New Zealand’s native conifers

Join Prof David Norton on a walk in the ngahere, to meet a few of Aotearoa New Zealand's impressive native conifer genera.

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Mixed podocarp forest, Pureora
Dense and diverse mixed podocarp forest, Pureora.

One of my favourite groups of New Zealand plants are our native conifers. Most people don’t realise that we have 21 described species and two undescribed species. These are spread across ten genera in three of the six global conifer families. And on a land area basis we have far more native species than the UK or mainland Australia, similar numbers to Tasmania and California but far fewer than New Caledonia!

Some of the things that make our conifers special include that they are all endemic to New Zealand (they occur nowhere else in the world), some are truly ancient (leaf fossils from kauri have been found in 25-30 million year old rocks), they are dominant in so many of our forests, we have some of the largest and smallest conifers in the world, and all our species apart from in Libocedrus, are southern in origin (Gondwanan).

I have started to post about each of the conifer genera on my Instagram @davidnortonnz, and will continue with these over the next few weeks – stay tuned!

One of our most impressive conifer-dominated forest is at Pureora in the Central North Island with matai, tōtara, kahikatea and rimu all growing as tall canopy trees, and several other conifers are also present. Sadly this forest is a tiny remnant of the once extensive conifer forests that occurred through this area before European settlement. But native conifers and conifer dominated forests are still widespread in many areas of New Zealand, especially on the west coast of South Island, and are a distinct feature of our landscapes.

The photos in my posts come from my many years of research, teaching and tramping through New Zealand’s forest and alpine landscapes.

New Zealand cedars

The genus Libocedrus, is our only genus in the cypress family (Cupressaceae). This family includes macrocarpa, redwood, western red cedar and juniper. Libocedrus is a small genus of six species found in New Zealand, New Caledonia and South America. Two species occur in New Zealand, Libocedrus bidwillii and Libocedrus plumosa. Māori names are a bit confusing but one or both have been variously called kaikawaka, kawaka and pāhutea and they are also known as New Zealand cedar.

Libocedrus bidwillii, South Westland.
Libocedrus bidwillii, South Westland.

Both species look similar, but are ecologically quite distinct. L. bidwillii is a tree of montane and subalpine forests in the North and South Islands and often occurs in single-species stands on frosty valley flats or in the subalpine zone. L. plumosa occurs in coastal and lowland forests in the northern half of the North Island and around Golden Bay in the South Island.

Both species have similar bark that peels off in strips, but differ in their foliage. In L. bidwillii the axial leaves are only slightly smaller than the lateral leaves giving a rounded appearance (third photo), while in L. plumosa the axial leaves are much smaller than the lateral leaves giving the foliage a distinct flattened appearance.

Kauri

The second conifer family we have in New Zealand is the Araucariaceae, with one native species, kauri. The Araucariaceae is a small family with three genera, Agathis (22 species), Araucaria (20 species including Norfolk pine) and Wollemia (1 species). Agathis extends from New Zealand through Australia and Melanesia to SE Asia.

Kauri-podocarp forest, Waitakere Ranges.
Kauri-podocarp forest, Waitakere Ranges.

Kauri (Agathis australis) is endemic to New Zealand but is similar to species in Australia and Melanesia. It is our largest tree by volume with adults having clear straight trunks with large spreading branches. Young trees are conical. The linear leathery leaves and small globose cones are distinctive. Kauri is restricted to the northern North Island and occurs in mixed stands with other conifers and angiosperm trees, or in dense stands of mainly kauri.

To Māori, kauri was a special tree which is reflected in the name Tane Mahuta given to the largest living kauri (first photo) – Tane is pivotal to the Maori creation story, having separated Ranginui and Papatunanuku, and in Māori history the creation of the whole forest domain including all plants and animals is attributed to Tane.

Sadly, kauri were heavily impacted by early European settlement, with fewer than 10% of the original old growth kauri forests remaining, and today these forests are threatened by kauri dieback disease (Phytophthora agathidicida).

Kahikatea

The Podocarpaceae (known as podocarps) is the third and largest family of native conifers in New Zealand with eight genera and 18 described species. The family is southern in its origins but today is most common in the subtropics and tropics and extends as far north as Japan and Central America, and are typically trees of moist forests. The podocarps are distinguished from other conifers by their highly modified and reduced cones with a swollen fleshy cone scale either enclosing the seed or with the seed on top of it. Unlike most other conifers, podocarp fruits are well adapted to bird dispersal.

The first podocarp genus in New Zealand I want to review is Dacrycarpus with one species here, Dacrycarpus dacrydioides or kahikatea. The genus has nine species and is distributed from New Zealand north into Melanesia and across to SE Asia and south China. Kahikatea, which only occurs in New Zealand, looks similar to Dacrycarpus imbricatus from SE Asia.

Kahikatea forest, South Westland.
Kahikatea forest, South Westland.

Kahikatea is our tallest tree (to 65 m) and forms dense stands on recent alluvial soils but also occurs in lower hill country mixed conifer-angiosperm forests throughout the country. Kahikatea regenerates after disturbance, especially river flooding, and can form extensive dense even-aged stands. The range of this species has been greatly diminished since human settlement but extensive stands of kahikatea can still be found on the flood plains of South Westland.

Kahikatea is easily distinguished from similar looking podocarps like matai and rimu by its dark grey bark that separates into round flakes which are black underneath, and its small scale-like leaves. When in fruit, trees turn bright red-orange and as the cones fall, they carpet the forest floor. Kahikatea forests provided rich habitat for native birds, especially when fruiting.

For anyone interested in the history of these beautiful and pivotal New Zealand ecosystems, ‘Ngā Uruora (The Groves of Life) Ecology and History in a New Zealand Landscape’ by the late Geoff Park, an outstanding New Zealand ecologist, is the seminal book and a must read.

Rimu

The next New Zealand podocarp genus I want to feature is Dacrydium, within which we have the one endemic species Dacrydium cupressinum or rimu. Dacrydium is the second largest genus of podocarps comprising 21 species extending from New Zealand north into Melanesia and then west across SE Asia and north to China. Over half the species occur in Fiji, Solomons, New Caledonia and New Guinea.

Dense rimu forest, South Westland.
Dense rimu forest, South Westland.

Rimu is perhaps the most widespread and dominant conifer in lowland New Zealand forests, occurring almost everywhere except in the dry eastern South Island, and even here there are isolated occurrences (e.g. Mt Oxford and on Banks Peninsula). Rimu grows across a range of soils and can form dense pure stands (as occur on the infertile outwash surfaces of South Westland) or as an emergent in mixed species conifer-broadleaved forests. It has been perhaps the most utilised native tree for timber in New Zealand and its range has been greatly diminished in many parts of New Zealand because of this.

Maximum height is usually 30-40 m and trees can live for 400-800 years. Rimu is readily distinguished from other similar looking native conifers by its pendulous foliage comprising small appressed leaves, and its distinctively patterned bark. Trees are either male or female, and the female cones have a fleshy red upturned aril with one black seed. Rimu is mast seeding, in that it only fruits heavily every 2-4 years, and its seeds are bird dispersed.

Conclusions

Over the next few weeks I will post about the other New Zealand conifer genera (Halocarpus, Lepidothamnus, Manoao, Phyllocladus, Podocarpus and Prumnopitys). After that, I will finish with a couple of posts on my thoughts about the future of our native conifers.

David Norton is a Professor at Te Kura Ngahere | School of Forestry at the University of Canterbury. He has taught about and researched the ecology and conservation of New Zealand’s unique biodiversity for over 35 years. Follow David on Instagram.