Seasonal Nutrient Dynamics of Tundra Vegetation at Barrow, Alaska

Seasonal patterns of nutrient concentration and standing stock were documented in aboveground plant biomass of wet meadow tundra vegetation at Barrow, Alaska. Mobile elements, such as nitrogen, phosphorus, and potassium, were present in higher concentrations in tundra than in comparable temperate species. These elements reached peak concentration within 10 days of snowmelt and decreased to about half their maximum concentration in the course of the growing season. The total standing stock of these elements increased more rapidly aboveground than did biomass itself. Nearly half of the total nitrogen, phosphorus, and potassium complement of aboveground material was retranslocated belowground before the end of the growing season. That portion of these nutrients remaining in standing dead material at the end of the growing season was leached at rates reflecting their respective solubilities in plant tissue. Calcium and magnesium increased in concentration and in total content in the course of the growing season. Dicots had higher concentrations of phosphorus and of cations than did monocots. This is discussed with respect to their differences in mycorrhizal association and distribution. The implications for herbivores of seasonal and species differences in nutrient concentration are discussed. Fertilization with nitrogen, phosphorus,