Effects of Salinity and Drainage on the Growth of Three Salt Marsh Grasses

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Abstract
Seedlings of Spartina alterniflora, S. cynosuroides and Distichlis spicata were grown in a controlled environment in a nutrient solution containing different concentrations of NaCl. In another experiment, seedlings of S. alterniflora and S. cynosuroides were grown in a greenhouse, in a 50-50 sediment-sand mixture under constantly flooded or drained substrate. Dry-weight accumulations of plants indicated that, of the 3 spp. tested, D. spicata was the most tolerant of high salinity. S. alterniflora and S. cynosuroides were similar in their response to salinity, but less tolerant than D. spicata. In general, increasing the salinity of the root medium reduced the shoot growth more than root growth. Roots of S. alterniflora grew better under flooded than drained conditions, while overall growth of S. cynosuroides was significantly better in drained than in flooded sediment. These findings are compared with field observations on the relative distribution of these species in the salt marsh, and the relative importance of salinity and flooding in determining plant distribution is briefly discussed.