Soil-Atmosphere Exchange of N2O and NO in Near-Natural Savanna and Agricultural Land in Burkina Faso (W. Africa)

N<sub>2</sub>O, NO, N<sub>2</sub> and CO<sub>2</sub> emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores

“…The initial watering led to N 2 O pulse emissions with peak emissions immediately after water addition, but they were, with 3 days duration, only short lived (a pattern that was previously reported for African savanna soil; Brümmer et al, 2008;Scholes et al, 1997). The occurrence of N 2 O pulsing emissions was previously reported by Grover et al (2012) for in situ measurements at a nearby savanna site, but emissions were, in accordance with our laboratory results, several magnitudes below reported break-of-seasons pulse emissions reported for tropical rainforests (Butterbach-Bahl et al, 2004b;Werner et al, 2007b).…”

“…Previous results also show a positive correlation between soil temperature and N 2 O emissions (Castaldi et al, 2010), but other authors found no clear linear correlation (Brümmer et al, 2008;Scholes et al, 1997), although observing clear diurnal patterns (Brümmer et al, 2008). Previous studies from tropical savanna and seasonally dry tropical forest sites identified changes in WFPS to dominate the N 2 O emission patterns (Brümmer et al, 2008;Castaldi et al, 2010;Davidson et al, 1993;Grover et al, 2012;Rees et al, 2006), but in general, N 2 O emissions from undisturbed savanna soil ranked lowest for seasonally dry ecosystems due to low nutrient availability and soil textures favoring quick drainage (Castaldi et al, 2006). In accordance, significant positive correlations were reported for clay content and soil volumetric water content (Castaldi et al, 2004), factors which strongly determine the pore space and water saturation and thus soil aeration and anaerobiosis.…”

“…Strong NO pulse emissions were reported for many sites from seasonally dry tropics (Brümmer et al, 2008;Levine et al, 1996;Scholes et al, 1997) and rainforests with seasonality (Butterbach-Bahl et al, 2004b) and are now an essential part in models simulating global NO emissions (Steinkamp and Lawrence, 2011;Yan et al, 2005;Yienger and Levy, 1995). The immediate emission of NO after watering was also observed by Pinto et al (2002), who measured up to 100-fold increased NO emissions above pre-watering levels to 105 µg N m −2 h −1 , but noted that results varied substantially between collars.…”

“…Significant N 2 O pulse emissions following the first rains after a dry season, often with a small temporal delay, have been reported for different seasonally dry (sub-)tropical ecosystems (Brümmer et al, 2008;Davidson et al, 1993;Scholes et al, 1997;Werner et al, 2007a) and are often preceded by significant CO 2 emissions immediately after the soil is re-moistured. We also measured significant CO 2 pulse emissions for all three watering levels immediately after water addition, but emissions dropped significantly in the following days.…”

From biota to chemistry and climate: towards a comprehensive description of trace gas exchange between the biosphere and atmosphere

“…Site-scale observations of NO x and N 2 O soil emissions are biased towards short-term studies in temperate/boreal croplands, pastures and forests while information from tropical and particular semi-arid and seasonally wet regions is in view of the global importance of this biome types still scarce (e.g. Martin et al, 2003;Brummer et al, 2008). Using space-based observations, Jaegle et al (2004) have recently suggested that soil NO x emissions from semiarid regions are significantly contributing to O 3 enhancement in tropical Africa.…”