Microarthropoda abundance and background data for the mesocosm experiment

Soil microarthropods have a pivotal role in soil nitrogen cycling in that
they affect microbial decomposers. A high abundance of microarthropods may
increase the mobility of inorganic nitrogen ions in the soil, mainly in
nitrogen-limited habitats. However, it is difficult to study ecological
processes with small-sized, soil-dwelling arthropods. The effects of soil
microarthropods on nitrogen cycling have mainly been studied in laboratory
microcosm experiments. Therefore, we face many practical issues in
investigating these effects under field conditions that remain to be
resolved. We developed an open-field mesocosm setup with growing plants.
In a two-part experiment, spring wheat and grass species were grown in
chernozem and sandy soils. Leached ammonium and nitrate ions were measured
with percolation lysimeters. Half of the mesocosms included natural
assemblages, and the other half included less abundant Acari and
Collembola assemblages. The application of nitrogen fertilisation assured
differences in nitrogen sources. We found a large difference in ammonium
and nitrate leaching between the two soil types. In chernozem soil, the
leached ion concentrations were higher in mesocosms with more abundant
mite and springtail assemblages. The expected patterns were less
pronounced in sandy soil. Adding nitrogen-fertiliser did not modify the
effects of soil microarthropods. Open-field mesocosms are promising for
studying the role of soil-dwelling mesofauna in ecological processes. We
solved the problem of keeping mesofauna abundance lower in treated plots
than that in control plots. Plants successfully grew in our semi-closed
systems with functioning percolation lysimeters. The use of the equipment
in the experiments in this study helped reveal that the role of
soil-dwelling microarthropods in nitrogen cycling depends on the soil type
and not on the application of nitrogen fertiliser.