NITROGEN-METABOLISM IN THE HEIGHT FORMS OF SPARTINA-ALTERNIFLORA IN NORTH-CAROLINA

Selected aspects of the N nutrition of salt marsh cordgrass S. alterniflora were investigated in Oak Island Marsh, North Carolina, USA. Nitrate was of minor importance as a N source for Spartina in this marsh as indicated by low soil interstitial water nitrate concentrations and low plant tissue nitrate concentrations and nitrate reductase activities. Spartina did have the capability of assimilating nitrate N when available. Interstitial water and plant tissue ammonium concentrations were 1-2 orders of magnitude greater than that for nitrate, which strongly indicated that ammonium was the dominant inorganic N source. Leaf and root N constituents (total N, soluble N, ammonium and nitrate) and N metabolism measured via glutamate dehydrogenase activity indicated that the N status of the short height form of Spartina was deficient relative to that of the tall form.