Journal
MARINE ECOLOGY PROGRESS SERIES
Volume 354, Issue -, Pages 35-46Publisher
INTER-RESEARCH
DOI: 10.3354/meps07170
Keywords
Spartina alterniflora; Spartina patens; plant ecophysiology; eutrophication; nitrogen isotopes; nitrogen cycling; marsh ecosystem
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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 (NO3-)-N-15 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 (similar to 17x 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 similar to 24.5 g NO3-N ha(-1) d(-1) in aboveground pools during midsummer, while fertilized plants sequestered similar to 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 (similar to 70 mu M 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 similar to 43% (tall S. alterniflora), 23 % (stunted S. alterniflora) and 15% (S. patens) more N per unit biomass than reference creek leaves.
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