Microclimate and habitat heterogeneity as important drivers of soil Collembola in a karst collapse doline in the temperate zone

Abstract

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.