Natural Decay Resistance of the Heartwood of Coast Redwood Sequoia Sempervirens (D. Don) Endl.

Decay resistance of outer heartwood of butt logs, collected in 1962 from 83 old-growth and 84 young-growth trees of Sequoia sempervirens (D. Don) Endl., was laboratory tested by the soil-block method with the wood rotters Poria placenta and Gloeophyllum trabeum. Outer heartwood samples (from the outer third of the heartwood radius) from 94 percent of the old-growth trees were resistant or very resistant to P. placenta and 100 percent were resistant or very resistant to G. trabeum. Corresponding values for the young-growth trees were 46 percent and 44 percent. The prevalence of very resistant outer heartwood varied markedly among localities in which the trees were grown, presumably reflecting genetic differences between stands. Overall, very resistant wood was about five times more prevalent in old-growth than in young-growth trees. Additionally, the heartwood of five old-growth and five young-growth trees was sampled extensively at both radial and longitudinal positions and appraised with the same test fungi. Decay resistance varied markedly within individual trees. In the first one or two logs, resistance decreased progressively from outer to inner heartwood, the magnitude of differences being sufficient to warrant selection of outer heartwood in old-growth trees for maximum durability. The most resistant wood was in the outer heartwood of the butt log; above this there was no practically significant variation in resistance in relation to height.

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