As anthropogenic nitrogen deposition has been suspected to be the main reason for the decline of macromycetous sporocarp production in forest ecosystems, various N-fertilization experiments started mid of the 1990s. The dynamics of ectomycorrhizal (root-inhabiting) and terricolous saprobic (litter-inhabiting) fungal communities was studied by exhaustive sporocarp inventories in a substitution Norway spruce (Picea abies) forest including 2 plots of 256 m2 sampled at one week and 1 m2 resolution between 1994 and 2007. Nitrogen was added to the soil twice per year in one plot from the fourth year onwards. The effects of nitrogen input and time on aboveground fungal communities were assessed using redundancy analysis, principal response curves and non-parametric MANOVA. Results of this long-term experiment revealed that both ectomycorrhizal and saprobic fungal communities responded to an increased soil nitrogen input. The ectomycorrhizal community reacted by a fast decrease in sporocarp production and in species richness, whereas the saprobic community was less affected. The response was highly species specific, especially for the saprobic community. The difference in species composition between control and fertilized plots was significant after one year of N addition for ectomycorrhizal fungi and only after three years for saprobic fungi. An aging effect affected sporocarp production in the whole area. For both communities, this unidirectional drift in species composition was as much important as the treatment effect. This result highlights the importance of considering the respective role of treatment and year effects in long-term field experiments on fungal communities.