EFFECTS OF INCREASED NITROGEN AND PHOSPHORUS AVAILABILITY ON THE PHOTOSYNTHESIS AND NUTRIENT RELATIONS OF 3 ARCTIC DWARF SHRUBS FROM SVALBARD

1. The effects of nitrogen and phosphorus additions on the relationshi p between leaf photosynthesis, biomass and nutrient concentrations wer e investigated in Cassiope tetrngona, Dryas octopetala and Salix polar is at Ny Alesund, Svalbard (79 degrees N). 2. Cassiope, an evergreen, had the greatest leaf biomass and specific leaf weight but the lowest nutrient concentrations, rates of photosynthesis and photosynthetic nu trient-use efficiencies. In contrast Salix, a deciduous shrub, had the lowest leaf biomass and specific leaf weight but the highest nutrient concentrations, rates of photosynthesis and photosynthetic nutrient-u se efficiencies. Dryas is intermediate in that it retains its leaves f or one winter and the measured parameters lay between those of the oth er two species. 3. The basic differences in the carbon and mineral nut rient economies of the shrubs, related to growth form, were reflected in the ability of the shrubs to respond to nitrogen and phosphorus tre atments. Cassiope was conservative and there were no significant treat ment effects. Salix was the most responsive, showing increases in leaf nitrogen concentration, biomass and photosynthetic rate. The response s of Dryas,as were again intermediate.