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Marine Ecology Progress Series

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MEPS 354:35-46 (2008)  -  DOI:

Plant nitrogen dynamics in fertilized and natural New England salt marshes: a paired 15N tracer study

D. C. Drake1,3,*, B. J. Peterson1, L. A. Deegan1, L. A. Harris1, E. E. Miller2, R. S. Warren2

1The Ecosystems Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, Massachusetts 02543, USA
2Connecticut College, Box 5362, New London, Connecticut 06320, USA
3Present address: National Institute for Water and Atmospheric Research, 10 Kyle Street, Riccarton, Christchurch, New Zealand

ABSTRACT: We examined the effects of increased nutrient availability on nitrogen (N) dynamics in dominant New England salt marsh plants (tall and stunted Spartina alterniflora and S. patens) using paired large-scale nutrient and 15NO3 tracer additions. This study is one component of a long-term, large-scale, salt marsh nutrient and trophic manipulation study (the Trophic Cascades and Interacting Control Processes in a Detritus-based Aquatic Ecosystem [TIDE] Project). We compared physiological variables of plants in fertilized (~17× ambient N and P in incoming tidal water) and reference marsh systems to quantify NO3 uptake and uptake efficiency, allocation of N to tissues, end-of-season N resorption, leaf litter quality and other potential responses to increased nutrient availability. Reference system plants sequestered ~24.5 g NO3-N ha–1 d–1 in aboveground pools during mid-summer, while fertilized plants sequestered ~140 g NO3-N ha–1 d–1. However, NO3 uptake efficiency (% of total incoming NO3-N sequestered aboveground) was higher in the reference system (16.8%) than in the fertilized system (2.6%), suggesting that our fertilization rate (~70 µM NO3 in incoming water) approaches or exceeds the uptake saturation point for this vegetation community. Leaf litter quality was clearly affected by N availability; N resorption efficiency was lower in all plants of the fertilized system; senesced leaves from the fertilized creek contained ~43% (tall S. alterniflora), 23% (stunted S. alterniflora) and 15% (S. patens) more N per unit biomass than reference creek leaves.

KEY WORDS: Spartina alterniflora · Spartina patens · Plant ecophysiology · Eutrophication · Nitrogen isotopes · Nitrogen cycling · Marsh ecosystem

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Cite this article as: Drake DC, Peterson BJ, Deegan LA, Harris LA, Miller EE, Warren RS (2008) Plant nitrogen dynamics in fertilized and natural New England salt marshes: a paired 15N tracer study. Mar Ecol Prog Ser 354:35-46.

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