The train millipede (Parafontaria laminata) mediates soil aggregation and N dynamics in a Japanese larch forest

The contributions of soil macroinvertebrates such as earthworms and termites to soil structure and nutrient cycling are well recognized, but few studies have examined the influence of geophagous millipedes on soil nutrients and structure. We conducted a soil incubation experiment to evaluate the effects of the train millipede (Parafontaria laminata), which is endemic to central Japan, on N mineralization, N2O emissions, and aggregation in soils. Larvae of P. laminata significantly increased development of soil aggregates > 2 mm during the 28-day incubation experiment. This soil aggregation was attributed to fecal pellets and molting chamber walls of P. laminata larvae. N mineralization, nitrification, and N2O–N emissions were also promoted by P. laminata, although these changes in N dynamics did not result in changes in the total amounts of C and N in the soil. N mineralization and N2O–N emissions were positively correlated with the amount of large (> 2 mm) soil aggregates. These correlations indicate that the biogenic structure produced by P. laminata significantly influences soil N dynamics, and suggest that the soil micro-environment associated with large aggregates promotes microbial processes related to N dynamics, especially N2O production.