The magnitude and persistence of soil NO, N₂O, CH₄, and CO₂ fluxes from burned tropical savanna in Brazil

Abstract

Among all global ecosystems, tropical savannas are the most severely and extensively affected by anthropogenic burning. Frequency of fire in cerrado, a type of tropical savanna covering 25% of Brazil, is 2 to 4 years. In 1992 we measured soil fluxes of NO, N2O, CH4, and CO2 from cerrado sites that had been burned within the previous 2 days, 30 days, 1 year, and from a control site last burned in 1976. NO and N2O fluxes responded dramatically to fire with the highest fluxes observed from newly burned soils after addition of water. Emissions of N‐trace gases after burning were of similar magnitude to estimated emissions during combustion. NO fluxes immediately after burning are among the highest observed for any ecosystem studied to date. These rates declined with time after burning and had returned to control levels 1 year after the burn. An assessment of our data suggested that tropical savanna, burned or unburned, is a major source of NO to the troposphere. Cerrado appeared to be a minor source of N2O and a sink for atmospheric CH4. Burning also elevated CO2 fluxes, which remained detectably elevated 1 year later.

Methane emission from tropical savanna <i>Trachypogon sp.</i> grasses

“…The clearance of the savanna soil surface (grasses and litter) by burning also produces a significant reduction of the methane production from the soil-grass system (Poth et al, 1995;Zepp et al, 1996). Actually, at the cerrado site in Brazil, the burned soils consume methane, whereas the unperturbed soils produce CH 4 (Poth et al, 1995), in good agreement with our clearing experiment at the Calabozo site. The consumption rate of −4.7 ng m −2 s −1 obtained in this work, during the wet season, is in the range of consumptions reported by Seiler et al (1984) in soils of a broad-leafed savanna in South Africa.…”

“…Emission of methane from tropical savanna soils have been reported at sites in Venezuela (Hao et al, 1988;Scharffe et al, 1990;Sanhueza et al, 1992), Brazil (Poth et al, 1995) and South Africa (Zepp et al, 1996), which now should be interpreted as fluxes from the soil-grass system. Table 1 presents a summary of fluxes from the soil-grass system reported in the literature, which are in relatively good agreement with the emissions rates observed in this work.…”

N2O and CH4 fluxes in undisturbed and burned holm oak, scots pine and pyrenean oak forests in central Spain

“…The short term effects of fires on forest soils have been widely studied Poth et al 1995;Castaldi and Fierro 2005;Certini 2005;Neary et al 1999;Castaldi and Aragosa 2002;Inclán et al 2010). However, less information is available on the long-term effects of wildfires (Wan et al 2001;Johnson et al 2009;Duran et al 2009).…”

Effects of soil rewetting and thawing on soil gas fluxes: a review of current literature and suggestions for future research

“…The magnitude of increased NO flux can be influenced by the duration and severity of antecedent dry periods (ButterbachBahl et al, 2004;McCalley and Sparks, 2008), change in soil moisture (Yienger and Levy, 1995) and temperature (Smart et al, 1999;McCalley and Sparks, 2008), vegetation type (Barger et al, 2005;McCalley and Sparks, 2008), soil type (Martin et al, 2003), microbial demand for N (Stark et al, 2002), frequency of wetting events (Davidson et al, 1991;Hartley and Schlesinger, 2000), previous disturbances (Levine et al, 1988;Poth et al, 1995), and agricultural management (Hutchinson and Brams, 1992). Interestingly, there are conflicting results on the magnitude of increased NO flux after rewetting, which were independent of both the size of rewetting pulse (Davidson, 1992b;Martin et al, 1998) and the periods of antecedent dry days (Martin et al, 1998).…”