Kauri is one of the forest trees of New Zealand that is known throughout many parts of the world because of the very large dimensions to which it grows and because of the superlative qualities of the timber. It is a conifer closely related to the pines. Several other species of Agathis grow in countries of the West Pacific including Australia, New Guinea, Indonesia, and Fiji. All possess fairly good timber qualities.
The true home of the New Zealand kauri extends from somewhat south of Auckland to the North Cape, though judging from the presence of pollen in bogs, it was present in the south of the South Island within recent geological times. Climatic change has driven it northwards. Mature trees are usually not more than 120 ft high, but diameters of the trunks occasionally reach 15 or more feet. The trunk is noted for its columnar, branchless form, the branches are shed by abscission. The crown is heavily branched, wide spreading and massive. The tree normally grows scattered or grouped, and the crowns form a distinctive, emergent upper canopy over secondary broad-leaved trees, the commonest of which are taraire (Beilschmiedia taraire) and tawa (B. tawa). Although slow by comparison with many introduced conifers, kauri is probably the fastest growing of New Zealand's native conifers. The ages of the largest trees are thought to be well over 1,000 years and are probably closer to 2,000 years. Around the trunk of older trees a litter of bark forms a mound known by the Maori name of puka. Leaf litter has the power of leaching soils and ultimately of forming a dense pan. Kauri forest soils are therefore notoriously poor for agriculture purposes. The tree produces a gum of commercial value. This gum was obtained by climbing the trees or digging the soil where Kauri forests had once existed.
The story of the extraction and milling of kauri timber and the winning of kauri gum is a romantic one, and is interwoven with the early history of New Zealand. Trees were first sought after by the Royal Navy for masts and spars, for which purpose they soon gained an excellent reputation. Later, the timber became one of the first exports, and in the 1850s, for a brief period, was the most important export from the country. The use of kauri firmly established timber as the traditional building material in New Zealand. Such was the demand that forests were soon almost cut out. Today the amount sawn is very small. The timber is used principally for finishing purposes and for boatbuilding.
The tree regenerates readily and some of the cut-over forests have been replaced by dense stands of manuka (Leptospermum spp.) in which kauri regeneration is plentiful. Foresters are managing such stands which should produce future supplies of timber.
by Alec Lindsay Poole, M.SC., B.FOR.SC., F.R.S.N.Z., Director-General of Forests, Wellington.