NITRIFICATION AND METHANE OXIDATION IN FOREST SOIL: ACID DEPOSITION, NITROGEN INPUT AND PLANT EFFECTS

摘要

In a laboratory incubation experiment, nitrification potential, methane oxidation, N_2O and CO_2 release were studied in the organic soil layer (0-10 cm) of field lysimeters containing reestablished soil profiles from a 100-year-old Scots pine (Pinus sylvestris) forest of Norway. The experiment was designed as a full factorial (3 factors; N fertilisation rates, soil acidification, and plants), with three replicates. The more acidic irrigation (pH 3) significantly reduced nitrification potential and N_2O fluxes, methane oxidation and CO_2 release. We concluded that the reduction in soil N_2O release by severe acid deposition is partly due to reduction in nitrification potential. The highest N_2O fluxes were observed in the combination of fertilised planted and less acidic pH treatment. N fertilisation (90 kg N ha~(-1) y~(-1) with NH_4NO_3) increased soil N_2O release by a factor of 8 and decreased CH_4 oxidation by 60-80% . Plant effects on soil nitrification potential and methane oxidation rates are discussed.