Wildfires shape various coniferous forest types in distinct ways: The three-year perspective from ground beetles

Before anthropogenic impacts, wildfires and large herbivores played a major role in shaping forests. Today, their influence on the landscape is substantially reduced. It is important to critically understand the effect of forest fires on invertebrate communities. The study examined a large bioindicator group of ground beetles (Coleoptera: Carabidae) over three consecutive years following the largest modern forest wildfire in Central Europe in 2022. Ground beetles were collected using standardized pitfall traps (48 per year; 144 in total). Over the three years, a total of 15,810 individuals belonging to 78 species were recorded. To assess the interaction between forest and wildfire, a factorial design has been employed comparing three forest types (dead spruce-logged, dead spruce-unlogged, and healthy) across two fire categories (burned vs. unburned) for pairwise comparison. The results showed that wildfire affects abundance and species richness differently across the forest types studied. Over the three-year period, i) wildfire had a positive effect on abundance and functional turnover in communities, ii) species richness showed a relatively neutral response, with large, brachypterous, shade-tolerant species being replaced by smaller, macropterous species preferring open habitats, and iii) post-fire ground beetle assemblages became highly similar, reducing the importance of pre-fire forest conditions for community composition. These shifts create new ecological niches that are occupied by habitat specialists with specific environmental requirements (e.g. pyrophilous and other open habitat species). Overall, it is important to critically evaluate the positive effects of forest fires on beetle communities and include them in potential conservation activities. Wildfire can create long-term valuable habitats for ground beetles, and it could therefore be important to leave the post-fire sites to develop for as long as possible.