The impact of natural disturbance dynamics on lichen diversity and composition in primary mountain spruce forests

Abstract

Aim: Natural disturbances influence forest structure, successional dynamics and consequently, the distribution of species through time and space. We quantified the longterm impacts of natural disturbances on lichen species richness and composition in primary mountain forests, with a particular focus on the occurrence of endangered species.Location: Ten primary mountain spruce forest stands across five mountain chains of the Western Carpathians, a European hotspot of biodiversity.Methods: Living trees, snags and downed logs were surveyed for epiphytic and epixylic lichens in 57 plots. Using reconstructed disturbance history, we tested how lichen species richness and composition was affected by the current forest structure and disturbance regimes in the past 250 years. We also examined differences in community composition among discrete microhabitats.Results: Dead standing trees as biological legacies of natural disturbances promoted lichen species richness and the occurrence of threatened species at the plot scale, suggesting improved growing conditions for rare and common lichens during the early stages of recovery post disturbance. However, high-severity disturbances compromised plot-scale species richness. Both species richness and the number of oldgrowth specialists increased with time since disturbance (i.e., long-term uninterrupted succession). No lichen species was strictly dependent on live trees as a habitat, but numerous species showed specificity to logs, standing objects or an admixture of tree species.Conclusions: Lichen species richness was lower in regenerating, young and uniform plots compared with overmature and recently disturbed areas. Natural forest dynamics and its legacies are critical to the diversity and species composition of lichens. Spatiotemporal consequences of natural dynamics require a sufficient area of protected forests for provisioning continual habitat variability at the landscape scale. Ongoing climatic changes may further accentuate this necessity. Hence, we highlighted the

Spruce- and beech-dominated primary forests in the western Carpathians differ in terms of forest structure and bird assemblages, independently of disturbance regimes

“…However, in a study relating disturbance histories with the data on occurrence of one species, Capercaillie (Tetrao urogallus), a significant relationship was found (Mikoláš et al 2017). The relationships between disturbance history variables and organism assemblages were found in other taxonomic groups such as fungi (Ferenčík et al 2022), lichens (Langbehn et al 2021) and saproxylic beetles (Kozák et al 2020). In our case this relationship was probably distorted by the high mobility of birds and by the impact of recent disturbances which occurred in approximately the last 20 years, which are not detectable by our methods.…”

“…However, there is emerging evidence that medium-to high-severity and scale disturbances were also historically a part of BDPF disturbance regimes, although to a much lower extent than in SDPF (Frankovič et al 2021). The diversity of disturbance regimes has differing effects on forest structure, which thereby has divergent effects on habitat availability for different taxonomic groups of species, thereby altering biological assemblages (Kozák et al 2020;Langbehn et al 2021;Ferenčík et al 2022). Therefore, disentangling the impacts of disturbances across different forest types is crucial in these times of rapid biodiversity decline.…”

The impact of climate aridification on rare lichen communities

“…This sensitivity is heightened by their structural characteristics, such as the lack of a protective cuticle, allowing direct exposure to environmental factors (Floqi et al, 2009). Current global trends show a growing concern for lichen diversity in various ecosystems, ranging from pristine natural habitats to those heavily influenced by human activities (Lyubchyk et al, 2019;Langbehn et al, 2021;Manzitto-Tripp et al, 2022;Lõhmus et al, 2023). This focus is not only driven by the need to understand their ecological role but also to use their responses to forecast environmental changes, including those induced by climate change.…”