Montclair State University Montclair State University Digital Commons Department of Earth and Environmental Studies Department of Earth and Environmental Studies Faculty Scholarship and Creative Works 9-2001 Carbon Dynamics in Peat Bogs: Insights From Substrate Macromolecular Chemistry Kuder Tomasz Southern Illinois University Michael A. Kruge Montclair State University, [email protected] Follow this and additional works at: https://digitalcommons.montclair.edu/earth-environ-studies- facpubs Part of the Environmental Sciences Commons, Geochemistry Commons, Geology Commons, and the Soil Science Commons MSU Digital Commons Citation Tomasz, Kuder and Kruge, Michael A., "Carbon Dynamics in Peat Bogs: Insights From Substrate Macromolecular Chemistry" (2001). Department of Earth and Environmental Studies Faculty Scholarship and Creative Works. 50. https://digitalcommons.montclair.edu/earth-environ-studies-facpubs/50 Published Citation Kuder, T., & Kruge, M. A. (2001). Carbon dynamics in peat bogs: Insights from substrate macromolecular chemistry. Global Biogeochemical Cycles, 15(3), 721-727. doi:https://doi.org/10.1029/2000GB001293 This Article is brought to you for free and open access by the Department of Earth and Environmental Studies at Montclair State University Digital Commons. It has been accepted for inclusion in Department of Earth and Environmental Studies Faculty Scholarship and Creative Works by an authorized administrator of Montclair State University Digital Commons. For more information, please contact [email protected]. GLOBAL BIOGEOCHEMICAL CYCLES, VOL. 15, NO. 3, PAGES 721-727, SEPTEMBER 2001 Carbon dynamics in peat bogs: Insights from substrate macromolecular chemistry TomaszKuder • and Michael A. Kruge Departmentof Geology,Southern Illinois University,Carbondale, Illinois, USA Abstract. The macromolecularcompositions of subfossilplants from borealSphagnum bogs and restiadbogs (New Zealand)have been studiedby pyrolysis-gaschromatography/mass spectrometryto evaluatethe extentof degradationin the anoxic zone (catotelm)of a peat bog. Degradationof vascularplant polysaccharideswas apparentonly into the upper catotelm. Sphagnumwas degradedmore slowly than vascularplants, but no cessationof degradationwas observed.The inferredrate of degradationvaried dependingon type of plant, extentof aerobic, precatotelmicdegradation, and mode of litter deposition(rooting versus at the surface). Environmentalforcing on anaerobiccarbon dynamics would potentially be largestif the hydrology was disturbedat a wet and vascularplant-rich site. Peat depositedunder a dry regime would be relativelyinert in anaerobicconditions. Although catotelmic degradation is usuallynot extensive, in somecases, if labile organicmatter is retainedin the aerobicphase (e.g., restiadbogs) a major fractionof peatis degradedin catotelm, potentially resulting in a delayedmajor export of 14C-old methane. 1. Introduction however, these studiesare necessarilylimited to severalyears of observationsand to the relativelyrapid acrotelmicprocesses. Peat About one third of global soil organicmatter (aM) is storedin stratigraphicprofiles, conversely,provide a record of cumulative peatlands[Gorham, 1991]. A low turnover rate, resulting in net degradationsince the initiationof deposition.The major benefit of aM accumulation,is attributedprimarily to watefiogging-induced suchan approachis the ability to detectslow processesoccurring anoxia in the catotelmlayer (in the senseof Ingram [1978]). The in the catotelm,perhaps the least understoodaspect of peatland primarypool of aM is severelydepleted by aerobicdegradation in OM dynamics. the acrotelmlayer (in the senseof Ingram [1978]) in the first years In the presentstudy, we use dataon macromolecularcomposition after deposition,before the permanentonset of anoxia. The rate of peat aM from severalbog siteswith variablevegetation history and extentof catotelmicdegradation are uncertain,but apparently to answer the question of whether and where does catotelmic slow [Ctymo,1983]. Characteristically,peatlands are major sources degradation take place. Interpretation of the result within the of CH4 [e.g., Dise et at., 1993] and dissolvedorganic carbon framework of peatland hydrology and carbon export will be (DaC) emissions[e.g., Schiffet at., 1998]. The informationon aM attempted.The challengeof a studyof peat chemicalcomposition dynamicscomes primarily from ca2, CH4, or Dac flux experi- is the botanical heterogeneityof the material. Analytical data on ments [e.g., Laine et at., 1996; Moore and Datva, 1997; Yavitt et bulk peat, especiallyfrom boreal bogs, must be approachedcau- at., 2000]. On the other hand, the substrateof the degradation tiouslybecause of the dominanceof botanical,rather than diage- productsis rarely defined chemically and botanically, even if netic, signaturesfor bulk Sphagnumpeat [Kuder, 2000]. Moreover, substratequality is a major factor affecting diagenesisrates [cf. rooting results in the introduction of fresh aM into older and Updegraff et at., 1995]. If chemical data are available, they alreadydegraded matrix, resultingin the "dilution" of the actual typically concernbulk peat, which imposescertain limitations on diageneticsignal. To overcomethis problem, fractions of individual interpretationsYavitt et at., 1997; Wittiamset at., 1998; Yavittet at., taxa are collectedfrom the peat matrix and analyzed separately. 2000]. The most informative results on the sourcesof methane, Sequencesof peat samples from the four sites were collected, ca2, and Dac were providedby radiocarbondating. CH4 emitted allowing temporalcoverage up to 8000 years B.P. Pyrolysis-gas fromthe bog surface is consistentlyshown to be of recent14C age, chromatography/massspectrometry (Py-GC/MS) was appliedas a indicating production at the expense of recently fixed carbon techniqueallowing a multifacetedcharacterization of macromolec- [Chantonet at., 1995; Charman et at., 1999; Schiff et at., 1998]. ular componentsin submilligramsamples of pure botanicalsub- When old substrateis degraded,the productsmay be retained fractionsof peat matrix [van Smerdijkand Boon, 1987]. within the depositor dischargedinto groundwater,thus remaining undetected[Charman et at., 1993]. An alternativeapproach to peatlandcarbon dynamicsis mon- 2. Methods itoring of temporaltrends of substratedegradation. This approach is widely used in litterbag experiments [e.g., Ctymo, 1983]; 2.1. Locations: Environmental Setting and Sampling Raw data for this papercome from previouslypublished studies 1Nowat Schoolof Geologyand Geophysics, University of Oklahoma, of a Sphagnumbog from Canada,a Sphagnumbog from Poland, Norman, Oklahoma, USA. and two restiadbogs from New Zealand. The Canadiansite ("Carling Lake" bog) is a part of a systemof Copyright2001 by the AmericanGeophysical Union. peatlandsdeveloped in the humid and cold climate of the Hudson Papernumber 2000GB001293. BayLowland (HBL) region(northern Ontario, 51 ø32•N, 81 ø36•W). 0886-6236/01/2000GB001293 $12.00 Thethickness of peatwas 265 cm,and •4C age was 4110 4- 70 721 722 KUDER AND KRUGE: PEAT BOG CARBON DYNAMICS years B.P. at the base [Klinger et al., 1994]. Severallakes occur The samplesfrom the Polish site were also extractedwith a D- next to or within the bog. The topographyof the HBL is flat, with a barrelcorer. Subsamples of •4 cm3 weretaken from a continuous seriesof parallel beach ridges and swales.They representancient seriesof intervalswith distinctvisual humificationor composition coastlinesof a sea retreating because of postglacial isostatic (2-5 cm per intervals with distinct color and fibrosity). The rebound.Peat accumulatedbetween ridges, because of impediment maximum depth of samplingwas •110 cm (a few centimeters of drainageon marine silts and clays and favorableclimate during shortof the bedrock).Plant macrofossilswere handpickedunder a the growing season(May-September). The mean annualtemper- binocular microscopefrom the selectedsubsamples, frozen, and atureis •0øC, growingseason temperature averages 11.3øC, and vacuumdried to preventfurther decomposition. Also, freshtissues mean growing seasonprecipitation is 80.3 mm. Peat depositional of the analyzedtaxa were collectedand preserved.The botanical environmentson the HBL rangefrom saltwatermarshes to fens to composition of peat in Canadian and Polish locations was bogs,a gradientobserved moving inlandfrom the modem shoreof describedto identify the details of stratigraphy.In the caseof the HudsonBay. Accordingly,it is observedthat in bog sitesthe basal New Zealandsite the physicalproperties were usedto differentiate peat was depositedunder the fen regime.Present-day vegetation is peat layers,because of more uniformbotanical characteristics than characteristicof ombrotrophicconditions, consisting of stunted observedin the boreal bogs. bog forests(Picea mariana, Larix laricina) and Sphagnumlawns with a numberof Ericaceae(including species of Andromedaand 2.2. Analytical Procedures Iraccinium).In the stratigraphicrecord few intervalswith abundant All chemical data were obtainedby pyrolysis-gaschromatog- sedges,probably Carex, occur. High amountsof occludedgas raphy/massspectrometry (Py-GC/MS) of peat macrofossils(Can- (CO2 and methane?)occurred below a depth of 200 cm. At the ada and Polandsites) and peat matrix (New Zealand). Selectionof moment of samplingthe water table was between 18 and 35 cm plant typesand organswas madeto accountfor the volumetrically below the surface,apparently representing an exceptionallydry dominantones, including