Plant-Soil Carbon Responses to a Thin Layer Placement Experiment in a Southern New England Salt Marsh (USA)

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Anna Puchkoff, Dr. Beth Lawrence

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Thin Layer Placement (TLP) of sediment is an increasingly used restoration method in coastal marshes to stimulate plant productivity, subsequently promoting soil accretion and resilience to accelerated sea level rise. However, few experimental field studies have investigated using dredge material for TLP in meso-tidal estuaries, and none holistically examine plant-soil carbon dynamics. Our goal was to investigate the biological and biogeochemical responses of applying dredge material for restoration of a coastal salt marsh in Connecticut, USA. Our objectives were to determine how application of varying levels of sediment affect: (1) above and belowground biomass allocation of Spartina alterniflora, and (2) soil carbon cycling processes including decomposition and carbon mineralization. We used an in situ experiment to manipulate soil surface elevation (low: +5cm, medium: +10cm, and high: +15cm). We monitored plant traits (above and belowground biomass, stem height, stem density, leaf area) and soil parameters (EC, pH, redox, NH4 +, sulfides, C:N, carbon mineralization, decomposition, bulk density). Preliminary analyses suggest low and medium treatments increased stem heights, but reduced stem density compared to controls. No stems grew in the high treatment but had similar root biomass in the medium treatments. These results demonstrate the ability of roots to penetrate the thickest sediment and may lead to increased belowground contributions and marsh resilience. Results from ongoing soil carbon analyses will elucidate relationships between sediment application, plant growth, and carbon cycling dynamics. Collectively, our work will guide wetland managers develop restoration specifications for protecting coastal marshes in the face of rising seas.

Resource Type:
Conference Presentation, SER2021

Pre-approved for CECs under SER's CERP program