The importance of episodic ebullition methane losses from three peatland microhabitats: a controlled‐environment study

Green, S. M.; Baird, Andrew J.

doi:10.1111/ejss.12015

Cited by 20 publications

(18 citation statements)

References 28 publications

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“…Across all three of our sites, our measurement of bubble accumulation was dominated by episodic ebullition events, which accounted for ~87% of the total seasonal bubble capture. This is in contrast to the findings in temperate peatlands, where episodic ebullition contributed less to the total CH 4 flux than steady state ebullition [ Green and Baird , ]. At our sites, few bubble traps contributed to episodic ebullition (hot spots); most of the traps in our measurement network were not associated with any episodic events.…”

Section: Discussioncontrasting

confidence: 99%

Controls on methane released through ebullition in peatlands affected by permafrost degradation

et al. 2014

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Permafrost thaw in peat plateaus leads to the flooding of surface soils and the formation of collapse scar bogs, which have the potential to be large emitters of methane (CH 4 ) from surface peat as well as deeper, previously frozen, permafrost carbon (C). We used a network of bubble traps, permanently installed 20 cm and 60 cm beneath the moss surface, to examine controls on ebullition from three collapse bogs in interior Alaska. Overall, ebullition was dominated by episodic events that were associated with changes in atmospheric pressure, and ebullition was mainly a surface process regulated by both seasonal ice dynamics and plant phenology. The majority (>90%) of ebullition occurred in surface peat layers, with little bubble production in deeper peat. During periods of peak plant biomass, bubbles contained acetate-derived CH 4 dominated (>90%) by modern C fixed from the atmosphere following permafrost thaw. Post-senescence, the contribution of CH 4 derived from thawing permafrost C was more variable and accounted for up to 22% (on average 7%), in the most recently thawed site. Thus, the formation of thermokarst features resulting from permafrost thaw in peatlands stimulates ebullition and CH 4 release both by creating flooded surface conditions conducive to CH 4 production and bubbling as well as by exposing thawing permafrost C to mineralization.

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Section: Discussioncontrasting

confidence: 99%

Controls on methane released through ebullition in peatlands affected by permafrost degradation

et al. 2014

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“…In the field, peat samples approximately 160 mm height and 160 mm diameter were cut out using the “scissor method” reported by Green and Baird [, ] which minimizes damage to the peat sample. Each sample was placed within a plastic container and transported to the laboratory where it was kept in cold storage (4°C).…”

Section: Methodsmentioning

confidence: 99%

The effect of pore structure on ebullition from peat

2016

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The controls on methane (CH 4 ) bubbling (ebullition) from peatlands are uncertain, but evidence suggests that physical factors related to gas transport and storage within the peat matrix are important. Variability in peat pore size and the permeability of layers within peat can produce ebullition that ranges from steady to erratic in time and can affect the degree to which CH 4 bubbles bypass consumption by methanotrophic bacteria and enter the atmosphere. Here we investigate the role of peat structure on ebullition in structurally different peats using a physical model that replicates bubble production using air injection into peat. We find that the frequency distributions of number of ebullition events per time and the magnitude of bubble loss from the physical model were similar in shape to ebullition from peatlands and incubated peats. This indicates that the physical model could be a valid proxy for naturally occurring ebullition from peat. For the first time, data on bubble sizes from peat were collected to conceptualize ebullition, and we find that peat structure affects bubble sizes. Using a new method to measure peat macrostructure, we collected evidence that supports the hypothesis that structural differences in peat determine if bubble release is steady or erratic and extreme. Collected pore size data suggest that erratic ebullition occurs when large amounts of gas stored at depth easily move through shallower layers of open peat. In contrast, steady ebullition occurs when dense shallower layers of peat regulate the flow of gas emitted from peat. RAMIREZ ET AL.THE EFFECT OF PORE STRUCTURE ON BUBBLES 1646 PUBLICATIONS

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“…The mechanics of bubble release from soil pores (buoyancy forces overcoming capillary resistive forces) are too complex to consider explicitly within the modeled pore networks [ Chen and Slater , ; Painter et al , ]. Recent studies highlight the important role of pore structure (of peat) in regulating bubble storage and release dynamics with characteristically intermittent ebullition events in time and heterogeneous in space [ Glaser , ; Green and Baird , ; Ramirez et al , ]. Evidence suggests that changes in overlaying water pressure (e.g., water table or tides) affect rates of gas bubble ebullition from the soil or sediments [ Chanton et al , ].…”

Section: Theoretical Considerationsmentioning

confidence: 99%

Mechanistic modeling of microbial interactions at pore to profile scale resolve methane emission dynamics from permafrost soil

Ebrahimi

2017

JGR Biogeosciences

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The sensitivity of polar regions to raising global temperatures is reflected in rapidly changing hydrological processes associated with pronounced seasonal thawing of permafrost soil and increased biological activity. Of particular concern is the potential release of large amounts of soil carbon and stimulation of other soil‐borne greenhouse gas emissions such as methane. Soil methanotrophic and methanogenic microbial communities rapidly adjust their activity and spatial organization in response to permafrost thawing and other environmental factors. Soil structural elements such as aggregates and layering affect oxygen and nutrient diffusion processes thereby contributing to methanogenic activity within temporal anoxic niches (hot spots). We developed a mechanistic individual‐based model to quantify microbial activity dynamics in soil pore networks considering transport processes and enzymatic activity associated with methane production in soil. The model was upscaled from single aggregates to the soil profile where freezing/thawing provides macroscopic boundary conditions for microbial activity at different soil depths. The model distinguishes microbial activity in aerate bulk soil from aggregates (or submerged profile) for resolving methane production and oxidation rates. Methane transport pathways by diffusion and ebullition of bubbles vary with hydration dynamics. The model links seasonal thermal and hydrologic dynamics with evolution of microbial community composition and function affecting net methane emissions in good agreement with experimental data. The mechanistic model enables systematic evaluation of key controlling factors in thawing permafrost and microbial response (e.g., nutrient availability and enzyme activity) on long‐term methane emissions and carbon decomposition rates in the rapidly changing polar regions.

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The importance of episodic ebullition methane losses from three peatland microhabitats: a controlled‐environment study

Cited by 20 publications

References 28 publications

Controls on methane released through ebullition in peatlands affected by permafrost degradation

Controls on methane released through ebullition in peatlands affected by permafrost degradation

The effect of pore structure on ebullition from peat

Mechanistic modeling of microbial interactions at pore to profile scale resolve methane emission dynamics from permafrost soil

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