Midstory removal facilitates growth but reduces competitiveness of oak reproduction prior to and after shelterwood establishment cutting

This study examined the influence of midstory removal applied 9 years prior to a shelterwood establishment cut on survival, growth, and competitive status of black oak (Quercus velutina Lam.), white oak (Quercus alba L.), and an oak competitor, red maple (Acer rubrum L.), immediately before and at 6 years following shelterwood cutting on intermediate productivity sites in the Central Hardwood Forest Region. We also examined height and density distributions of the regenerating cohort to quantify seedling establishment and to elucidate relative oak competitiveness at each time period. Although oak seedlings were taller 9 years after midstory removal than in undisturbed controls, the midstory removal treatment reduced the frequency of free-to-grow oaks (relative to understory competitors) and increased the size of red maple and relative density of large competitors. Height growth of all three species following establishment cutting was increased by prior midstory removal and dependent on seedling competitive position immediately before shelterwood establishment. Additionally, we observed increased seedling densities 6 years following shelterwood establishment cutting and greater white oak seedling establishment when midstory removal preceded the shelterwood treatment. Study Implications: The shelterwood system is commonly prescribed for oak regeneration on intermediate- and high-quality sites in the eastern United States. Our research indicates that midstory removal as an initial practice associated with the shelterwood system produces larger, more abundant oak reproduction, particularly white oak. However, the treatment also resulted in taller competitors (e.g., red maple and yellow poplar) that frequently overtopped oaks. Thus, whereas midstory removal distinctly improves the pool of advance oak reproduction within a shelterwood system, the treatment's effect on oak's primary competitors suggests its necessity should be evaluated in the context of size and density distributions of oak and competitor species, and the treatment intensity required to increase oak growth while inhibiting regeneration of competitors. Additionally, lower levels of local understory competition resulted in taller oak reproduction after establishment cutting, which may suggest the utility of competition control treatments prior to or following establishment cutting to improve growth and competitiveness of oak. Although oak faces a challenging competitive environment on the sites studied, the combination of midstory removal and subsequent shelterwood establishment cutting yielded a notable density of large reproduction that could be cultured through subsequent silvicultural practices targeting oak recruitment.