Nitrous oxide emissions and denitrification N-losses from forest soils in the bornhoved lake region (Northern Germany)

In situ denitrification N-losses and nitrous oxide emissions were measured over 12 months from a beech and a drained black alder forest of Northern Germany. Annual N-losses from the alder forest soil were approximately 15 times greater than from the beech forest soil (denitrification: 7.0 vs 0.4 kg N ha^-1 y^-1; nitrous oxide: 4.9 vs 0.4 kg N ha^-1 y^-1 respectively). These results were attributed to the soil moisture content, and contents of nitrate and water-soluble organic C compounds in the alder forest soil being significantly greater than in the beech forest soil. The ratio denitrification N-losses-to-nitrous oxide emissions revealed high denitrifier activity in the alder forest soil while in the beech forest soil nitrification predominated. The time course of nitrous oxide emissions and denitrification N-losses on both sites were similar and underwent seasonal changes. The best predictor for the emissions of the alder forest soil was the soil temperature (r² = 0.63 and 0.44 for nitrous oxide and denitrification, respectively).