Shifts of soil enzyme activities in wetlands exposed to elevated CO2

Elevated CO2 increased DOC concentrations in the pore-water, by which soil microbes appeared to be affected. Enzyme activities exhibited various responses. For example, elevated CO2 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 CO2 when nutrient limitation is strongly exerted.