%0 Generic %D 1994 %T Effects of atmospheric ammonia and ammonium sulphate on vesicular-arbuscular mycorrhizal colonisation in three heathland species %A Heijine, B. %A Dueck, T.A. %A Van der Eerden, L.J.M. %A Heil, G. %B New Phytologist %V 127 %P 685-696 %0 Conference Proceedings %D 1993 %T Nitrogen eutrophication and critical load for nitrogen based upon changes in flora and fauna in (semi)-natural terrestrial ecosystems %A Bobbink, R. %A Boxman, D. %A Fremstad, E. %A Heil, G. %A Houdijk, A. %A Roelofs, J. %S Critical loads for nitrogen. Proceedings of a UN-ECE workshop at Lökeberg, Sweden, 6-10 April 1992 %I Nordic Council of Ministers, Copenhagen, Denmark %C Lökeberg, Sweden %P pp. 111-159 %0 Generic %D 1983 %T Raised nutrient levels change heathland into grassland %A Heil, G. %A Diemont, W.M. %B Vegitation %V 53 %P 113-120