Long-termoak seedling dynamics and regeneration ability in a deciduous forest in Hungary

Long-term structural dynamics and regeneration ability of oak seedlings were not extensively reported in published studies in Central Europe. At the LTER study area 63.0% of adult oak died from 1979-80 in a mixed oak forest, an area covered by a sessile oak–Turkey oak forest (Quercetum petraeae-cerris). The research site of the nature reserve is located in the Bükk Mountains of northeastern Hungary. The goals of this study were to determine the conditions of oak seedlings and saplings and the survival of low oaks in studied plots over a 40-year period after the serious oak decline. The oak specimens of the vegetation lower than 1.0 m in height were categorized as low oaks. Over the 40 years of observation, three oak species were continuously observed in the understory, sessile oak (Quercus petraea Matt. L.), Turkey oak (Quercus cerris L.) and downy oak (Quercus pubescens Willd.). The most abundant oak species was sessile oak. Total seedlings and saplings density averaged 12.031 ha-1; sapling numbers for all oaks were low (averaged 336 ha-1). From 1993 to the last measurement there was a poor regeneration rate with only 14 ha-1 oak specimens taller than 0.5 m. The mean height and diameter distribution of low oaks varied between 7.9-25.2 cm and between 1.4-3.7 mm. The tendency of mean size condition saw a clear-cut decrease from 1972 to 2012. Our results suggest that the seedling regeneration ability is a limited and the oak seedlings’ structural condition did not affect by oak decline