Effects of increased nitrogen and phosphorus availability on the photosynthesis and nutrient relations of three arctic dwarf shrubs from Svalbard

The effects of nitrogen and phosphorus additions on the relationship between leaf photosynthesis, biomass and nutrient concentrations were investigated in Cassiope tetragona, Dryas octopetala and Salix polaris at Ny Alesund, Svalbard (79 ⚬N). 2. Cassiope, an evergreen, had the greatest leaf biomass and specific leaf weight but the lowest nutrient concentrations, rates of photosynthesis and photosynthetic nutrient-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-use efficiencies. Dryas is intermediate in that it retains its leaves for one winter and the measured parameters lay between those of the other two species. 3. The basic differences in the carbon and mineral nutrient economies of the shrubs, related to growth form, were reflected in the ability of the shrubs to respond to nitrogen and phosphorus treatments. Cassiope was conservative and there were no significant treatment effects. Salix was the most responsive, showing increases in leaf nitrogen concentration, biomass and photosynthetic rate. The responses of Dryas were again intermediate.