Sara King

Mentor: Tom Mozdzer

Biology                                        

Soil Respiration in Spartina alterniflora: Pulse-Chase experiment

Foundation species in salt marshes, specifically Spartina alterniflora, are crucial to the stability of coastal salt marshes. As nutrient pollution increases globally, this can alter trajectories of future salt marsh ecosystems. Previous work on the TIDE project within the Plum Island Ecosystems LTER has found that elevated nutrient levels cause instability in the marsh. Studies have also reported stimulated microbial respiration with nitrogen enrichment. The fertilized marshes have been found to increase aboveground biomass production, and decrease root production. It is currently unclear if the increases in soil respiration are due to changes in root respiration or microbial respiration.

A pulse-chase experiment will be used to distinguish between heterotrophic respiration and the autotrophic respiration. By exposing the plants to 13CO2 for 4 hours, the CO2 released from the soil through root respiration will be enriched with the carbon isotope tracer. This study will help differentiate root respiration from the microbial respiration that can otherwise be difficult to separate. In comparing the differences between microbial versus root respiration in fertilized and non-fertilized plants, we can better understand how nitrogen enrichment may alter carbon cycling in the future.