Nutrient effect on maximum photosynthesis in arctic plants

Abstract

The effect of a 1976 nitrogen, phosphorus, and nitrogen‐phosphorus‐potassium fertilization at Eagle Creek, Alaska, on photosynthetic rates was investigated in 1978 in eight vascular and three nonvascular plant species. While NPK fertilization increased the growth rate of shoots of most vascular plant species, this treatment depressed photosynthetic rates in all vascular species. Therefore, it appears that nutrient limitation of growth is a direct limitation and not mediated through nutrient effect on carbon uptake rates and levels of available photosynthate. The reason for the reduction in photosynthetic rates with fertilization is not known. It is speculated that increases in growth with fertilization causes a dilution of other nutrients or factors, the effect of which is to depress photosynthesis.Moss photosynthesis is stimulated with fertilization, High NPK fertilizer levels stimulate photosynthesis more than low NPK fertilizer levels. This may indicate basic differences in the ecology or physiology of the two growth forms. It is not yet known if the growth of mosses in this area is stimulated by NPK fertilization.