Is There Any Difference?—Carabid Beetle Assemblages (Coleoptera: Carabidae) in Managed Coniferous and Deciduous Forests and Their Relevance for Sustainable Forest Management

Unsustainable forest management in the past and current climate change are altering the species composition and spatial structure of forest vegetation. As a result of these transformations affecting the entire forest ecosystem, both the quality and quantity of animal communities are also being modified. Insects are especially sensitive to environmental changes, and among them, carabid beetles (Carabidae) are widely regarded as model organisms. The aim of this study was to examine alterations in the structure of carabid beetle assemblages found in coniferous (CON) and deciduous (DEC) forests. The study was carried out in north-eastern Poland in four forest habitat types: deciduous fresh forest (Df), deciduous mixed fresh forest (DMf), coniferous mixed fresh forest (CMf), and coniferous fresh forest (Cf). Carabid beetles were captured using pitfall traps from May to October in 2013 and 2014. A total of 20,125 individuals representing 79 Carabidae species were collected. The recorded carabid beetles showed high ecological plasticity. Most species were distributed across both forest types despite differences in structure and environment, including vegetation characteristics and microclimatic conditions. No significant differences were observed between coniferous and deciduous forest assemblages in terms of carabid beetle abundance, species richness, or diversity. The differences observed between deciduous and coniferous forests were primarily related to species composition and the ecological structure of Carabidae. Unexpectedly, most of the distinguished ecological groups differed from the established pattern found in the literature, which states that deciduous forest communities are the primary refuge for forest carabid beetles. The similar species richness and diversity levels observed in both groups, together with the balanced distribution of predatory, winged and open-habitat carabid beetles across forest types, suggest the presence of detrimental ecological processes. Forest management is known to homogenize the qualitative, quantitative, and spatial structure of vegetation, which, along with climate change, may result in negative transformations reflected in carabid beetle assemblages. Therefore, maintaining structurally diverse forest stands and supporting habitat continuity may be important for biodiversity conservation, and incorporating biodiversity indicators such as carabid beetles into forest monitoring may support the long-term sustainability and resilience of forest ecosystems.