In the year 2000 we set out to document the relationship between respiration and cambial activity in a Gymnosperm, balsam fir (Abies balsamea), a ring-porous Angiosperm, white ash (Fraxinus americana) and and a diffuse-porous Angiosperm red maple (Acer rubrum). To this end two sets of neighbouring trees were selected for each species. One set was fitted with respiration chambers and respiration was measured three times per week throughout the experiment from March through July. The other set had wood samples extracted at three times, 21 March, 4 May, and 6 June, for anatomical study. On the final sampling date, 21 July, samples were taken from stems beneath the centre of the respiration chambers for microscopic examination. We found that respiration did increase during cambial reactivation. This occurred first in balsam fir followed by ash, both species had new xylem and phloem in the May samples, and finally by red maple. In the maple there was evidence of new phloem production in the May sample, however, the increase in respiration and xylem cell production occurred starting after the June wood sample date. Thus, it appears that respiration rate is a good marker for xylem cell production. Moreover, rate of respiration at the peak of the growing season, on 21 July, was correlated to the number of tracheids or fibres produced by the cambium up to that point in the growing season, and this correlation is across the three species.

Key words: Abies balsamea, Acer rubrum, cambium, Fraxinus americana, respiration, xylem