Production and dynamics of experimentally enriched salt marsh vegetation: Belowground biomass. Limnology and Oceanography

Root growth increased during the early growing season in Spartina altemiflora salt marsh plots. While fertilization with nitrogenous fertilizer did not affect initial growth, a marked dccrcase in root biomass followed tbe spring peak particularly where nutrient doses were highest. A sharp reduction in roots occurred in enriched arcas covered by Spadina patens, although, as with S. alterniflora, aboveground biomass increased. Roots disappcarcd during autumn leaving rhizomes as the only part of the plants to overwinter. The maximum standing crop for roots was O-2 cm deep, for rhizomes 2-5 cm. Net annual underground production was calculated from annual increments in dead matter bclow-ground. Total production, underground and aboveground, exceeds that of any marine vegetation, ranging from 3,900 to 6,600 g m2 yr- ’ in S. akemiflora areas and 3,200 to 6,200 g n-F yr-l in S. patens arcas. Fertilization incrcascd production particularly aboveground whcro-dead plant parts are subject to export. Al though production of aboveground vcgctation in salt marshes has received con