Shifts of soil enzyme activities in wetlands exposed to elevated CO ₂

Wetlands play a key role in global biogeochemical cycles, and as such, the effects of global climatic changes on these systems are of great importance. In this study, we assessed impacts of elevated CO ₂ on soil enzyme activities in different types of wetlands. We hypothesised that elevated CO ₂, by increasing DOC supply into the soil, would modify enzyme activities. Intact soil cores collected from four wetlands (a bog, a fen, a gully mire, and a marsh) in north Wales and Korea were incubated either under ambient conditions (370 ppm) or elevated CO ₂ conditions (double ambient) for 4-2 months. Elevated CO ₂ increased DOC concentrations in the pore-water, by which soil microbes appeared to be affected. Enzyme activities exhibited various responses. For example, elevated CO ₂ had no effect on β-glucosidase activity in any soil, suggesting little direct impact on carbon mineralisation. However, N-acetylglucosaminidase activity increased significantly (P<0.05, n=5) in the cores from the bog, whilst a similar response was found in the gully mire for phosphatase activity. Such changes were absent from the fen and marsh where inorganic nutrients were abundant, suggesting that enzyme activities involved in N or P mineralisation only increase under elevated CO ₂ when nutrient limitation is strongly exerted.