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1. Autochamber CH4 Fluxes and δ13C Values at Stordalen Mire

   https://doi.org/10.5281/zenodo.13377109  

   McCalley, Carmody K; Varner, Ruth; Crill, Patrick; Saleska, Scott (August 2024, Zenodo)

   Autochamber-based CH4 fluxes and δ13C values measured with a Tunable Infrared Laser Direct Absorption Spectrometer (TILDAS, Aerodyne Research Inc.); and ancillary data, including CO2 fluxes (measured with a LGR Greenhouse Gas Analyzer), temperatures, atmospheric pressure, and photosynthetically active radiation (PAR). In addition to the data published here, data from 2011 is also available in the supplementary files to McCalley et al. (2014) under the Source data to Fig. 1 link.   METHODS: Methane fluxes were measured using a system of 8 automatic gas-sampling chambers made of transparent Lexan (n=3 each in the palsa and bog habitats, and n=2 in the fen habitat). Chambers were initially installed in the three habitat types at Stordalen Mire in 2001 (Bäckstrand et al., 2008) and the chamber lids were replaced in 2011 with the current design, similar to that described by Bubier et al 2003. Chambers cover an area of 0.2 m2 (45 cm x 45 cm), with a height ranging from 15-75 cm depending on habitat vegetation. At the Palsa and bog site the chamber base is flush with the ground and the chamber lid (15 cm in height) lifts clear of the base between closures. At the fen site the chamber base is raised 50–60 cm on lexon skirts to accommodate large stature vegetation. The chambers are instrumented with thermocouples measuring air and surface ground temperature, and water table depth and thaw depth are measured manually 3–5 times per week. The chambers are connected to the gas analysis system, located in an adjacent temperature-controlled cabin, by 3/8” Dekoron tubing through which air is circulated at approximately 2.5 L min-1. Each chamber lid is closed once every 3 hours for a period of 8 min, with a 5 min flush period before and after lid closure. We measured methane concentration using a Tunable Infrared Laser Direct Absorption Spectrometers (TILDAS, Aerodyne Research Inc.) connected to the main chamber circulation using ¼” Dekoron tubing (McCalley et al 2014). Calibrations were done every 90 min using 3 calibration gases spanning the observed concentration range (1.8–10 ppm). For each autochamber closure we calculated flux using a method consistent with that detailed by Bäckstrand et al 2008 for CO2 and total hydrocarbons, using a linear regression of changing headspace CH4 concentration over a period of 2.5 min. Eight 2.5 min regressions were calculated, staggered by 15 sec, and the most linear fit (highest r2) was then used to calculate flux. Daily average flux for each chamber was used to calculate daily flux and standard error for each cover type. References: Bäckstrand, K., Crill, P. M., Mastepanov, M., Christensen, T. R. & Bastviken, D. Total hydrocarbon flux dynamics at a subarctic mire in northern Sweden. Journal of Geophysical Research 113, (2008). Bubier, J. L., Crill, P. M., Mosedale, A., Frolking, S. & Linder, E. Peatland responses to varying interannual moisture conditions as measured by automatic CO2 chambers. Global Biogeochemical Cycles 17, (2003). McCalley, C.K., B.J. Woodcroft, S.B. Hodgkins, R.A. Wehr, E-H. Kim, R. Mondav, P.M. Crill, J.P. Chanton, V.I. Rich, G.W. Tyson, S.R. Saleska (2014), Methane dynamics regulated by microbial community response to permafrost thaw, Nature, 514:478-481, doi:10.1038/nature13798.   FILES: Files are named with the year or date range, followed by a suffix indicating data resolution: *_CH4output_clean_ckm.txt - Individual measurements of CH4 fluxes (CH4Flux), CO2 fluxes (CO2flux; for select years), and δ13C signature of emitted CH4 (Flux13CH4) for each chamber closure. CH4FluxRsq is the R2 value of the linear fit used to calculate CH4 flux, CO2Rsq is the R2 value of the linear fit used to calculate CO2 flux, and Flux13CH4_stdev is the standard deviation of the δ13C signature (standard deviation of the intercept of the Keeling plot). *_DailyCH4output_ckm.txt - Daily average CH4 fluxes (CH4Flux) and δ13C values (13CH4), grouped by site: Palsa, Bog, Fen, and Chamber 9 (bog/fen transition); along with standard deviations (stdev) and standard errors (se) of the flux or δ13C for each site type. For the Palsa, Bog, and Fen sites, these averages are calculated by chamber (n=3 for Palsa and Bog, n=2 for Fen), so each chamber's daily average is calculated, and then a daily average for that site is calculated as the average of the chambers. For Chamber 9 (bog/fen intermediate; n=1 chamber), averages are calculated by day as there are no chamber replicates. MEASUREMENT UNITS (same for both file types): CH4 flux: mg CH4 m−2 hr−1 CO2 flux: mg C m−2 h−1 δ13C: ‰ Temperature: °C Air pressure: mbar PAR: µmol photons m−2 s−1   FUNDING: This research is a contribution of the EMERGE Biology Integration Institute, funded by the National Science Foundation, Biology Integration Institutes Program, Award # 2022070.We thank the Swedish Polar Research Secretariat and SITES for the support of the work done at the Abisko Scientific Research Station. SITES is supported by the Swedish Research Council's grant 4.3-2021-00164.This study was also funded by the Genomic Science Program of the United States Department of Energy Office of Biological and Environmental Research, grant #s DE-SC0004632, DE-SC0010580, and DE-SC0016440.Autochamber measurements between 2013 and 2017 were supported by a grant from the US National Science Foundation MacroSystems program (NSF EF 1241037, PI Varner). 

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2. Stordalen Mire habitat classifications map (2014)

   https://doi.org/10.5281/zenodo.15042233  

   Palace, Michael; Herrick, Christina (March 2025, Zenodo)

   Stordalen Mire landcover classifications (including 3 permafrost thaw stages: Palsa, Bog, and Fen), based on WorldView-2 satellite imagery acquired on August 8, 2014.  This image is a GeoTIFF with embedded georeferencing information.   FUNDING: National Aeronautics and Space Administration, Interdisciplinary Science program: From Archaea to the Atmosphere (award # NNX17AK10G) National Science Foundation, Biology Integration Institutes Program: EMERGE Biology Integration Institute (award # 2022070) United States Department of Energy Office of Biological and Environmental Research, Genomic Science Program: The IsoGenie Project (grant #s DE-SC0004632, DE-SC0010580, and DE-SC0016440) National Science Foundation, MacroSystems program (grant # EF-1241037) 

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3. Summaries of autochamber CH4 fluxes and δ13C values prior to peat sampling in Stordalen Mire, 2011-2016

   https://doi.org/10.5281/zenodo.14834760  

   McCalley, Carmody K (February 2025, Zenodo)

   This dataset provides summaries of methane (CH4) flux, and δ13C isotopic composition of emitted CH4, prior to the collection of peat samples from Stordalen Mire, Sweden, in 2011-2016. Both flux and isotope values include the average of the chamber replicates (n=3 for Palsa and Bog, n=2 for Fen) and standard error, over timespans of 1, 2, 3, and 4 weeks prior to each Coring Date. Fluxes units are: mg CH4 m−2 hr−1. Fluxes and isotopes were measured with a Tunable Infrared Laser Direct Absorption Spectrometer (TILDAS, Aerodyne Research Inc.). The source data are available at https://doi.org/10.5281/zenodo.13377109.   FUNDING: This research is a contribution of the EMERGE Biology Integration Institute, funded by the National Science Foundation, Biology Integration Institutes Program, Award # 2022070.We thank the Swedish Polar Research Secretariat and SITES for the support of the work done at the Abisko Scientific Research Station. SITES is supported by the Swedish Research Council's grant 4.3-2021-00164.This study was also funded by the Genomic Science Program of the United States Department of Energy Office of Biological and Environmental Research, grant #s DE-SC0004632, DE-SC0010580, and DE-SC0016440.Autochamber measurements between 2013 and 2017 were supported by a grant from the US National Science Foundation MacroSystems program (NSF EF 1241037, PI Varner). 

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4. Carbon Accumulation, Flux, and Fate in Stordalen Mire, a Permafrost Peatland in Transition

   https://doi.org/10.1029/2021GB007113  

   Holmes, M. E.; Crill, P. M.; Burnett, W. C.; McCalley, C. K.; Wilson, R. M.; Frolking, S.; Chang, K. ‐Y.; Riley, W. J.; Varner, R. K.; Hodgkins, S. B.; et al (January 2022, Global Biogeochemical Cycles)

   Abstract Stordalen Mire is a peatland in the discontinuous permafrost zone in arctic Sweden that exhibits a habitat gradient from permafrost palsa, toSphagnumbog underlain by permafrost, toEriophorum‐dominated fully thawed fen. We used three independent approaches to evaluate the annual, multi‐decadal, and millennial apparent carbon accumulation rates (aCAR) across this gradient: seven years of direct semi‐continuous measurement of CO₂and CH₄exchange, and 21 core profiles for²¹⁰Pb and¹⁴C peat dating. Year‐round chamber measurements indicated net carbon balance of −13 ± 8, −49 ± 15, and −91 ± 43 g C m⁻² y⁻¹for the years 2012–2018 in palsa, bog, and fen, respectively. Methane emission offset 2%, 7%, and 17% of the CO₂uptake rate across this gradient. Recent aCAR indicates higher C accumulation rates in surface peats in the palsa and bog compared to current CO₂fluxes, but these assessments are more similar in the fen. aCAR increased from low millennial‐scale levels (17–29 g C m⁻² y⁻¹) to moderate aCAR of the past century (72–81 g C m⁻² y⁻¹) to higher recent aCAR of 90–147 g C m⁻² y⁻¹. Recent permafrost collapse, greater inundation and vegetation response has made the landscape a stronger CO₂sink, but this CO₂sink is increasingly offset by rising CH₄emissions, dominated by modern carbon as determined by¹⁴C. The higher CH₄emissions result in higher net CO_{2‐equivalent}emissions, indicating that radiative forcing of this mire and similar permafrost ecosystems will exert a warming influence on future climate. 

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5. Stordalen Mire mire-wide survey: Pairwise geographic distances between plots

   https://doi.org/10.5281/zenodo.15048219  

   Hodgkins, Suzanne (March 2025, Zenodo)

   Pairwise geographic distances (m) between mire-wide plots in Stordalen Mire, northern Sweden. Distances are in the file Mirewide_Plots_distances-m.csv. This file was generated with the script Mirewide_Plots_Distances.R, using Mirewide_Plots_GPS.csv as input, and geosphere package version 1.5-10. Details of the plots, including latitude, longitude, and vegetation cover, are in the dataset "Stordalen Mire mire-wide survey: Vegetation cover" (https://doi.org/10.5281/zenodo.15048198). The latitude & longitude provided in that dataset represent more precise versions of the coordinates in Mirewide_Plots_GPS.csv (which also omits plot 8); the coordinates are otherwise identical in both datasets. FUNDING: National Aeronautics and Space Administration, Interdisciplinary Science program: From Archaea to the Atmosphere (award # NNX17AK10G). National Science Foundation, Biology Integration Institutes Program: EMERGE Biology Integration Institute (award # 2022070). United States Department of Energy Office of Biological and Environmental Research, Genomic Science Program: The IsoGenie Project (grant #s DE-SC0004632, DE-SC0010580, and DE-SC0016440). We thank the Swedish Polar Research Secretariat and SITES for the support of the work done at the Abisko Scientific Research Station. SITES is supported by the Swedish Research Council's grant 4.3-2021-00164. 

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