In April 1994 a15N tracer pulse study was started in a 140-year-old spruce stand (Picea abies[L.] Karst.) located at the Fichtelgebirge (NE Bavaria). Highly enriched (98%) [15N]ammonium and [15N]nitrate were applied simulating wet deposition. For two growing seasons the pathways and dynamics of the tracer were followed in all compartments of spruce (needles and twigs of all age classes, stem wood and bark, roots) and understorey vegetation and in soils of the organic (L/Of and Oh) and mineral horizons (A0–5and A5–10). By variations of the application time on different plots within the growing season (spring, summer and autumn) a seasonal effect of labelling on uptake and distribution patterns was tested.