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Spatial Variability in Deep SOC Storage in Georgia (USA) Salt Marshes.

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Title: Spatial Variability in Deep SOC Storage in Georgia (USA) Salt Marshes.
Authors: Ahrens, M. B.1 (AUTHOR), Sharma, R.2 (AUTHOR), Hao, J.3 (AUTHOR), Mishra, D. R.2 (AUTHOR), Kim, S.2 (AUTHOR), Ramaswamy, L.2 (AUTHOR), Sutter, L. A.1 (AUTHOR) sutterl@uncw.edu
Source: Journal of Geophysical Research. Biogeosciences. Feb2026, Vol. 131 Issue 2, p1-18. 18p.
Subject Terms: *Salt marshes, *Carbon in soils, *Carbon sequestration, Spatial variation, Radiocarbon dating, Density, Stable isotopes
Geographic Terms: United States, Georgia
Abstract: Coastal Georgia's (USA) salt marshes function as soil organic carbon (SOC) sinks because of their high primary productivity and slow decomposition rates. Quantifying SOC stocks is essential to establish a baseline for long‐term SOC trends and to highlight their capacity for long‐term carbon (C) sequestration. From 2021 to 2023, 28 soil cores (25–165 cm deep) were collected from six Georgia marshes and analyzed for SOC%, total nitrogen (N), bulk density (BD), and particle size by horizon. Stable C isotopes were examined in three marshes to identify C sources, and a small subset of samples was analyzed for radiocarbon. Surface SOC (0–5 cm) ranged from 1.4% to 8.5% (SE = 0.28), while SOC across all depths ranged from 0.08% to 8.8% (mean = 3.7%, SE = 0.07). Mainland sites exhibited significantly higher surface SOC than island sites and were dated to be younger with radiocarbon testing. Stable isotopes indicated shifts in C3 and C4 vegetation dominance over time. Georgia salt marshes store an estimated 16,777,000 Mg C to 70 cm depth. Calculated to 60 cm, the mean SOC density was 88.5 Mg C ha−1, approximately 55% of the total U.S. national average for tidal salt marshes. Variations in SOC content were primarily explained by clay content, depth, and BD. These results provide SOC estimates for Georgia's salt marshes and help address a regional data gap for southeastern U.S. coastal wetlands, underscoring the importance of broad scale assessments for improving national C accounting and understanding spatial variability in C storage. Plain Language Summary: Salt marshes buffer climate change by capturing greenhouse gases, storing carbon in plants, and converting the plants into soil, called soil organic carbon, or SOC. We analyzed soil from 28 cores taken from six salt marshes across Georgia (USA) to determine how much SOC they store and what factors might influence that storage. Physical soil properties were measured, as was nitrogen to help detect historical events. In three marshes, we used the varying mass of atoms (stable carbon isotopes) to identify carbon sources, and a smaller set of samples was dated using a technique (radiocarbon) that can estimate formerly living things to be about 50,000 years old. SOC varied mainly with clay content, depth, and bulk density. Contrary to what we expected, surface soils in mainland marshes were younger and contained more SOC than those on islands, perhaps from deposits made from the river, which shows that carbon storage differs across marsh settings. Overall, Georgia salt marshes store an average of 88.5 Mg carbon per hectare to 60 cm depth, just over half the U.S. average for salt marshes. These results highlight the need for more state and regional level assessments to understand how salt marshes store carbon differently across various locations. Key Points: Soil organic carbon (SOC) in Georgia (USA) varies with bulk density, particle size, and depthSOC concentrations at the surface are higher in marshes on the mainland than they are in marshes on islandGeorgia salt marsh SOC density is 55% of the national average for tidal salt marshes [ABSTRACT FROM AUTHOR]
Copyright of Journal of Geophysical Research. Biogeosciences is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Spatial Variability in Deep SOC Storage in Georgia (USA) Salt Marshes.
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  Data: <searchLink fieldCode="JN" term="%22Journal+of+Geophysical+Research%2E+Biogeosciences%22">Journal of Geophysical Research. Biogeosciences</searchLink>. Feb2026, Vol. 131 Issue 2, p1-18. 18p.
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  Data: *<searchLink fieldCode="DE" term="%22Salt+marshes%22">Salt marshes</searchLink><br />*<searchLink fieldCode="DE" term="%22Carbon+in+soils%22">Carbon in soils</searchLink><br />*<searchLink fieldCode="DE" term="%22Carbon+sequestration%22">Carbon sequestration</searchLink><br /><searchLink fieldCode="DE" term="%22Spatial+variation%22">Spatial variation</searchLink><br /><searchLink fieldCode="DE" term="%22Radiocarbon+dating%22">Radiocarbon dating</searchLink><br /><searchLink fieldCode="DE" term="%22Density%22">Density</searchLink><br /><searchLink fieldCode="DE" term="%22Stable+isotopes%22">Stable isotopes</searchLink>
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  Label: Geographic Terms
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  Data: <searchLink fieldCode="DE" term="%22United+States%22">United States</searchLink><br /><searchLink fieldCode="DE" term="%22Georgia%22">Georgia</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Coastal Georgia's (USA) salt marshes function as soil organic carbon (SOC) sinks because of their high primary productivity and slow decomposition rates. Quantifying SOC stocks is essential to establish a baseline for long‐term SOC trends and to highlight their capacity for long‐term carbon (C) sequestration. From 2021 to 2023, 28 soil cores (25–165 cm deep) were collected from six Georgia marshes and analyzed for SOC%, total nitrogen (N), bulk density (BD), and particle size by horizon. Stable C isotopes were examined in three marshes to identify C sources, and a small subset of samples was analyzed for radiocarbon. Surface SOC (0–5 cm) ranged from 1.4% to 8.5% (SE = 0.28), while SOC across all depths ranged from 0.08% to 8.8% (mean = 3.7%, SE = 0.07). Mainland sites exhibited significantly higher surface SOC than island sites and were dated to be younger with radiocarbon testing. Stable isotopes indicated shifts in C3 and C4 vegetation dominance over time. Georgia salt marshes store an estimated 16,777,000 Mg C to 70 cm depth. Calculated to 60 cm, the mean SOC density was 88.5 Mg C ha−1, approximately 55% of the total U.S. national average for tidal salt marshes. Variations in SOC content were primarily explained by clay content, depth, and BD. These results provide SOC estimates for Georgia's salt marshes and help address a regional data gap for southeastern U.S. coastal wetlands, underscoring the importance of broad scale assessments for improving national C accounting and understanding spatial variability in C storage. Plain Language Summary: Salt marshes buffer climate change by capturing greenhouse gases, storing carbon in plants, and converting the plants into soil, called soil organic carbon, or SOC. We analyzed soil from 28 cores taken from six salt marshes across Georgia (USA) to determine how much SOC they store and what factors might influence that storage. Physical soil properties were measured, as was nitrogen to help detect historical events. In three marshes, we used the varying mass of atoms (stable carbon isotopes) to identify carbon sources, and a smaller set of samples was dated using a technique (radiocarbon) that can estimate formerly living things to be about 50,000 years old. SOC varied mainly with clay content, depth, and bulk density. Contrary to what we expected, surface soils in mainland marshes were younger and contained more SOC than those on islands, perhaps from deposits made from the river, which shows that carbon storage differs across marsh settings. Overall, Georgia salt marshes store an average of 88.5 Mg carbon per hectare to 60 cm depth, just over half the U.S. average for salt marshes. These results highlight the need for more state and regional level assessments to understand how salt marshes store carbon differently across various locations. Key Points: Soil organic carbon (SOC) in Georgia (USA) varies with bulk density, particle size, and depthSOC concentrations at the surface are higher in marshes on the mainland than they are in marshes on islandGeorgia salt marsh SOC density is 55% of the national average for tidal salt marshes [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Journal of Geophysical Research. Biogeosciences is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.1029/2025JG008762
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 18
        StartPage: 1
    Subjects:
      – SubjectFull: Salt marshes
        Type: general
      – SubjectFull: Carbon in soils
        Type: general
      – SubjectFull: Carbon sequestration
        Type: general
      – SubjectFull: Spatial variation
        Type: general
      – SubjectFull: Radiocarbon dating
        Type: general
      – SubjectFull: Density
        Type: general
      – SubjectFull: Stable isotopes
        Type: general
      – SubjectFull: United States
        Type: general
      – SubjectFull: Georgia
        Type: general
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      – TitleFull: Spatial Variability in Deep SOC Storage in Georgia (USA) Salt Marshes.
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              Text: Feb2026
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              Y: 2026
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