The sink for nitrous oxide in soils

Background/Question/Methods

The atmospheric budget for nitrous oxide, a powerful greenhouse gas, is currently unbalanced, showing an excess of sources over sinks.  Soils are a net source of nitrous oxide to the atmosphere, but periodically some soils show net uptake.  I compiled the maximum rate of uptake reported in more than 100 studies of soil nitrous oxide flux to assess the potential sink for nitrous oxide in soils.

Results/Conclusions

The compiled values for N₂O uptake, ranging from < 1.0 μg N m^-2 hr^-1 to 181 μg N m^-2 hr^-1, are log-normally distributed. Nearly all values are in a range from 1.0 to 10 μg N m^-2 hr^-1. Among upland habitats, soil N₂O uptake is remarkably similar across biomes ranging from the tropics to the poles. Reports of N₂O uptake in excess of 20 μg N m^-2 hr^-1 are largely derived from wetlands and peatlands. The large values for wet soils suggest that consumption during denitrification is relatively efficient, despite the slow inward diffusion of N₂O that might be expected in flooded soils.The values for the maximum uptake of N₂O by soils are poorly correlated with concurrent reports of the mean rate of its emission in the same soils.  However, nearly all soils with high N₂O emissions have limited N₂O uptake potential, and nearly all soils with high N₂O uptake potential have low mean N₂O flux to the atmosphere.  The global uptake of nitrous oxide by soils is in the range of 0.1 to 0.5 Tg/yr.