Wetland shear strength with emphasis on the impact of nutrients, sediments, and sea level rise

Jafari, Navid H.; Harris, Brian D.; Cadigan, Jack A.; Day, John W.; Sasser, Charles E.; Kemp, G. Paul; Wigand, Cathleen; Freeman, Angelina M.; Sharp, Leigh Anne; Pahl, James W.; Shaffer, Gary; Holm, Guerry O.; Lane, Robert R.

doi:10.1016/j.ecss.2019.106394

Cited by 33 publications

(23 citation statements)

References 75 publications

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“…5a) in tandem with processes actively reworking sediment may also contribute to lower soil shear strength values (Silliman et al, 2019). Enhanced nutrient loading, particularly in wetlands undergoing eutrophication, at the marsh edge weakens soils and may also influence shear strength variability at the seaward boundary (Johnson et al, 2016;Turner et al, 2020;Wigand et al, 2018). It is unclear why similar spatial patterns were not observed in the freshwater marsh locations.…”

Section: Discussionmentioning

confidence: 97%

Biophysical controls of marsh soil shear strength along an estuarine salinity gradient

Gillen

Messerschmidt²,

Kirwan³

2021

Earth Surf. Dynam.

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Abstract. Sea-level rise, saltwater intrusion, and wave erosion threaten coastal marshes, but the influence of salinity on marsh erodibility remains poorly understood. We measured the shear strength of marsh soils along a salinity and biodiversity gradient in the York River estuary in Virginia to assess the direct and indirect impacts of salinity on potential marsh erodibility. We found that soil shear strength was higher in monospecific salt marshes (5–36 kPa) than in biodiverse freshwater marshes (4–8 kPa), likely driven by differences in belowground biomass. However, we also found that shear strength at the marsh edge was controlled by sediment characteristics, rather than vegetation or salinity, suggesting that inherent relationships may be obscured in more dynamic environments. Our results indicate that York River freshwater marsh soils are weaker than salt marsh soils, and suggest that salinization of these freshwater marshes may lead to simultaneous losses in biodiversity and erodibility.

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Section: Discussionmentioning

confidence: 97%

Biophysical controls of marsh soil shear strength along an estuarine salinity gradient

Gillen

Messerschmidt²,

Kirwan³

2021

Earth Surf. Dynam.

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“…Soil shear strength was measured using a Humboldt H-4227 Shear Vane to infer a relative measure for the erodibility of marsh soils surrounding ponds (Jafari et al, 2019). We measured shear strength at four depths below the soil surface (10, 25, 35, and 55 cm) to capture a profile of soil strength above and below the vegetation rooting depth (approximately 30 cm in the study area) (Schepers, 2017).…”

Section: Characteristics Of Stable and Unstable Pondsmentioning

confidence: 99%

Mechanisms of Pond Expansion in a Rapidly Submerging Marsh

et al. 2021

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The development and expansion of ponds within otherwise vegetated coastal marshes is a primary driver of marsh loss throughout the world. Previous studies propose that large ponds expand through a wind wave-driven positive feedback, where pond edge erosion rates increase with pond size, whereas biochemical processes control the formation and expansion of smaller ponds. However, it remains unclear which mechanisms dominate at a given scale, and thus how, and how fast, ponds increase their size. Here, we use historical photographs and field measurements in a rapidly submerging microtidal marsh to quantify pond development and identify the processes involved. We find that as small ponds emerge on the marsh platform, they quickly coalesce and merge, increasing the number of larger ponds. Pond expansion rates are maximized for intermediate size ponds and decrease for larger ponds, where the contribution of wave-driven erosion is negligible. Vegetation biomass, soil shear strength, and porewater biogeochemical indices of marsh health are higher in marshes adjacent to stable ponds than in those adjacent to unstable ponds, suggesting that pond growth rates are negatively related to the health of the surrounding marsh. We find that the model of Vinent et al. (2021) correctly predicts measured pond growth rates and size distribution, which suggest the different mechanisms driving pond growth are a result of marsh drowning due to sea level rise (SLR) and can be estimated by simplified physical models. Finally, we show that all relevant processes increasing pond size can be summarized by an empirical power-law equation for pond growth which predicts the temporal change of the maximum pond size as a lower bound for the total pond area in the system. This gives a timescale for the growth of ponds by merging and thus the critical time window for interventions to prevent the irreversible pond expansion associated with large scale pond merging.

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“…Losses to OM accrual in wetland soils can reduce nutrient storage functions, wetland soil stability, and carbon sequestration (Turner et al, 2009). River diversion projects receive varying degrees of support from the scientific community because of large uncertainties in predicting impacts from river diversion derived sediment and nutrient enrichment (Quirk et al, 2019;White et al, 2019;Jafari et al, 2019). This study provided the first significant spatial data set covering over a decade of time as an opportunity to define river reconnection influence on receiving wetland soils.…”

Section: Spatial P Distributionmentioning

confidence: 99%

“…Root systems of wetland plant communities are an important structural component for highly organic soils (DeLaune and . Soils rich with organic material tend to have higher buoyancy and are less resistant to physical stress such as storms (Turner et al, 2009;Jafari et al, 2019).…”

Section: Sedimentation From Diversion Influencementioning

confidence: 99%

Spatial and temporal changes to a hydrologically-reconnected coastal wetland: Implications for restoration

Spera

White

Corstanje

2020

Estuarine, Coastal and Shelf Science

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Mississippi River Delta wetlands were isolated from river influence due to leveeing in the 1900's. Surface water diversions were primarily designed to manage salinity and maintain marsh vegetation by reintroducing Mississippi River water and nutrients into adjacent wetlands.Phosphorus (P) is a major limiting nutrient that can control productivity, but in excess can contribute to wetland eutrophic conditions and water quality degradation. Most wetland soil characterization assessments consider soil total P, however, this parameter alone cannot describe P bioavailability due to difference in organic and inorganic forms. A soil characterization of the Davis Pond diversion was done in 2007, before full-scale operation began, and in 2018 after 11 years of river loading. The top 10 cm of soil from 140 stations each year were analyzed for physiochemical properties and both organic and inorganic P forms. Mineral content is used to delineate areas of river diversion influence and compare P stocks between hydrologically isolated marsh areas and where effective river diversion reconnection took place. The river diversion resulted in a nearly 100% increase in soil mineral content and 58% increase in bulk density. The dominant source of soil P has changed from organic P to inorganic P in 29% of the wetland area, significantly associated with mineral content of the soil. Inorganic P stocks in diversion influenced areas are 9 times higher than those which remained isolated from riverine materials. The study showed that long-term addition of mineral sediments and inorganic P did not lead to deleterious effects in the wetland. This is the first study in the Mississippi River delta

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Wetland shear strength with emphasis on the impact of nutrients, sediments, and sea level rise

Cited by 33 publications

References 75 publications

Biophysical controls of marsh soil shear strength along an estuarine salinity gradient

Biophysical controls of marsh soil shear strength along an estuarine salinity gradient

Mechanisms of Pond Expansion in a Rapidly Submerging Marsh

Spatial and temporal changes to a hydrologically-reconnected coastal wetland: Implications for restoration

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