Natural durability of plantation-grown coast redwood (Sequoia sempervirens) in New Zealand
D O’Callahan, T Jones, C Low, C Chittenden
There is wide variation in the wood properties of plantation-grown coast redwood in New Zealand. Contributing factors are the seed source, silviculture, growth and age of the trees in the plantation forests. Little is known about how these factors affect the variation of wood properties among and within the trees of New Zealand’s coast redwood forests. Heartwood of plantation-grown coast redwood from three forests in the North Island, New Zealand, was evaluated using butt log and breast height discs and cores, for natural durability using in vitro decay tests. The heartwood content of the trees showed a wide range of durability which was strongly influenced by the age and size of the trees rather than the site. Inner heartwood was more susceptible to fungal degrade than outer heartwood with trees from the older forest stands having a higher proportion of durable heartwood.
Faster diameter growth is likely to increase the heartwood content, and longer rotations will increase the quantity of durable heartwood. The variation among trees suggests there is potential for genetic improvement.
Keywords: natural durability, Sequoia sempervirens, New Zealand, plantation-grown