Canopy airspace of riparian forest mitigates soil N2O emission during hot moments

Abstract

Riparian forests are known as hot spots of N cycling in landscapes and climate warming speeds up the cycle. Here we present results from the first multi-annual high temporal-frequency study of soil, stem and ecosystem (eddy covariance) fluxes of N2O from a typical riparian forest in Europe.Hot moments (extreme events of N2O emission) last a quarter of the study period but contribute more than a half of soil fluxes. For the first time we demonstrate that high soil emissions of N2O do not reach the ecosystem level. During the drought onset, soil N2O emission peaks at intermediate soil water content. Rapid water content change is the main determinant of the emissions. The freeze–thaw period is another hot moment. However, according to the eddy covariance measurements the riparian forest is a modest source of N2O. We propose photochemical reactions and dissolution in canopy-space water as consumption mechanisms.