Effects of experimental warming and reduced moisture on oribatid mite communities in boreal peatlands

Temperature and moisture are two key factors that are expected to change under current and future climate projections, with significant impacts on ecosystems and biological communities. In northern latitudes, boreal peatlands, known as major carbon stores, are particularly vulnerable to these changes. Changes in temperature and moisture levels are predicted to shift boreal peatlands from carbon sinks to carbon sources by altering decomposition dynamics, primarily through effects on below-ground communities such as microarthropods, as well as effects on below-ground processes such as decomposition and nutrient cycling. Oribatid mites are one of the most dominant microarthropod communities in boreal peatlands as well as other terrestrial systems; they contribute to carbon flux and soil nutrient cycling by feeding on decomposing organic matter and regulating microbial communities. Here, I used both field and controlled lab experiments to study the effects of experimental warming and moisture reduction on oribatid mite communities. I observed significant changes in oribatid mite community composition under warmer temperatures, driven by a decline in diversity and evenness due to an increase in smaller (< 300 μm) oribatid mites. This compositional shift towards smaller oribatid mites also led to a decline in average community body size. Overall, my results show that temperature was a strong driver of shifts in oribatid mite communities in boreal peatlands.