Saproxylic beetles in disturbed boreal forests: Temporal dynamics, habitat associations, and community structure

Abstract

Early postfire habitats harbour numerous saproxylic species. Some are opportunistic feeders, while others are closely associated with burned forests. This distinction is important for developing sound postfire forest management aimed at conserving biodiversity, as concerns should be mostly directed towards burn-associated saproxylic beetles rather than opportunistic species. Here, we examine species—habitat associations, temporal dynamics, and community structure of saproxylic beetles in black spruce and jack pine stands disturbed by wildfire and by a “non-fire” disturbance generated by girdling trees to mimic the small-scale gap dynamics characterizing old-growth boreal forests in Canada. We used flight-interception traps and reared logs to compare abundance, species richness, and species composition of saproxylic beetles among treatments. We found that over 30% of saproxylic beetles had an affinity with jack pine or black spruce affected by either fire or girdling. Assemblages consistently differed between disturbance types over the 3 y of the study. We found that successional changes in species composition were more pronounced in burned sites than those with the girdling treatment, which indicates that the contribution of fire-generated habitats to regional diversity increases over time. While postfire forests are notable for their early-colonizing saproxylic species, our results show that they can also have substantial value for supporting mid-successional species such as Acmaeops pratensis, which is already on European red lists. This forewarns us about long-term negative consequences that postfire salvage logging could have for certain species.