Humidity and gap history drive predation pressure on large carabids in a managed temperate forest
Predation is one of the key ecological processes that shape animal communities and ecosystem functioning. However, its strength and variability across structurally heterogeneous forest habitats remain poorly understood, especially in ground-dwelling insects. Using 3D-printed decoys mimicking the large carabid beetle Carabus coriaceus, we investigated the predation pressure in a long-term monitored research system of managed oak-hornbeam forests in Hungary. We compared small-scale canopy gaps that differed in age and management history, either established in closed-canopy forest or stands after preparation cuts, and their unmanaged control plots. In addition, we tested whether the time of day and local microclimatic conditions (relative humidity, air temperature, and soil moisture) affected attack rates. Out of 2000 observations, 4.8% showed signs of predation in the form of turns, relocations, or broken parts of decoys. Regression tree analysis revealed that relative humidity was the strongest predictor of predation pressure. During very humid conditions, attack rates increased, particularly for gaps in preparation cuts. Soil moisture provided an additional effect in the other gap types and controls, while temperature and time of day did not affect predation events. Our results suggest that high humidity conditions may enhance the foraging activity of small-bodied predators, possibly due to relaxed physiological constraints or reduced availability of alternative prey. These findings underline the importance of considering management history, surrounding forest matrix, and fine-scale abiotic variation when assessing predator–prey interactions and the ecological consequences of silvicultural practices.