The Role of the Upper Tidal Estuary in Wetland Blue Carbon Storage and Flux. Issue 5 (16th May 2018)

• Record Type: Journal Article
• Authors: Krauss, Ken W.; Noe, Gregory B.; Duberstein, Jamie A.; Conner, William H.; Stagg, Camille L.; Cormier, Nicole; Jones, Miriam C.; Bernhardt, Christopher E.; Graeme Lockaby, B.; From, Andrew S.; Doyle, Thomas W.; Day, Richard H.; Ensign, Scott H.; Pierfelice, Katherine N.; Hupp, Cliff R.; Chow, Alex T.; Whitbeck, Julie L.
• Is Part Of: Global biogeochemical cycles. Volume 32:Issue 5(2018:May)
• Page Start: 817
• Page End: 839
• Publication Date: 2018-05-16
• Subjects: Wetland -- Swamp forest -- Tide -- Carbon budget -- Marsh; Biogeochemical cycles -- Periodicals; Electronic journals; 577.1405
• DOI: 10.1029/2018GB005897
• Languages: English
• ISSNs: 0886-6236

Abstract

Abstract: Carbon (C) standing stocks, C mass balance, and soil C burial in tidal freshwater forested wetlands (TFFW) and TFFW transitioning to low‐salinity marshes along the upper estuary are not typically included in "blue carbon" accounting, but may represent a significant C sink. Results from two salinity transects along the tidal Waccamaw and Savannah rivers of the U.S. Atlantic Coast show that total C standing stocks were 322–1, 264 Mg C/ha among all sites, generally shifting to greater soil storage as salinity increased. Carbon mass balance inputs (litterfall, woody growth, herbaceous growth, root growth, and surface accumulation) minus C outputs (surface litter and root decomposition, gaseous C) over a period of up to 11 years were 340–900 g C · m −2 · year −1 . Soil C burial was variable (7–337 g C · m −2 · year −1 ), and lateral C export was estimated as C mass balance minus soil C burial as 267–849 g C · m −2 · year −1 . This represents a large amount of C export to support aquatic biogeochemical transformations. Despite reduced C persistence within emergent vegetation, decomposition of organic matter, and higher lateral C export, total C storage increased as forests converted to marsh with salinization. These tidal river wetlands exhibited high N mineralization in salinity‐stressed forested sites and considerable P mineralization in low‐salinity marshes. Large C standing stocks and rates of C sequestration suggest that TFFW and oligohaline marshes are considerably important globally to coastal C dynamics and in facilitating energy transformations in areas of the world in which they occur. Plain Language Summary: Tidal wetlands that occur along the upper reaches of river‐associated estuaries are not normally considered when determining the amount of carbon stored, exchanged, or exported from terrestrial ecosystems globally. Examples of these wetland types include tidal freshwater forested wetlands and low‐salinity marshes, as well as wetlands at different stages of transition between forest and marsh as salinity intrudes and sea levels rise. However, these tidal wetlands store more carbon than many coastal wetland types documented throughout the world, including classically defined "blue carbon" wetlands, and they support high rates of annual carbon sequestration (uptake of CO2 from the atmosphere) and lateral carbon export into aquatic environments that can influence critical near‐shore and marine energy transformations. Key Points: C dynamics in upper tidal estuarine wetlands are understudied and poorly understood globally Upper estuarine wetlands serve as significant C sinks and transformers of C along salinity and structural gradients Accurate global wetland C accounting depends on inclusion of the upper estuary, which stores 322–1, 264 Mg C/ha