Northern Red Oak, White Oak, and Black Walnut Diameter Growth for the First 3 Years after Thinning in a Mixed Planting

We established a study to investigate short-term morphological responses of northern red oak (Quercus rubra L.), white oak (Quercus alba L.), and black walnut (Juglans nigra L.) to a 43% basal area reduction in a mixed planting. Although the effect was not statistically confirmed, thinned northern red oak showed a 23% gain in relative diameter growth and a 25% gain in relative crown surface area expansion compared with nonthinned trees; white oak showed gains of 15 and 10%, respectively. Similar trends were found in percentage of basal area increase for northern red oak (45%) and white oak (37%). Black walnut did not appear to respond to thinning and may have been under less competition from first-tier neighbors than the oaks were. Both northern red oak and white oak were in intermediate and suppressed crown classes, whereas black walnut was in a codominant position. Trends from this study suggest that northern red oak and white oak may respond favorably to thinning when found in lower crown classes where the amount of competition from neighboring trees is high.