Understory Condition in an Oak Forest After 4 Decades for Oak Decline in Hungary

At the study area serious oak decline was detected from 1979-80 in a mixed oak forest, an area covered by a sessile oak–Turkey oak forest (Quercetum petraeae-cerridis). The shrub community was divided into low (lower than 1.0 m in height) and high shrub layer (≥ 1.0 m). The goals of this study were to determine the conditions of shrub layer and analyse the possible changes in the shrub layer after 4 decades of the serious oak decline. In 2017, 17 shrub species were continuously observed in the understory. The density of shrub layer was 25,103 specimens ha-1. The significant part of shrubs lived (91.6%) in the low shrub layer, with only a small part of them (8.4%) forming the high shrub layer. The most common species of the shrub community was Euonymus verrucosus with 1989 shoots in the monitoring plot. The mean height and mean diameter of the high shrub species changed between 1.29-8.74 m and between 0.81-9.61 cm. The mean cover of the high shrub species changed between 0.56 m2 and 12.67 m2. Our results suggest that three woody species, Acer campestre, Acer tataricum and Cornus mas responded successfully to the oak decline.