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.

Ten-Year Responses of Underplanted Northern Red Oak to Silvicultural Treatments, Herbivore Exclusion, and Fertilization

Establishing adequate advanced oak reproduction prior to final overstory removal is crucial for regenerating oak forests in the eastern U.S. Many management approaches exist to this end, but benefits associated with any individual technique can depend on the suite of techniques employed and the geographic location. At four mixed-hardwood upland forest sites in central and southern Indiana, we tested factorial combinations of deer fencing, controlled-release fertilization, and various silvicultural techniques (midstory removal, crown thinning, and a shelterwood establishment cut) for promoting the growth and survival of underplanted red oak seedlings. Crown thinning resulted in slow growth and low survival. Midstory removal and the shelterwood establishment cut were nearly equally effective for promoting seedling growth. Seedling survival was strongly influenced by fencing, and differences in survival between silvicultural treatments were minimal when fencing was employed. Fertilization had minimal effects overall, only increasing the probability that unfenced seedlings were in competitive positions relative to surrounding vegetation. We suggest that underplanting oak seedlings can augment natural reproduction, but the practice should be accompanied by a combination of midstory removal and fencing, at a minimum, for adequate growth and survival.

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.

Response of Advance Cherrybark Oak Reproduction to Midstory Removal and Shoot Clipping

Midstory competition control and shoot clipping have been proposed to increase the vigor and height of advance bottomland oak reproduction. Results from a study in east-central Mississippi showed that advance cherrybark oak (Quercus pagoda Raf.) released from midstory competition had greater survival than nonreleased seedlings, 64% and 48%, respectively, 9 yr after treatment. Released seedlings were also 2.5-3.4 ft taller than nonreleased seedlings depending on site. However, this significant growth response was not observed until 3 to 5 yr after release. Clipping oak seedlings at the time of release did not result in greater seedling heights after 9 yr, but subsequent sprouts were similar in height to unclipped seedlings. Midstory competition control is recommended to increase the vigor and height of advance bottomland oak reproduction. This practice may need to be conducted 5 to 10 yr prior to final overstory removal to maximize height growth of advance reproduction. South J. Appl. For. 24(1):45-50.