Surrounding landscape composition influences saproxylic beetle assemblages after prescribed burning

Biodiversity is affected by local and landscape factors, yet which of
these is most important seems to vary depending on species group and
context. Understanding how environmental factors affect species at
different spatial scales is crucial for effective conservation planning.
Here, we examine the influence of local and landscape characteristics on
saproxylic and fire-favored beetle populations after prescribed
burning.  Beetles (Coleoptera) were collected using flight
intercept traps at 23 sites across three regions in Sweden. Prescribed
burning had been conducted on the sites 4–7 years earlier. We analyzed the
relationships between species richness, abundance community composition,
and environmental variables at both local (burn sites) and landscape
scales (2, 5, 10, and 20 km radius around the burn sites). Local variables
were deadwood volume, canopy cover, and burn extent. Landscape variables
included area of forests that were: protected, old (>120 years),
clear-cut and burned, and the standing timber volume of Scots pine, Norway
spruce, and deciduous trees.  In total we recorded 3094
saproxylic beetles, belonging to 188 species. Of these 1153 individuals
(37 species) were classified as fire-favored. No local variables had a
significant influence on beetle richness or abundance. For landscape
relationships, 5 and 10 km scales were most relevant for analyzing
saproxylic beetle responses. At these scales saproxylic beetle richness
was positively associated with the protected forest area, whereas
abundance showed a negative relationship. In contrast, richness of
saproxylic beetles was negatively associated with the area of clear-cuts,
while abundances of saproxylic and fire-favored species were positively
associated. Species richness was similar across regions, whereas species
composition varied. The proportion of old forests was an important
variable contributing to regional dissimilarity in species
composition.  Synthesis and applications. Our study highlights
the importance of the surrounding landscape for shaping saproxylic beetle
communities after prescribed burning. Forest management and conservation
measures within a 5-10 km radius of prescribed burns can influence beetle
assemblages post-burn and should be considered when planning burns aimed
at promoting saproxylic beetles. In addition, as species composition
varied across regions, this indicates that prescribed burning in different
regions complements each other.