Radial Growth Responses of Three Co-Occurring Species to Small Canopy Disturbances in a Secondary Hardwood Forest on the Cumberland Plateau, Tennessee

Abstract

We analyzed the radial growth patterns of Liriodendron tulipifera, Acer rubrum, and Acer saccharum growing in 39 canopy gaps in a mature secondary hardwood forest on the Cumberland Plateau in Tennessee to compare species-specific growth responses to small canopy disturbances. We tested for differences between mean radial growth increases during the year of release initiation (i.e., first year of discernible growth increase) over the year prior, mean percent growth increases during the year of release initiation over the year prior, mean release durations, and mean lag times between canopy gap formation and radial growth response. At each level of analysis (i.e., by species, canopy position, and gap position) only the radial growth increase during the year of release initiation over the year prior revealed significant differences. In each case where a systematic difference was noted, the growth increase of L. tulipifera was greater than one or both of the Acer species. However, field observation indicated accelerated growth of L. tulipifera was largely negated in the relatively small and short-lived gaps. Our findings provide information on the successional pathway of the forest, the physiological responses of these species to small canopy openings, and the applicability of these species to reconstruct canopy gap formation in secondary stands from tree-ring records.