On the impact of bio-geomorphological gradients on soil organic carbon storage in tidal wetlands

Climate change is one of the most challenging problems facing society today. Evaluating effects of global warming from rising atmospheric carbon dioxide (CO₂) concentrations requires resolving the processes that drive Earth’s carbon stocks and flows. Although biogeomorphic wetlands (peatlands, mangroves, salt marshes, and seagrass meadows) cover only 1% of Earth’s surface, they store 20% of the global organic ecosystem carbon. Carbon budgets and carbon storage rates in coastal wetlands, and more specifically temperate salt marshes, are assessed by ignoring bio-geomorphic gradients and vegetation distribution. Generic estimations of carbon across the wetland leads to major inaccuracies in, estimated carbon stocks, and unclear predictions in how climate change might alter biogeomorphic feedbacks (i.e. reciprocal organism-landform interactions) that can switch these ecosystems from carbon sinks into sources. This study focuses on disentangling the impact of bio-geomorphological gradients, on distribution of sediments, plant species composition and soil organic carbon (SOC). We carried out stratified field surveys on sediment characteristics (e.g., soil organic matter content and grainsize distribution) and compared results to a remote sensing analysis on plant species distributions and drainage pathways of water and sediment. Results indicate that soil organic carbon content follows distinct spatial patterns arising from bio-geomorphic interactions between allochthonous suspended particle transport and autochthonous production. These relationships can be used to improve estimates of carbon stocks in tidal wetlands and spatial upscaling.