Analysis of Local Variation in the Standing Crop of Spartina alterniflora

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Measurements of standing crop biomass and height of the tell form of Spartina alterniflora on twelve Rhode Island salt marshes suggest that the nutrients in municipal sewage inputs may increase growth of the grass. Spartina biomass in the Providence River and upper Narragansett Bay was 39% greater than in the lower by and 107% greater than in Block Island Sound. Height of the plants increased 5% and 67% over those in the lower bay and sound, respectively. Even with enhanced growth from eutrophication, calculations show that treatment of marsh areas with sewage effluents is not a realistic hope for the recycling of wastes from coastal cities, or for providing low cost tertiary treatment. The mean dry weight at the end of the growing season was 840 ± 321 g/m2 for all marshes, with a range from 433 ± 80 g/m2 to 1380 ± 220 g/m2. Grass height averaged 112 ± 28 cm on all sites, with a range from 50 ± 12 cm to 142 = 16 cm. Multiple regression analysis indicated that concentrations of ammonia, sediment phosphorus, and sediment nitrogen could account for 77% of the between site variation in Spartina standing crop. Grass height was correlated with sediment iron in a manner suggesting this element as a possible limiting factor. Half of the 12 marshes were significantly different from all other sites in terms of grass height, demonstrating the importance of having samples from a variety of marshes in each area when analysis of large climatic gradients on production are attempted. © 1973, Walter de Gruyter. All Rights Reserved.

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Botanica Marina