Impacts of Nitrogen Addition on Nitrous Oxide Emission: Model-Data Comparison

Abstract

Abstract.The contributions of long-lived nitrous oxide (N2O) to the global climate and environment have received increasing attention. Especially, atmospheric nitrogen (N) deposition has substantially increased in recent decades due to extensive use of fossil fuels in industry, which strongly stimulates the N2O emissions of the terrestrial ecosystem. Several models have been developed to simulate N2O emission, but there are still large differences in their N2O emission simulations and 15 responses to atmospheric deposition over global or regional scales. Using observations from N addition experiments in a subtropical forest, this study compared six widely-used N2O models (i.e. DayCENT, DLEM, DNDC, DyN, NOE, and NGAS) to investigate their performances for reproducing N2O emission, and especially the impacts of two types of N additions (i.e. ammonium and nitrate: NH4 + and NO3 -, respectively) and two levels (low and high) on N2O emission. In general, the six models reproduced the seasonal variations of N2O emission, but failed to reproduce relatively larger N2O emissions due to 20 NH4 + compared to NO3 -additions. Few models indicated larger N2O emission under high N addition levels for both NH4 + and NO3 -. Moreover, there were substantial model differences for simulating the ratios of N2O emission from nitrification and denitrification processes due to disagreements in model structures and algorithms. This analysis highlights the need to improve representation of N2O production and diffusion, and the control of soil water-filled pore space on these processes in order to simulate the impacts of N deposition on N2O emission. 25

Soil nitrogen substrates determine global N2O emission more than climate and other soil properties

“…However, there are large uncertainties in the projections of soil N 2 O emission (Del Grosso et al 2010;, which ranges from 3.3 to 13.3 Tg N yr -1 using different models and the relative predictive error is up to 235% (Zhang et al 2018). Moreover, the simulated N 2 O emission does not match the observed data well (Zhang et al 2018). To optimize the models, it is urgent to understand the drivers of soil N 2 O emission at a global scale.…”