Methane consumption in a frequently nitrogen‐fertilized and limed spruce forest soil after clear‐cutting

Abstract

Abstract. The effects of especially frequent nitrogen (N) additions (from 1959 to 1986, totalling 860 kg N ha−1) and liming (in 1958 and 1980, totalling 6000 kg CaCO3 ha−1) on CH4 uptake by a boreal forest soil were studied in a stand of Norway spruce. Except for a forested reference plot, the stand was clear‐cut in January 1993 and the following year one‐half of each clear‐cut plot was prepared by mounding. Fluxes of CH4 were measured with static chambers in the autumn before clear‐cutting and during the following four summers. The average CH4 uptake during 1993–96 in the forested reference plot was 82 μg CH4 m−2 h−1(ranging from 10 to 147 units). In the first summer after clear‐cutting, the cleared plot showed 42% lower CH4 uptake rate than the forested reference plot, but thereafter the difference became less pronounced. The short‐term decrease in CH4 consumption after clear‐cutting was associated with increases in soil NH4+ and NO3−concentrations. Mounding tended at first to stimulate CH4 uptake but later to inhibit it. Neither liming nor N‐fertilization had significant effects on CH4 consumption. Our results suggest that over the long term, in N‐limited upland boreal forest soils, N addition does not decrease CH4 uptake by the soil.