Effects of set-aside management on soil macrodecomposers in Hungary

• We studied the effects of set-aside management on soil macrodecomposers.
• Set-aside fields were more favourable habitats for macrodecomposers than wheat fields.
• Species richness and abundance of macrodecomposers increased with the age of set-aside fields.
• Species composition of macrodecomposers depended on habitat type and plant species richness.

Increased agricultural production demands have decreased the area of set-aside fields in the European Union during the last decade. In contrast, set-aside still remains a management practice in Hungary, where the establishment of sown set-aside fields is a requirement of certain agri-environmental schemes in High Nature Value Areas (HNVA). We tested the effects of set-aside management on the communities of macrodecomposer arthropods: isopods (Isopoda: Oniscidea) and millipedes (Diplopoda). We assessed the effects of habitat type, plant species richness and vegetation cover on species richness and abundance of these taxa. Pairs of wheat and set-aside fields of different ages (1, 2, 3 years) and additional semi-natural grasslands were sampled using pitfall traps. Isopods showed a significantly higher species richness and abundance in set-aside fields compared to wheat fields. Older set-aside fields had a more positive influence on the diversity and abundance of the studied macrodecomposers than one-year-old fields. Three-year-old set-aside fields had significantly higher species richness of millipedes compared to grasslands. Plant diversity had a significant positive effect on almost all species while vegetation cover showed significant influence in the case of Brachyiulus bagnalli, Iulus terrestris and Leptoiulus cibdellus. Habitat type and plant species richness significantly affected the composition of macrodecomposer communities. Our results highlight the importance of set-aside fields as habitats for soil arthropods, particularly after an initial establishment period of two years. Set-aside fields that are out of a crop rotation for more than 2 years could be a valuable option for establishing ecological focus areas under the Common Agricultural Policy (CAP) 2013 reform in the EU, as these fields may simultaneously conserve elements of above- and belowground diversity.