THE OCCURRENCE OF NON-RING PRODUCING BRANCHES IN ABIES-LASIOCARPA

Lack of annual growth ring production at the base of branches in the l ower portion of the crown is a commonly observed phenomenon. In this s tudy, branches with missing rings were found on 47 of 49 Abies lasioca rpa trees sampled. The number of missing rings on the lowest live bran ch in the crown averaged 12, and ranged as high as 28. The lower one-t hird of the live crown tended to consist of branches without rings; th ese branches contained an average of 30% of the total crown leaf area. The ratio of foliage weight to total branch weight, in combination wi th position of the branch in the canopy, was an effective discriminato r of non-ring producing branches. This suggests that both structural a nd environmental factors influence the cessation of ring production. T he potential ecological implications of branches that fail to produce rings are discussed.