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Carabid functional diversity is enhanced by conventional flowering fields, organic winter cereals and edge habitats

Gayer, Christoph, Lövei, Gábor L., Magura, Tibor, Dieterich, Martin, Batáry, Péter
Agriculture, ecosystems & environment 2019 v.284 pp. 106579
Camelina, Carabidae, Triticum aestivum subsp. spelta, agri-environmental policy, agricultural land, biodiversity conservation, body size, carnivores, edge effects, flight, flowering, functional diversity, funding, intercropping, landscapes, lentils, organic production, pitfall traps, spring, winter, winter wheat, Europe
The continued decline in farmland biodiversity in Europe despite substantial funding for agri-environment schemes (AES) has prompted calls for more effective biodiversity conservation measures. The current AES regime allows for both holistic measures, such as organic farming, that broadly target the agricultural environment and biodiversity-specific measures, such as flowering fields, but little is known of their relative efficacies. To address this gap, we studied carabids in 48 arable fields that presented four crop types under different management practices along a gradient of landscape complexity: (a) conventionally managed crop (winter wheat), (b) biodiversity-specific AES under conventional management (sown flowering field), (c) organically managed mono-crop (winter spelt) and (d) organically managed lentil-mixedcrop (lentil intercropped with cereal or camelina). For these crop-use types, we compared functional diversity of carabid assemblages at the edge and center of the fields. Using pitfall traps, we collected more than 55,000 carabids of 95 species over two years. We characterized diversity using community weighted means and functional divergence of three ecological traits – body size, feeding type, and flight ability. Conventional flowering fields and organic winter spelt, but not organic spring sown lentil-mixed-crop, increased the proportion of plant-feeding carabids; moreover, trait characteristics and their divergences were most affected by field edges, with smaller, less carnivorous and more flight-enabled carabid assemblages found there than in the center. Divergence of body size and feeding type but not of flight ability was larger at the field edges than centres. Surrounding landscape complexity did not affect carabid traits. We conclude that future AES policy should avoid strict decisions between biodiversity specific- and holistic measures. Instead, priority should be given to a diversity of different measures, targeting the enhancement of edge habitats as well as productive and non-productive measures.