Diversity and community structure of soil Oribatida (Acari) in an arable field with alluvial soils

Abstract

A small-scale field study was carried out in the floodplain area of the Ondava River in the East-Slovak Lowland, Slovakia. The study aims were to compare soil oribatid mite diversity at sites within agricultural land and to assess the role of different land components as potential diversity sources. An arable field was sampled weekly on 12 sampling occasions at five sites along a transect line from a drainage ditch with a willow tree belt (hedgerow at field margin) and across the field, which had a terrain depression without water outflow. A spring-time investigation period was chosen when the field depression and the drainage ditch would have been waterlogged. Oribatid abundances at the uncultivated willow hedgerow and the depression were significantly different, not only from the rest of field sites but also from each other. The euryvalent species Oppiella nova, Oppiella obsoleta and Tectocepheus velatus dominated in the arable soils beyond the depression. The community species spectrum at the bottom of the depression, which had considerably higher soil moisture was similar to other field sites but hygro- and halotolerant Oxyoppia europaea, Microppia minus prevailed in this community. Low competitive ability and wide tolerance to environmental changes is probably the reason for the distribution pattern of these species. In the hedgerow a different community was established, with the dominant species Dissorhina ornata, Ramusella insculpta and Hermaniella dolosa being abundant usually in forest and meadow habitats rich in organic matter. Distinct environmental conditions at this site (no cultivation, leaf litter layer on the soil surface) enabled a more diverse oribatid community to establish itself, which was comprised of more specialized (less tolerant) species. We observed a high turnover rate of accidental species in field sites and more stable communities in hedgerow and depression sites. The results document that even small landscape units may serve as important diversity sources (corridors) for restitution of local microarthropod communities in arable fields (α-diversity), provided that management practices avoid drastic changes leading to the disturbance and degradation of arable soils.