Biogenic structures produced by soil ecosystem engineers mediate soil functions and ecosystem services. Ant mounds are important biogenic structures in marsh wetlands, where they can occur at high densities. However, little information is available on their roles in the C and N cycling in these ecosystems.

　　We studied Corg, dissolved organic carbon (DOC), TN, NO3- and NH4+ concentrations in above-ground ant mounds and in soils under mounds for three ant species (Lasius flavus, Lasius niger and Formica candida), and estimated their contribution to the total soil nutrient pools in a marsh wetland. Ant impacts were greatest in above-ground soils. All measured nutrient concentrations in above-ground mounds were significantly higher than the average values in reference soils (upper 25 cm). However, except for DOC, no significant differences for nutrient concentrations existed between soils under mounds and reference soils. The impacts of ant mounds on soil C and nutrient concentrations varied by ant species. L. niger above-ground mounds store less Corg, TN and NO3- than F. candida and L. flavus mounds, or reference soils. At the ecosystem scale, soils in above-ground mounds and under ant mounds all contained less Corg per hectare than the reference soils. Total amounts in nutrient pools from mounds of the three ant species comprised from 5.3 to 7.6% of the total in natural marsh soils.

　　In further, we measured CO2, CH4 and N2O emissions from ant mounds and estimated their contribution to the total gas emissions of soils. Average CO2 emissions from ant mounds ranged from 0.84-1.95 g CO2 m-2 h-1 and were 1.08-3.09 times higher than from the surrounding marsh soils. Soil CO2 emissions from ant mounds were significantly influenced by mound type and sampling season. On the whole, average soil CO2 emissions from L. niger mounds were lower in comparison to those from F. candida mounds and L. flavus mounds. Ant mound soils were CH4 sinks (-0.39～-0.19 mg m-2 h-1) while the control marsh soils were CH4 emission sources (0.13-0.76 mg m-2 h-1). Soil CH4 and N2O emissions did not significantly differ among the three different types of ant mounds. Compared with control marsh soils (0.034-0.045 mg m-2 h-1), N2O emissions from ant mounds (0.007-0.13 mg m-2 h-1) were influenced more by sampling season. Overall, ant mounds contributed measurable amounts to soil gas emissions from the wetland, averaging 7.02%, -4.28% and 3.35% of total soil CO2, CH4 and N2O emission, respectively. Ant mounds also increased the spatial and temporal heterogeneity of soil gas emissions in the marsh.

　　Thus ant mounds may be important to a complete understanding of wetland ecosystem C and N cycles and balances. Research on more ant species from more ecosystems is needed to establish ant mound impacts on soil gas emissions at a global scale.