Directionality of compression wood in balsam fir wave forest trees

• Published in: Canadian Journal of Forest Research
• Main Author: Robertson, Alexander
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1990
• Subjects: Ecology; Forestry; Global and Planetary Change; Newfoundland
• Online Access: http://dx.doi.org/10.1139/x90-152; http://www.nrcresearchpress.com/doi/pdf/10.1139/x90-152

Wind is often cited as one of the main causes of compression wood formation. While many papers have alluded to direction of compression wood, this paper provides a detailed circular statistical analysis of the angular distribution of compression-wood zones in balsam fir trees. Discs were sampled from trees in a balsam fir (Abiesbalsamea (L.) Mill.) wave forest in northwestern Newfoundland, from sapling to mature stages. The directionality, with respect to compass bearing, of compression-wood zones in basal discs was found to be initially randomly distributed around the pith, becoming unidirectional towards the northeast at about 10 mm from the pith. Random circular distribution of compression-wood zones mostly within 10 mm of the pith is interpreted as resulting from a combination of environmental perturbations, such as glaze and rain loading, and asymmetric crown growth due to competition. Because of the very high density of immature stands, wind turbulence is not expected to be a major factor stimulating compression wood in saplings. The role of snow loading, which causes bending of stems for long periods during the winter (dormant season), is uncertain. In older trees, i.e., beyond approximately 10 mm from the pith, compression wood gradually becomes directional towards the northeast, indicating that prevailing southwesterly winds are mainly responsible for compression-wood formation.