Individual decisions drive the changes in movement patterns of ground beetles between forestry management types

Abstract

Moving from one habitat to another, the dispersal of individuals has consequences for their conditions, population dynamics and gene flow. Our major motivation was to explore the effects of different forestry treatments, such as preparation (partial) cuts and clear cuts, on the selected population of the forest ground beetle, Carabus coriaceus (Coleoptera: Carabidae). We tagged six individuals (three males and three females) with small radio-transmitters and each was released in the treatment habitat core, at the edges and in the core of control forests respectively. The recorded trajectories were divided into two major movement phases: a random walk and a directional movement using hidden Markov models. Our results revealed that in the core zone of preparation cuts, the random walk and the directional movement were equally distributed in the trajectory. A clear directional movement was observed in the clear cuts suggesting the beetles moved directly toward the adjacent (control) forest interior. The trajectories at the edges of both treatments were dominated by the random walk and so for the controls. These results suggest that forest ground beetles can avoid the forestry treatments especially clear cuts, however edge habitats and (the studied) preparation cuts can mitigate the migration constraints due to their more favorable environmental conditions compared to clear cuts.

Unequivocal Differences in Predation Pressure on Large Carabid Beetles between Forestry Treatments

“…Some large carabids, including C. coriaceus, can penetrate clear cuts and preparation cuts in relatively high numbers, likely for foraging, since there is a high competition for the limited resources in the structurally homogeneous undisturbed forest [28]. This kind of habitat utilization is rather transient, since individuals are able to leave the treatment sites within a couple of days [8,28]. There is a high risk of predation in both treatments modified by forestry practices; therefore, these habitats may act as an ecological trap for carabids.…”

“…(2) Preparation cut (P) was created when 30% of the total basal area of the dominant tree layer and the whole secondary tree layer were removed in a spatially uniform way in a circle of 80 m diameter. These two treatments were chosen due to their strong effects on carabids at different levels, from community composition to individual activity [8,16,17].…”

“…We recorded the cover of bare soil, litter, herbal and shrub layer (in %) in a one-meter-radius circle around each decoy and the number of surrounding trees (see summary Table 1). These environmental variables can potentially affect the distribution of carabids via the availability of shelters [7,8]. In total, 90 C. coriaceus decoys were installed per season.…”

“…In some individuals, regardless of sex, this no-movement behavior dominated during the tracking period [7]. Elek et al [8] suggested that these periods when beetles are hidden and not moving could be a predator avoidance strategy.…”

“…In this paper, we experimentally tested the predation pressure on carabids in the Hungarian managed temperate forest using real-sized 3D-printed models as decoys. As a model organism for 3D decoys, we selected a forest generalist, Carabus coriaceus L., 1758, a large species commonly occurring in Hungarian oak-hornbeam forests that sensitively reacts to forestry practices [8,28]. Two distinct types of forestry treatments, clear cuts and preparations cuts, were used for the field experiment.…”