A Comparison of the Survival and Development of the Seedlings of Four Upland Oak Species Grown in Four Different Understory Light Environments

Abstract

Oak (Quercus spp.) research and management often focus on northern red oak (Quercus rubra) and assume that associated upland oaks have similar growth patterns. To test this premise, we measured the survival and development of four species of acorn-origin oak seedlings growing in four different levels of understory sunlight for 8 years. Northern red oak had better survival than black (Quercus velutina), chestnut (Quercus montana), and white oak (Quercus alba) in 5% sunlight, but none of the species exhibited much growth. In 15 and 40% sunlight, survival was equal among species, but for growth the seedlings formed two groups with chestnut/northern red oak growing more than black/white oak. In 75% sunlight, survival was equal among species, but northern red oak grew faster than the other three species. Assuming that other oaks have growth habits similar to those of northern red oak could lead to a reduction in or the inadvertent loss of an oak species. Management and Policy Implications This study points out key differences in the survival and growth of black, chestnut, northern red, and white oak seedlings at the light levels created by a three-cut shelterwood sequence. Important management recommendations based on those differences include the following: In advance of an acorn crop, decrease dense shade to diffuse or partial shade (15–40% sunlight) by removing the midstory and understory canopies. If premasting shade control is not possible, begin regeneration treatments no later than 1–2 years after black, chestnut, and white oaks mast or no later than 3–5 years after northern red oak produces acorns. Conduct species-specific inventories for oak seedlings rather than grouping them together as oak reproduction. To emphasize chestnut or northern red oak, use the two-cut or three-cut shelterwood sequence because seedlings of these two oak species can grow reasonably well in 15–40% sunlight. To emphasize black or white oak, use a two-cut shelterwood because seedlings of these species need approximately 40% sunlight or more to initiate and sustain vigorous height growth.