Structural changes in the shrub layer were analysed in a Hungarian oak forest after the oak decline pandemics. This paper focuses on the following questions: (1) which of the woody species tolerated better the forest conditions after oak decline? (2) What are the ecological factors that explain the successful response of woody species to changes in light and thermal conditions? In the monitoring plot, the structural condition of specimens only above 8.0 m was observed. After the appearance of oak decline some Acer campestre, Cornus mas and Acer tataricum specimens appeared that reached between 8.0-13.0 m in height. Significant differences were revealed between top canopy density and foliage cover of the subcanopy and between top canopy density and mean cover of field maple. The findings of the study indicate that the forest responded to oak decline with significant structural rearrangement in the shrub layer and that three woody species compensated for the remarkable foliage loss in the top canopy. These species formed a second crown layer directly below the canopy formed by oaks.
Soil enzyme activities are “sensors” of soil organic matter (SOM) decomposition since they integrate information about microbial status and physico-chemical condition of soils. We measured dehydrogenase enzyme activity in a deciduous temperate oak forest in Hungary under litter manipulation treatments. The Síkfőkút Detritus Input and Removal Treatments (DIRT) Project includes treatments with doubling of leaf litter and woody debris inputs as well as removal of leaf litter and trenching to prevent root inputs. We hypothesized that increased detrital inputs increase labile carbon substrates to soils and would increase enzyme activities particularly that of dehydrogenase, which has been used as an indicator of soil microbial activity. We also hypothesized that enzyme activities would decrease with detritus removal plots and decrease labile carbon inputs to soil. After ten years of treatments, litter removal had a stronger effect on soil dehydrogenase activity than did litter additions. These results showed that in this forest ecosystem the changed litter production affected soil microbial activity: reduced litter production decreased the soil dehydrogenase activity; increased litter production had no significant effect on the enzyme activity.