Regeneration Dynamics Following the Formation of Understory Gaps in a Slovakian Beech Virgin Forest

The frequency and size of canopy gaps largely determine light transmission to lower canopy strata, controlling structuring processes in the understory. However, quantitative data from temperate virgin forests on the structure of regeneration in gaps and its dynamics over time are scarce. We studied the structure and height growth of tree regeneration by means of sapling density, shoot length growth and cumulative biomass in 17 understory gaps (29 to 931 m2 in size) in a Slovakian beech (Fagus sylvatica L.) virgin forest, and compared the gaps with the regeneration under closed-canopy conditions. Spatial differences in regeneration structure and growth rate within a gap and in the gap periphery were analyzed for their dependence on the relative intensities of direct and diffuse radiation (high vs. low). We tested the hypotheses that (i) the density and cumulative biomass of saplings are higher in gaps than in closed-canopy patches, (ii) the position in a gap influences the density and height growth of saplings, and (iii) height growth of saplings increases with gap size. Sapling density and biomass were significantly higher in understory gaps than under closed canopy. Density of saplings was positively affected by comparatively high direct, but low diffuse radiation, resulting in pronounced spatial differences. In contrast, sapling shoot length growth was positively affected by higher levels of diffuse radiation and also depended on sapling size, while direct radiation intensity was not influential. Conclusively, in this forest, regeneration likely becomes suppressed after a short period by lateral canopy expansion in small gaps (<100 m2), resulting in a heterogeneous understory structure. In larger gaps (≥100 m2) saplings may be capable even at low plant densities to fill the gap, often forming a cohort-like regeneration layer. Thus, gaps of different sizes imprint on the resulting canopy structure in different ways, enhancing spatial heterogeneity

Aboveground biomass stocks and net primary production of three primeval European beech forests in eastern Slovakia

The study took place in three primeval European beech forest reserves in eastern Slovakia and in three close by production forests with similar site conditions. Three compartments of aboveground biomass stocks (live woody tree biomass, litter biomass, regeneration biomass, coarse and fine woody debris) and two compartments of aboveground net primary production (anual woody biomass increment and litter production) were inventoried. Stand structural data (tree diameter, coordinates, height and more) was inventoried on 40 500 m^2 plots per primeval forest and on 10 plots of the same size per production forest (low intensity plots - 150 LIPs in total). This data was used to estimate live woody biomass on basis of allometric equations. The structural data of the plots were used to classify the primeval forest plots into three stages of the natural development cycle (growth, optimal, terminal). The classification was used as a basis to select four plots per development stage and four plots per production forest for the recording of the remaining biomass and productivity compartments (high intensity plots - 48 HIPs in total). Litter biomass and production was estimated using litter traps. Regeneration biomass was recorded by counting regeneration trees on sub-plots of the 48 HIPs. Coarse woody debris was estimated by measuring dimensions of all downed logs with base diameters >= 20 cm. Fine woody debris was estimated with line intersect sampling on 4 6.5 m long transects per plot. Annual woody biomass was estimated by taking repeated readings of permanent increment tapes. Upscaling to tree level was done with allometric equations

Reduction in rat phosphatidylethanolamine binding protein-1 (PEBP1) after chronic corticosterone treatment may be paralleled by cognitive impairment: a first study

Chronic stress is associated with hippocampal atrophy and cognitive dysfunction. This study investigates how long-lasting administration of corticosterone as a mimic of experimentally induced stress affects psychometric performance and the expression of the phosphatidylethanolamine binding protein (PEBP1) in the adult hippocampus of one-year-old male rats. Psychometric investigations were conducted in rats before and after corticosterone treatment using a holeboard test system. Rats were randomly attributed to 2 groups (n = 7) for daily subcutaneous injection of either 26.8 mg/kg body weight corticosterone or sesame oil (vehicle control). Treatment was continued for 60 days, followed by cognitive retesting in the holeboard system. For protein analysis, the hippocampal proteome was separated by 2D electrophoresis (2DE) followed by image processing, statistical analysis, protein identification via peptide mass fingerprinting and gel matching and subsequent functional network mapping and molecular pathway analysis. Differential expression of PEBP1 was additionally quantified by Western blot analysis. Results show that chronic corticosterone significantly decreased rat hippocampal PEBP1 expression and induced a working and reference memory dysfunction. From this, we derive the preliminary hypothesis that PEBP1 may be a novel molecular mediator influencing cognitive integrity during chronic corticosterone exposure in rat hippocampus