Suppression and Release During Canopy Recruitment in Fagus grandifolia

Abstract

Stem radial growth patterns were used to reconstruct the history of suppression and release during canopy recruitment of Fagus grandifolia Ehrh. (beech) in three old-growth northern hardwood forests. Overall, eighty percent of the cores showed periods of suppression prior to recruitment. The average number of periods of suppression in the 3 stands ranged from 1.9-2.4, and the average total length of suppression ranged from 45-52 years. At recruitment, trees averaged 66-80 years old with diameters of 5.1-7.4 cm at 1 m height. In comparison with Acer saccharum Marsh. (sugar maple) in the same stands, beech trees reached final release after fewer and shorter total length of suppression, and at much smaller sizes. Calculations using average height growth rates for suppressed and released saplings of both species suggest that beech saplings achieve half of their height at final release while suppressed, while growth of sugar maple saplings during suppression accounts for only 15% of their height at final release. The frequency and duration of periods of release in beech indicate that canopy gaps were short-lived relative to the time required for canopy recruitment in this shade-tolerant species, and that saplings responded to gaps created by the deaths of nearby canopy trees before replacing the canopy tree directly overhead.