Bat species show contrasting responses to stand structure and age in old managed forests

Old managed forests constitute habitats of critical conservation interest to support biodiversity dependent on late-seral forest characteristics. Few studies have examined how increasing forest age and abundance of old-growth attributes relate to the activity of different bat species and functional groups in these habitats. Here, we explored the habitat use of bats with different functional traits in response to stand structure, age, and forest type. Bat activity was estimated using acoustic recordings across > 130-year-old managed forests in Czechia in beech- and oak-dominated forests (classified as natural habitats) and in pine plantations. Structural characteristics explained variation in activity in line with their functional adaptations to forage. The activity of Pipistrellus species and Barbastella barbastellus decreased linearly with stem density, while the more clutter-tolerant genus Myotis spp. tended to a unimodal response. Pipistrellus pygmaeus and nyctaloids responded positively to forest age, while the activity of B. barbastellus tended to increase in response to the basal area of snags. The activity of P. pygmaeus was positively associated with broadleaved forests, density of rot hole-bearing trees and old forest coverage. These responses may reflect the importance of roost availability for those tree-dwelling species. Barbastella barbastellus is known to roost under exfoliating bark on snags, while increasing forest age drove the abundance of rot holes and woodpecker cavities. To support viable bat communities, conservation and management should protect old forests, promote old-growth and disturbance-related features such as living and dead habitat trees with tree-related microhabitats, and enhance structural heterogeneity and connectivity at the landscape scale.