Nitrogen cycling drives a strong within-soil CO₂-sink

Abstract

For about three decades, it has not been possible to completely balance global carbon emissions into known pools. A residual (or 'missing') sink remains. Here evidence is presented that part of soil respiration is allocated into an internal soil CO2-sink localized to the saprophytic subsystem (roots excluded). The process occurs in forest, agricultural and grassland soils and is favoured by high N-deposition. Chemoautotrophic nitrification has a key role, and the most efficient internal CO2-sequestration occurs concurrently with lowest soil nitrate (NO3-) concentrations, despite considerable N-loading. Not until drastic N-supply occurs, does the CO2-sink successively breakdown, and nitrate concentrations increase, leading to NO3--leaching. Within-soil CO2-uptake seems to be of the same magnitude as the missing carbon sink. It may be gradually enforced by the ongoing input of nitrogen to the biosphere

Responses of soil greenhouse gas emissions to land use conversion and reversion—A global meta‐analysis

“…The results of RFR identified that NH 4 + , WFPS, and soil clay with the importance of 0.249, 0.092, and 0.088, respectively, which were the relatively important driving factors for CO 2 emission response under land use conversion (Figure 6a). Previous study indicated that the increasing of added NH 4 + improved nitrification and reduced CO 2 emission until reaching the minimum value, and the further NH 4 + addition inhibited nitrification process gradually and resulted in the increase of CO 2 release (Fleischer & Bouse, 2008). Thus, the NH 4 + addition during the land use conversion would make the response fluctuation of CO 2 .…”