Carbon-isotope ratios and carbon, nitrogen and sulfur abundances in flora and soil organic matter from a temperate-zone bog and marsh.

Hornibrook, Edward R. C.; Longstaffe, Frederick J.; Fyfe, W. S.; Bloom, Y

doi:10.2343/geochemj.34.237

Cited by 63 publications

(54 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The C content of the fen soil under study was, in some parts of the profile, low compared to other organic soils (Hornibrook et al, 2000c), but the isotopic signature of the soil organic matter was more or less consistently −27‰. Only small differences in δ 13 C in this peat suggested that the isotopic signature of CO 2 formed by respiration should not vary much with depth.…”

Section: Respiration and Methanogenesismentioning

confidence: 88%

Fluxes and 13C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought

2008

View full text Add to dashboard Cite

Abstract. Peatlands contain a carbon stock of global concern and significantly contribute to the global methane burden. The impact of drought and rewetting on carbon cycling in peatland ecosystems is thus currently debated. We studied the impact of experimental drought and rewetting on intact monoliths from a temperate fen over a period of ~300 days, using a permanently wet treatment and two treatments undergoing drought for 50 days. In one of the mesocosms, vegetation had been removed. Net production of CH4 was calculated from mass balances in the peat and emission using static chamber measurements. Results were compared to 13C isotope budgets of CO2 and CH4 and energy yields of acetoclastic and hydrogenotrophic methanogenesis. Drought retarded methane production after rewetting for days to weeks and promoted methanotrophic activity. Based on isotope and flux budgets, aerobic soil respiration contributed 32–96% in the wet treatment and 86–99% in the other treatments. Drying and rewetting did not shift methanogenic pathways according to δ13C ratios of CH4 and CO2. Although δ13C ratios indicated a prevalence of hydrogenotrophic methanogenesis, free energies of this process were small and often positive on the horizon scale. This suggests that methane was produced very locally. Fresh plant-derived carbon input apparently supported respiration in the rhizosphere and sustained methanogenesis in the unsaturated zone, according to a 13C-CO2 labelling experiment. The study documents that drying and rewetting in a rich fen soil may have little effect on methanogenic pathways, but result in rapid shifts between methanogenesis and methanotrophy. Such shifts may be promoted by roots and soil heterogeneity, as hydrogenotrophic methanogenesis occurred locally even when conditions were not conducive for this process in the bulk peat.

show abstract

Section: Respiration and Methanogenesismentioning

confidence: 88%

Fluxes and 13C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought

2008

View full text Add to dashboard Cite

show abstract

“…This leads to higher atomic C/N values (>50) in Sphagnum spp. than in vascular plants (10-40) (Aerts et al, 1999;Hornibrook et al, 2000;Biester et al, 2003;Schellekens et al, 2015a). However, the C/Nvalues ofthe same plant species can vary between sites, being prominent for Sphagnum (Schellekens et al, 2015a).…”

Section: Cjnmentioning

confidence: 99%

“…C/Nis also a proxy for degree ofmass loss, with lowervalues indicating greater decomposition as there is a preferential depletion of C vs. N during decomposition (Kuhry and Vitt, 1996;Hornibrook et al, 2000;Malmer and Wallen, 2004). According to Muller et al (2008), the use of the C/N as a proxy for mass loss is useful for mires, as increasing peat humification and decomposition produce low values.…”

Section: Cjnmentioning

confidence: 99%

“…On the basis of the atomic C/N values measured in peat-forming plants (Aerts et al, 1999;Hornibrook et al, 2000;Biester et al, 2003;Schellekens et al, 2015a), those of Las Conchas record may indicate a mixed contribution of Sphagnum, vascular plants and probably bacteria to peat, the latter probably being predominant, at least at presento However, similar atomic C/N values were also observed in the neighboring Sphagnum-dominated Roñanzas peat bog and other mires in Asturias (López-Días et al, 2013a) and the Netherlands (d. Verhoeven, 1992). Moreover, a greater contribution of Sphagnum was inferred from the n-alkane indices along the record.…”

Section: Cjnmentioning

confidence: 99%

See 1 more Smart Citation

Biomarkers and inorganic proxies in the paleoenvironmental reconstruction of mires: The importance of landscape in Las Conchas (Asturias, Northern Spain)

Ortíz

Borrego

Gallego

et al. 2016

Organic Geochemistry

View full text Add to dashboard Cite

A B S T R A C TWe determined the lipid distributions (n-alkanes, n-alkan-2-ones, n-alkanoic acids), total organic carbon (TOC), total nitrogen (TN), CajMg and ash content in Las Conchas mire, a 3.2 m deep bryophytedominated mire in Northern Spain covering 8000 cal yr BP. Bog conditions developed in the bottom 20 cm of the profile, and good preservation of organic matter (OM) was inferred from n-alkanoic acid distribution, with the exception of the uppermost 20 cm (last ca. 200 yr). Microbial synthesis of long chain saturated fatty acids from primary OM likely produced a dominance of short chain n-alkanoic acids with a bimodal distribution, as well as the lack of correspondence between the n-alkane and n-alkanoic acid profiles in the upper 20 cm. This was accompanied by an increase in ash content, a decrease in TOC and variation in n-alkane ratio s, thereby suggesting significant changes in the mire, namely drainage and transformation to a meadow, in the last ca. 200 yr. The distribution of n-alkan-2-ones indicated an increase in bacterial source from the bottom of the record to 94 cm, whereas their distribution in the upper part could be attributed mainly to plant input andjor the microbial oxidation of n-alkanes. The different n-alkane proxies showed variations, which we interpreted in terms of changes in vegetation (Sphagnum vs. non-Sphagnum dominated phases) during the last 8000 cal yr BP. C 23 was the most abundant homolog throughout most ofthe record, thereby suggesting dominant humid conditions alternating with short drier phases. However, such humid conditions were not linked to paleoclimatic variation but rather to geomorphological characteristics: Las Conchas mire, at the base of the Cuera Range, receives continuous runoff-even during drier periods-which is not necessarily accompanied by additional mineral input to peat, producing the development of Sphagnum moss typical of waterlogged ecotopes and damp habitats. Thus, although geochemical proxies indicated an ombrotrophic regime in the mire, geomorphological characteristics may make a considerable contribution to environmental conditions.

show abstract

“…The accumulation of phenolic compounds is usually accompanied by an increase in C / N ratios (Hornibrook et al, 2000;Werth and Kuzyakov, 2010), which is not the case in the top 10 cm of the mofette soil. Therefore, lignin accumulation is not likely to have caused the depletion in the top 10 cm of both mofettes.…”

Section: Quantification Of Som Isotope Shifts By Combinedmentioning

confidence: 99%

Autotrophic fixation of geogenic CO2 by microorganisms contributes to soil organic matter formation and alters isotope signatures in a wetland mofette

et al. 2015

View full text Add to dashboard Cite

Abstract.To quantify the contribution of autotrophic microorganisms to organic matter (OM) formation in soils, we investigated natural CO 2 vents (mofettes) situated in a wetland in northwest Bohemia (Czech Republic). Mofette soils had higher soil organic matter (SOM) concentrations than reference soils due to restricted decomposition under high CO 2 levels. We used radiocarbon ( 14 C) and stable carbon (δ 13 C) isotope ratios to characterize SOM and its sources in two mofettes and compared it with respective reference soils, which were not influenced by geogenic CO 2 .The geogenic CO 2 emitted at these sites is free of radiocarbon and enriched in 13 C compared to atmospheric CO 2 . Together, these isotopic signals allow us to distinguish C fixed by plants from C fixed by autotrophic microorganisms using their differences in 13 C discrimination. We can then estimate that up to 27 % of soil organic matter in the 0-10 cm layer of these soils was derived from microbially assimilated CO 2 .Isotope values of bulk SOM were shifted towards more positive δ 13 C and more negative 14 C values in mofettes compared to reference soils, suggesting that geogenic CO 2 emitted from the soil atmosphere is incorporated into SOM. To distinguish whether geogenic CO 2 was fixed by plants or by CO 2 assimilating microorganisms, we first used the proportional differences in radiocarbon and δ 13 C values to indicate the magnitude of discrimination of the stable isotopes in living plants. Deviation from this relationship was taken to indicate the presence of microbial CO 2 fixation, as microbial discrimination should differ from that of plants. 13 CO 2 -labelling experiments confirmed high activity of CO 2 assimilating microbes in the top 10 cm, where δ 13 C values of SOM were shifted up to 2 ‰ towards more negative values. Uptake rates of microbial CO 2 fixation ranged up to 1.59 ± 0.16 µg g −1 dw d −1 . We inferred that the negative δ 13 C shift was caused by the activity of autotrophic microorganisms using the Calvin-Benson-Bassham (CBB) cycle, as indicated from quantification of cbbL/cbbM marker genes encoding for RubisCO by quantitative polymerase chain reaction (qPCR) and by acetogenic and methanogenic microorganisms, shown present in the mofettes by previous studies. Combined 14 C and δ 13 C isotope mass balances indicated that microbially derived carbon accounted for 8-27 % of bulk SOM in this soil layer.The findings imply that autotrophic microorganisms can recycle significant amounts of carbon in wetland soils and might contribute to observed radiocarbon reservoir effects influencing 14 C signatures in peat deposits.

show abstract

Carbon-isotope ratios and carbon, nitrogen and sulfur abundances in flora and soil organic matter from a temperate-zone bog and marsh.

Cited by 63 publications

References 38 publications

Fluxes and <sup>13</sup>C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought

Fluxes and <sup>13</sup>C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought

Biomarkers and inorganic proxies in the paleoenvironmental reconstruction of mires: The importance of landscape in Las Conchas (Asturias, Northern Spain)

Autotrophic fixation of geogenic CO<sub>2</sub> by microorganisms contributes to soil organic matter formation and alters isotope signatures in a wetland mofette

Contact Info

Product

Resources

About

Carbon-isotope ratios and carbon, nitrogen and sulfur abundances in flora and soil organic matter from a temperate-zone bog and marsh.

Cited by 63 publications

References 38 publications

Fluxes and &lt;sup&gt;13&lt;/sup&gt;C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought

Fluxes and &lt;sup&gt;13&lt;/sup&gt;C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought

Biomarkers and inorganic proxies in the paleoenvironmental reconstruction of mires: The importance of landscape in Las Conchas (Asturias, Northern Spain)

Autotrophic fixation of geogenic CO&lt;sub&gt;2&lt;/sub&gt; by microorganisms contributes to soil organic matter formation and alters isotope signatures in a wetland mofette

Contact Info

Product

Resources

About

Fluxes and <sup>13</sup>C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought

Fluxes and <sup>13</sup>C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought

Autotrophic fixation of geogenic CO<sub>2</sub> by microorganisms contributes to soil organic matter formation and alters isotope signatures in a wetland mofette