The effects of mechanical damage on residual coastal Douglas-fir (Pseudotsuga menziesii [Mirbel] Franco following commercial thinning.

摘要

Commercial thinning operations can result in damage to residual stems. A literature review revealed that little was known about the effects of residual logging wounds with regard to rotation-age commercial conifers, particularly Douglas-fir. An experiment to examine fungal colonization of Douglas-fir following logging damage showed that while damage was significant in total numbers of fungi, there were no significant differences in the numbers of total fungal taxa, known decay taxa, or frequency of fungi related to radial distance inward. The study fails to support existing models of active tree response to invasion and instead corroborates the model of passive response to fungal invasion following damage to wood tissue. An examination of wood tissue following wounding supports the compartmentalization of damaged wood tissue as described by the CODIT model. However the lack of evidence of compartmentalized tissue in the presence of fungi in undamaged trees supports the idea of passive response mechanisms rather than an active defense response. Reductions in wood quality volume were quantified for damaged trees. Consideration of a selective milling option is shown to increase value in the lower log by as much as 8 .5 percent. Results also show significant increases in sapwood distance along the undamaged side of the bole. However, there were no significant differences in radial increment or in sapwood area before or after damage suggesting that damaged trees may delay conversion of sapwood to heartwood to maintain necessary sapwood area for crown requirements. An experiment was conducted to determine if tree and stand-level differences in growth and yield could be detected between damaged and undamaged trees following damage. No significant differences were found for total height or DBH to total height curves. Examination of basal area increment before and after thinning showed no significant differences. No significant difference was found for live crown length except between the damaged and adjacent undamaged trees; however, this may be explained by differences in diameter between the two groups. No significant differences were found for height to crown base or the height to crown base/tree diameter relationship.