Abstract
Research highlights: shifts in the composition and functional diversity of lichen biota reflect changes in the environment caused by climate warming and eutrophication. Background and objectives: studies on lichen functional diversity and refinement in the functional traits of lichen biota under the pressure of changing environmental factors are currently of great scientific interest. The obtained results are interpreted in relation to specific habitat properties and their modifications due to the potential effects of climate change and atmospheric pollution. The aim of the work was to investigate changes in lichen species composition and functional diversity, as well as to identify factors responsible for them at different forest ecosystem scales. Materials and Methods: we identified factors responsible for changes in lichen biota in a unique Białowieża Forest ecosystem by analyzing shifts in species optima and functional diversity at the forest community, tree phorophyte, and substrate levels. We examined individual lichen species’ responses and temporal shifts in the species composition for each historical and resampled dataset using a community-weighted means of functional lichen traits and Wirth ecological indicator values. Results: the most evident change took place at the level of individual species, which shifted their realized optima: 25 species demonstrated a shift to co-occur with lichens of higher nitrogen demands, 15 demonstrated higher light demands, 14 demonstrated higher temperature preferences, and six demonstrated lower moisture preferences. At the level of forest communities, biota shifted towards the higher proportion of nitrogen-demanding and the lower proportion of moisture-demanding species. At the level of phorophyte species, biota changed towards an increased proportion of lichens of higher temperature preferences. For the substrate level, no directional shifts in lichen species composition were found. Conclusions: climate change has influenced lichen biota in Białowieża Forest, but the main driver of lichen species composition was found to be eutrophication. We suppose that other overlapping factors may contribute to biota shifts, e.g., the extinction and expansion of phorophyte tree species.
Highlights
Lichens are extremely vulnerable to any modification in their environment, to which they react by changes, for example, in species composition and abundance [1]
The functional traits of lichens are related to specific habitat conditions, and a higher functional diversity indicates a higher number of microhabitats and species realized niche diversity [17]
Considering the results of the detrended correspondence analysis performed for the substrate level, we found no directional changes in lichen species composition over time, indicating their high substrate-specificity
Summary
Lichens are extremely vulnerable to any modification in their environment, to which they react by changes, for example, in species composition and abundance [1]. Lichen functional traits are morphological (e.g., thallus type), anatomical (e.g., photobiont type, shape, and septation of spores), and biochemical (e.g., lichen secondary metabolites) characteristics of species They reflect adaptations of lichens to specific habitat conditions, and they provide information on their life strategies [2,8,9,15,16,17,18]. A higher frequency of species with smaller ascospores has been reported in coniferous communities than in deciduous forest communities [17], which is related to harsher habitat conditions due to lower moisture, higher temperatures, and higher light availability. Studies on changes in lichen functional diversity and the frequency of species with specific functional traits could be related to certain environmental conditions, as well as modified by global factors [8,19]. Increasing temperatures may promote a higher contribution of species associated with Trentepohlia photobionts [9], and the increase of climate drought events promotes lichens with higher fertility demands than those present in wetter climates at the same levels of N air pollution [20]
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