The study analysed changes in environmental conditions and the response of forest vegetation to different management intensities in Dinaric fir-beech forests in Slovenia. The experimental design consisted of three study sites (Trnovski gozd, Snežnik, Kočevski Rog) in which tree cutting of different intensities was performed in 2012 on a circular area of 0.4 ha: control (closed stands without cutting), 50% cutting of stand growing stock (thinned stands) and 100% cutting (canopy gaps). Nine karst sinkholes were selected at each site, and each cutting intensity was implemented in one third of the plots. Vegetation surveys on larger sampling plots were conducted before cutting (2012), two years (2014) and six years (2018) after cutting. On smaller sampling plots located in different within-sinkhole positions, we measured air temperature, relative humidity and soil parameters. We found that the degree of change in ecological factors and vegetation was proportional to the intensity of cutting. Microclimatic conditions were significantly influenced by the interaction between cutting intensity and local topography associated with rugged karst terrain. Composition of plant functional traits differed significantly between control stands and canopy gaps. The proportion of annuals/biennials, grasses and sedges, tall-statured herbaceous plants, species with lighter seeds, greater dispersal ability and longer flowering duration increased after cutting. Canopy gaps and thinned stands were mainly colonized by ruderal, disturbance-adapted pioneer species. We also observed that majority of typical forest plant species were able to survive after cutting. The coexistence of typical forest species, regeneration layer of tree species and new colonists with different functional properties was manifested in the increased species/functional diversity of plant communities, which may contribute to a favourable conservation status of the forest habitat type (Natura 2000). We additionally examined the effects of natural and anthropogenic disturbances on the understory vegetation in different forest ecosystems across Slovenia and thus also analysed the relative importance of abiotic and biotic mechanisms during the process of vegetation community assembly.
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