National-Scale Inventory based Climate Impact Analysis of the Nitrogen Balance, including all Nitrogen Fluxes using Process-Based Modelling with the LandscapeDNDC Model and EURO-CORDEX Ensembles for Greece

Abstract. In this study, we have simulated inventories of arable production and soil carbon and nitrogen cycling on a national scale (0.25 × 0.25-degree) for Greece with the bio-geochemical ecosystem model LandscapeDNDC. Based on observation data, we have aggregated for each grid cell 4 most likely crop rotations, including nitrogen and manure fertilization, tilling and irrigation. The arable management was continuously projected into the future until 2100, while plant phenology was adapted to local conditions, general properties of the arable management were kept constant into the future, such as the selection of crops or the share of irrigated arable land. To understand the impacts of climate change, we used the EURO-CORDEX-11 regional climate ensemble to drive the LandscapeDNDC impact model under scenarios RCP4.5 (16 datasets) and RCP8.5 (32 datasets). The simulation timespan was from 1990 until 2100, using the first 10 years as spin-up to obtain equilibrium in the model's internal carbon and nitrogen pools from the model initialization.

Arable production declines from 2045 onwards by 9.5% or 144 kg C ha^-1 yr^-1 under RCP4.5 and by 29% or 484 kg C ha^-1 yr^-1 towards 2100. At present, the ensemble results show an average soil carbon loss of 122.1 kg C ha^-1 yr^-1 versus 139.7 kg C ha^-1 yr^-1 in the future. The gaseous outfluxes of the ensemble simulations show N₂O emissions of 0.494  to 0.453 kg N₂O–N ha⁻¹ yr⁻¹, NO emissions of 0.031 kg NO–N ha⁻¹ yr⁻¹, N₂ emissions of 4.806 to 3.377 kg N₂–N  ha⁻¹ yr⁻¹, NH₃ emissions of 24.662 to 35.040 or 34.205 kg NH₃–N  ha⁻¹ yr⁻¹ and nitrate leaching losses from 54.304 to 58.213 kg NO₃-N ha⁻¹ yr⁻¹ comparing present versus future conditions. The overall nitrogen balance of the ensemble simulations reveals a mean nitrogen loss of 4.7 versus 5.7 kg-N ha^-1 yr^-1 comparing present to future conditions.