Reply - Effects of adventitious roots on age determination in balsam fir regeneration

In many Canadian boreal forests, balsam fir (Abies balsamea (L.) Mill.) seedlings established under closed canopy generally develop adventitious roots. Adventitious roots induce the formation of a reverse taper, i.e., a reduction of the diameter and of the number of growth rings towards the true collar (hypocotyl region). Consequently, ring count at any level of the trunk underestimates the true age of firs, and we recommend a reassessment of balsam fir dynamics inferred from studies based on ages estimated by ring count. Recently, Kneeshaw and Claveau (D.D. Kneeshaw and Y. Claveau. 2001. Can. J. For. Res. 31: 1292-1295) presented data from a subsample of fir seedlings to demonstrate that ring count is an accurate aging technique for most fir regeneration. A careful examination of the methodology, data, and samples presented suggests that true collars were not precisely located. we also present data collected on seedlings sampled in the same study area as Kneeshaw and Claveau. Most of the seedlings (57 of 60 seedlings, <50 cm in height) had adventitious roots, and ring count was not an appropriate aging method. According to our study, Kneeshaw and Claveau either did not locate the true collar or presented atypical balsam fir seedlings.