The Effects of Stand Structure After Thinning on the Growth of an Allegheny Hardwood Stand

Abstract A 50-year-old Allegheny hardwood stand in which the crown canopy had stratified into distinct species groups was thinned to 60% relative density leaving dramatically different stand structures and species composition. Treatments included combined thinning, thin from middle, thin from above, thin from below, and unthinned control. Individual tree growth was stimulated most by thinnings that created openings in the main crown canopy and still retained adequate numbers of the larger stems of the faster growing species. Thinning from below, which removed primarily noncommerdal saplings and small poles of the shade-tolerant species, did not affect diameter growth of the larger stems. Total stand growth in basal area and volume was dramatically reduced by thinning from above, which removed nearly all of the larger stems and faster growing species. Treatments that reduced growing stock in the largest size classes, where most of the stand value is concentrated, had a detrimental effect on future timber values. Best individual tree growth, and best stand growth in basal area, cubic volume, board volume, and dollar value occurred in the combined thin treatment. Future yields after any thinning can be viewed as the net effect of reduction in the amount of growing-stock capital and increases in residual tree growth resulting from reduced competition. Recommendations for appropriate types of thinning and timing of the first thinning in stands such as this are provided. For. Sci. 37(4):1182-1200.