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Vegetation Zonation Predicts Soil Carbon Mineralization and Microbial Communities in Southern New England Salt Marshes


Coastal marshes are important blue carbon reservoirs, but it is unclear how vegetation shifts associated with tidal restoration and sea level rise alter soil microbial respiration rates and bacterial community composition. Within 20 Connecticut salt marshes (10 without tidal restrictions, 10 tidally restored), we sampled three vegetation zones dominated by Spartina alterniflora (short-form, < 30 cm tall), S. patens, and Phragmites australis to estimate microbial respiration rates (SIR, substrate-induced respiration; carbon mineralization), root zone bacterial 16S rRNA genes, and a suite of plant and soil characteristics. Carbon density was greater in unrestricted marshes than tidally restored marshes and was the only parameter that differed among sites with varying restoration histories. We observed strong differences among vegetation zones, with vegetation being a top predictor of both SIR and carbon mineralization. Electrical conductivity (EC) was also a top predictor for SIR, and we observed strong, positive correlations between EC and both metrics of microbial respiration, with elevated rates in more frequently inundated S. alterniflora than P. australis zones. We also observed distinct root zone microbial communities associated with vegetation zones, with greater abundance of sulfate-reducing bacteria in Spartina spp. zones. Our findings suggest that dominant salt marsh vegetation zones are useful indicators of hydrologic conditions and could be used to estimate microbial respiration rates; however, it is still unclear whether differences in microbial respiration and community composition among vegetation zones are driven by plant community, environmental conditions, or their interactions.

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This manuscript is a resulting product from project R/CMB-42-CTNY funded under award LI96172701, U.S. Environmental Protection Agency, on behalf of Connecticut Sea Grant, and in collaboration with New York Sea Grant. The statements, findings, conclusions, views and recommendations are those of the authors and do not necessarily reflect the views of any of those organizations. This project was also supported by the Connecticut Institute for Resilience and Climate Adaptation’s (CIRCA) Matching Funds Program. BS was supported by the USDA National Institute of Food and Agriculture Hatch Grant 1006211. Roger Wolfe and Harry Yamalis provided logistical support, and Branford Land Trust, Groton Long Point Association, Milford Land Trust and the town of Guilford granted us access to their property. Alaina Bisson, Kayleigh Granville, Olivia Johnson, and Samantha Walker assisted with field sampling and laboratory processing.

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Correspondence to B. A. Lawrence.

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The authors declare no competing interests.

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Communicated by Lijun Hou

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Barry, A., Ooi, S.K., Helton, A.M. et al. Vegetation Zonation Predicts Soil Carbon Mineralization and Microbial Communities in Southern New England Salt Marshes. Estuaries and Coasts 45, 168–180 (2022).

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