Long-Term Growth of Crop Trees after Release in Northern Hardwoods

Abstract

Diameter growth of crop trees of paper birch, sugar maple, yellow birch, white ash, beech, and red maple was remeasured for 31 yr following a heavy release, light release, species removal, and control applied to an evenaged 25 yr old northern hardwood stand in New Hampshire. Under all regimes, final dbh of sampled crop trees was positively related to initial dbh. Wliite ash showed no significant or consistent increase in final dbh in response to treatment, expressed in terms of residual basal area per acre. Paper birch, beech, and red maple had final average diameters up to about 2 in. larger due to heavy release as compared with the control. Sugar maple showed a gain of up to I in. in final dbh over the 31 yr period, while yellow birch showed a similar, though nonsignificant, gain. The study shows the long-term effects of release treatments, and the importance of releasing larger trees and responsive species.