Abstract
There is wide variation in the wood properties of plantation-grown coast redwood (Sequoia sempervirens (D.Don) Endl.) in New Zealand. Contributing factors are the seed source, silviculture, growth rate 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. The wood of plantation-grown coast redwood trees from three forests in the North Island, New Zealand, was evaluated using butt log and breast height discs and cores, and in vitro decay tests with brown- and white-rot fungal cultures, to determine the variation in the heartwood content, basic density, and red colour and natural durability of the heartwood. The heartwood content of the coast redwood trees was strongly influenced by the age and size of the trees. The basic density of the wood varied widely among the trees in the forests. There were strong radial trends of heartwood colour and natural durability within the stems of trees, with differences among trees at the same growth rings. The heartwood showed a wide range of natural durability, with trees from the older forest stands having a higher proportion of durable heartwood. The diameter growth and age of the coast redwood trees, and the variation among and within the stems of trees will affect the wood properties. 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.
Highlights
There is wide variation in the wood properties of plantation-grown coast redwood (Sequoia sempervirens (D.Don) Endl.) in New Zealand
The natural durability varied from the inner to outer heartwood within the tree stems, with the most durable heartwood occurring adjacent to the sapwood, and the susceptibility to decay increasing towards the pith (Sherrard and Kurth 1933; Clark and Scheffer 1983)
The trees selected from the Kinleith Forest stand were larger than the stand average, and given the increase in heartwood content with the size of the trees (Figure 3), this would suggest the heartwood content of the Kinleith Forest trees was higher than expected on average for this stand
Summary
There is wide variation in the wood properties of plantation-grown coast redwood (Sequoia sempervirens (D.Don) Endl.) in New Zealand. The plantation-grown resource of coast redwood (Sequoia sempervirens (D.Don) Endl.) in New Zealand occurs largely in the North Island (Knowles and Miller 1993), and comprises forest stands of trees from both Californian and New Zealand seed sources, and sites with different soil and climatic conditions. The wood of New Zealand-grown coast redwood varies widely in quality, due to the seed source, silviculture, growth and age of the trees, Coast redwood trees in the North Island of New. Zealand have a heartwood content that averaged 54% (range 44–66%) for 38 year-old trees from Mangatu Forest in Gisborne (Cown and McKinley 2009), and 52% (range 45–62%) for 45-year-old trees from Tauranga in the Bay of Plenty (Colbert and McConchie 1983). The natural durability varied from the inner to outer heartwood within the tree stems, with the most durable heartwood occurring adjacent to the sapwood, and the susceptibility to decay increasing towards the pith (Sherrard and Kurth 1933; Clark and Scheffer 1983)
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