Field Observation of Lateral Detritus Carbon Flux in a Coastal Wetland

The lateral transport of carbon has been increasingly recognized as an important component of carbon budget in wetlands. We studied a typical coastal salt marsh located at the estuary of the Yangtze River by measuring lateral transfer of macro-detritus carbon within a creek during each month’s largest spring tide period, and simultaneously, we measured the gross primary production (GPP) by the eddy covariance (EC) method. The results showed a bimodal seasonal pattern of net detritus carbon export, with one peak associated with mainly green/fresh carbon materials and the other peak associated with mainly yellow-dark/senescent carbon materials. We also found that the export of green detritus carbon was highly correlated with plant phenology and the height of tides, suggesting influences from both the standing stock of living biomass and the force of tides. GPP measured by the EC technique (GPPEC) and by remote sensing (GPPRS) differed substantially. We found this difference was correlated well with the net export of green macro-detritus. In general, we concluded that the lateral flux is an important component of the carbon budget in the marsh and that to cross validate between GPPEC and GPPRS, it must be included as a calibration term for computing GPPEC.