Soil fauna diversity increases CO 2 but suppresses N 2 O emissions from soil

Soil faunal activity can be a major control of greenhouse gas (GHG) emissions from soil. Effects of single faunal species, genera or families have been investigated, but it is unknown how soil fauna diversity may influence emissions of both carbon dioxide (CO , end product of decomposition of organic matter) and nitrous oxide (N O, an intermediate product of N transformation processes, in particular denitrification). Here, we studied how CO and N O emissions are affected by species and species mixtures of up to eight species of detritivorous/fungivorous soil fauna from four different taxonomic groups (earthworms, potworms, mites, springtails) using a microcosm set-up. We found that higher species richness and increased functional dissimilarity of species mixtures led to increased faunal-induced CO emission (up to 10%), but decreased N O emission (up to 62%). Large ecosystem engineers such as earthworms were key drivers of both CO and N O emissions. Interestingly, increased biodiversity of other soil fauna in the presence of earthworms decreased faunal-induced N O emission despite enhanced C cycling. We conclude that higher soil fauna functional diversity enhanced the intensity of belowground processes, leading to more complete litter decomposition and increased CO emission, but concurrently also resulting in more complete denitrification and reduced N O emission. Our results suggest that increased soil fauna species diversity has the potential to mitigate emissions of N O from soil ecosystems. Given the loss of soil biodiversity in managed soils, our findings call for adoption of management practices that enhance soil biodiversity and stimulate a functionally diverse faunal community to reduce N O emissions from managed soils.