N2O emission from plant surfaces – light stimulated and a global phenomenon

Nitrous oxide (N2O) is an important long-lived greenhouse gas and precursor of stratospheric ozone depletingmono-nitrogen oxides. The atmospheric concentration of N2O is persistently increasing; however, large uncertaintiesare associated with the distinct source strengths. Here we investigate for the first time N2O emission fromterrestrial vegetation in response to natural solar ultra violet radiation. We conducted field site measurementsto investigate N2O atmosphere exchange from grass vegetation exposed to solar irradiance with and withoutUV-screening. Further laboratory tests were conducted with a range of species to study the controls and possibleloci of UV-induced N2O emission from plants. Plants released N2O in response to natural sunlight at rates of c.20-50 nmol m-2 h-1, mostly due to the UV component. The emission rate is temperature dependent with a ratherhigh activation energy indicative for an abiotic process. The prevailing zone for the N2O formation appears to beat the very surface of leaves. However, only c. 26% of the UV-induced N2O appears to originate from plant-N.Further, the process is dependent on atmospheric oxygen concentration. Our work demonstrates that ecosystememission of the important greenhouse gas, N2O, may be up to c. 30% higher than hitherto assumed.