Soil mite communities (Acari, Mesostigmata) in pure stands on post-agricultural lands: does season matter?

Post-agricultural land differs from typical forest land in physical, chemical and biological features. In addition, the environment of this land type is determined, among other things, by the introduced tree species. These differences may be revealed by the biodiversity and abundance of the soil fauna. We analysed the abundance, species richness and diversity of different instars of mesostigmatid mites inhabiting three different habitat types on post-agricultural land (shaped by pure Pinus sylvestris L., Tilia cordata Mill. and Betula pendula Roth stands). We collected 288 soil samples from eight plots in three stands. The collection was conducted in July and October in two consecutive vegetation seasons (2021 and 2022) for Mesostigmata mites community. Soil characteristics (determination of soil group and analysis of physical and chemical properties of soil and litter) were done in July 2021. In total, 399 individuals (266 females, 50 males and 83 juveniles) were classified into 38 taxa (33 species, five genera). Most individuals belonged to the Parasitidae, Laelapidae and Veigaiidae families. The most abundant species were Hypoaspis aculeifer (Canestini) (21.6% of all recorded mites), Veigaia nemorensis (C.L.Koch) (7.8%) and Trachytes aegrota (C.L.Koch) (7.0%). Abundance, species richness and diversity were shaped by collection month and Fe content in soil. The abundance was influenced by N litter content and was significantly lower in P. sylvestris stand in July (0.57 +/- 0.23; mean +/- SE) than in P. sylvestris (2.17 +/- 0.54) and T. cordata (2.15 +/- 0.48) stands in October. Moreover, abundance in P. sylvestris stand in October was higher than in B. pendula stand in July (0.78 +/- 0.26). Similarly, species richness was significantly lower in P. sylvestris stand in July than in P. sylvestris and T. cordata stands in October (2.17 +/- 0.54 and 2.15 +/- 0.48, respectively). Higher Shannon's diversity of mite communities was reported in P. sylvestris stand in October (0.40 +/- 0.10) than in P. sylvestris and B. pendula stands in July (0.12 +/- 0.06 and 0.14 +/- 0.08, respectively). Large fluctuations of abundance, species richness and diversity of soil mite communities in P. sylvestris and B. pendula stands between collection months give the insights for creating mixed stands on post-agricultural land. It is worth noticing that the wet season creates the most favourable living environment for mesostigmatid mites in P. sylvestris litter.