• Allen, S. E. (1989). Chemical Analysis of Ecological Materials. BlackWell Scientific Publications.
  • Binns, W. O., Mayhead, G. J. & Mackenzie, J. M. (1980). Nutrient Deficiencies of Conifers in British Forests. An Illustrated Guide. Forestry Commission Leaflet 76. HMSO.
  • Clarkson, D. T. (1986). Regulation of the absorption and release of nitrate by plain cells: a review of current ideas and methodology. In: Fundamental, Ecological and Agricultural Aspects of Nitrogen Metabolism m Higher Plants (Ed. by H.Lambers, J.J.Neetson & I.Stulen), pp. 327. Martinus Nijhoff.
  • Farquhar, G. D., Firth, P. M., Wetselaar, R. & Weir, B. (1980). On the gaseous exchange of ammonia between leaves and the environment: determination of the ammonia compensation point. Plant Physiology 66, 710714.
  • Hallgren. J. & Nasholm, T. (1988). Critical load for nitrogen; effects on forest canopies. In: Critical Loads for Sulphur and Nitrogen. Report from a Workshop at Skokloster, Sweden, 19–24 March, 1988 (Ed. by J. Nilsson & P. Grennfelt), pp. 323342. Nordic Council of Ministers Miljorapport 1988: 15.
  • Haynes, R. J. (1986). Uptake and assimilation of mineral nitrogen by plants. In: Mineral Nitrogen in the Plant soil System (Ed. by R. J.Haynes), pp. 303358. Academic Press.
  • Klemm, O. (1989). Leaching and uptake of ions through above-ground Norway spruce tree parts. In: Forest Decline and Air Pollution. A Study of Spruce on Acid Soils. Ecological Studies 77 (Ed. by E. D.Schulze, O. L.Lange & R.Oren), pp. 210233. Springer-Verlag, Berlin .
  • McLeod. A. R., Holland, M. R., Shaw, P. J. A., Sutherland, P. M., Darrall, N. M. & Skeffington, R. A. (1990). Enhancement of nitrogen deposition to forest trees exposed to SO2. Nature 347, 277279.
  • Mcleod, A. R., Shaw, P. J. A. & Holland, M. R. (1992). The Liphook forest fumigation project: studies of sulphur dioxide and ozone effects on coniferous trees. Forest Ecology and Management (in the press).
  • Miller, H. G. (1984). Deposition-plant-soil interactions. Philosophical Transactions of the Royal Society of London B305, 339352.
  • Nihlgard, B. (1985). The ammonium hypothesis - an additional explanation to the forest dieback in Europe. Ambio 14 (1), 18.
  • Parker, G. G. (1983). Throughfall and stemflow in the forest nutrient cycle. Advances in Ecological Research 13, 58135.
  • Persson, G. & Broberg, O. (1985). Nutrient concentrations in the acidified Lake Gardsjon: the role of transport and retention of phosphorus, nitrogen and DOC in watershed and lake. Ecological Bulletin 37, 158175.
  • Raven, J. A. (1988). Acquisition of nitrogen by the shoots of land plants: its occurrence and implications for acid base balance. New Phytologist 109, 120.
  • Riederer, M. (1989). The cuticles of conifers: structure, composition and transport properties. In: Forest Decline and Air Pollution. A Study of Spruce on Acid Soils. Ecological Studies 77 (Ed. by E. D.Schulze, O. L.Lange & R.Oren), pp. 210233. Springer-Verlag.
  • Roelofs, J. G. M. & van Dijk, H. F. G. (1986). The effect of airborne ammonium deposition on canopy ion-exchange in coniferous trees. In: Direct Effects of Dry and Wet Deposition on Forest Ecosystems–in Particular Canopy Interactions. Air Pollution Research Report 4, Commission of the European Communities, pp. 3439.
  • Schaefer, D. A. & Reiners, W. A. (1990). Throughfall chemistry and canopy processing mechanisms. In: Acidic Precipitation, vol. 3, Sources, Deposition and Canopy Interactions (Ed. by S. E.Linderberg, A. L.Page & S. A.Norton), pp. 241278. Springer-Verlag, Berlin .
  • Schaefer, D. A., Reiners, W. A. & Olsen, R. K. (1988). Factors controlling the chemical alteration of throughfall in a subalpine-balsam fir canopy. Environmental and Experimental Botany 28 (3), 175189.
  • Schulze, E. D. (1989). Air pollution and forest decline in a spruce (Picea abies) forest. Science 244, 776783.
  • Skeffington, R. A. & Wilson, E. J. (1988). Excess nitrogen deposition : issues for consideration and heather. Environmental Pollution 54 (3, 4), 159185.
  • Skiba, U., Peirson-Smith, T. J. & Cresser, M. S. (1986). Effects of simulated precipitation acidified with sulphuric and/or nitric acid on the throughfall chemistry of Sitka spruce Picea sitchensis and heather. Environmental Pollution 11, 255270.
  • Smirnoff, N., Todd, P. & Stewart, G. R. (1984). The occurrence of nitrate reduction in the leaves of woody plants. Annals of Botany 54, 363374.
  • Van Dijk, H. F. G., & Roelofs, J.G. M. (1988). Effects of excessive ammonium deposition on the nutritional status and condition of pine needles. Physiologia Plantarum 73, 494501.
  • Ulrich, B. (1983). Interaction of forest canopies with atmospheric constituents: SO2, alkali and earth alkali cations and chloride. In: Effects of Accumulation of Air Pollutants in Forest Ecosystems (Ed. by B.Ulrich & J.Pankrath), pp. 3347.