PARENT SESSION
Poster Session #14: Plant Competition.
Tuesday, August 7, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Do forest canopy gaps enhance the stem diameter growth of adjacent overstory trees?

PEDERSEN, BRIAN¹, HOWARD, JESSICA¹, ¹

ABSTRACT- An understanding of the cycles of tree recruitment, growth, and death is essential for understanding forest responses to stresses and disturbances. Numerous studies have examined how understory trees respond to the death of nearby overstory trees, deaths that form gaps in a forest canopy. But less attention has been devoted to how overstory trees respond to the death of adjacent overstory trees. For example, strong growth responses by overstory trees surrounding a canopy gap may limit the recruitment and growth of understory trees within the gap. Our study site is a red oak - mixed hardwood forest stand in south-central Pennsylvania. We identified 14 canopy gaps intersecting 870 m of line transects. Cores were taken from all 160 overstory trees neighboring these gaps (5-33 trees/gap) and from 186 trees representative of the entire stand (null gap trees). Annual stem diameter growth rates are being determined from tree ring width measurements. Stand basal area is 17.6 m²/ha (≥5 cm diameter at breast height [dbh]) and the gap fraction is 16%. For the gap neighbors, the median and maximum tree dbh's are 37.0 cm and 93.7 cm, respectively. Hierarchical regression analysis is being applied to compare the recent stem diameter growth rates of the gap neighbors to the null gap trees after accounting for growth rate differences due to species, dbh, and crown class.

KEY WORDS: forest stand dynamics, Pennsylvania, red oak - mixed hardwood forest, tree ring width