Greenhouse gas fluxes of coniferous forest floors as affected by wood ash addition

Wood ash has been used to alleviate nutrient deficiencies of peat forests and to combat acidification of forest soils. Ash may change the activities of soil microbes, including those producing or consuming greenhouse gases, such as methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2). We studied the effects of wood ash (loose wood ash originating from pulp mill or power plants) on the fluxes of CH4, N2O and CO2 in forests with mineral or peat soils in northern Finland. The ash doses were from 3 to 8 t ha−1. Gas fluxes were measured with a closed chamber method from five recently fertilized experiments for 1 year after application of ash and from five long-term trials 14–50 years after application. Wood ash did not affect N2O gas fluxes. In the long-term experiments, wood ash increased the soil CO2 production and the CH4 uptake and lowered the CH4 emissions.