1. Mixed signals of environmental change and a trend towards ecological homogenization in ground vegetation across different forest typesJanez Kermavnar, Lado Kutnar, 2024, izvirni znanstveni članek 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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2. Congruence between vascular plants and bryophytes in response to ecological conditions in sustainably managed temperate forests (taxonomic- and trait-based levels)Lado Kutnar, Janez Kermavnar, Marko S. Sabovljević, 2023, izvirni znanstveni članek Povzetek: Vascular plant species (VP) and bryophytes (B) constitute a significant portion of forest biodiversity and respond to both management intensity and natural disturbances within forests. In this study, we investigated the cross-taxa congruence between understorey VP and B at both diversity and composition levels across a wide range of sustainably managed forests in Slovenia. The taxonomic and functional characteristics of the selected plant groups were studied, with a particular emphasis on ground-dwelling species. We employed a trait-based approach to examine the functional characteristics. On average, the species richness of B in sustainably managed temperate forests increased with the corresponding number of VP. Furthermore, a moderate positive correlation in species composition between the studied groups of ground-dwelling organisms was also observed. The ground-dwelling VP and B were congruent in terms of trait-based composition, which was influenced by soil reaction and nutrients and light availability, while trait-based diversity was only slightly similar in response to moisture. A negative correlation between the composition of stress-tolerant VP and B hemeroby was found, indicating forest environments with a low level of disturbance. This is likely due to the sustainable management of Slovenian forests, where climate change and natural disturbances have intensified in recent years. A cross-taxon comparison of the two groups at four different levels, namely taxonomic-based diversity and composition and trait-based diversity and composition, revealed varying degrees of congruence. It is therefore important to monitor the status and temporal trends of both groups from different aspects to draw reliable conclusions.
Ključne besede: understory, mosses, terricolous species, diversity, composition, taxonomy, life-history traits, environmental gradients, managed forest, ICP Forests program, Slovenia
Objavljeno v DiRROS: 10.10.2023; Ogledov: 456; Prenosov: 170
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3. Comparing observer performance in vegetation records by efficiency graphs derived from rarefaction curvesWalter Seidling, Leena Hamberg, František Máliš, Maija Salemaa, Lado Kutnar, Janusz Czerepko, Thomas Kompa, Václav Buriánek, Jean-Luc Dupouey, Anna Vodálová, Roberto Canullo, 2020, izvirni znanstveni članek Povzetek: Species richness is a key variable in measuring diversity of ecological communities. It is crucial to get reliable estimates for the number of plant species in space (mapping) and % even more important in the context of monitoring % over time. Therefore, knowledge on error rates related to recordings of species numbers should be considered in such inventories. The performance of observers in four field tests to capture species numbers carried out in forest ecosystems in central and southern Europe were compared. Observer-related species accumulation (rarefaction) curves and derived efficiency curves were analysed, resulting in mean error rates of 29.7% and 39.4% over series of plots sized 4m2 and 100m2 respectively. As a new approach individual rarefaction and efficiency curves reveal site-specific and spatially differentiated capabilities of observers to register plant species. Since expertise and individual searching strategies are difficult to parametrise, reasons for variation in error rates remain largely unknown. However, statistical modelling with site- and scale-specific mean error rates gave an overview on important influential factors like location, scale, spatial integration, and their interactions. Our results underline the importance to incorporate specific training and inter-comparison measures in monitoring programs and critical perception of results on temporal changes of species richness.
Ključne besede: species richness, observer error, overlooking rate, misidentification rate, singleton species, ICP Forests
Objavljeno v DiRROS: 20.02.2020; Ogledov: 1601; Prenosov: 627
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