Wood-pastures promote environmental and ecological heterogeneity on a small spatial scale

Wood-pastures harbor critical natural and social values and are among the most ancient land use forms of Europe. The crucial conservation value of these silvopastoral systems is generally contributed to their characteristic landscape elements, the solitary trees, which provide microhabitats for a variety of organisms. However, by accommodating four habitat types (grasslands, solitary trees, forests, and forest edges) on a relatively small spatial scale, wood-pastures might host functionally and compositionally distinct arthropod communities, thus enhancing the landscape-level biodiversity. To test this, we assessed the fine-scale microclimatic conditions of the four different habitat types of three wood-pastures and investigated the effects of these conditions on ant activity and community organization patterns. Besides microclimate, niche breadths (quantified by four-dimensional niche hypervolumes), niche overlaps, and interspecific interactions were also considered to assess the importance of interspecific competition in shaping the studied ant communities. The four habitat types showed notable differences in the previous aspects, which resulted in different patterns of ant activity and community organization. Posing ideal conditions (high solar irradiance and temperatures above 25 °C) for ant activity, the grasslands were monopolized by usually 2-3 dominant species with large hypervolumes, while the subordinates mostly occurred under environmental extremities. Despite their vicinity to the grasslands, solitary trees showed a different pattern, where in total 8 subordinate species associated with specific microclimates were present. The forest edges hosted the most species-rich communities, with 18 species in total, where interspecific interactions played a major role in shaping the activity patterns. A similar result was obtained for forests, although the mild environmental conditions of these habitat types resulted in low overall ant activity. Our results unveil that by posing various microclimatic and structural conditions, wood-pastures enable the coexistence of four ecologically and functionally distinct communities, which makes them ideal targets for biodiversity conservation.