Michal Marcin

Enclosed surficial karst dolines are geomorphologically diverse habitats with the potential to strongly shape community structure and the distribution of functional groups of organisms. Forest habitats in karst landscapes are characterized by lower soil temperatures and microclimatic fluctuations compared to open habitats; therefore, they may provide favorable conditions for cold-adapted/psychrophilic species, which are highly vulnerable to climate warming. We compared the diversity and structure of soil Collembola communities at sites along microclimatic gradients in open and forested karst dolines. The effect of topography and related environmental conditions on the distribution of ecological groups of soil Collembola was analyzed, and the function of the dolines as potential climate refugia for psychrophilic arthropods was assessed. The karst dolines revealed significant habitat heterogeneity, including warm plateaus and S-facing slopes and colder and wetter bottoms and N-facing slopes. The inner sites of the dolines had an overall higher abundance and species richness compared to the plateau sites. Nonmetric multidimensional scaling ordination revealed a clear delimitation of Collembola communities in terms of warmer and cooler sites in the open dolines, while the forested dolines did not reveal such a clear pattern. The studied dolines showed a potential to serve as microrefugia in the context of global climate change. Dolines could support the long-term persistence of at least some species such as cold-adapted species. Karst dolines in the temperate zone play a key role in maintaining biodiversity; therefore, they should be central in biodiversity conservation programs.

Karst dolines, as geomorphologically diverse natural landforms, usually exhibit more or less steep microclimatic gradients that provide a mosaic of diverse microhabitat conditions, resulting in a high diversity of soil biota with numerous rare endemic and/or relict species occupying these habitats. In this study, we investigated the spatial patterns of Collembola abundance, species richness, community structure and distribution of functional groups at topographically and microclimatically different sites across three open (unforested) karst dolines in a north-south direction in the Slovak Karst, Slovakia. We also assessed the refugial capacity of dolines for collembolan communities. The Friedman ANOVA test confirmed the significant differences in soil mean temperatures between the sites of all the dolines selected. The diverse soil microclimatic conditions within the dolines supported higher Collembola diversity (species numbers, diversity indices) compared with sites on the karst plateau and showed a potential to facilitate the persistence of some species that are absent or very rare in the surrounding landscape. In dolines with circular morphology and comparable size, the topography and soil microclimate had a stronger effect on community composition and structure than soil organic carbon. Shallow solution dolines provided microhabitats for various functional groups of soil Collembola in relation to the microclimatic character of the individual sites. It was observed that such landforms can also function as microclimatic refugia for cold-adapted species through the accumulation of colder air and the buffering of the local microclimate against the ambient mesoclimate, thus underlying the necessity of adequate attention in terms of the conservation of the karst natural phenomena.

Changes in well‐delimited Collembola communities along a steep microclimatic gradient at the entrance of Silická ľadnica Ice Cave, Slovakia, were investigated after 10 years (2007, 2017). We focused on the occurrence of psychrophilic and endemic species occupying this unique karst collapse doline and their response to climatic singularities in the given years as well as the increasing trend in regional air temperature. The soil temperature means at sites across the doline slope corresponded with climatic trends in the periods 2006–2007 and 2016–2017. Significantly lower average soil temperatures but significantly higher mean abundances, species richness, and diversity indices of the collembolan communities were recorded at sites during the second study period, which was characterized by more favorable soil microclimatic conditions (temperature and moisture content) compared to the first period. The dominance structure and community composition of the studied assemblages appeared to be relatively constant after 10 years, indicating stable collembolan communities, especially at cold sites at the bottom of the doline. Redundancy ordination analysis documented a clear delimitation of the communities in relation to the soil temperature, pH, and C:N ratio in both periods. Long‐term (30‐year) regional climatic data showed an increasing trend of annual air temperature means and precipitation. However, an increase in the number and abundance of xerothermophilous species and a decline in psychrophilic species (mostly endemic) along the gradient as a potential response of the increasing regional temperature were not observed, suggesting the high resilience of these communities. Microclimate and habitat heterogeneity are probably major drivers of soil Collembola communities along the steep microclimatic gradient of a karst collapse doline, which was observed by the repeated sampling after 10 years. Karst dolines as potentially important local sources of ɑ‐diversity will likely become increasingly indispensable refugia for local biodiversity under ongoing global warming, thus deserving reliable conservation.