Drought, windthrow and forest operations strongly affect oribatid mite communities in different microhabitats

Climate change is enhancing the annual mean temperature and the risk for droughts and natural disasters. Hot and dry summers not only have a negative impact on forest performance, but also affect fundamental ecosystem processes such as litter decomposition and nutrient cycling and the organisms involved. Oribatid mites are sexually or parthenogenetically reproducing soil-living microarthropods substantially involved in these processes. We compare oribatid mite communities (abundance, species richness, effective Shannon diversity and life-history parameters such as sex ratio, gravidity, number of eggs) in four microhabitats (litter, dead wood, moss and bare soil) before (2016) and after a sequence of disturbance events (2020). These disturbances include the severe drought of 2018/2019 in Germany, a single summer storm event in August 2019, and subsequent forest operations in spring 2020. Abundance and species richness were reduced up to 87% in all microhabitats and so was the effective Shannon diversity in moss (65%). Communities in moss were most affected, while effects were buffered in litter. In litter and moss, sexual species suffered slightly more than parthenogenetic species. Life history parameters were largely unaffected. In bare soil, microarthropods were almost absent. Our study demonstrates that consequences of climate change – drought, windthrow, necessary forest operations – are not restricted to above-ground systems but also strongly affect soil-living microarthropod communities. If natural and human-introduced disturbances remain in the long-term, severe consequences for forest soil arthropods must be expected. Since life-history parameters were unaffected, species probably recover over time if climate becomes more moderate in the short-term.