Pathways of aeration and the mechanisms and beneficial effects of humidity- and Venturi-induced convections in Phragmites australis (Cav.) Trin. ex Steud.

Armstrong, J.; Armstrong, W.; Beckett, P. M.; Halder, Joydev; Lythe, S.; Holt, R. W.; Sinclair, A. H.

doi:10.1016/0304-3770(96)01044-3

Cited by 143 publications

(103 citation statements)

References 18 publications

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“…Methane emission was higher than methanogenesis during the day, showing that CH 4 accumulated in the sediments during the night and was emitted to the atmosphere mainly through the plants during the day. Peaks in emission rates were associated with high solar illumination, high air temperatures and low humidities, factors that are known to stimulate pressurised convective flow in P. australis (Armstrong et al, 1996;Brix et al, 1996). We therefore, conclude that the diurnal pattern observed in CH 4 emission was largely due to the diurnal changes in internal convective flow in the plants.…”

Section: Discussionmentioning

confidence: 70%

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Methanogenesis and methane emissions: effects of water table, substrate type and presence of Phragmites australis

1999

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Section: Discussionmentioning

confidence: 70%

“…ex Steud.) is a dominant plant species in much of the land-water ecotone throughout Europe, and is known to have particularly high rates of convective flow (Brix et al, 1992;Armstrong et al, 1996). Phragmitesdominated wetlands therefore provide a significant source of CH 4 emission to the atmosphere (Brix et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

Methanogenesis and methane emissions: effects of water table, substrate type and presence of Phragmites australis

1999

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“…The pronounced diurnal methane emission dynamics from BA Phragmites-Carex and GK Phragmites-Lemna with 5-fold flux increases from morning to midday result from active air transport in Phragmites australis aerenchyma in the growing season driven by sun light (Armstrong and Armstrong, 1991;Brix et al, 1992;Armstrong et al, 1996). In contrast to other studies ( Van der Nat and Middelburg, 2000;Günther et al, 2013) we did not find a significant impact of chamber transparency on measured methane emission rates, maybe because enclosed plants were connected by rhizomes with culms outside the chamber.…”

Section: Robustness Of Annual Ghg Balances 421 Methanementioning

confidence: 99%

Water level, vegetation composition, and plant productivity explain greenhouse gas fluxes in temperate cutover fens after inundation

et al. 2016

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Abstract. Peat extraction leaves a land surface with a strong relief of deep cutover areas and higher ridges. Rewetting inundates the deep parts, while less deeply extracted zones remain at or above the water level. In temperate fens the flooded areas are colonized by helophytes such as Eriophorum angustifolium, Carex spp., Typha latifolia or Phragmites australis dependent on water depth. Reeds of Typha and Phragmites are reported as large sources of methane, but data on net CO 2 uptake are contradictory for Typha and rare for Phragmites. Here, we analyze the effect of vegetation, water level and nutrient conditions on greenhouse gas (GHG) emissions for representative vegetation types along water level gradients at two rewetted cutover fens (mesotrophic and eutrophic) in Belarus. Greenhouse gas emissions were measured campaign-wise with manual chambers every 2 to 4 weeks for 2 years and interpolated by modelling.All sites had negligible nitrous oxide exchange rates. Most sites were carbon sinks and small GHG sources. Methane emissions generally increased with net ecosystem CO 2 uptake. Mesotrophic small sedge reeds with water table around the land surface were small GHG sources in the range of 2.3 to 4.2 t CO 2 eq. ha −1 yr −1 . Eutrophic tall sedge -Typha latifolia reeds on newly formed floating mats were substantial net GHG emitters in the range of 25.1 to 39.1 t CO 2 eq. ha −1 yr. They represent transient vegetation stages. Phragmites reeds ranged between −1.7 to 4.2 t CO 2 eq. ha −1 yr −1 with an overall mean GHG emission of 1.3 t CO 2 eq. ha −1 yr −1 . The annual CO 2 balance was best explained by vegetation biomass, which includes the role of vegetation composition and species. Methane emissions were obviously driven by biological activity of vegetation and soil organisms.Shallow flooding of cutover temperate fens is a suitable measure to arrive at low GHG emissions. Phragmites australis establishment should be promoted in deeper flooded areas and will lead to moderate, but variable GHG emissions or even occasional sinks. The risk of large GHG emissions is higher for eutrophic than mesotrophic peatlands. Nevertheless, flooding of eutrophic temperate fens still represents a safe GHG mitigation option because even the hotspot of our study, the floating tall sedge -Typha latifolia reeds, did not exceed the typical range of GHG emissions from drained fen grasslands and the spatially dominant Phragmites australis reed emitted by far less GHG than drained fens.

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“…Eriophorum sedges at the Mer Bleue bog possess aerenchymatous tissues that act as gas conduits between the soil and atmosphere (Greenup et al, 2000). By generating a pressure gradient, turbulence can induce a plant-mediated convective flow of gases from deep in the root zone to the atmosphere via the aerenchyma (Armstrong et al, 1996). In addition, the large pool of CH 4 stored belowground causes the sedge sites to be highly susceptible to advective transport mechanisms (Forbrich et al, 2010).…”

Section: The Influence Of Atmospheric Turbulence and Chamber Deploymementioning

confidence: 99%

The effect of atmospheric turbulence and chamber deployment period on autochamber CO<sub>2</sub> and CH<sub>4</sub> flux measurements in an ombrotrophic peatland

et al. 2012

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Abstract. Accurate quantification of soil-atmosphere gas exchange is essential for understanding the magnitude and controls of greenhouse gas emissions. We used an automatic, closed, dynamic chamber system to measure the fluxes of CO 2 and CH 4 for several years at the ombrotrophic Mer Bleue peatland near Ottawa, Canada and found that atmospheric turbulence and chamber deployment period had a considerable influence on the observed flux rates. With a short deployment period of 2.5 min, CH 4 flux exhibited strong diel patterns and both CH 4 and nighttime CO 2 effluxes were highly and negatively correlated with ambient friction velocity as were the CO 2 concentration gradients in the top 20 cm of peat. This suggests winds were flushing the very porous and relatively dry near-surface peat layers and reducing the belowground gas concentration gradient, which then led to flux underestimations owing to a decrease in turbulence inside the headspace during chamber deployment compared to the ambient windy conditions. We found a 9 to 57 % underestimate of the net biological CH 4 flux at any time of day and a 13 to 21 % underestimate of nighttime CO 2 effluxes in highly turbulent conditions. Conversely, there was evidence of an overestimation of ∼ 100 % of net biological CH 4 and nighttime CO 2 fluxes in calm atmospheric conditions possibly due to enhanced near-surface gas concentration gradient by mixing of chamber headspace air by fans. These problems were resolved by extending the deployment period to 30 min. After 13 min of chamber closure, the flux rate of CH 4 and nighttime CO 2 became constant and were not affected by turbulence thereafter, yielding a reliable estimate of the net biological fluxes. The measurement biases we observed likely exist to some extent in all chamber flux measurements made on porous and aerated substrate, such as peatlands, organic soils in tundra and forests, and snowcovered surfaces, but would be difficult to detect unless high frequency, semi-continuous observations were made.

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Pathways of aeration and the mechanisms and beneficial effects of humidity- and Venturi-induced convections in Phragmites australis (Cav.) Trin. ex Steud.

Cited by 143 publications

References 18 publications

Methanogenesis and methane emissions: effects of water table, substrate type and presence of Phragmites australis

Methanogenesis and methane emissions: effects of water table, substrate type and presence of Phragmites australis

Water level, vegetation composition, and plant productivity explain greenhouse gas fluxes in temperate cutover fens after inundation

The effect of atmospheric turbulence and chamber deployment period on autochamber CO<sub>2</sub> and CH<sub>4</sub> flux measurements in an ombrotrophic peatland

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Pathways of aeration and the mechanisms and beneficial effects of humidity- and Venturi-induced convections in Phragmites australis (Cav.) Trin. ex Steud.

Cited by 143 publications

References 18 publications

Methanogenesis and methane emissions: effects of water table, substrate type and presence of Phragmites australis

Methanogenesis and methane emissions: effects of water table, substrate type and presence of Phragmites australis

Water level, vegetation composition, and plant productivity explain greenhouse gas fluxes in temperate cutover fens after inundation

The effect of atmospheric turbulence and chamber deployment period on autochamber CO&lt;sub&gt;2&lt;/sub&gt; and CH&lt;sub&gt;4&lt;/sub&gt; flux measurements in an ombrotrophic peatland

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The effect of atmospheric turbulence and chamber deployment period on autochamber CO<sub>2</sub> and CH<sub>4</sub> flux measurements in an ombrotrophic peatland