The Occurrence of Non-Ring Producing Branches in Abies lasiocarpa
Trees - Structure and Function
Lack of annual growth ring production at the base of branches in the lower portion of the crown is a commonly observed phenomenon. In this study, branches with missing rings were found on 47 of 49 Abies lasiocarpa trees sampled. The number of missing rings on the lowest live branch in the crown averaged 12, and ranged as high as 28. The lower one-third of the live crown tended to consist of branches without rings; these branches contained an average of 30% of the total crown leaf area. The ratio of foliage weight to total branch weight, in combination with position of the branch in the canopy, was an effective discriminator of non-ring producing branches. This suggests that both structural and environmental factors influence the cessation of ring production. The potential ecological implications of branches that fail to produce rings are discussed.
Roberts, S.D. (1994). The occurrence of non-ring producing branches in Abies lasiocarpa. Trees, 8:263-267.