.
Rimu is a prominent podocarp conifer widespread throughout the country, and the most common emergent tree in conifer-broadleaf forests, towering high above the broadleaf canopy. It consistently reaches 35 metres in height, and 60 m giants have been known, associating with kauri and the other large podocarps. Previously abundant in lowland and mid-altitude forest up to 700 m, rimu was extensively logged until the late 1960s as a popular timber for all aspects of wood-frame housing construction. Its' height and bright green foliage was easily spotted in mature forests, and dragged up hillsides to logging roads. Otherwise rimu has a long life span of 600-800 years, and sometimes living 1000 years.
Northern rataMetrosideros robusta
The flowering Northern rata is also a tall emergent tree in conifer-broadleaf forests, reaching up to more than 30 m. It starts life high up as an epiphyte, often in rimu, then sends down roots that engulf the host trunk, and become its' trunk when the host dies. Rata in full flower is an exceptional sight, providing a plentiful supply of nectar to the pollinating birds, tui, saddleback and bellbird. Hordes of insects are also attracted to the nectar, including bees that produce a delicate, delicious rata honey. As with pohutukawa Metrosideros excelsa, possum gorge on new leaf shoots, eventually stripping vegetation and killing the tree.
The variety P. totara var. totara is found throughout New Zealand and is the largest of four species of the genus Podocarpus, mostly reaching 30 m in height with a 2 m diameter trunk. It can be more than 40 m tall with a 4 m trunk. Totara is a lowland tree up to an elevation of 480 m, preferring well drained, fertile soils, and associating with the other podocarps rimu, matai and kahikatea. In the open (right) it has a broad, more rounded form, but in the forest it grows tall with the other big trees. Totara is long-living - up to 900 years or more. The smaller P. totara var. waihoensis is 10 to 15 m tall, only occurring in South Westland from the Waihau River to the Cascade Range.