Modeling of carbon sequestration in coastal marsh soils

Two transects were established across submerging coastal landscapes in Dorchester County, Maryland. Extensive sampling protocol was performed along the submerging upland tidal marsh soils to model C sequestration. Coastal marsh soils are accreting vertically and migrating laterally over the low-lying forest soils to keep pace with sealevel rise. The predictive C sequestration model was a two-step linear function. Therefore, C sequestration will continue to occur by accumulation in the organic horizons and sea-level rise is the driving force. During the last 150 yr, the rate of C sequestration averaged 83.5 +/- 23 g m(-2) yr(-1). Before the last few hundred years, the predicted longterm rate of C sequestration averaged 29.2 +/- 5.35 g m(-2) yr(-1). Sampling protocol and model validation ascertain the validity of the model and placed 80% confidence and 10% accuracy on rates of C sequestration and the predictive model. The model indicated that coastal marsh soils have higher C storage capacity than upland forest soils, and soils in the Cumulic subgroup of Mollisols. In general, C storage in mineral soils tends to reach a steady-state condition, whereas C sequestration in coastal marsh soils is a continuous phenomenon. During the next century, future C sequestration in the newly formed coastal marsh soils averaged 400 +/- 162 g m(-2) yr(-1). Modeling C sequestration in coastal marsh ecosystems indicated that C storage under positive accretionary balance acts as a negative feedback mechanism to global warming.