Quantification of nitrate leaching from German forest ecosystems by use of a process oriented biogeochemical model

Simulations with the process oriented Forest-DNDC model showed reasonable to good agreement with observations of soil water contents of different soil layers, annual amounts of seepage water and approximated rates of nitrate leaching at 79 sites across Germany. Following site evaluation, Forest-DNDC was coupled to a GIS to assess nitrate leaching from German forest ecosystems for the year 2000. At national scale leaching rates varied in a range of 0–>80 kg NO3–N ha−1 yr−1 (mean 5.5 kg NO3–N ha−1 yr−1). A comparison of regional simulations with the results of a nitrate inventory study for Bavaria showed that measured and simulated percentages for different nitrate leaching classes (0–5 kg N ha−1 yr−1:66% vs. 74%, 5–15 kg N ha−1 yr−1:20% vs. 20%, >15 kg N ha−1 yr−1:14% vs. 6%) were in good agreement. Mean nitrate concentrations in seepage water ranged between 0 and 23 mg NO3–N l−1.

► Forest-DNDC was successfully tested for prediction of annual NO3 leaching rates. ► Coupled to GIS it generated regional estimates of NO3 leaching for German forests. ► At national scale rates varied in a range of 0–>80 (mean 5.5) kg NO3–N ha−1 yr−1. ► Mean NO3 concentrations in seepage water were between 0 and 23 mg NO3–N l−1. ► Indication of potential risk for groundwater pollution and plant biodiversity.