Electron accepting capacity of dissolved and particulate organic matter control CO2 and CH4 formation in peat soils

Gao, Chuanyu; Sander, Michael; Agethen, Svenja; Knorr, Klaus‐Holger

doi:10.1016/j.gca.2018.11.004

Cited by 77 publications

(113 citation statements)

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“…However, several studies have demonstrated relatively high rates of decomposition in peat (as heterotrophic production of CO 2 ) when the thermodynamic yield indicated by inorganic TEAs would suggest otherwise (Deppe et al, 2010;Dettling et al, 2006;Kane et al, 2013;Keller & Bridgham, 2007;Vile et al, 2003). A growing body of literature draws attention to the importance of humic substances and organometallic complexes in governing anaerobic metabolism in organic soil (Gao et al, 2019;Heitmann et al, 2007;Klüpfel et al, 2014;Lipson et al, 2010). Humic substances are rapid scavengers of oxidants (Bauer et al, 2007;Brouns et al, 2014) and as such would be expected to be particularly effective electron acceptors in peatlands with a fluctuating WT or with increased colonization of sedges (cf.…”

Section: Introductionmentioning

confidence: 99%

Reduction‐Oxidation Potential and Dissolved Organic Matter Composition in Northern Peat Soil: Interactive Controls of Water Table Position and Plant Functional Groups

et al. 2019

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Globally important carbon (C) stores in northern peatlands are vulnerable to oxidation in a changing climate. A growing body of literature draws attention to the importance of dissolved organic matter (DOM) in governing anaerobic metabolism in organic soil, but exactly how the reduction-oxidation (redox) activities of DOM, and particularly the phenolic fraction, are likely to change in an altered climate remain unclear. We used large mesocosms in the PEATcosm experiment to assess changes in peatland DOM and redox potential in response to experimental manipulations of water table (WT) position and plant functional groups (PFGs). WT position and PFGs interacted in their effects on redox potential and quantity and quality of DOM. Phenolics were generally of higher molecular weight and more oxidized with sedges in lowered WTs. Altered DOM character included changes in dissolved nitrogen (N), with higher N:[phenolics] with higher E4:E6 (absorbance ratio λ = 465:665) DOM in the lowered WT and sedge PFG treatments. Conversely, biomolecular assignments to amino-sugars were largely absent from low-WT treatments. Low WT resulted in the creation of unique N compounds, which were more condensed (lower H:C), that changed with depth and PFG. The accumulation of oxidized compounds with low WT and in sedge rhizospheres could be very important pools of electron acceptors beneath the WT, and their mechanisms of formation are discussed. This work suggests the effects of changes in vegetation communities can be as great as WT position in directly and interactively mediating peat redox environment and the redox-activity of DOM. Plain Language Summary Peatlands are important ecosystems in both the global carbon (C)cycle and the Earth's climate system owing to their ability to store vast quantities of C taken from the atmosphere. Peat C stays locked up in these ecosystems largely owing to cool and wet conditions, and as such, these C stores are vulnerable to release back to the atmosphere if the climate or water levels change. Water table level and plant species composition have a combined effect on C and nitrogen (N) cycling in peatlands. We manipulated both factors in an experimental setting composed of 24 large bins into which we put intact peatland miniecosystems. Sedges play a big role in producing N compounds below the peat surface, and this work suggests these compounds can actually be synthesized into larger, less accessible compounds. In addition, activities of sedge roots and other dominant plant communities (such as shrubs in the heath family of plants) may interact in the synthesis of oxidized, larger molecules. These molecules can allow microbes to continue to decompose peat even in the absence of oxygen. This could increase the release of greenhouse gas carbon dioxide to the atmosphere, while reducing inputs of the stronger greenhouse gas methane.

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Section: Introductionmentioning

confidence: 99%

Reduction‐Oxidation Potential and Dissolved Organic Matter Composition in Northern Peat Soil: Interactive Controls of Water Table Position and Plant Functional Groups

et al. 2019

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“…Other factors might include the role of humic substances, soil heterogeneity and microsites, salinity, pH, and a breakdown of the REDOX ladder conceptual framework. For example, there is evidence that humic substances can suppress CH 4 production, by becoming anaerobic election acceptors (Blodau and Deppe, 2012), and more recently particulate organic matter itself has been shown to be an important electron acceptor in peat soils (Gao et al, 2019). Microsites (< 10 µm) with limited gas and water exchange with surrounding soil pore space may also affect overall soil REDOX potential and CH 4 production by permitting localized electron acceptor depletion or abundance (Sey et al, 2008).…”

Section: Discussionmentioning

confidence: 99%

Low methane emissions from a boreal wetland constructed on oil sand mine tailings

2020

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Abstract. A 58 ha mixed upland and lowland boreal plains watershed called the Sandhill Fen Watershed was constructed between 2008 and 2012. In the years following wetting in 2013, methane emissions were measured using manual chambers. The presence of vegetation with aerenchymous tissues and saturated soils were important factors influencing the spatial variability of methane emissions across the constructed watershed. Nevertheless, median methane emissions were equal to or less than 0.51 mg CH4 m−2 h−1 even from the saturated organic soils in the lowlands. Although overall methane emissions remained low, observations of methane ebullition increased over the 3 study years. Ebullition events occurred in 10 % of measurements in 2013, increasing to 21 % and 27 % of measurements in 2014 and 2015, respectively, at the plots with saturated soils. Increasing metal ion availability and decreasing sulfur availability was measured using buried ion exchange resins at both seasonal and annual timescales potentially as a result of microbial reduction of these ions. Using principle component analysis, methane fluxes had a significant positive correlation to the leading principle component which was associated with increasing ammonium, iron, and manganese and decreasing sulfur availability (r=0.31, p<0.001). These results suggest that an abundance of alternative inorganic electron acceptors may be limiting methanogenesis at this time.

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“…Whereas the potential of inorganic electron acceptors to suppress methanogenic activity is well studied (Yao et al, 1999;Fenchel et al, 2012), information on the role of humic substances as organic electron acceptors remain scarce. Klüpfel et al (2014) revealed the potential of humic substances to be reduced 90 and re-oxidized at oxic-anoxic interfaces in peatlands, sediments or soils underlying water table fluctuations and it has recently been shown that availability of EAC in OM controls CO2 and CH4 production in peat soils poor in inorganic EAs (Gao et al, 2019). As sediments from the lake under study here are also rich in OM, we wanted to verify if electron accepting (EAC) and donating capacities (EDC) of humic substances also play a role in explaining spatial variabilities of CO2 and CH4 production 95 in lake sediments that are not subjected to water table fluctuations but might to a small extent in the upper parts of the sediments be influenced by oxygen from the water column due to the in our case prevalent perennial circulation (Lau et al, 2016).…”

Section: Ch3cooh  Co2 + Ch4mentioning

confidence: 99%

Organic matter and sediment properties determine in-lake variability of sediment CO2 and CH4 production and emissions of a small and shallow lake

Praetzel¹,

Plenter²,

Schilling³

et al. 2019

Preprint

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Abstract. Inland waters are significant sources of CO2 and CH4 to the atmosphere, following recent studies this is particularly the case for small and shallow lakes. The spatial in-lake heterogeneity of CO2 and CH4 production processes and their drivers in the sediment yet remain poorly studied. We thus measured potential CO2 and CH4 production in sediment incubations from 12 sites within the small and shallow crater lake Windsborn in Germany as well as fluxes at the water-atmosphere interface at four sites. Production rates were highly variable and ranged from 7.2 and 38.5&#8201;&#181;mol&#8201;CO2&#8201;g&#8201;C&#8722;1&#8201;d&#8722;1 and from 5.4 to 33.5&#8201;&#181;mol&#8201;CH4&#8201;g&#8201;C&#8722;1&#8201;d&#8722;1. Fluxes lay between 4.5 and 26.9&#8201;mmol&#8201;CO2&#8201;m&#8722;2&#8201;d&#8722;1 and between 0 and 9.8&#8201;mmol&#8201;CH4&#8201;m&#8722;2&#8201;d&#8722;1. Both CO2 and CH4 production rates and CH4 fluxes were significantly negative (p&#8201;<&#8201;0.05, rho&#8201;<&#8201;&#8722;&#8201;0.6) correlated with the prevalence of recalcitrant organic matter compounds in the sediment as identified by FTIR spectroscopy. The C&#8201;/&#8201;N ratio was significantly (p&#8201;<&#8201;0.01, rho&#8201;=&#8201;&#8722;&#8201;0.88) correlated with CH4 fluxes, but neither with production rates nor CO2 fluxes. Inorganic (nitrate, sulfate, ferric iron) and organic (humic acids) electron acceptors together could explain differences in CH4 production rates (R2&#8201;=&#8201;0.22) whereas we did not find clear relationships between organic matter quality, methanogenic pathways (acetoclastic vs. hydrogenotrophic) and electron accepting capacity of the organic matter. Grain size distribution could sufficiently (p&#8201;<&#8201;0.05, rho&#8201;=&#8201;&#177;&#8201;0.65) explain differences in CH4 fluxes. Surprisingly, sediment gas storage, potential production rates and water&#8211;atmosphere fluxes were decoupled from each other and did not show any correlations. Our results show that there exists a significant spatial variability of sediment gas production even within small lakes which can be explained by the origin and pre-processing, and therefore the degradability of the organic matter. We highlight that measuring production rates is not a suitable way to replace in-situ flux measurements as it neglects physical sediment properties and production and oxidation processes in the water column.

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Electron accepting capacity of dissolved and particulate organic matter control CO2 and CH4 formation in peat soils

Cited by 77 publications

References 54 publications

Reduction‐Oxidation Potential and Dissolved Organic Matter Composition in Northern Peat Soil: Interactive Controls of Water Table Position and Plant Functional Groups

Reduction‐Oxidation Potential and Dissolved Organic Matter Composition in Northern Peat Soil: Interactive Controls of Water Table Position and Plant Functional Groups

Low methane emissions from a boreal wetland constructed on oil sand mine tailings

Organic matter and sediment properties determine in-lake variability of sediment CO<sub>2</sub> and CH<sub>4</sub> production and emissions of a small and shallow lake

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Electron accepting capacity of dissolved and particulate organic matter control CO2 and CH4 formation in peat soils

Cited by 77 publications

References 54 publications

Reduction‐Oxidation Potential and Dissolved Organic Matter Composition in Northern Peat Soil: Interactive Controls of Water Table Position and Plant Functional Groups

Reduction‐Oxidation Potential and Dissolved Organic Matter Composition in Northern Peat Soil: Interactive Controls of Water Table Position and Plant Functional Groups

Low methane emissions from a boreal wetland constructed on oil sand mine tailings

Organic matter and sediment properties determine in-lake variability of sediment CO&lt;sub&gt;2&lt;/sub&gt; and CH&lt;sub&gt;4&lt;/sub&gt; production and emissions of a small and shallow lake

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Organic matter and sediment properties determine in-lake variability of sediment CO<sub>2</sub> and CH<sub>4</sub> production and emissions of a small and shallow lake