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Povzetek: Questions The long-term response of understorey vegetation to increasing tree mortality has rarely been addressed in resurvey studies. For two Quercus-dominated forest types, we asked: (a) How did overstorey alterations, induced by canopy mortality, affect understorey diversity and composition? (b) Is there a signal of global change effects on understorey communities? (c) Are these assemblages experiencing a homogenization process? Location Five sites in Quercus robur (QR) and four sites in Q. petraea (QP) forests, Slovenia. Methods We studied changes in vascular plants in the understorey layer from 1992/1993 to 2023 across 45 permanent 20 m × 20 m plots in QR and QP forests, respectively. Vegetation surveys were carried out following the standard Braun-Blanquet method. We compared original surveys with recent resurveys using multivariate analysis, ecological indicator values (EIV), plant traits and methods that quantify changes in individual species. Results Since the early 1990s, tree layer cover decreased from 95% to an average of 55% in QR, whereas it remained relatively high (77%) in QP plots. This resulted in denser understorey vegetation and a significant increase in plot-level species richness in QR forests, but a slight decrease in QP forests. The extensive loss of canopy cover and disturbance effects in QR forests caused significant changes in species composition. Species turnover in QR was driven by colonization of new disturbance-tolerant taxa characterized by ruderal traits, whereas the compositional shift in QP was to a greater extent due to species losses. We detected a process of vegetation thermophilization (increase in EIV-temperature), suggesting an effect of rapid climatic warming. Understorey communities are now more similar to each other than 30 years ago, indicating a decrease in beta-diversity (floristic homogenization). Conclusions Despite some common trends, vegetation responses were forest type-specific. Our study presents evidence of understorey vegetation changes triggered by increased canopy mortality (a strong local driver particularly in QR plots) and also points to the signal of global change symptoms (thermophilization, homogenization), which acted rather independently from the observed decline in tree layer cover.
Ključne besede: floristic homogenization, forest disturbances, permanent vegetation plots, Quercus robur, Quercus petraea, resurvey study, Slovenia, thermophilization, tree layer cover
Objavljeno v DiRROS: 11.11.2024; Ogledov: 114; Prenosov: 54
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Povzetek: The effect of past environmental changes on the demography and genetic diversity of natural populations remains a contentious issue and has rarely been investigated across multiple, phylogenetically distant species. Here, we perform comparative population genomic analyses and demographic inferences for seven widely distributed and ecologically contrasting European forest tree species based on concerted sampling of 164 populations across their natural ranges. For all seven species, the effective population size, Ne, increased or remained stable over many glacial cycles and up to 15 million years in the most extreme cases. Surprisingly, the drastic environmental changes associated with the Pleistocene glacial cycles have had little impact on the level of genetic diversity of dominant forest tree species, despite major shifts in their geographic ranges. Based on their trajectories of Ne over time, the seven tree species can be divided into three major groups, highlighting the importance of life history and range size in determining synchronous variation in genetic diversity over time. Altogether, our results indicate that forest trees have been able to retain their evolutionary potential over very long periods of time despite strong environmental changes.
Ključne besede: genetic diversity, forest trees, environmental changes
Objavljeno v DiRROS: 29.10.2024; Ogledov: 105; Prenosov: 51
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Ključne besede: entinel-2 time-series, forest canopy, precipitation, temperature, lagging effects
Objavljeno v DiRROS: 03.09.2024; Ogledov: 278; Prenosov: 1405
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Ključne besede: soil microbiome, next-generation sequencing, climate change, forest soil, fungi, bacteria
Objavljeno v DiRROS: 02.09.2024; Ogledov: 291; Prenosov: 84
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Ključne besede: isturbance, pioneer species, nurse crop, forest trees
Objavljeno v DiRROS: 02.09.2024; Ogledov: 195; Prenosov: 62
Celotno besedilo (473,16 KB)