AbstractSphagnum magellanicumBrid. andSphagnum fallax(Klinggr.) Klinggr. react differently to several nutrient applications.S. fallaxis significantly promoted by additional nitrate and ammonium in the hollows and partly in the lawns while no positive effects of these treatments onS. magellanicumcould be detected. On the hummocks nitrate and to a lesser extent ammonium reduces the growth of both species. Under lower than recent input levels the growth rates of both species decrease, indicating that the growth of theseSphagnumspecies used to be N limited in bogs.S. fallaxcan be characterized as a competitive species whileS. magellanicumexhibits a stress-tolerant strategy. Under increased N deposition levelsS. fallaxis able to outcompeteS. magellanicumin the hollows and if the water supply is sufficient also at lawn level. The atmospheric nitrogen supply may therefore be responsible for the present-day success of this species in the bog vegetation of central and north-eastern Europe.