Accuracy and Precision of Tidal Wetland Soil Carbon Mapping in the Conterminous United States

Holmquist, James R.; Windham‐Myers, Lisamarie; Bliss, Norman B.; Crooks, Stephen; Morris, James T.; Megonigal, J. Patrick; Troxler, Tiffany G.; Weller, Donald E.; Callaway, John C.; Drexler, Judith Z.; Ferner, Matthew C.; Gonneea, M. E.; Kroeger, K. D.; Schile-Beers, Lisa; Woo, Isa; Buffington, Kevin J.; Breithaupt, Joshua L.; Boyd, Brandon; Brown, Lauren N.; Dix, Nicole; Hice, Lyndie A.; Horton, Benjamin P.; MacDonald, Glen M.; Moyer, Ryan P.; Reay, William G.; Shaw, Timothy A.; Smith, Erik M.; Smoak, Joseph M.; Sommerfield, Christopher K.; Thorne, Karen M.; Velinsky, David J.; Watson, E. B.; Grimes, Kristin Wilson; Woodrey, Mark S.

doi:10.1038/s41598-018-26948-7

Cited by 113 publications

(132 citation statements)

References 70 publications

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“…Mean sediment carbon density in vegetated sites averaged 0.034 ± 0.011 g C org cm −3 , similar to both the conterminous U.S. mean of 0.027 ± 0.013 g C org cm −3 (Holmquist et al, 2018a) and the global mean of 0.039 ± 0.003 g C org cm −3 for tidal wetlands (Chmura et al, 2003). The mean carbon burial rate within the high marshes/scrub-shrubs of all estuaries, 81 ± 36 g C org m −2 yr −1 , was additionally comparable to the global burial flux of 91 ± 19 g C org m −2 yr −1 (IPCC, 2013; Figure 5d).…”

Section: Blue Carbon Burial Ratessupporting

confidence: 62%

Controls on Sediment Accretion and Blue Carbon Burial in Tidal Saline Wetlands: Insights From the Oregon Coast, USA

2020

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Oregon estuaries provide important opportunities to assess controls on tidal saline wetland carbon burial and sediment accretion as both rates of relative sea level rise (RSLR; −1.4 ± 0.9 to 2.8 ± 0.8 mm yr−1) and fluvial suspended sediment load relative to estuary area (0.23 to 17 × 103 t km−2 yr−1) vary along the coast. We hypothesized that vertical accretion, measured using excess 210Pb in least‐disturbed wetlands within seven Oregon estuaries, would vary with either RSLR or sediment load relative to estuary area, and carbon burial would correlate strongly to sediment accretion. Mean rates of high marsh accretion (0.8 ± 0.2 to 4.1 ± 0.2 mm yr−1) indicate that Oregon tidal wetlands have mainly kept pace with twentieth‐century RSLR with the exception that the accretionary balance in the central coast is negative, suggesting drowning. Experiencing the fastest rates of RSLR, central‐coast estuaries may foreshadow the fates of other Oregon estuaries under future accelerated sea level rise. Comparison of mass accumulation rates with sediment loads, however, indicates low trapping efficiency and therefore no fluvial sediment limitation. Thus, nonlinear feedback between RSLR and sediment accretion may enhance wetland resistance to drowning. Among wetlands keeping pace with or exceeding RSLR, sediment accretion displays no significant relationship with elevation but rather appears controlled by both the rate of RSLR and relative sediment load, highlighting the importance of incorporating both factors into future studies of tidal saline wetlands. Carbon burial rates, controlled by sediment accretion, will likely increase with future accelerated sea level rise.

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Section: Blue Carbon Burial Ratessupporting

confidence: 62%

Controls on Sediment Accretion and Blue Carbon Burial in Tidal Saline Wetlands: Insights From the Oregon Coast, USA

2020

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“…Carbon content averaged 13.9 ± 0.5%, and carbon densities averaged 0.0270 ± 0.0009 g C/cm 3 (Unger et al, ; Table S2), yielding a total POC load from the marsh complex to the estuary of 1,291 Mg C/year. Note that this carbon density value matches the CONUS‐wide carbon density estimate of Holmquist et al ().…”

Section: Resultssupporting

confidence: 84%

Role of Tidal Wetland Stability in Lateral Fluxes of Particulate Organic Matter and Carbon

et al. 2019

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Tidal wetland fluxes of particulate organic matter and carbon (POM, POC) are important terms in global budgets but remain poorly constrained. Given the link between sediment fluxes and wetland stability, POM and POC fluxes should also be related to stability. We measured POM and POC fluxes in eight microtidal salt marsh channels, with net POM fluxes ranging between −121 ± 33 (export) and 102 ± 28 (import) g OM·m−2·year−1 and net POC fluxes ranging between −52 ± 14 and 43 ± 12 g C·m−2·year−1. A regression employing two measures of stability, the unvegetated‐vegetated marsh ratio (UVVR) and elevation, explained >95% of the variation in net fluxes. The regression indicates that marshes with lower elevation and UVVR import POM and POC while higher elevation marshes with high UVVR export POM and POC. We applied these relationships to marsh units within Barnegat Bay, New Jersey, USA, finding a net POM import of 2,355 ± 1,570 Mg OM/year (15 ± 10 g OM·m−2·year−1) and a net POC import of 1,263 ± 632 Mg C/year (8 ± 4 g C·m−2·year−1). The magnitude of this import was similar to an estimate of POM and POC export due to edge erosion (−2,535 Mg OM/year and − 1,291 Mg C/year), suggesting that this system may be neutral from a POM and POC perspective. In terms of a net budget, a disintegrating wetland should release organic material, while a stable wetland should trap material. This study quantifies that concept and demonstrates a linkage between POM/POC flux and geomorphic stability.

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“…Therefore, some assumptions are necessary for estimating and comparing OC burial rates between the MH and 210 Pb techniques. We assumed that the OC density of the MH cores was the same as that of the 210 Pb cores, which is supported by both regional and national observations that OC density in tidal wetlands does not have a depth trend (Breithaupt et al, 2014;Holmquist et al, 2018). Therefore, if the MH accretion rate was 50% of the 210 Pb accretion rate for the corresponding time interval, we assumed that the MH OC burial rate was also 50% of the 210 Pb OC burial rate.…”

Section: Comparing Oc Burial Rates With 210 Pb and Mhsmentioning

confidence: 93%

Increasing Rates of Carbon Burial in Southwest Florida Coastal Wetlands

et al. 2020

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Rates of organic carbon (OC) burial in some coastal wetlands appear to be greater in recent years than they were in the past. Possible explanations include ongoing mineralization of older OC or the influence of an unaccounted‐for artifact of the methods used to measure burial rates. Alternatively, the trend may represent real acceleration in OC burial. We quantified OC burial rates of mangrove and coastal freshwater marshes in southwest Florida through a comparison of rates derived from 210Pb, 137Cs, and surface marker horizons. Age/depth profiles of lignin: OC were used to assess whether down‐core remineralization had depleted the OC pool relative to lignin, and lignin phenols were used to quantify the variability of lignin degradation. Over the past 120 years, OC burial rates at seven sites increased by factors ranging from 1.4 to 6.2. We propose that these increases represent net acceleration. Change in relative sea‐level rise is the most likely large‐scale driver of acceleration, and sediment deposition from large storms can contribute to periodic increases. Mangrove sites had higher OC and lignin burial rates than marsh sites, indicating inherent differences in OC burial factors between the two habitat types. The higher OC burial rates in mangrove soils mean that their encroachment into coastal freshwater marshes has the potential to increase burial rates in those locations even more than might be expected from the acceleration trends. Regionally, these findings suggest that burial represents a substantially growing proportion of the coastal wetland carbon budget.

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Accuracy and Precision of Tidal Wetland Soil Carbon Mapping in the Conterminous United States

Cited by 113 publications

References 70 publications

Controls on Sediment Accretion and Blue Carbon Burial in Tidal Saline Wetlands: Insights From the Oregon Coast, USA

Controls on Sediment Accretion and Blue Carbon Burial in Tidal Saline Wetlands: Insights From the Oregon Coast, USA

Role of Tidal Wetland Stability in Lateral Fluxes of Particulate Organic Matter and Carbon

Increasing Rates of Carbon Burial in Southwest Florida Coastal Wetlands

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