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Povzetek: Forest ground vegetation may serve as an early warning system for monitoring anthropogenic global-change impacts on temperate forests. Climate warming may induce a decline of cool-adapted species to the benefit of more thermophilous plants. Nitrogen deposition has been documented to potentially result in soil eutrophication or acidification, which can increase the proportion of species with higher nutrient requirements and species impoverishment caused by competitive exclusion. Abiotic forest disturbances are changing the light conditions in the forest understorey environment. In this resurvey study, we tested the magnitude and direction of change in alpha (species richness) and beta (within-site dissimilarity) diversity and composition of forest ground vegetation in forests of different types in Slovenia over fifteen years. Using plant-derived characteristics (Ellenberg-type indicator values) and by testing a priori predictions concerning expected effects of environmental drivers, we show that the magnitude and direction of forest ground vegetation diversity and floristic changes varies greatly between forest sites. Divergent responses at different sites resulted in low net change of alpha and beta diversity and a weak overall environmental signal. The largest decrease in species number was observed in lowland oak-hornbeam forests, which were also among the sites with the greatest compositional shifts. Changes in beta diversity did not show any consistent trend, and anticipated floristic convergence was not confirmed when all sites were considered. Thermophilization was mainly detected in montane beech sites and alpine spruce forests whereas eutrophication signal was most significant on nutrient-poor sites. Vegetation responses were strongly dependent on initial site conditions. Shrinkage of ecological gradients (process of ecological homogenization) suggests that sites positioned at the ends of the gradients are losing their original ecological character and are becoming more similar to mid-gradient sites that generally exhibit smaller changes. Our results point to the importance of local stand dynamics and overstorey disturbances in explaining the temporal trends in forest ground vegetation. Ground vegetation in Slovenian forests is changing in directions also dictated by multiple regional and global change drivers.
Ključne besede: vegetation resurvey, thermophilization, eutrophication, forest disturbances, alpha and beta diversity, initial site conditions, ICP-Forests network
Objavljeno v DiRROS: 09.04.2024; Ogledov: 71; Prenosov: 28
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Povzetek: Bryophytes respond to a variety of environmental factors, including tree species composition and geological conditions, which are influenced by both natural and anthropogenic factors. Bryophytes growing on a variety of substrates were identified in ICP Forests monitoring plots in a wide range of close-to-nature managed forests, from lowland to high mountain areas in Slovenia. Based on data on tree layer composition (broadleaves vs. conifers) and on bedrock and soil type (calcareous vs. siliceous bedrock), all study plots were classified into five groups representing forest types. Different ordination analyses and statistical tests were used to represent differences between forest types in bryophyte composition, richness and functional traits. Almost 200 bryophyte species were identified in managed forests, with the most common being Hypnum cupressiforme, Brachytheciastrum velutinum and Polytrichum formosum. Bryophyte species composition varied considerably along the tree species composition and edaphic gradients represented by the selected forest types. Bryophyte species richness was significantly higher on calcareous bedrock than on siliceous bedrock. The higher occurrence of rocks on the ground surface may significantly increase the availability of various microhabitats for bryophytes. Bedrock had a significant influence on the functional diversity and composition of bryophytes, while tree species composition had less influence. Bedrock and tree species composition are important drivers of bryophyte species composition and diversity at taxonomic and functional trait levels. The high diversity of bryophyte species in Slovenian forests can also be attributed to close-to-nature and sustainable forest management practices that preserve favourable microclimatic conditions in forest stands and maintain diverse substrates.
Ključne besede: mosses, species richness, functional diversity, site conditions, overstory, sustainable managed forests, European temperate zone
Objavljeno v DiRROS: 05.04.2023; Ogledov: 475; Prenosov: 155
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Povzetek: In the period 1970-2000, 152 fenced-in areas were built in the Kočevje Forest Management Region with an aim to protect tree seedlings and saplings from ungulatesć activity and to monitor the influence of roe and red deer on natural regeneration. The average surface area of fenced areas is 0.71 ha. Using the pair comparison technique (fenced vs. unfenced areas), the structureand the composition of the natural regeneration of tree species as well as complete shrub and herb vegetation were analysed in the research site Trnovec. Furthermore, the vegetation was investigated using the Braun-Blanquetmethod. The research results show significant differences between fenced and unfenced areas, both in tree species composition and in theheight structure of the sapling community. In fenced areas the total numberof saplings taller than 50 cm is higher and an increase is also evident in the number of saplings of silver fir Abies alba, sycamore Acer pseudoplatanus, elm Ulmus glabra and other minor tree species. There are also significant differences in species composition and in the abundance of plant species in the herb layer. The results show that natural regeneration of Dinaric fir-beech forests is successful, provided the influence of ungulates is excluded.
Ključne besede: natural forest regeneration, Fagus sylvatica, roe deer, fir-beech forest, Abies alba, fenced area, seedling browsing, Kočevje forest region, research site Trnovec
Objavljeno v DiRROS: 12.07.2017; Ogledov: 4493; Prenosov: 2015
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