Invasive Species Compendium

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Abstract

Directionality of compression wood in balsam fir wave forest trees.

Abstract

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 (Abies balsamea) in NW Newfoundland. Ninety discs were sampled from the balsam fir wave forest, representing an immature, a mature and a decadent stand in the forest. 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 strong prevailing southwesterly winds are mainly responsible for compression wood formation.