The effects of fire on biogenic soil emissions of nitric oxide and nitrous oxide

Authors:
  • JLJoel S. Levine
    Joel S. Levine
  • WCWesley R. Cofer
    Wesley R. Cofer
  • DSDaniel I. Sebacher
    Daniel I. Sebacher
  • EWEdward L. Winstead
    Edward L. Winstead
  • SSShirley Sebacher
    Shirley Sebacher
  • PBPenelope J. Boston
    Penelope J. Boston
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Abstract
Measurements of biogenic soil emissions of nitric oxide (NO) and nitrous oxide (N2O) before and after a controlled burn conducted in a chaparral ecosystem on June 22, 1987, showed significantly enhanced emissions of both gases after the burn. Mean NO emissions from heavily burned and wetted (to simulate rainfall) sites exceeded 40 ng N m−2 s−1, an increase of 2 to 3 compared to preburn wetted site measurements. N2O emissions from burned and wetted sites ranged from 9 to 22 ng N m−2 s−1. Preburn N2O emissions from these wetted sites were all below the detection level of the instrumentation, indicating a flux below 2 ng N m−2 s−1. The flux of NO exceeded the N2O flux from burned wetted sites by factors ranging from 2.7 to 3.4. These measurements coupled with preburn and postburn measurements of ammonium and nitrate in the soil of this chaparral ecosystem and measurements of NO and N2O emissions obtained under controlled laboratory conditions suggest that the postfire enhancement of NO and N2O emissions is due to production of these gases by nitrifying bacteria.

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