Modeling Nitrogen Saturation from PnET model

The model operates in a monthly time step and at the stand-to-watershed scale, and is validated against data on annual net primary productivity, monthly carbon and water balances, annual net N mineralization, nitrification, foliar N concentration and annual and monthly N leaching losses for two sites, Hubbard Brook (West Thornton, NH) and Harvard Forest (Petersham, MA).

It is then used to predict transient responses in function resulting from changes in land use and N deposition, as well as the maximum rate of N cycling which can be sustained for any given combination of site, climate and species. Model predictions suggest a very long legacy effect of land use history on N cycling. Even with only one 'active' soil organic matter pool, complete recovery from three modest harvests at Hubbard Brook is predicted to require more than two centuries at current N deposition rates.