Heartwood decay resistance by vertical and radial position in Douglas-fir trees from a young stand

Heartwood durability of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) was studied as a function of vertical and radial position in boles of trees with a wide range of leaf area/sapwood area ratios. Six 34-year-old trees were harvested from each of three plots established 14 years before: very dense, thinned, and thinned and fertilized. Heartwood samples from three radial positions and five heights were incubated with the decay fungus Postia placenta (Fr.) M. Larsen et Lombard. There were no significant differences in wood mass loss (decay resistance) by vertical or radial position. One could expect that trees with high leaf area/sapwood area could have the carbon to produce heartwood that is more resistant to decay than trees with lower leaf area/sapwood area. However, we found no relationship between leaf area above node 20, sapwood area there, or their ratio, and the decay resistance of outer heartwood at that node. These results suggest that, for young Douglas-fir trees, heartwood durability does not vary with position in the bole or with environments that alter the tree's balance of sapwood and leaf area. We suggest that young stands may thus be robust with respect to the effect of silvicultural regimes on heartwood durability.