Changes in Forest Structure Associated with Oak Decline in Severely Impacted Areas of Northern Arkansas

Four mature northern red oak (Quercus rubra L.)-white oak (Quercus alba L.) stands in the Boston Mountains of northern Arkansas were studied to describe the vegetation dynamics of forests heavily impacted by oak decline. Northern red oak was the species most susceptible to decline. Across the four stands, 51-75% of red oak density (trees/ha) was dead or dying, as was 40-70% of the red oak basal area. Red oak damage occurred across a range of tree sizes. Healthy red oak had low populations of red oak borer (Enaphalodes rufulus Haldeman), and dead/dying red oak supported large numbers of borers. Impacts on white oak were less severe and generally limited to smaller trees. Decline had changed what once were red oak-dominated stands to more mixed forests of white oak, hickory (Carya spp.), red oak, blackgum (Nyssa sylvatica Marsh.), and red maple (Acer rubrum L.). Understory trees and seedlings were predominantly blackgum, red maple, hickory, black cherry (Prunus serotina Ehrh), flowering dogwood (Cornus florida L.), and sassafras (Sassafras albidum [Nutt.] Nees). However, well-developed red and white oak advance regeneration was present in all stands. It is unclear if the death of overstory trees will favor the regeneration of nonoaks, or whether oak regeneration will successfully recruit within canopy gaps created by this disturbance.