Managing coniferous production forests towards bat conservation

Abstract

Context Forest management has impacts on bats worldwide. Given that many forest bats are threatened and that bats are important providers of ecosystem services, understanding the effects of forest management practices on their activity is fundamental for the implementation of conservation measures. Despite these important issues, studies on the effects of management practices on bats are scarce. Aims To propose management measures for coniferous production forests, to ensure sustainability of bat populations. Methods We evaluated bat species richness and activity during gestation, lactation and mating/swarming/dispersion seasons in differently managed pine stands to evaluate how vegetation structure influences those variables. Bat activity was surveyed using acoustic monitoring in 28 sampling plots within stands with distinct management records in Portugal. We also sampled arthropods using light traps to ascertain how prey availability influenced bat species richness and activity in those plots. Key results Bat species richness and activity varied along the three phenological seasons and were higher in autumn, when mating, swarming and dispersion from nurseries to hibernacula took place. Prey availability varied, but was higher during the lactation season. We hypothesise that the lower levels of bat species richness and activity registered during that period were due to a reduced availability of roosts, rather than food scarcity. Species richness was positively correlated with canopy cover and prey taxa richness, and negatively associated with dry branches cover. Total bat activity was positively correlated with tree height and prey taxa richness, and negatively associated with dry branches cover. The activity of edge-space foragers was positively associated with average tree height and prey taxa richness, while the activity of open-space foragers was negatively associated with dry branches cover. Conclusions Coniferous production forests are of great importance for bats during the mating/swarming/dispersion season. Canopy cover, dry branches cover, tree height and prey taxa richness influence bat species richness and activity as a whole, particularly the activity of open- and edge- foraging guilds. Implications Based on our results, two straightforward management actions should be implemented in coniferous production forests to increase their value for bat assemblages: the maintenance of old coniferous stands, and the cutting of dry branches at the subcanopy level.