Effect of Crown Growing Space on the Development of Young Hardwood Crop Trees

Abstract Crown release of individual crop trees can be used to increase the growth and competitiveness of selected trees in young hardwood stands. Forest managers need information on the response of individual trees to such thinnings to prescribe stand treatments that meet specific management objectives. Codominant northern red oak (Quercus rubra L.), chestnut oak (Quercus prinus L.), black cherry (Prunus serotina Ehrh.), and yellow-poplar (Liriodendron tulipifera L.) crop trees in stands 12 to 16 yr old were given a crown-touching release by cutting all adjacent trees that touched the crown of a selected crop tree. A heavier thinning, which entailed cutting all competing trees whose crowns were within 5 ft of the crown of a selected crop tree, was also applied to black cherry and yellow-poplar crop trees on one study site. Stand and individual-tree response was monitored for control and treated plots for 10 yr. Both release treatments increased periodic stand basal area growth and had a negligible effect on the proportion of high-value species among overstory trees. Individual-tree development was affected by total growing space, defined as the initial area occupied by the crop-tree crown plus the area of free growing space resulting from release. As total growing space increased, there was a positive effect on dbh, crown ratio, and crown diameter growth, and a negative effect on clear stem development. Total height growth was reduced by heavy release but not by the more moderate crown-touching release. North. J. Appl. For. 17(1):25-35.