Small canopy gaps do not affect the predation pressure on large ground beetles (Coleoptera: Carabidae) in a managed forest

Continuous cover forestry is a silvicultural system designed to mimic natural forest dynamics and maintain the structure of uneven-aged semi-natural forests. One of the key steps in this approach is to create small gaps in the canopy by logging small groups of trees or individual trees. In gap-cutting, the main goal is to determine the optimal shape and size of these gaps in order to ensure spontaneous natural regeneration of the major tree species in the canopy. Yet, it remains relatively unknown how various arthropods respond to such forestry practices. Carabid beetles (Coleoptera: Carabidae) play an important role as predators of various small invertebrates and their predators are mostly vertebrates. The interactions between carabids and their predators might change due to shifts in the distribution of patches of suitable habitat as a result of forest management. Here, the aim was to determine whether gaps in the canopy of two different sizes (small vs. large) and shapes (circular vs. elongated) can affect the predation pressure on large carabids in a Hungarian oak-hornbeam forest. Using 3D-printed decoys of the largest common carabid in the area, Carabus coriaceus, placed in each of the four gap treatments and control plots, the seasonal, diurnal, and treatment-specific aspects of predation pressure was estimated. This revealed no significant effects of any of the variables included in this study, which indicates that predation pressure in undisturbed controls located in closed forests and small canopy gaps did not differ significantly. Creating gaps in the canopy by felling few trees seems to be a good strategy for maintaining the forest ecological network with minimal disruption compared clear-felling large areas.