Evaluating initial responses of natural and underplanted oak reproduction and a shade-tolerant competitor to midstory removal

This study evaluated the effect of midstory removal on the survival, growth, and competitiveness of natural advance reproduction and underplanted white oak (Quercus alba L.), northern red oak (Quercus rubra L.), and black oak (Quercus velutina Lam.). The response of the predominant shade-tolerant competitor, red maple (Acer rubrum L.), was also evaluated. After six growing seasons, relative height and groundline diameter (GLD) growth of all oak species were significantly greater in the midstory removal treatment than in the control but did not differ between reproduction types. Survival of oak advance reproduction was high (> 96%) and was not affected by midstory removal. However, underplanted oaks had significantly lower survival than the oak advance reproduction. Competitiveness (i.e., percent of seedlings with heights ≥ 80% of understory competitors) was not affected by midstory removal, but underplanted white oak had a greater percentage of competitive seedlings than white oak advance reproduction. For red maple, midstory removal significantly increased 6-year relative height growth but not relative GLD growth, percent survival, or competitiveness. Six-year total height of red maple was similar to all but one of the oak reproduction types evaluated; only natural white oak reproduction was shorter than red maple in the midstory removal treatment. In addition to quantifying seedling responses, we found that the midstory removal treatment altered canopy structure by maintaining a greater height to the forest canopy and a lower canopy closure (60 and 90 degree photo angles) than the control 6 years after treatment.