Canopy gaps and tree regeneration patterns in multi-species unmanaged natural forest Sitno (preliminary results)

The study of canopy gaps structure and tree regeneration patterns was conducted in mixed old-growth forest Sitno. We asked the following questions: What is the spatial scale of disturbance events? How does gap size affect the density of tree seedlings and saplings? Are there any differences in species composition of seedlings and saplings between the closed canopy and expanded gap? The research was conducted on a 2.5-ha (250 × 100 m) research plot. In total, 25 canopy openings were recorded. Canopy gaps and expanded gaps covered 22.8 % and 59.5 % of the research area. The most frequent were canopy gaps with the size up to 300 m2(64 %). Regarding the number of gapmakers, we recorded a quite large variability with the highest frequency of the gaps with 1 and 4 gapmakers. Regeneration structure (density and frequency) was sampled in 3.14 m2circular plot (n = 216) established on the grid intersections (10 × 10 m). A total of 8 tree species were identified in natural regeneration. The difference between overall density of natural regeneration under closed canopy and in expanded gaps was observed. The density of all tree species seedlings (except ofCarpinus betulus) was higher under closed canopy than in expanded gaps. The most frequent were seedlings ofAcer pseudoplatanusandAcer platanoideswhich occurred on 80 % and 73 % of the plots under closed canopy, and 75 % and 68 % of the plots in expanded gaps. Seedlings ofQuercus petraeawere not recorded. Density of saplings was higher in expanded gaps than under canopy (except of saplings ofAcer platanoidesandTilia cordata). The density of saplings ofAcer pseudoplatanusandAcer platanoidesincreased with increasing size of expanded gap, whileFraxinus excelsiorsaplings density decreased. There was no significant relationship between density of other species seedlings and saplings and expanded gap size.