Coniferous forests as “secondary agricultural” sources of nitrous oxide

• Published in: Atmospheric environment (1994) 1998-10, Vol.32 (19), p.3321-3330
• Main Authors: Ineson, P., Coward, P.A., Benham, D.G., Robertson, S.M.C.
• Format: Article
• Language: English
• Subjects: ammonia; carbon dioxide; intensive agriculture; methane; Nitrogen; pigs; pollution
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/S1352-2310(98)00022-3

Measurements of the emissions of the trace gas N 2O were made for the forest floor of a coniferous plantation down-wind from an intensive animal unit, and receiving an inorganic N deposition in excess of 100 kg N ha -1 a -1. Field measurements were made using a mobile laboratory over two periods in August 1993 and July 1994, with peak flux rates of up to 120 μg N 2ON m -2 h -1 being recorded. These flux rates are very high when compared to published data from other temperate coniferous forests and are related to the high N deposition at this N polluted site. Rainfall incidents were associated with pulses of increased N 2O and CO 2 production and an increase in the net CH 4 consumption rate during the 1994 measurement campaign. It appears that NH 3 derived from agriculture is being converted to N 2O in the forest floor, with the forest acting as a “secondary agricultural” source of N 2O. Despite the high levels of N input to the forest, CH 4 consumption was still significant, at mean rates of 17 and 24 μg CH 4 m -2 h -1 for the 1993 and 1994 measurement periods, respectively. A marked positive correlation was observed between net CH 4 consumption and CO 2 flux.