Spatial variability of nitrous oxide emissions in an unmanaged old‐growth beech forest

Abstract

Abstract Nitrous oxide (N 2 O) is a high‐impact greenhouse gas. Due to the scarcity of unmanaged forests in Central Europe, its long‐term natural background emission level is not entirely clear. We measured soil N 2 O emissions in an unmanaged, old‐growth beech forest in the Hainich National Park, Germany, at 15 plots over a 1‐year period. The average annual measured N 2 O flux rate was (0.49 ± 0.44) kg N ha –1 y –1 . The N 2 O emissions showed background‐emission patterns with two N 2 O peaks. A correlation analysis shows that the distance between plots (up to 380 m) does not control flux correlations. Comparison of measured data with annual N 2 O flux rates obtained from a standard model (Forest‐DNDC) without site‐specific recalibration reveals that the model overestimates the actual measured N 2 O flux rates mainly in spring. Temporal variability of measured N 2 O flux was better depicted by the model at plots with high soil organic C (SOC) content. Modeled N 2 O flux rates were increased during freezing only when SOC was > 0.06 kg C kg –1 . The results indicate that the natural background of N 2 O emissions may be lower than assumed by most approaches.