Nitrogen-rich organic soils under warm well-drained conditions are global nitrous oxide emission hotspots

Abstract

Nitrous oxide (N2O) is a powerful greenhouse gas and the main driver of stratospheric ozone depletion. Since soils are the largest source of N2O, predicting soil response to changes in climate or land use is central to understanding and managing N2O. Here we find that N2O flux can be predicted by models incorporating soil nitrate concentration (NO3−), water content and temperature using a global field survey of N2O emissions and potential driving factors across a wide range of organic soils. N2O emissions increase with NO3− and follow a bell-shaped distribution with water content. Combining the two functions explains 72% of N2O emission from all organic soils. Above 5 mg NO3−-N kg−1, either draining wet soils or irrigating well-drained soils increases N2O emission by orders of magnitude. As soil temperature together with NO3− explains 69% of N2O emission, tropical wetlands should be a priority for N2O management.

Global soil nitrous oxide emissions since the preindustrial era estimated by an ensemble of terrestrial biosphere models: Magnitude, attribution, and uncertainty

“…Regarding the CLIM effect, experiment-based studies illustrated that warming generally enhanced soil N 2 O emissions (Smith, 1997) and the denitrifying bacteria community may adapt to higher temperature (Pärn et al, 2018), which is in line with the results simulated by the NMIP models. The positive feedbacks between soil N 2 O emissions and climate warming should be seriously taken into consideration when designing national climate change policies.…”

Short-term flooding increases CH4 and N2O emissions from trees in a riparian forest soil-stem continuum

“…N 2 O is produced in the soil mainly via nitrification under aerobic conditions, where ammonia is oxidised, and by denitrification, which occurs under anaerobic conditions, where nitrate is sequentially reduced to nitrite, N 2 O and pure molecular nitrogen (N 2 ) 35 . The gaseous nitrogen losses directly depend on soil nitrate content and soil moisture which affects oxygen availability in the soil 36 . Soils at a water content of 0.5-0.6 m 3 m -3 emit the largest amounts of N 2 O 36 .…”

Soil degradation determines release of nitrous oxide and dissolved organic carbon from peatlands

“…The releases of C and N from peatlands are closely linked to peat type such as bogs or fens (Martikainen et al 1993, Repo et al 2009, to anthropogenic activities such as land use and water management (IPCC 2014, Pärn et al 2018, and to peat degradation (Leifeld and Menichetti 2018). In previous studies, selected soil properties (e.g.…”

“…In previous studies, selected soil properties (e.g. C/N ratio of top soils (0-30 cm), carbon quality, soil pH) and vegetation types have been used to predict the magnitude of N 2 O emissions and DOC concentrations or fluxes from peatlands (Aitkenhead and McDowell 2000, Klemedtsson et al 2005, Couwenberg et al 2011, Sihi et al 2016, Kang et al 2018, Leifeld and Menichetti 2018, Leifeld 2018, Pärn et al 2018. To a certain extent, the mentioned parameters reflect peat degradation and the resulting biogeochemical responses.…”

“…To a certain extent, the mentioned parameters reflect peat degradation and the resulting biogeochemical responses. However, in addition to biogeochemical reactions, peatland degradation significantly alters the porous structure of the soil that controls soil moisture and water flow patterns, both of which are factors that impact N 2 O emissions and DOC fluxes (Holden et al 2012, Pärn et al 2018. The stage of peat degradation has been neglected or insufficiently accounted for in the national and global estimates of N 2 O and DOC fluxes (IPCC 2014, Leifeld and Menichetti 2018).…”