Response to 'The European nitrogen cycle: Response to Schulze et al, Global Change Biology (2010) 16, pp. 1451-1469'

Winniwarter and colleagues present alternative estimates for several of the nitrogen (N) fluxes provided by Schulze and colleagues. They reason that numeric discrepancies between largely dependent estimates and lack of detail in Schulze's estimates urges caution in interpreting these numbers. In this reply we provide methodological details enhancing the transparency of Schulze's estimates and argue that convergence between land- and atmosphere-based estimates should be reached before individual estimates can be rejected. Only for the nitrous oxide and NO_x fluxes a balance between atmosphere and land-based estimates has been reached. Convergence between independent estimates has not been reached yet for NO-, NH₃- and N-deposition estimates. As stated by Schulze and colleagues these N-fluxes remain potentially biased and therefore come with a large uncertainty, irrespective of the reported precision.