Restoring forests by bark beetle outbreaks – implications from mountain forest flagship species

Abstract

Although forest managers have tried to supress natural disturbances, such as windstorms, wildfire and outbreaks of insect pests, climate change has led to increasing frequencies and intensities of natural disturbances in European mountain forests during the last decades. In addition to that, intensive human use altered European mountain forests over the last centuries, resulting not only in a loss of biodiversity and old-growth forest structures, but also in an enhanced vulnerability against disturbances. The impacts of natural disturbances on forest stands and the following succession can vary greatly and consequently species responses are difficult to predict. Using two species of conservation concern this talk illustrates the impacts of bark beetle infestations on biodiversity. We investigated the response of the foraging activity and roost selection of barbastelle bats (Barbastella barbastellus) in a forest disturbed by bark beetles. A combination of acoustic surveys, radio telemetry, and airborne light detection and ranging (LiDAR) was used to characterize B. barbastellus habitat use on different scales. In the same study area, we analysed the response of Capercaillie (Tetrao urogallus) and Hazel grouse (Tetrastes bonasia), to bark beetle outbreaks. We combined a 23-year time series of aerial photography with LiDAR data to quantify present-day forest structures as well as stand disturbance history to test the effects of natural disturbances on the probability of grouse presence as mediated by changes in forest structure. Our results increase our understanding of how to manage natural disturbances for species conservation and highlight the potential of post-disturbance biological legacies for maintaining and restoring biodiversity.