Chemical and biological effects of artificially increased nitrogen deposition to the ground in a Swedish beech forest

During 1985–90, effects of N deposition to a beech forest floor in south Sweden were studied by supplying 12 and 36 kg N ha‐1, as NH4NO3, on 25 occasions, i.e. 60 and 180 kg ha‐1 yr‐1, corresponding to ca. 3 and 9 times the ambient deposition rate. Treatments raised the output of NO‐ 3 and several base and metal cations from the soil. There was some increase in the total N content of the leaves and a considerable increase in the contents of free amino acids, whereas phenols decreased. Leaf concentrations of Ca, P and K were lower than in controls. Throughfall chemistry was generally little influenced by the treatments. There was no measurable change in the wood production. Fruitbody production of ectomycorrhizal fungi almost ceased, whereas that of major decomposer species increased considerably. The biomass of most field layer species was reduced to some extent in the treated plots and no new vascular plant species appeared during this five‐year period as a result of the treatments.