Cold-season nitrous oxide dynamics in a drained boreal peatland differ depending on land-use practice
Drained peat soils are important sources of greenhouse gases such as nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2). These gases are produced in soil and they can be emitted year-round. We measured N2O and CH4 flux rates and total respiration (RTOT) over a year from a drained peatland with one subsite as a grass field and another forested. The field acted annually as a small source (0.36 ± 0.73 kg C·ha–1) and the forest as a sink (–1.93 ± 0.50 kg C·ha–1) for CH4. Mean annual RTOT rates were 660 and 297 mg·m–2·h–1 in the field and in the forest, respectively. Annual N2O emission rates were 34.8 ± 2.4 kg N·ha–1 from the field and 25.5 ± 5.5 kg N·ha–1 from the forest. More than 80% of the annual N2O emissions took place during winter. In the field, high emissions were detected during thawing in April when N2O accumulated in soil during the winter was released. In the forest, N2O emissions peaked when the top soil was freezing in January and accumulation of N2O in soil was less than in the field. The timing of the episodic high N2O emissions thus differed depending on the land use.