A new study from a 2021 wildfire site in south-eastern Sweden shows that different tree species, even when burned in the same fire, host strikingly different communities of saproxylic beetles. In contrast, the broader arthropod fauna climbing fire-damaged trunks varies only weakly among tree species. These findings offer new insights into how post-fire forests support biodiversity — and how conservation efforts can better protect threatened beetle species.
Researchers monitored arthropods on burned trunks of four common boreal trees — birch (Betula pubescens), aspen (Populus tremula), pine (Pinus sylvestris) and oak (Quercus robur) — using collar traps that operated for 189 days. In total, the team collected 9,178 arthropods from 16 major taxonomic groups. This included 1,427 beetles spanning 96 species, 13 of which are red-listed.
While the overall arthropod community differed only slightly among tree species, the beetle community showed strong and clear patterns. Host species identity explained more than half of the variation in beetle assemblages (52 %), indicating that beetles remain highly tree-specific even after a wildfire. Birch supported the greatest number of species (52 species), while aspen hosted by far the most individuals (848 beetles, 60 % of the total catch). Species turnover between tree species was high, with low similarity values (Jaccard index 0.17–0.36).
Notably, 30 beetle species — including the Vulnerable Dircaea australis and the Near-Threatened Triplax rufipes — showed significant preferences for a single tree species. This highlights how individual burned trees can act as specialized habitat patches for rare or threatened species immediately after a fire.
These results underscore the importance of retaining a diverse mosaic of burned trunks across multiple tree species in post-fire landscapes. While many arthropods show broad ecological tolerance, beetles — particularly saproxylic and red-listed species — depend on the presence of specific host trees for survival. Ensuring that burned forests maintain structural and species diversity will be crucial for maximizing beetle richness and supporting vulnerable taxa in a changing climate.
