Overstory Density Affects Field Performance of Underplanted Red Oak (Quercus rubra L.) in Ontario

Abstract

Red oak seedlings were iinderplanted in a closed-canopy mature northern hardwood stand and an adjacent sheltenvood in central Ontario. Overstory density effects on seedling survival and growth were assessed 2 yr after planting. After 2 yr, seedling survival was 90% in the uncut stand and over 99% in the sheltenvood. Seedlings in the uncut stand experienced negligible or negative annual increments in stem diameter and height. Seedlings in the sheltenvood were about 2 mm larger in diameter and nearly twice as tall as those in the uncut stand after 2 yr. Second-year stem diameter and height distributions of planted oak were significantly different in the sheltenvood and the uncut stand. Root volume, area, and dry mass were substantially larger for seedlings grown in the sheltenvood than those in the uncut stand. Loss of vigor, growth declines, and increased mortality of planted oak were largely a result of extremely low undcrstory light levels in the uncut stand. Results of this study suggest that red oak iindcrplanted in an uncut stand 2 or more years before a sheltenvood harvest will be at a competitive disadvantage once they are released. Establishment and performance of iinderplanted red oak is promoted by sheltenvoods that provide adequate light at the forest floor and should exhibit a strong positive growth response following final ovcrstory removal.