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The role of the upper tidal estuary in wetland blue carbon storage and flux

350 210 Stroud Water Research Center

Krauss K.W., G.B. Noe, J.A. Duberstein, W.H. Conner, C.L. Stagg, N. Cormier, M.C. Jones, C.E. Bernhardt, B.G. Lockaby, A.S. From, T.W. Doyle, R.H. Day, S.H. Ensign, K.N. Pierfelice, C.R. Hupp, A.T. Chow, and J.L. Whitbeck. 2018. Global Biogeochemical Cycles 32:817–839.

https://doi.org/10.1029/2018GB005897

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.