Soil organic carbon in tidal wetlands of the Northeast United States
Date
2021
Authors
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Publisher
University of Delaware
Abstract
Tidal wetlands are important soil organic carbon (SOC) pools, however efforts are needed to accurately represent their spatial variability. We used a harmonized SOC dataset derived from seven publicly available sources to predict SOC stocks and associated uncertainty at 3 m resolution in Northeast U.S. (Maine to Delmarva) tidal wetlands. A digital soil mapping approach modeled SOC variables within distinct cover types (eight cover types) and four soil depths: 0-5 cm, 0-30 cm, 0-100 cm and 0- 200 cm. SOC stocks and uncertainty (denoted after ±) in Northeast tidal wetlands ranged from 7.03 ± 7.68 teragrams (Tg) (0-5 cm) to 150.73 ± 258.65 Tg (0-200 cm). The high marsh cover type represented the largest area and had the highest SOC stocks (2.52 ± 2.49 Tg (0-5 cm) to 56.87 ± 91.49 Tg (0-200 cm)). When evaluating SOC based upon density, pools/pannes contained the highest densities for the two surficial depths (0-5 cm, 0-30 cm) with Phragmites and terrestrial border containing the highest SOC densities for the two deeper depths (0-100, 0-200 cm). In all cases, uncertainty increased with depth which reflected decreases in available training data and a larger range of possible SOC stocks with depth. Previous estimates of total SOC for the studied region either underestimate stocks by >100% or overestimate stocks by 77% when compared to our results. This work highlights the need to incorporate soil information at deeper depths, report uncertainty, and the influence of wetland cover types for understanding the variability of SOC across these important ecosystems.
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Keywords
Soil organic carbon, Tidal wetlands, Northeast United States