BIOGENIC SOIL EMISSIONS OF NITRIC-OXIDE (NO) AND NITROUS-OXIDE (N2O) FROM SAVANNAS IN SOUTH-AFRICA - THE IMPACT OF WETTING AND BURNING

In this paper we report on the first measurements of microbial soil em issions of nitric oxide (NO) and nitrous oxide (N2O) from the savannas in South Africa. In addition to natural, unperturbed emission measure ments, we investigated the impact of natural rainfall, artificial irri gation, and fire on these emissions. Wetting and burning resulted in a significant enhancement in the emissions of NO. Mean background NO em issions from the dry sites ranged from 0.4 to 6.2 ng N m(-2) s(-1) and from the wetted sites ranged from 4.7 to 34.0 ng N m(-2) s(-1). After burning, the mean NO emissions from the dry sites increased and range d from 13.3 to 15.2 ng N m(-2) s(-1) and from the wetted sites increas ed, exceeding 60 ng N m(-2) s(-1). Measurements of biogenic emissions of N2O were attempted, but emissions were not detected throughout the measurement period, indicating emissions below the minimum delectabili ty of the instrumentation (2 ng N m(-2) s(-1)).