Marsh vertical accretion via vegetative growth |
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| Authors: | John A Nyman Russel J Walters Ronald D Delaune William H Patrick Jr |
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| Institution: | aSchool of Renewable Natural Resources, Louisiana State University, Baton Rouge, LA 70803, USA;bDepartment of Biology, University of Louisiana at Lafayette, P.O. Box 42451, Lafayette, LA 70504-2451, USA;cWetland Biogeochemistry Institute, Louisiana State University, Baton Rouge, LA 70803, USA |
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| Abstract: | Coastal marshes accrete vertically in response to sea-level rise and subsidence. Inadequate accretion and subsequent conversion of coastal marshes to open water generally is attributed to inadequate mineral sedimentation because mineral sedimentation is widely assumed to control accretion. Using 137Cs dating to determine vertical accretion, mineral sedimentation, and organic matter accumulation, we found that accretion varied with organic accumulation rather than mineral sedimentation across a wide range of conditions in coastal Louisiana, including stable marshes where soil was 80% mineral matter. These results agreed with previous research, but no mechanism had been proposed to explain accretion via vegetative growth. In an exploratory greenhouse experiment, we found that flooding stimulated root growth above the marsh surface. These results indicated the need for additional work to determine if flooding controls accretion in some marshes by stimulating root growth on the marsh surface, rather than by mineral accumulation on the marsh surface. Restoration or management that focus on mineral sedimentation may be ineffective where a relationship between accretion and mineral sedimentation is assumed rather than tested. |
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| Keywords: | wetlands coastal marshes sea-level change accretion sedimentation peat United States Louisiana |
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