| dc.description.abstract | The estimated magnitude of organic carbon (OC) stocks contained in the first meter of US coastal wetland soils represents ~10% of the entire OC stock in US soils (4 vs. 52 Pg, respectively). Because this stock extends to several meters below the surface for many coastal wetlands, it becomes paramount to understand the fate of OC under ecosystem shifts, varying natural environmental constraints, and changing land use. In this project we used total hydrolysable carbohydrates, and lignin phenols at two study sites located on the Texas coastline, to characterize composition and degradation state of sedimentary organic matter (OM) to elucidate mechanisms controlling carbon burial in mangrove (A.germinans) and salt marsh (S. alterniflora) dominated wetlands. Carbohydrates are used as specific decomposition indicators of the polysaccharide component of wetland plants, acid/aldehyde ratios of vanillyl (V) and syringyl (S) phenols ([Ad/Al]S,V) help track the decomposition of lignin. The contribution of carbohydrates and lignin phenols to the total OC pool in litter and surface sediments correspond to 20-60% and 10-40%, respectively. Sharp declines of yields with depth occur parallel to increasing [Ad/Al]S,V ratios indicating decomposition of both the polysaccharide and lignin components of litter detritus. Although results show surface sediment and plant litter OC to be higher in S. alterniflora, rapid disappearance with depth is observed relative to A. germinans OC. Litter biochemistry is determined to be a greater control of OC burial then total detrital input to sediment. | |
