Does litter decomposition affect mite communities (Acari, Mesostigmata)? A five-year litterbag experiment with 14 tree species in mixed forest stands growing on a post-industrial area

Decomposition and topsoil microclimate, mainly humidity and soil temperature, affects the availability of nutrients, as well as the edaphon structure, including soil mites, springtails, nematodes, insects and oligochaetes. Soil arthropod decomposers are the food base for predators in the soil trophic chains, including mesostigmatid (gamasid) mites. The aim of our study was to describe the succession of mesostigmatid assemblages on decomposed litter of 14 tree species in mixed stands growing on a reclaimed post-mining site. We hypothesized that litter species would significantly affect the gamasid abundance, species richness and diversity. Moreover, we hypothesized that mesostigmatid abundance, species richness and diversity would be higher in deciduous litter compared to pioneer Scots pine litter. Additionally, along with the decomposition process, the gamasid diversity, species richness and abundance would be significantly affected by soil temperature and differ among collection dates, with the lowest values at the beginning and the end, and with the highest values in the middle of the study period. In December 2011, 1389 litterbags (mesh size = 1 mm) containing leaf litter (initial dry mass = 8.004–10.772 g) were placed on research plots and collected after 3, 6, 9, 13, 19, 25, 31, 37, 43 and 58 months after the experiment started. We determined the percentage litter mass loss for each sample and mean soil temperature on each research plot. Soil microarthropods were extracted from litterbag samples using Berlese-Tullgren funnels, and mesostigmatid mites were selected using a stereomicroscope. The mites were identified to genus and/or species level including developmental stages, using a microscope with high magnification and acarological keys. In total, 19,296 gamasid mites were selected and classified into 52 taxa. The dominant species were Trachytes aegrota (C.L. Koch) (49.9% of all gamasid mites found), Veigaia nemorensis (C.L. Koch) (8.9%) and Gamasellodes bicolor (Berlese) (7.7%). We found that time of litterbag sampling did not affect abundance, species richness and diversity of gamasid mites. Moreover, litter species affected species richness and diversity of gamasid mite assemblages, however, abundance was affected when calculated per sample, but not when calculated per dry litter mass. Additionally, we found that mean soil temperature and percentage litter mass loss also significantly affected abundance and species richness, however, the impact on diversity was insignificant. Our results may help to better understand of the importance of soil fauna that has a decisive impact on soil-forming processes on degraded areas. Results could also help to choose the right tree species to improve revitalization of degraded areas by creating better conditions for edaphic fauna, including species not directly involved in the decomposition process.