Effect of midstory removal on understory light availability and the 2-year response of underplanted cherrybark oak seedlings

This study evaluates the effects of four midstory removal intensities on residual stand structure, understory light availability, and the 2-year growth and survival of underplanted cherrybark oak (Quercus pagoda Raf.) seedlings. It also examines whether survival and growth were affected by the removal of competing understory vegetation <1.4 m tall. The study was conducted in western Georgia, in a mature riparian hardwood forest possessing a dense midstory canopy and an understory dominated by highly competitive nonnative and native species. The removal of all midstory trees increased survival and height and basal diameter growth of cherrybark oak after two growing seasons. Understory light availability increased only when at least half of all midstory trees were removed. Although understory vegetation removal increased 2-year height growth of cherrybark oak, the actual growth difference between treatments was only 5 cm. The removal of understory vegetation had no effect on basal diameter growth or survival. Results suggests that a combination of underplanting and complete midstory removal may be a useful treatment for enhancing advance oak reproduction in riparian hardwood stands. This treatment combination may have utility as the initial step in a shelterwood system when advance reproduction is insufficient.