Dissertation Defense

Salt marshes rely on organic matter production and ecogeomorphic feedbacks to maintain elevation relative to rising sea-level and avoid drowning. This dissertation builds and applies observational geoinformatics tools to assess salt marsh production and resilience to sea-level rise through ecogeomorphic feedbacks. First, we investigated spatiotemporal variation of production in coastal Georgia Spartina alterniflora marshes. This allowed us to describe belowground response, a key component of organic matter accumulation, across a wider range of environmental conditions than previously available. We then advanced and applied a remote sensing biomass prediction tool for Georgia S. alterniflora marshes. We found that over the past decade, aboveground biomass broadly increased, while belowground biomass widely declined. This portrayed a marsh drowning pathway, where sea-level rise hindered belowground production, and this limited vertical accretion potential. We observed distinct examples of marsh dieback and potential drowning following loss of belowground biomass. Finally, to expand model applicability, we measured production in Texas Coastal Bend marshes. To overcome variation introduced by regional tidal characteristics and species diversity, we developed a framework to identify universal productivity traits and predictor metrics. With these, we created a region- and species-invariant biomass prediction model targeted for wider application. This work has quantified spatially-explicit coastal response to climate change through innovative techniques and developed tools to uncover subtle but severe signs of ecosystem deterioration and vulnerability.