2.5 Objective 3

Examine biotic versus abiotic controls of mangrove soil organic carbon in allochthonous hydrogeomorphological settings

Hypothesis: Remotely sensed metrics of hydrogeomorphology at the landscape scale will explain across-site variation in soil organic carbon stocks for mangroves in allochthonous settings

Rationale: Mangroves are known to stock vast amounts of organic carbon in their deep, anaerobic soils. Studies have shown that in low-energy environments (i.e., environments characterized by low wave and tidal energy), mangroves exhibit autochthonous sedimentary patterns and are capable of accreting peat to adjust surface elevation relative to sea level rise. In these sites, SOC stocks are vast given that up to 80% of the soil may comprise of organic matter. However, for allochthonous settings the mechanistic processes of accretion of SOC are less well understood. Recent studies have found that SOC density is lower in allochthonous settings, but these sites account for the majority of mangroves globally, as well as the largest extents of forests (e.g., the Sundarbans).

Methods: This study will couple field-based datasets from my second research objective with remotely sensed metrics of hydrogeomorphology identified through my first research objective to examine correlations between biological versus hydrogeomorphological contributions to SOC. Areas of interest for which comprehensive field data of forest structure, species composition and SOC exists at multiple sites will be identified. Remotely sensed metrics of hydrogeomorphology such as near-shore total suspended sediment, upland watershed size, extent of tidal flooding, or geometric analyses of forest fractionation (to distinguish between dominant geomorphological settings) will be derived for each of the sites. Models will be used to examine correlations between the biological (i.e., vegetative) and hydrogeomorphological components of the forests.