Inorganic nitrogen availability after severe stand-replacing fire in the Greater Yellowstone ecosystem

Abstract

Understanding ecosystem processes as they relate to wildfire and vegetation dynamics is of growing importance as fire frequency and extent increase throughout the western United States. However, the effects of severe, stand-replacing wildfires are poorly understood. We studied inorganic nitrogen pools and mineralization rates after stand-replacing wildfires in the Greater Yellow- Laboratory incubations using 15 N isotope pool dilution revealed that gross production of ammonium was reduced and ammonium consumption greatly exceeded gross production during the initial postfire years. Our results suggest a microbial nitrogen sink for several years after severe, stand-replacing fire, confirming earlier hypotheses about postdisturbance succession and nutrient cycling in cold, fire-dominated coniferous forests. Postfire forests in Yellowstone seem to be highly conservative for nitrogen, and microbial immobilization of ammonium plays a key role during early succession.nitrification ͉ nitrogen mineralization ͉ Rocky Mountains ͉ Pinus contorta ͉ lodgepole pine

Changes in assembly processes in soil bacterial communities following a wildfire disturbance

“…As succession proceeds, however, our data suggest that this increase in b diversity reflects an increase in niche-based processes. Other work has demonstrated that fire tends to increase biogeochemical heterogeneity, likely due to variation in the severity of the burn across the landscape (for example, Turner et al, 2007;Hamman et al, 2008). Thus, these increases in environmental variation may be reflected, at least to some degree, in the changes in community composition observed in the burned soils, combined with an increase in niche-based processes in shaping communities.…”

How wildfires affect soil properties. A brief review

“…During combustion, most N is lost by volatilization at 200 o C (Chandler et al, 1983;Prichett and Fisher, 1987;Fisher and Binkley, 2000;Turner et al, 2007). However, some authors have shown increases by the addition of partially pyrolyzed materials (Giovannini et al, 1988;Prieto-Fernández et al, 1993;Grogan et al, 2000).…”

“…Volatilization of N during combustion is directly related to the temperatures reached in soil and the amount of organic matter consumed, but nitrification conditions usually are improved after burning (Mataix-Solera and Guerrero, 2007). Inorganic N concentrations tend to increase in burned areas more than in unburned control areas in the first years after fire (Smithwick et al, 2005;Turner et al, 2007;Boerner et al, 2009). Fire-induced changes in soil inorganic N content can be attributed to a combination of direct and indirect effects of fire, N release from dead roots and compounds where it was previously immobilized (Smithwick et al, 2005;Rivas et al, 2012).…”

Un incendie modifie la configuration spatiale de la disponibilité des éléments nutritifs dans les sols de forêts de Pinus canariensis

“…Several studies have tested fire impacts on soil resource availability (Carreira et al, 1994;DeLuca and Sala, 2006;Quintana et al, 2007;Romanya et al, 2001;Turner et al, 2007;Wienhold and Klemmedson, 1992). Ashes may provide an important source of available N after a forest fire on a short-term basis (Raison, 1979).…”