Nitrous oxide dynamics in managed northern forest soil profiles: is production offset by consumption?

Abstract

This study investigates soil N 2 O dynamics in forest soils representing early (3-years) and late ([50 years) post-harvest succession in Atlantic Canada over a 9-month snow-free period in order to develop a better understanding of the role of managed forests as sources and sinks of N 2 O. We couple measurement of surface flux with detailed measurements of subsurface N 2 O concentrations at four mineral soil depths (0, 5, 20 and 35 cm) at 40 plots located within four sites. Median surface fluxes were similar at all sites regardless of the management stage (-5 to ?19 ugN 2 O-N/m 2 /day), with all sites behaving as net sinks and sources of N 2 O over the measurement period. Subsurface mineral soil N 2 O concentrations at early (3-year) post-harvest succession sites, which ranged from median values of 362 ppbv at 0 cm to 1783 ppbv at 35 cm depth, were significantly higher than late post-harvest succession sites where median concentrations ranged from 329 ppbv at 0 cm to 460 ppbv at 35 cm depth. Examination of relationships between subsurface gas storage and surface flux magnitudes, suggested although recently harvested forest soils may be producing N 2 O at a greater rate than mature forest soils, observed patterns are consistent with a strong sink for this gas that prevents its conservative transport through the soil profile, and ultimate emission to the atmosphere through the majority of the measurement period.

Snow depth, soil freezing and nitrogen cycling in a northern hardwood forest landscape

“…In our previous study, annual fluxes of N 2 O ranged from 40 to over 200 mg N m -2 y -1 , with consistent treatment effects (Groffman et al 2006b), while in this study, annual N 2 O flux ranged from 4 to 78 mg N m -2 y -1 with few treatment effects. Several dates in fall and spring showing net N 2 O consumption, as has been occasionally observed in other forest studies (Goldberg and Gebauer 2009;Kellman and Kavanaugh 2008), may have reduced both treatment effects and annual emission estimates.…”

Soil greenhouse gas fluxes from different tree species on Taihang Mountain, North China

“…Soil water status thus appear to be important driving factors for N 2 O capture (Goldberg and Gebauer, 2009;Peichl et al, 2010;Gundersen et al, 2012). Forest soils serving as sinks for atmospheric N 2 O have been reported across a broad spectrum of studies (Chapuis-Lardy et al, 2007;Kellman and Kavanaugh, 2008;Peichl et al, 2010;Eickenscheidt and Brumme, 2012;Inclán et al, 2012;Ma et al, 2012;Stewart et al, 2012). Rosenkranz et al (2006) pointed out that the negative N 2 O fluxes were mainly due to very low N availability and high soil C content.…”

Measurement of Carbon Dioxide, Methane, Nitrous oxide, and Water Potential in Soil Ecosystems

“…While CO 2 is not consumed below ground by soil organisms in significant quantities in most ecosystems (Kellman and Kavanaugh, 2008;Risk et al, 2002), both CH 4 and N 2 O may be oxidized or reduced, respectively, by some functional groups of soil microorganisms depending on local and sometimes transient physical and chemical conditions (Smith et al, 2003). Methane is produced almost exclusively under very wet or saturated conditions, by methanogenic bacteria and archaea that may be either facultative or obligate anaerobes.…”

“…Nitrous oxide is reduced by denitrifiers under more strictly anaerobic conditions, when they use it as an electron acceptor in the absence of other electron acceptors such as O 2 (McBride, 1994). Diffusion of N 2 O from regions of production to regions of consumption can occur in soils, especially where adjacent soil layers differ in water and oxygen content (Kellman and Kavanaugh, 2008). Surface flux estimates of N 2 O are particularly vulnerable to underestimation of N 2 O production due to transient or microhabitatassociated zones of consumption (Chapuis-Lardy et al, 2007).…”