Long-Term Effects of Crop Tree Release on Growth and Quality in White-Oak (Quercus alba L.)-Dominated Stands

Abstract

Abstract Crop tree release (CTR) can be an effective intermediate silvicultural treatment for culturing high-value stems in mixed hardwood stands. The lengthy rotation of hardwoods requires long-term evaluations if silvicultural treatment effectiveness is to be fully evaluated. Our study provides a 35-year evaluation of individual-tree and stand response to CTR imposed in small sawtimber-sized white-oak (Quercus alba L.)-dominated stands. The focus on white oak is justified based on the significant biologic and economic values of the species, and this study furthers our ability to optimize use of CTR as management tool for sustaining our oak resources. The replicated experiment included three treatment levels: 20 crop trees ac−1, 34 crop trees ac−1, and a control. Using a repeated-measures framework, we analyzed (1) how CTR affects growth and stem quality of white oak crop trees and (2) stand-level effects of CTR on basal area, stocking, and ingrowth. CTR increased crop tree diameter growth and proportion of crop trees reaching their maximum potential grade. However, crop tree diameter growth and proportion achieving maximum potential grade did not differ between the 20 and 34 crop trees ac−1 treatments. Finally, CTR stimulated stand-wide growth without altering the patterns of ingrowth density or species distributions.