Understanding the fate of soil organic matter in submerging coastal wetland soils: A microcosm approach

Steinmuller, Havalend E.; Dittmer, Kyle M.; White, John R.; Chambers, Lisa G.

doi:10.1016/j.geoderma.2018.08.020

Cited by 38 publications

(20 citation statements)

References 46 publications

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“…There is much concern about the potential for SLR to cause degradation and loss of wetland SOM (Hopkinson et al, ; Steinmuller et al, ), including coastal peat collapse (Chambers et al, ) in the coming century. However, these data and our analysis suggest that OC burial in coastal wetlands may be more responsive to SLR than previously thought, including periodic assistance from large storms.…”

Section: Resultsmentioning

confidence: 99%

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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Section: Resultsmentioning

confidence: 99%

Increasing Rates of Carbon Burial in Southwest Florida Coastal Wetlands

et al. 2020

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“…For example, a laboratory study mimicking the introduction of aerobic coastal waters into a brackish marsh soil found a 66% increase in CO 2 production (Steinmuller et al. ). Extensive investigations have addressed the impacts of NO 3 − loading (or NO 3 − + phosphate) on coastal wetland systems, which combines the addition of an alternative electron acceptor with commonly limiting nutrients.…”

Section: Mechanisms Of Coastal Wetland Peat Collapsementioning

confidence: 99%

“…In coastal wetlands, significant de-watering is less likely, but soils may still be exposed to O 2 dissolved in the water column, such as an influx of oxygenated seawater along the wetland edge, or a newly formed open water pond. For example, a laboratory study mimicking the introduction of aerobic coastal waters into a brackish marsh soil found a 66% increase in CO 2 production (Steinmuller et al 2018). Extensive investigations have addressed the impacts of NO 3 À loading (or NO 3 À + phosphate) on coastal wetland systems, which combines the addition of an alternative electron acceptor with commonly limiting nutrients.…”

Section: Soil Organic Matter Compaction and Transformationmentioning

confidence: 99%

“…This represents an important loss of habitat and coastal resources, while also exposing a vast reservoir of previously sequestered soil carbon (C) and nutrients to oxygenated coastal waters. Aerobic aquatic environments, such as shallow bays and ponds, can increase the potential for soil C mineralization (conversion to CO 2 ) and nitrogen (N) and phosphorus (P) release (Steinmuller et al 2018). Implications include a climate feedback that has not yet been accounted for in global and regional C models, additional dissolved inorganic C (DIC) within the coastal zone that could contribute to pH shifts, and increased potential for coastal eutrophication with the additional source of N and P.…”

Section: Introductionmentioning

confidence: 99%

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Toward a mechanistic understanding of “peat collapse” and its potential contribution to coastal wetland loss

Chambers

Steinmuller

Breithaupt

2019

Ecology

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Coastal wetlands are susceptible to loss in both health and extent via stressors associated with global climate change and anthropogenic disturbance. Peat collapse may represent an additional phenomenon contributing to coastal wetland loss in organic‐rich soils through rapid vertical elevation decline. However, the term “peat collapse” has been inconsistently used in the literature, leading to ambiguities regarding the mechanisms, timing, and spatial extent of its contribution to coastal wetland loss. For example, it is unclear whether peat collapse is distinct from general subsidence, or what biogeochemical changes or sequence of events may constitute peat collapse. A critical analysis of peer‐reviewed literature related to peat collapse was supplemented with fundamental principles of soil physics and biogeochemistry to develop a conceptual framework for coastal wetland peat collapse. We propose that coastal wetland peat collapse is a specific type of shallow subsidence unique to highly organic soils in which a loss of soil strength and structural integrity contributes to a decline in elevation, over the course of a few months to a few years, below the lower limit for emergent plant growth and natural recovery. We further posit that coastal wetland peat collapse is driven by severe stress or death of the vegetation, which compromises the supportive structure roots provide to low‐density organic soils and shifts the carbon balance of the ecosystem toward a net source, as mineralization is no longer offset by sequestration. Under these conditions, four mechanisms may contribute to peat collapse: (1) compression of gas‐filled pore spaces within the soil during dry‐down conditions; (2) deconsolidation of excessively waterlogged peat, followed by transport; (3) compaction of aerenchyma tissue in wetland plant roots, and possibly collapse of root channels; and (4) acceleration of soil mineralization due to the addition of labile carbon (dying roots), oxygen (decreased flooding), nutrients (eutrophication), or sulfate (saltwater intrusion). Scientists and land managers should focus efforts on monitoring vegetation health across the coastal landscape as an indicator for peat collapse vulnerability and move toward codifying the term “peat collapse” in the scientific literature. Once clarified, the contribution of peat collapse to coastal wetland loss can be evaluated.

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“…Ca) adsorbed inorganic pools (Romanyà and Rovira 2009;Alvarez et al 2018). Microbial mineralization, transformation and exchange of both N and P is relatively fast in non-flooded soil with deep oxygen penetration (Steinmuller et al 2019). However, the prevailing anoxic conditions in soil submerged by seawater substantially diminishes organic matter reactivity (Steinmuller et al 2019) and adsorption capacity of DIN and DIP, particularly in deeper soils (Mohanty et al 2013).…”

Section: N and P Exchange Patterns And The Underlying Mechanismsmentioning

confidence: 99%