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Dendroprovenancing: A preliminary assessment of potential to geo-locate kauri timbers in northern New Zealand

Boswijk, Gretel, Fowler, Anthony M.
Dendrochronologia 2019 v.57 pp. 125611
Agathis australis, archaeology, buildings, cities, dendroclimatology, growth rings, provenance, spatial variation, trees, wood, wood industry, New Zealand
After 1840, New Zealand kauri (Agathis australis) became the focus of a large-scale timber industry in the upper North Island, which converted trees into timber that was then used in construction. Cities such as Auckland and Wellington relied on importing kauri to meet local demand for construction and other uses. Kauri timbers from buildings and in-ground features, mostly in Auckland city, have been collected for tree-dating and master chronology development. Although the use of timber at archaeological sites is understood, the geographic origin of the timber from within the natural range of kauri (north of 38 °S) is largely unknown. This limits interpretation of archaeological wood and constrains use of the tree-ring data in dendroclimatology. In this paper, we consider the potential to provenance kauri timbers used in 19th and early 20th century New Zealand buildings, using a combination of documentary sources, t-value mapping, and refined statistical matching using spatial patterns of correlations. Analysis of documentary sources for a test period of 1861–1865 CE indicates that there is sufficient information about the kauri timber industry to provide a geographic context for provenancing kauri in the upper North Island. The use of t-values for provenancing may be confounded by the relatively small size of the kauri growth region and a lack of sufficient spatial differentiation in growth patterns between the sub-regions. However, a new approach of using indexed residual chronologies and field correlations has promise for geo-locating timber in a relatively small region. The research highlights the value of establishing kauri provenance to New Zealand dendroclimatology, dendroarchaeology and environmental history.