ModernSphagnumδ13C signatures follow a surface moisture gradient in two boreal peat bogs, James Bay lowlands, Québec

Loisel, Julie; Garneau, Michelle; Hélie, Jean‐François

doi:10.1002/jqs.1221

Cited by 74 publications

(73 citation statements)

References 29 publications

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“…Even if the herbaceous species contain only small amounts of lignin it may make up the vast majority of organic matter below the turning point because of selective preservation. Loisel et al (2009) determined similar patterns in boreal hummocks and Zaccone et al (2008) for the preservation of phenolic compounds in temperate ombrotrophic mountainous peats.…”

Section: Isotope Depth Profiles In the Hummocksmentioning

confidence: 67%

“…Higher water table depth causes enrichment in δ 13 C because a water film on the leaves will act as diffusion barrier for CO 2 . The latter will result in lower fractionation factors during CO 2 uptake and thus a relative enrichment in the plants under high water saturation or vice versa a relative depletion under low water saturation (Price et al, 1997 for Sphagnum;Pancost et al, 2003 for bulk peat with changes of +4 ‰ from dry to wet; Loisel et al, 2009). If a shift in hydrology is the explanation for the δ 13 C depth profile this would indicate an increase in water saturation up to the turning point and then a decrease again.…”

Section: Change In Hydrologymentioning

confidence: 99%

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Stable carbon isotopes as indicators for environmental change in palsa peats

et al. 2011

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Abstract. Palsa peats are unique northern ecosystems formed under an arctic climate and characterized by a high biodiversity and sensitive ecology. The stability of the palsas are seriously threatened by climate warming which will change the permafrost dynamic and induce a degradation of the mires.We used stable carbon isotope depth profiles in two palsa mires of Northern Sweden to track environmental change during the formation of the mires. Soils dominated by aerobic degradation can be expected to have a clear increase of carbon isotopes (δ 13 C) with depth, due to preferential release of 12 C during aerobic mineralization. In soils with suppressed degradation due to anoxic conditions, stable carbon isotope depth profiles are either more or less uniform indicating no or very low degradation or depth profiles turn to lighter values due to an enrichment of recalcitrant organic substances during anaerobic mineralisation which are depleted in 13 C.The isotope depth profile of the peat in the water saturated depressions (hollows) at the yet undisturbed mire Storflaket indicated very low to no degradation but increased rates of anaerobic degradation at the Stordalen site. The latter might be induced by degradation of the permafrost cores in the uplifted areas (hummocks) and subsequent breaking and submerging of the hummock peat into the hollows due to climate warming. Carbon isotope depth profiles of hummocks indicated a turn from aerobic mineralisation to anaerobicCorrespondence to: C. Alewell (christine.alewell@unibas.ch) degradation at a peat depth between 4 and 25 cm. The age of these turning points was 14 C dated between 150 and 670 yr and could thus not be caused by anthropogenically induced climate change. We found the uplifting of the hummocks due to permafrost heave the most likely explanation for our findings. We thus concluded that differences in carbon isotope profiles of the hollows might point to the disturbance of the mires due to climate warming or due to differences in hydrology. The characteristic profiles of the hummocks are indicators for micro-geomorphic change during permafrost up heaving.

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Section: Isotope Depth Profiles In the Hummocksmentioning

confidence: 67%

Section: Change In Hydrologymentioning

confidence: 99%

Stable carbon isotopes as indicators for environmental change in palsa peats

et al. 2011

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“…This interpretation has been applied to raised peat bogs to reconstruct paleoenvironmental conditions (Xie et al, 2004;Zhou et al, 2005Zhou et al, , 2010Zheng et al, 2007). However, this can be misleading because Sphagnum and other (brown) mosses, which affect this ratio can grow either under wet fen or dry bog conditions (Blackford, 2000;Loisel et al, 2009). These mosses can have a significant input of n-C 25 alkane (Vonk and Gustafsson, 2010), and hence the P aq ratio can become biased.…”

Section: Saturated Lipids N-alkanesmentioning

confidence: 99%

Multi-proxy study of soil organic matter dynamics in permafrost peat deposits reveal vulnerability to climate change in the European Russian Arctic

et al. 2014

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Soil organic carbon (SOC) in permafrost terrain is vulnerable to climate change.Perennially frozen peat deposits store large amounts of SOC, but we know little about its chemical composition and lability. We used plant macrofossil and biomarker analyses to reconstruct the Holocene paleovegetation and paleoenvironmental changes in two peat plateau profiles from the European Russian Arctic. Peat plateaus are the main stores of permafrost soil C in the region, but during most of the Holocene peats developed as permafrost-free rich fens with woody vegetation, sedges and mosses. Around 2200 cal BP, permafrost aggraded at the site resulting in frost heave and a drastic reduction in peat accumulation under the drier uplifted surface conditions. The permafrost dynamics (aggradation, frost-heave and thaw) ushered changes in plant assemblages and carbon accumulation, and consequently in the biomarker trends too. 2Detailed biomarker analyses indicate abundant neutral lipids, which follow the general pattern: n-alkanols > sterols ≥ n-alkanes ≥ triterpenols. The lignin monomers are not as abundant as the lipids and increase with depth. The selected aliphatic and phenolic compounds are source specific, and they have different degrees of lability, which is useful for tracing the impact of permafrost dynamics (peat accumulation and/or decay associated with thawing). However, common interpretation of biomarker patterns, and perceived hydrological and climate changes, must be applied carefully in permafrost regions. The increased proportion (selective preservation) of n-alkanes and lignin is a robust indicator of cumulative decomposition trajectories, which is mirrored by functional compounds (e.g. n-alkanol, triterpenol, and sterol concentrations) showing opposite trends. The distribution of these compounds follows first order decay kinetics, and concurs with the downcore diagenetic changes. In particular, some of the biomarker ratios (e.g. stanol/sterol and higher plant alkane index) seem promising for tracing SOC decomposition despite changes in botanical imprint, and sites spanning across different soil types and locations. Carbon accumulation rate calculated at these sites varies from 18.1 to 31.1 gC m -2 yr -1 , and it is evident selective preservation, molecular complexity of organic compounds, and freezing conditions enhance the long-term stability of SOC. Further, our results suggest permafrost dynamics strongly impact the more undecomposed SOC that could be rapidly remobilized through ongoing thermokarst expansion.

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“…Huang et al (2013) proposed that the climatic significance of d 13 C values in peat bogs may vary from region to region, and that independent studies of modern processes are required to properly ascertain the relationship between d 13 C TOC values and climate factors in a certain location. Various factors can influence the d 13 C value of plant tissue, but in certain ecosystems and locations many of these factors are nearly constant or their differences are negligible (Skrzypek et al, 2007a(Skrzypek et al, , 2010, and precipitation and temperature are considered the main controlling factors (Menot and Burns, 2001;Skrzypek et al, 2007bSkrzypek et al, , 2011Loisel et al, 2009;Tillman et al, 2010;Holzkämper et al, 2012). Wang et al (2013) reported a strong relationship between mean annual temperature and d 13 C values in C3 plants sampled from the 400 mm mean annual precipitation isoline in north China.…”

Section: Organic Proxy Recordmentioning

confidence: 99%