scholarly journals Organic sediment formed during inundation of a degraded fen grassland emits large fluxes of CH<sub>4</sub> and CO<sub>2</sub>

2011 ◽  
Vol 8 (6) ◽  
pp. 1539-1550 ◽  
Author(s):  
M. Hahn-Schöfl ◽  
D. Zak ◽  
M. Minke ◽  
J. Gelbrecht ◽  
J. Augustin ◽  
...  
Keyword(s):  
Organic Matter ◽  
Plant Litter ◽  
Electron Acceptors ◽  
Sediment Layer ◽  
Organic Substrates ◽  
Peat Layer ◽  
Ch4 Production ◽  
Fresh Plant ◽  
Fresh Organic Matter ◽  
Organic Sediment

Abstract. Peatland restoration by inundation of drained areas can alter local greenhouse gas emissions as CO2 and CH4. Factors that can influence these emissions include the quality and amount of substrates available for anaerobic degradation processes and the sources and availability of electron acceptors. In order to learn about possible sources of high CO2 and CH4. emissions from a rewetted degraded fen grassland, we performed incubation experiments that tested the effects of fresh plant litter in the flooded peats on pore water chemistry and CO2 and CH4. production and emission. The position in the soil profile of the pre-existing drained peat substrate affected initial rates of anaerobic CO2 production subsequent to flooding, with the uppermost peat layer producing the greatest specific rates of CO2 evolution. CH4 production rates depended on the availability of electron acceptors and was significant only when sulfate concentrations were reduced in the pore waters. Very high specific rates of both CO2 (maximum of 412 mg C d−1 kg−1 C) and CH4 production (788 mg C d−1 kg−1 C) were observed in a new sediment layer that accumulated over the 2.5 years since the site was flooded. This new sediment layer was characterized by overall low C content, but represented a mixture of sand and relatively easily decomposable plant litter from reed canary grass killed by flooding. Samples that excluded this new sediment layer but included intact roots remaining from flooded grasses had specific rates of CO2 (max. 28 mg C d−1 kg−1 C) and CH4 (max. 34 mg C d−1 kg−1 C) production that were 10–20 times lower than for the new sediment layer and were comparable to those of a newly flooded upper peat layer. Lowest rates of anaerobic CO2 and CH4 production (range of 4–8 mg C d−1 kg−1 C and <1 mg C d−1 kg−1 C) were observed when all fresh organic matter sources (plant litter and roots) were excluded. In conclusion, the presence of fresh organic substrates such as plant and root litter originating from plants killed by inundation has a high potential for CH4 production, whereas peat without any fresh plant-derived material is relatively inert. Significant anaerobic CO2 and CH4 production in peat only occurs when some labile organic matter is available, e.g. from remaining roots or root exudates.

scholarly journals Organic sediment formed during inundation of a degraded fen grassland emits large fluxes of CH<sub>4</sub> and CO<sub>2</sub>

2010 ◽  
Vol 7 (6) ◽  
pp. 9273-9303
Author(s):  
M. Hahn-Schöfl ◽  
D. Zak ◽  
M. Minke ◽  
J. Gelbrecht ◽  
J. Augustin ◽  
...  
Keyword(s):  
Organic Matter ◽  
Plant Litter ◽  
Electron Acceptors ◽  
Sediment Layer ◽  
Organic Substrates ◽  
Peat Layer ◽  
Ch4 Emissions ◽  
Ch4 Production ◽  
Fresh Plant ◽  
Fresh Organic Matter

Abstract. Peatland restoration by inundation of drained areas can alter local greenhouse gas emissions by altering rates of CO2 and CH4 emissions. Factors that can influence these emissions include the quality and amount of substrates available for anaerobic degradation processes and the sources and availability of electron acceptors. In order to learn about possible sources of high CO2 and CH4 emissions from a rewetted degraded fen grassland, we performed incubation experiments that tested the effects of fresh plant litter in the flooded peats on pore water chemistry and CO2 and CH4 production and emission. The position in the soil profile of the pre-existing drained peat substrate affected initial rates of anaerobic CO2 production subsequent to flooding, with the uppermost peat layer producing the greatest specific rates of CO2 evolution. CH4 production rates depended on the availability of electron acceptors and was significant only when sulfate concentrations were reduced in the pore waters. Very high specific rates of both CO2 (maximum of 412 mg C d−1 kg−1 C) and CH4 production (788 mg C d−1 kg−1 C) were observed in a new sediment layer that accumulated over 2.5 years since the site was flooded. This new sediment layer was characterized by overall low C content, but represented a mixture of sand and relatively easily decomposable plant litter from reed canary grass killed by flooding. Samples that excluded this new sediment layer but included intact roots remaining from flooded grasses had specific rates of CO2 (max. 28 mg C d−1 kg−1 C) and CH4 (max. 34 mg C d−1 kg−1 C) production that were 10–20 times lower, and were comparable to those of newly flooded upper peat layer. Lowest rates of anaerobic CO2 and CH4 production (range of 4–8 mg C d−1 kg−1 C and <1 mg C d−1 kg−1 C) were observed when all fresh organic matter sources (plant litter and roots) were excluded. In conclusion, the presence of fresh organic substrates such as plant and root litter originating from plants killed by inundation has a high potential for CH4 production, whereas peat without any fresh plant-derived material is relatively inert. Anaerobic CO2 and CH4 production in peat only occurs when some labile organic matter is available, e.g. from remaining roots or root exudates.

scholarly journals Drying and rewetting conditions differentially affect the mineralization of fresh plant litter and extant soil organic matter

2018 ◽  
Vol 124 ◽  
pp. 81-89 ◽  
Author(s):  
Luis Lopez-Sangil ◽  
Iain P. Hartley ◽  
Pere Rovira ◽  
Pere Casals ◽  
Emma J. Sayer
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Plant Litter ◽  
Fresh Plant ◽  
Drying And Rewetting

Age distribution and organic matter degradation in bioturbated sediment

2020 ◽  
Author(s):  
Matthias Kuderer ◽  
Jack J Middelburg
Keyword(s):  
Organic Matter ◽  
Mixed Layer ◽  
Accumulation Rate ◽  
Mixed Layer Depth ◽  
Age Distribution ◽  
Minor Effect ◽  
Sediment Layer ◽  
Organic Matter Degradation ◽  
Mixing Coefficient ◽  
Fresh Organic Matter

&lt;p&gt;Bioturbation is an important process in the early diagenesis of soft marine sediment. Benthic infaunal activity, such as feeding, burrowing and ploughing redistributes particles within the topmost layers of the sediment. Recently deposited particles are mixed into deeper sediment depth layers and old material remains longer near the surface. A sediment layer thus contains an assemblage of particles from young to very old ages. Under certain assumptions, bioturbational mixing can be modelled as a diffusive process with the macroscopic mixing coefficient D&lt;sub&gt;B&lt;/sub&gt;. Here we model the age distribution of the bioturbated sedimentary record with a depth dependent mixing coefficient D&lt;sub&gt;B&lt;/sub&gt;(z). The potential age bias introduced by mixing is typically higher than multiples of the mean mixed layer residence time, which scales linearly with the ratio of mixed layer depth and sediment accumulation rate. Scaling the mixing intensity has only a minor effect, as most marine environments are mixing dominated.&lt;/p&gt;&lt;p&gt;The rate of organic matter degradation can been modelled empirically as an age dependent process, with recently deposited, fresh organic matter having higher reactivities than older and more refractory material. With insights into the age distribution, this allows to couple the degradation of organic matter with bioturbation and estimate the burial of carbon.&lt;/p&gt;

Organic sulfur and organic matter redox processes contribute to electron flow in anoxic incubations of peat

2016 ◽  
Vol 13 (5) ◽  
pp. 816 ◽  
Author(s):  
Zhi-Guo Yu ◽  
Jörg Göttlicher ◽  
Ralph Steininger ◽  
Klaus-Holger Knorr
Keyword(s):  
Carbon Dioxide ◽  
Organic Matter ◽  
Electron Acceptor ◽  
Electron Acceptors ◽  
Organic Sulfur ◽  
Co2 Production ◽  
Bacterial Sulfate Reduction ◽  
Sulfur Species ◽  
Ch4 Production

Environmental contextThe extent to which organic matter decomposition generates carbon dioxide or methane in anaerobic ecosystems is determined by the presence or absence of particular electron acceptors. Evaluating carbon dioxide and methane production in anaerobic incubation of peat, we found that organic matter predominated as an electron acceptor over considered inorganic electron acceptors. We also observed changes in organic sulfur speciation suggesting a contribution of organic sulfur species to the electron-accepting capacity of organic matter. AbstractAn often observed excess of CO2 production over CH4 production in freshwater ecosystems presumably results from a direct or indirect role of organic matter (OM) as electron acceptor, possibly supported by a cycling of oxidised and reduced sulfur species. To confirm the role of OM electron-accepting capacities (EACOM) in anaerobic microbial respiration and to elucidate internal sulfur cycling, peat soil virtually devoid of inorganic electron acceptors was incubated under anaerobic conditions. Thereby, production of CO2 and CH4 at a cumulative ratio of 3.2:1 was observed. From excess CO2 production and assuming a nominal oxidation state of carbon in OM of zero, we calculated a net consumption rate of EACOM of 2.36µmol electron (e–)cm–3day–1. Addition of sulfate (SO42–) increased CO2 and suppressed CH4 production. Moreover, subtracting the EAC provided though SO42–, net consumption rates of EACOM had increased to 3.88–4.85µmol e–cm–3day–1, presumably owing to a re-oxidation of sulfide by OM at sites otherwise not accessible for microbial reduction. As evaluated by sulfur K-edge X-ray absorption near-edge structure spectroscopy, bacterial sulfate reduction presumably involved not only a recycling of inorganic sulfur species, but also a sulfurisation of OM, yielding reduced organic sulfur, and changes in oxidised organic sulfur species. Organic matter thus contributes to anaerobic respiration: (i) directly by EAC of redox-active functional groups; (ii) directly by oxidised organic sulfur; and (iii) indirectly by re-oxidation of sulfide to maintain bacterial sulfate reduction.

scholarly journals Belowground in situ redox dynamics and methanogenesis recovery in a degraded fen during dry-wet cycles and flooding

2012 ◽  
Vol 9 (8) ◽  
pp. 11655-11704 ◽  
Author(s):  
C. Estop-Aragonés ◽  
K.-H. Knorr ◽  
C. Blodau
Keyword(s):  
Organic Matter ◽  
Water Table ◽  
Methane Production ◽  
Solid Phase ◽  
Electron Flow ◽  
Organic Matter Content ◽  
Matter Content ◽  
Electron Acceptors ◽  
Oxygen Penetration ◽  
Ch4 Production

Abstract. Climate change induced drying and flooding may alter the redox conditions of organic matter decomposition in peat soils. The seasonal and intermittent changes in pore water solutes (NO3−, Fe2+, SO42−, H2S, acetate) and dissolved soil gases (CO2, O2, CH4, H2) under natural water table fluctuations were compared to the response under a reinforced drying and flooding in fen peats. Oxygen penetration during dryings led to CO2 and CH4 degassing and to a regeneration of dissolved electron acceptors (NO3−, Fe3+ and SO42−). Drying intensity controlled the extent of the electron acceptor regeneration. Iron was rapidly reduced and sulfate pools ~ 1 mmol L−1 depleted upon rewetting and CH4 did not substantially accumulate until sulfate levels declined to ~ 100 μmoll−1. The post-rewetting recovery of soil methane concentrations to levels ~ 80 μmoll−1 needed 40–50 days after natural drought. This recovery was prolonged after experimentally reinforced drought. A greater regeneration of electron acceptors during drying was not related to prolonged methanogenesis suppression after rewetting. Peat compaction, solid phase content of reactive iron and total reduced inorganic sulfur and organic matter content controlled oxygen penetration, the regeneration of electron acceptors and the recovery of CH4 production, respectively. Methane production was maintained despite moderate water table decline of 20 cm in denser peats. Flooding led to accumulation of acetate and H2, promoted CH4 production and strengthened the co-occurrence of iron and sulfate reduction and methanogenesis. Mass balances during drying and flooding indicated that an important fraction of the electron flow must have been used for the generation and consumption of electron acceptors in the solid phase or other mechanisms. In contrast to flooding, dry-wet cycles negatively affect methane production on a seasonal scale but this impact might strongly depend on drying intensity and on the peat matrix, whose structure and physical properties influence moisture content.

scholarly journals Proximity to charred logs in burned forests likely affects decomposition processes in the soil

Silva Fennica ◽  
2020 ◽  
Vol 54 (1) ◽  
Author(s):  
Mihails Cugunovs ◽  
Eeva-Stiina Tuittila ◽  
Jari Kouki
Keyword(s):  
Organic Matter ◽  
Forest Fires ◽  
Woody Debris ◽  
Plant Litter ◽  
Organic Substrates ◽  
Decomposition Rates ◽  
Decomposition Rate Constant ◽  
Cellulose Material ◽  
Mesh Bags ◽  
Hardwood Pulp

We studied the spatial decomposition rates of standardised organic substrates in soils (burned boreal pine-dominated sub-xeric forests in eastern Finland), with respect to charred and non-charred coarse woody debris (CWD). Decomposition rates of rooibos plant litter inside teabags (C:N = 42.870 ± 1.841) and pressed-sheet Nordic hardwood pulp (consisting of mainly alpha-cellulose) were measured at 0.2 m distance from 20 charred (LC0.2) and 40 non-charred logs (LNC0.2). We also measured decomposition at 60 plots located 3–10 m away from downed logs (L3,10). The rooibos decomposition rate constant ‘k’ was 8.4% greater at the LNC0.2 logs than at the L3,10 or LC0.2 logs. Cellulose decomposed more completely in 1 micron mesh bags at LNC0.2 (44% of buried bags had leftover material) than at LC0.2 (76%) or L3,10 (70%). Decomposition of cellulose material was rapid but varied greatly between sampling plots. Our results indicate that decomposition of the standardised organic matter was more rapid close to CWD pieces than further away. However, only the plots located near non-charred logs (LNC0.2) exhibited high decomposition rates, with no corresponding increase observed at the charred logs (LC0.2). This suggests a possible noteworthy indirect effect of forest burning on soil organic matter (SOM) decomposition rates close to charred CWD after forest fires. We urge for more studies on this tentative observation as it may affect the estimates on how fires affect carbon cycling in forests.

scholarly journals Belowground in situ redox dynamics and methanogenesis recovery in a degraded fen during dry-wet cycles and flooding

2013 ◽  
Vol 10 (1) ◽  
pp. 421-436 ◽  
Author(s):  
C. Estop-Aragonés ◽  
K.-H. Knorr ◽  
C. Blodau
Keyword(s):  
Organic Matter ◽  
Water Table ◽  
Methane Production ◽  
Solid Phase ◽  
Electron Flow ◽  
Organic Matter Content ◽  
Matter Content ◽  
Electron Acceptors ◽  
Oxygen Penetration ◽  
Ch4 Production

Abstract. Climate change induced drying and flooding may alter the redox conditions of organic matter decomposition in peat soils. The seasonal and intermittent changes in pore water solutes (NO3−, Fe2+, SO42−, H2S, acetate) and dissolved soil gases (CO2, O2, CH4, H2) under natural water table fluctuations were compared to the response under a reinforced drying and flooding in fen peats. Oxygen penetration during dryings led to CO2 and CH4 degassing and to a regeneration of dissolved electron acceptors (NO3−, Fe3+ and SO42−). Drying intensity controlled the extent of the electron acceptor regeneration. Iron was rapidly reduced and sulfate pools ~ 1 mM depleted upon rewetting and CH4 did not substantially accumulate until sulfate levels declined to ~ 100 μmol L−1. The post-rewetting recovery of soil methane concentrations to levels ~ 80 μmol L−1 needed 40–50 days after natural drought. This recovery was prolonged after experimentally reinforced drought. A greater regeneration of electron acceptors during drying was not related to prolonged methanogenesis suppression after rewetting. Peat compaction, solid phase content of reactive iron and total reduced inorganic sulfur and organic matter content controlled oxygen penetration, the regeneration of electron acceptors and the recovery of CH4 production, respectively. Methane production was maintained despite moderate water table decline of 20 cm in denser peats. Flooding led to accumulation of acetate and H2, promoted CH4 production and strengthened the co-occurrence of iron and sulfate reduction and methanogenesis. Mass balances during drying and flooding indicated that an important fraction of the electron flow must have been used for the generation and consumption of electron acceptors in the solid phase or other mechanisms. In contrast to flooding, dry-wet cycles negatively affect methane production on a seasonal scale, but this impact might strongly depend on drying intensity and on the peat matrix, of which structure and physical properties influence moisture content.

scholarly journals Adding organic matter to restore wetland soils may increase methane generation and is not needed for hydric soil development

2021 ◽  
Author(s):  
Brian Scott ◽  
Andrew Baldwin ◽  
Stephanie Yarwood
Keyword(s):  
Organic Matter ◽  
Global Warming ◽  
Sandy Loam ◽  
Phase 1 ◽  
Organic Amendments ◽  
Gas Production ◽  
Phase 2 ◽  
Methane Generation ◽  
Ch4 Production ◽  
Fresh Organic Matter

Abstract. Methane (CH4) emissions are a potent contributor to global warming and wetlands can be a significant CH4 source. In a microcosm study we evaluated how the practice of amending soils with organic matter as part of wetland restoration projects may affect CH4 production potential. Organic amendments including hay, manure, biosolids and compost were evaluated at three different levels. Using 1-liter glass microcosms, we measured the production of biogenic gases over 60 days in two soils, a sandy loam (SL) and a sandy clay loam (SCL). Fresh organic amendments increased CH4 production, leading to potentially higher global warming potential and wetland C loss, particularly in sandy soils. Organic amendments increased biogenic gas production in two sequential steady state phases: Phase 1 produced some CH4 but was mostly carbon dioxide (CO2) followed by Phase 2, two to six weeks later, with much higher total gas and nearly equal amounts of CH4 and CO2. The CH4 from the SCL soil ranged from 0.003–0.8 cc/Kg/day in Phase 1 to 0.75–28 in Phase 2 and the SL range from 0.03–16 cc/Kg/day in Phase 1 to 1.8–64 in Phase 2. We had set out to identify an organic amendment that would promote iron (Fe) reduction without excess CH4, but amendments were not needed to produce Fe and make soils hydric. Adding fresh organic matter (hay) resulted in both excess Fe2+ and CH4 whereas composted amendments had little effect. The potential for excess methanogenesis should be taken into account when considering organic matter amendments in mitigation wetlands.

scholarly journals 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

2020 ◽  
Vol 17 (20) ◽  
pp. 5057-5078
Author(s):  
Leandra Stephanie Emilia Praetzel ◽  
Nora Plenter ◽  
Sabrina Schilling ◽  
Marcel Schmiedeskamp ◽  
Gabriele Broll ◽  
...  
Keyword(s):  
Organic Matter ◽  
Negative Correlation ◽  
Sediment Quality ◽  
Significant Negative Correlation ◽  
Electron Acceptors ◽  
Co2 Production ◽  
Emission Rates ◽  
Production Rates ◽  
Sediment Properties ◽  
Ch4 Production

Abstract. Inland waters, particularly small and shallow lakes, are significant sources of carbon dioxide (CO2) and methane (CH4) to the atmosphere. However, the spatial in-lake heterogeneity of CO2 and CH4 production processes and their drivers in the sediment remain poorly studied. We measured potential CO2 and CH4 production in slurry incubations from 12 sites within the small and shallow crater lake Windsborn in Germany, as well as fluxes at the water–atmosphere interface of intact sediment core incubations from four sites. Production rates were highly variable and ranged from 7.2 to 38.5 µmol CO2 gC−1 d−1 and from 5.4 to 33.5 µmol CH4 gC−1 d−1. Fluxes ranged from 4.5 to 26.9 mmol CO2 m−2 d−1 and from 0 to 9.8 mmol CH4 m−2 d−1. Both CO2 and CH4 production rates and the CH4 fluxes exhibited a significant and negative correlation (p<0.05, ρ<−0.6) with a prevalence of recalcitrant organic matter (OM) compounds in the sediment as identified by Fourier-transformed infrared spectroscopy. The carbon / nitrogen ratio exhibited a significant negative correlation (p<0.01, ρ=-0.88) with CH4 fluxes but not with production rates or CO2 fluxes. The availability of inorganic (nitrate, sulfate, ferric iron) and organic (humic acids) electron acceptors failed to explain differences in CH4 production rates, assuming a competitive suppression, but observed non-methanogenic CO2 production could be explained up to 91 % by prevalent electron acceptors. We did not find clear relationships between OM quality, the thermodynamics of methanogenic pathways (acetoclastic vs. hydrogenotrophic) and electron-accepting capacity of the OM. Differences in CH4 fluxes were interestingly to a large part explained by grain size distribution (p<0.05, ρ=±0.65). Surprisingly though, sediment gas storage, potential production rates and water–atmosphere fluxes were decoupled from each other and did not show any correlations. Our results show that within a small lake, sediment CO2 and CH4 production shows significant spatial variability which is mainly driven by spatial differences in the degradability of the sediment OM. We highlight that studies on production rates and sediment quality need to be interpreted with care, though, in terms of deducing emission rates and patterns as approaches based on production rates only neglect physical sediment properties and production and oxidation processes in the water column as major controls on actual emissions.

The Metazoan Meiofauna in Its Biogeochemical Environment: The Case of an Antarctic Coastal Sediment

1998 ◽  
Vol 78 (2) ◽  
pp. 411-434 ◽  
Author(s):  
S. Vanhove ◽  
H.J. Lee ◽  
M. Beghyn ◽  
D. Van Gansbeke ◽  
S. Brockington ◽  
...  
Keyword(s):  
Organic Matter ◽  
Standing Stock ◽  
Austral Summer ◽  
Fine Sand ◽  
Coastal Sediment ◽  
Feeding Guild ◽  
Fresh Organic Matter ◽  
Benthic Environment ◽  
Metazoan Meiofauna ◽  
Deposit Feeding

The metazoan meiobenthos was investigated in an Antarctic coastal sediment (Factory Cove, Signy Island, Antarctica). The fine sands contained much higher abundances compared to major sublittoral sediments worldwide. Classified second after Narrangansett Bay (North Atlantic) they reached numbers of 13 × 106ind m-2. The meiofauna was highly abundant in the surface layers, but densities decreased sharply below 2 cm. Vertical profiles mirrored steep gradients of microbiota, chloropigments and organic matter and were coincident with chemical stratification. Spatial patchiness manifested especially in the surface layer. Nematodes dominated (up to 90%), andAponema, Chromctdorita, Diplolaimella, Daptonema, MicrolaimusandNeochromadoraconstituted almost the entire community. Overall, the nematode fauna showed a strong similarity with fine sand communities elsewhere. The dominant trophic strategies were epistrarum and non-selective deposit feeding, but the applied classification for feeding guild structure of the nematodes of Factory Cove is discussed. High standing stock, low diversity and shallow depth distribution may have occurred because of the high nutritive (chlorophyll exceeded lOOOmgm-2and constituted almost 50% of the organic pool) and reductive character of the benthic environment. These observations must have originated from the substantial input of fresh organic matter from phytoplankton and microphytobenthic production, typical for an Antarctic coastal ecosystem during the austral summer.

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