Deltas are globally important locations of diverse ecosystems, human settlement and economic activity that are threatened by reductions in sediment delivery, accelerated sea level rise, and increased subsidence. Wetlands within these coastal floodplains actively receive water from river systems and play an important ecological role of trapping sediment, sequestering carbon during net ecosystem productivity, and removing or retaining riverine nitrate to improve water quality. Coastal deltaic ecosystems are responsible for ~40-50% of global coastal and oceanic carbon burial globally as they are the main depocenters for terrestrial sediments in addition to high in situ production. We will present a framework to understand how to scale soil organic carbons dynamics within deltaic wetlands as it has direct implications on coastal restoration efforts and its effects on the global carbon cycle. Organic carbon burial and land building are a function of the relationship between organic matter accumulation and hydrogeomorphology in these mineral-rich high depositional zones. Hydrogeomorphic position is the vertical position in the floodplain that is subject to different inundation periods and biological and geophysical feedback mechanisms. Changes in the organic fraction both spatially on the delta top and in the stratigraphic record provide information about environmental conditions and ecological succession in the landscape and carbon sequestration through time.
Results/Conclusions
We will describe how the newly emergent coastal deltaic floodplains of the Wax Lake Delta provide the unique opportunity to test conceptual ecologic models on primary successional ecosystem development and landscape self-organization patterns resulting in biogeochemical processes of carbon sequestration. The flood pulse concept improves upon the river continuum concept for alluvial-floodplain systems. It argues that the lateral gradient of river channel to floodplain connectivity is more influential on the landscape features that the upstream-downstream longitudinal gradient. Additionally, over time flood frequency and duration becomes more predictable as the hydrogeomorphic system develops and biota adapt to the emergent landscape. In coastal deltaic floodplains, patterns in soil nutrient content and nutrient stoichiometry are a result of both landscape morphology and vegetation distribution and increasing biological influences over time. We will describe these spatial patterns of ecological development in the soils and sediments of the emergent coastal floodplain, the Wax Lake Delta. These patterns will help to create a conceptual model to describe changes in soil biogeochemistry, carbon storage during deltaic land development which is relevant to present and future Mississippi River delta restoration efforts.