Interactions between earthworms and mesofauna affect CO2 and N2O emissions from soils under long-term conservation tillage

Soil carbon dioxide (CO2) and nitrous oxide (N2O) emissions contribute significantly to global warming. Studies have shown that soil fauna can significantly affect greenhouse gas emissions. To date, although there were some studies on the effect of interactions of soil fauna on soil CO2 and N2O emissions, the role of soil fauna on CO2 and N2O emissions is far from settled, especially for a wide variety of soil and human practices. Therefore, we studied how the interactions between different groups of soil fauna affect soil CO2 and N2O emissions from an arable black soil (Typic Hapludoll, USDA Soil Taxonomy) subjected to conservation tillage for 13 years. We conducted a 35-day microcosm experiments with black arable soil and hay residues. The following soil fauna groups were included in our experiments: earthworms (Eisenia fetida (Savigny 1826)), Collembola (Thalassaphorura encarpata (Denis 1931) and Allonychiurus songi (Sun and Wu 2012)) and predatory mites (Hypoaspis kirinensis (Chang et al., 1963)). The presence of earthworm and Collembola significantly enhanced soil N2O emissions (P < 0.01) but did not significantly affect CO2 emissions (16 days later) (P > 0.05). The addition of micro-size predator mites to microcosms did not enhance soil CO2 or N2O emissions. This suggests the presence of earthworms in microcosms can increase soil CO2 and N2O emissions. In addition, the effects of predators with different species and their interactions with other groups on soil properties should be considered. This study indicates that earthworm plays the dominant roles in soil CO2 and N2O emissions, especially with other soil mesofauna, such as Collembola. Also, our data analyses demonstrate that higher contents of available soil C and N can result in higher CO2 and N2O emissions.