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  • 1.
    Andersson, Rina Argelia
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Kuhry, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Meyers, Philip
    Department of Earth and Environmental Sciences, The University of Michigan, Ann Arbor, Michigan, U.S.A..
    Zebür, Yngve
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Mörth, Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Impacts of paleohydrological changes on n-alkane biomarker compositions of a Holocene peat sequence in the eastern European Russian Arctic2011Ingår i: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 42, nr 9, s. 1065-1075Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coupled analyses of n-alkane biomarkers and plant macrofossils from a peat plateau deposit in the northeast European Russian Arctic were carried out to assess the effects of past hydrology on the molecular contributions of plants to the peat. The n-alkane biomarkers accumulated over 9.6 kyr of local paleohydrological changes in this complex peat profile in which a succession of vegetation changes occurred during a transition from a wet fen to a relatively dry peat plateau bog. This study shows that the contribution of the n-C31 alkane from rootlets to peat layers rich in fine and dark roots is important. The results further indicate that the n-alkanePaqandn-C23/n-C29 biomarker proxies that have been useful to reconstruct past water table levels in many peat deposits can be misleading when the contributions of Betulaand Sphagnum fuscum to the peat are large. Under these conditions, the C23/(C27+ C31) n-alkane ratio seems to correct for the presence of BetulaandS. fuscum and provides a better description for the relative amounts of moisture. The average chain length (ACL) n-alkane proxy also appears to be a good paleohydrology proxy in having larger values during dry and cold conditions in this Arctic bog setting.

  • 2. Balathandayuthabani, Sivakiruthika
    et al.
    Wallin, Marcus B.
    Klemedtsson, Leif
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper. Stockholms universitet, Naturvetenskapliga fakulteten, Bolincentret för klimatforskning (tills m KTH & SMHI).
    Bastviken, David
    Aquatic carbon fluxes in a hemiboreal catchment are predictable from landscape morphology, temperature, and runoff2023Ingår i: Limnology and Oceanography Letters, E-ISSN 2378-2242, Vol. 8, nr 2, s. 313-322Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aquatic networks contribute greenhouse gases and lateral carbon (C) export from catchments. The magnitudes of these fluxes exceed the global land C sink but are uncertain. Resolving this uncertainty is important for understanding climate feedbacks. We quantified vertical methane (CH4) and carbon dioxide (CO2) emissions from lakes and streams, and lateral export of dissolved inorganic and organic carbon from a hemiboreal catchment for 3 yr. Lateral C fluxes dominated the total aquatic C flux. All aquatic C fluxes were disproportionately contributed from spatially restricted areas and/or short-term events. Hence, consideration of local and episodic variability is vital. Temperature and runoff were the main temporal drivers for lake and stream C emissions, respectively. Whole-catchment aquatic C emissions scaled linearly with these drivers within timeframes of stable land-cover. Hence, temperature and runoff increase across Northern Hemisphere humid areas from climate change may yield proportional increases in aquatic C fluxes. 

  • 3. Bastviken, David
    et al.
    Santoro, Ana Lucia
    Marotta, Humberto
    Pinho, Luana Queiroz
    Calheiros, Debora Fernandes
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Enrich-Prast, Alex
    Methane Emissions from Pantanal, South America, during the Low Water Season: Toward More Comprehensive Sampling2010Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 44, nr 14, s. 5450-5455Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Freshwater environments contribute 75% of the natural global methane (CH4) emissions. While there are indications that tropical lakes and reservoirs emit 58-400% more CH4 per unit area than similar environments in boreal and temperate biomes, direct measurements of tropical lake emissions are scarce. We measured CH4 emissions from 16 natural shallow lakes in the Pantanal region of South America, one of the world's largest tropical wetland areas, during the low water period using floating flux chambers. Measured fluxes ranged from 3.9 to 74.2 mmol m(-2) d(-1) with the average from all studied lakes being 8.8 mmol m(-2) d(-1) (131.8 mg CH4 m(-2) d(-1)), of which ebullition accounted for 91% of the flux (28-98% on individual lakes). Diel cycling of emission rates was observed and therefore 24-h long measurements are recommended rather than short-term measurements not accounting for the full diel cycle. Methane emission variability within a lake may be equal to or more important than between lake variability in floodplain areas as this study identified diverse habitats within lakes having widely different flux rates. Future measurements with static floating chambers should be based on many individual chambers distributed in the various subenvironments of a lake that may differ in emissions in order to account for the within lake variability.

  • 4. Bastviken, David
    et al.
    Tranvik, Lars J.
    Downing, John A.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Enrich-Prast, Alex
    Freshwater Methane Emissions Offset the Continental Carbon Sink2011Ingår i: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 331, nr 6013, s. 50-50Artikel i tidskrift (Refereegranskat)
  • 5. Berchet, Antoine
    et al.
    Pison, Isabelle
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Thornton, Brett
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Bousquet, Philippe
    Thonat, Thibaud
    Hocking, Thomas
    Thanwerdas, Joël
    Paris, Jean-Daniel
    Saunois, Marielle
    Using ship-borne observations of methane isotopic ratio in the Arctic Ocean to understand methane sources in the Arctic2020Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 20, nr 6, s. 3987-3998Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Characterizing methane sources in the Arctic remains challenging due to the remoteness, heterogeneity and variety of such emissions. In situ campaigns provide valuable datasets to reduce these uncertainties. Here we analyse data from the summer 2014 SWERUS-C3 campaign in the eastern Arctic Ocean, off the shore of Siberia and Alaska. Total concentrations of methane, as well as relative concentrations of (CH4)-C-12 and (CH4)-C-13, were measured continuously during this campaign for 35 d in July and August. Using a chemistry-transport model, we link observed concentrations and isotopic ratios to regional emissions and hemispheric transport structures. A simple inversion system helped constrain source signatures from wetlands in Siberia and Alaska, and oceanic sources, as well as the isotopic composition of lower-stratosphere air masses. The variation in the signature of lower-stratosphere air masses, due to strongly fractionating chemical reactions in the stratosphere, was suggested to explain a large share of the observed variability in isotopic ratios. These results point towards necessary efforts to better simulate large-scale transport and chemistry patterns to make relevant use of isotopic data in remote areas. It is also found that constant and homogeneous source signatures for each type of emission in a given region (mostly wetlands and oil and gas industry in our case at high latitudes) are not compatible with the strong synoptic isotopic signal observed in the Arctic. A regional gradient in source signatures is highlighted between Siberian and Alaskan wetlands, the latter having lighter signatures (more depleted in C-13). Finally, our results suggest that marine emissions of methane from Arctic continental-shelf sources are dominated by thermogenicorigin methane, with a secondary biogenic source as well.

  • 6. Bolduc, Benjamin
    et al.
    Hodgkins, Suzanne B.
    Varner, Ruth K.
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    McCalley, Carmody K.
    Chanton, Jeffrey P.
    Tyson, Gene W.
    Riley, William J.
    Palace, Michael
    Duhaime, Melissa B.
    Hough, Moira A.
    Saleska, Scott R.
    Sullivan, Matthew B.
    Rich, Virginia
    The IsoGenie database: an interdisciplinary data management solution for ecosystems biology and environmental research2020Ingår i: PeerJ, E-ISSN 2167-8359, Vol. 8, artikel-id e9467Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Modern microbial and ecosystem sciences require diverse interdisciplinary teams that are often challenged in speaking to one another due to different languages and data product types. Here we introduce the IsoGenie Database (IsoGenieDB;https://isogenic-db.asc.ohio-state.edu/), a de novo developed data management and exploration platform, as a solution to this challenge of accurately representing and integrating heterogenous environmental and microbial data across ecosystem scales. The IsoGenieDB is a public and private data infrastructure designed to store and query data generated by the IsoGenie Project, a similar to 10 year DOE-funded project focused on discovering ecosystem climate feedbacks in a thawing permafrost landscape. The IsoGenieDB provides (i) a platform for IsoGenie Project members to explore the project's interdisciplinary datasets across scales through the inherent relationships among data entities, (ii) a framework to consolidate and harmonize the datasets needed by the team's modelers, and (iii) a public venue that leverages the same spatially explicit, disciplinarily integrated data structure to share published datasets. The IsoGenieDB is also being expanded to cover the NASA-funded Archaea to Atmosphere (A2A) project, which scales the findings of IsoGenie to a broader suite of Arctic peatlands, via the umbrella A2A Database (A2A-DB). The IsoGenieDB's expandability and flexible architecture allow it to serve as an example ecosystems database.

  • 7.
    Bubier, J.L.
    et al.
    Mount Holyoke College.
    Moore, T.
    McGill Univ.
    Savage, K.
    McGill Univ.
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    A comparison of methane flux in a boreal landscape between a dry and a wet year.2005Ingår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 19, nr GB1023Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We used field measurements of methane (CH4) flux from upland and wetland soils in the Northern Study Area (NSA) of BOREAS (BOReal Ecosystem-Atmosphere Study), near Thompson, Manitoba, during the summers of 1994 and 1996 to estimate the overall CH4 emission from a 1350 km2 landscape. June–September 1994 and 1996 were both drier and warmer than normal, but summer 1996 received 68 mm more precipitation than 1994, a 40% increase, and had a mean daily air temperature 0.6°C warmer than 1994. Upland soils consumed CH4 at rates from 0 to 1.0 mg m−2 d−1, with small spatial and temporal variations between years, and a weak dependence on soil temperature. In contrast, wetlands emitted CH4 at seasonal average rates ranging from 10 to 350 mg CH4 m−2 d−1, with high spatial and temporal variability, and increased an average of 60% during the wetter and warmer 1996. We used Landsat imagery, supervised classification, and ground truthing to scale point CH4 fluxes (<1 m2) to the landscape (>1000 km2). We performed a sensitivity analysis for error terms in both areal coverage and CH4 flux, showing that the small areas of high CH4 emission (e.g., small ponds, graminoid fens, and permafrost collapse margins) contribute the largest uncertainty in both flux measurements and mapping. Although wetlands cover less than 30% of the landscape, areally extrapolated CH4 flux for the NSA increased by 61% from 10 to16 mg CH4 m−2 d−1 between years, entirely attributed to the increase in wetland CH4 emission. We conclude that CH4 fluxes will tend to be underestimated in areas where much of the landscape is covered by wetlands. This is due to the large spatial and temporal variability encountered in chamber-based measurements of wetland CH4 fluxes, strong sensitivity of wetland CH4 emission to small changes in climate, and because most remote sensing images do not adequately identify small areas of high CH4 flux.

  • 8. Burke, S. A.
    et al.
    Wik, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Lang, A.
    Contosta, A. R.
    Palace, M.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Varner, R. K.
    Long-Term Measurements of Methane Ebullition From Thaw Ponds2019Ingår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 124, nr 7, s. 2208-2221Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Arctic regions are experiencing rapid warming, leading to permafrost thaw and formation of numerous water bodies. Although small ponds in particular are considered hot spots for methane (CH4) release, long-term studies of CH4 efflux from these surfaces are rare. We have collected an extensive data set of CH4 ebullition (bubbling) measurements from eight small thaw ponds (<0.001 km(2)) with different physical and hydrological characteristics over four summer seasons, the longest set of observations from thaw ponds to date. The measured fluxes were highly variable with an average of 20.0 mg CH4 . m(-2) . day(-1) (median: 4.1 mg CH4 . m(-2) . day(-1), n = 2,063) which is higher than that of most nearby lakes. The ponds were categorized into four types based on clear and significant differences in bubble flux. We found that the amount of CH4 released as bubbles from ponds was very weakly correlated with environmental variables, like air temperature and atmospheric pressure, and was potentially more related to differences in physical characteristics of the ponds. Using our measured average daily bubble flux plus the available literature, we estimate circumpolar thaw ponds <0.001 km(2) in size to emit between 0.2 and 1.0 Tg of CH4 through ebullition. Our findings exemplify the importance of high-frequency measurements over long study periods in order to adequately capture the variability of these water bodies. Through the expansion of current spatial and temporal monitoring efforts, we can increase our ability to estimate CH4 emissions from permafrost pond ecosystems now and in the future.

  • 9.
    Burrows, E.H.
    et al.
    Univ New Hampshire.
    Bubier, J.L.
    Mount Holyoke College.
    Mosedale, A.
    Univ New Hampshire.
    Cobb, G.W.
    Mount Holyoke College.
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Net Ecosystem Exchange of Carbon Dioxide in a Temperate Poor Fen: A Comparison of Automated and Manual Chamber Techniques,2005Ingår i: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 76, nr 1, s. 21-45Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We used five analytical approaches to compare net ecosystem exchange (NEE) of carbon dioxide (CO2) from automated and manual static chambers in a peatland, and found the methods comparable. Once per week we sampled manually from 10 collars with a closed chamber system using a LiCor 6200 portable photosynthesis system, and simulated four photosynthetically active radiation (PAR) levels using shrouds. Ten automated chambers sampled CO2 flux every 3 h with a LiCor 6252 infrared gas analyzer. Results of the five comparisons showed (1) NEE measurements made from May to August, 2001 by the manual and automated chambers had similar ranges: -10.8 to 12.7 μmol CO 2 m-2 s-1 and -17.2 to 13.1 μmol CO 2 m-2 s-1, respectively. (2) When sorted into four PAR regimes and adjusted for temperature (respiration was measured under different temperature regimes), mean NEE did not differ significantly between the chambers (p < 0.05). (3) Chambers were not significantly different in regression of ln( - respiration) on temperature. (4) But differences were found in the PAR vs. NEE relationship with manual chambers providing higher maximum gross photosynthesis estimates (GPmax), and slower uptake of CO 2 at low PAR (α) even after temperature adjustment. (5) Due to the high variability in chamber characteristics, we developed an equation that includes foliar biomass, water table, temperature, and PAR, to more directly compare automated and manual NEE. Comparing fitted parameters did not identify new differences between the chambers. These complementary chamber techniques offer a unique opportunity to assess the variability and uncertainty in CO 2 flux measurements.

  • 10.
    Bäckstrand, Kristina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Crill, Patrick, M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Jackowicz-Korczyński, Marcin
    Mastepanov, Mikhail
    Christensen, Torben, R.
    Bastviken, David
    Annual carbon gas budget for a subarctic peatland, northern Sweden2010Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 7, nr 1, s. 95-108Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Temperatures in the Arctic regions are rising, thawing permafrost and exposing previously stable soil organic carbon (OC) to decomposition. This can result in northern latitude soils, which have accumulated large amounts of OC potentially shifting from atmospheric C sinks to C sources with positive feedback on climate warming. In this paper, we estimate the annual net C gas balance (NCB) of the subarctic mire Stordalen, based on automatic chamber measurements of CO2 and total hydrocarbon (THC; CH4 and NMVOCs) exchange. We studied the dominant vegetation communities with different moisture and permafrost characteristics; a dry Palsa underlain by permafrost, an intermediate thaw site with Sphagnum spp. and a wet site with Eriophorum spp. where the soil thaws completely. Whole year accumulated fluxes of CO2 were estimated to 29.7, −35.3 and −34.9 gC m−2 respectively for the Palsa, Sphagnum and Eriophorum sites (positive flux indicates an addition of C to the atmospheric pool). The corresponding annual THC emissions were 0.5, 6.2 and 31.8 gC m−2 for the same sites. Therefore, the NCB for each of the sites was 30.2, −29.1 and −3.1 gC m−2 respectively for the Palsa, Sphagnum and Eriophorum site. On average, the whole mire was a CO2 sink of 2.6 gC m−2 and a THC source of 6.4 gC m−2 over a year. Consequently, the mire was a net source of C to the atmosphere by 3.9 gC m−2 (based on area weighted estimates for each of the three plant communities). Early and late snow season efflux of CO2 and THC emphasize the importance of winter measurements for complete annual C budgets. Decadal vegetation changes at Stordalen indicate that both the productivity and the THC emissions increased between 1970 and 2000. Considering the GWP100 of CH4, the net radiative forcing on climate increased 21% over the same time. In conclusion, reduced C compounds in these environments have high importance for both the annual C balance and climate.

  • 11.
    Bäckstrand, Kristina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Crill, Patrick, M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Mastepanov, Mikhail
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Christensen, Torben, R.
    INES, University of Lund.
    Bastviken, David
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Nonmethane volatile organic compound flux from a subarctic mire in northern Sweden2008Ingår i: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 60, nr 2, s. 226-237Artikel i tidskrift (Refereegranskat)
  • 12.
    Bäckstrand, Kristina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Crill, Patrick, M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Mastepanov, Mikhail
    GeoBiosphere Science Centre, Physical Geography and Ecosystem Analysis, Lund University.
    Christensen, Torben, R.
    GeoBiosphere Science Centre, Physical Geography and Ecosystem Analysis, Lund University.
    Bastviken, David
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Total hydrocarbon flux dynamics at a subarctic mire in northern Sweden2008Ingår i: Journal of Geophysical Research – Biogeosciences, Vol. 113, s. G03026-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This is a study of the spatial and temporal variability of total hydrocarbon (THC) emissions from vegetation and soil at a subarctic mire, northern Sweden. THCs include methane (CH4) and nonmethane volatile organic compounds (NMVOCs), both of which are atmospherically important trace gases and constitute a significant proportion of the carbon exchange between biosphere and atmosphere. Reliable characterization of the magnitude and the dynamics of the THC fluxes from high latitude peatlands are important when considering to what extent trace gas emissions from such ecosystems may change and feed back on climate regulation as a result of warmer climate and melting permafrost. High frequency measurements of THC and carbon dioxide (CO2) were conducted during four sequential growing seasons in three localities representing the trophic range of plant communities at the mire. The magnitude of the THC flux followed the moisture gradient with increasing emissions from a dry Palsa site (2.2 ± 0.1 mgC m−2 d−1), to a wet intermediate melt feature with Sphagnum spp. (28 ± 0.3 mgC m−2 d−1) and highest emissions from a wet Eriophorum spp. site (122 ± 1.4 mgC m−2 d−1) (overall mean ±1 SE, n = 2254, 2231 and 2137). At the Palsa site, daytime THC flux was most strongly related to air temperature while daytime THC emissions at the Sphagnum site had a stronger relation to ground temperature. THC emissions at both the wet sites were correlated to net ecosystem exchange of CO2. An overall spatial correlation indicated that areas with highly productive vegetation communities also had high THC emission potential.

  • 13. Chang, Kuang-Yu
    et al.
    Riley, William J.
    Brodie, Eoin L.
    McCalley, Carmody K.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Grant, Robert F.
    Methane Production Pathway Regulated Proximally by Substrate Availability and Distally by Temperature in a High-Latitude Mire Complex2019Ingår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 124, nr 10, s. 3057-3074Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Projected 21st century changes in high-latitude climate are expected to have significant impacts on permafrost thaw, which could cause substantial increases in emissions to the atmosphere of carbon dioxide (CO2) and methane (CH4, which has a global warming potential 28 times larger than CO2 over a 100-year horizon). However, predicted CH4 emission rates are very uncertain due to difficulties in modeling complex interactions among hydrological, thermal, biogeochemical, and plant processes. Methanogenic production pathways (i.e., acetoclastic [AM] and hydrogenotrophic [HM]) and the magnitude of CH4 emissions may both change as permafrost thaws, but a mechanistic analysis of controls on such shifts in CH4 dynamics is lacking. In this study, we reproduced observed shifts in CH4 emissions and production pathways with a comprehensive biogeochemical model (ecosys) at the Stordalen Mire in subarctic Sweden. Our results demonstrate that soil temperature changes differently affect AM and HM substrate availability, which regulates magnitudes of AM, HM, and thereby net CH4 emissions. We predict very large landscape-scale, vertical, and temporal variations in the modeled HM fraction, highlighting that measurement strategies for metrics that compare CH4 production pathways could benefit from model informed scale of temporal and spatial variance. Finally, our findings suggest that the warming and wetting trends projected in northern peatlands could enhance peatland AM fraction and CH4 emissions even without further permafrost degradation.

  • 14. Chang, Kuang-Yu
    et al.
    Riley, William J.
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Grant, Robert F.
    Saleska, Scott R.
    Hysteretic temperature sensitivity of wetland CH4 fluxes explained by substrate availability and microbial activity2020Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 17, nr 22, s. 5849-5860Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Methane (CH4) emissions from wetlands are likely increasing and important in global climate change assessments. However, contemporary terrestrial biogeochemical model predictions of CH4 emissions are very uncertain, at least in part due to prescribed temperature sensitivity of CH4 production and emission. While statistically consistent apparent CH4 emission temperature dependencies have been inferred from meta-analyses across microbial to ecosystem scales, year-round ecosystem-scale observations have contradicted that finding. Here, we show that apparent CH4 emission temperature dependencies inferred from year-round chamber measurements exhibit substantial intra-seasonal variability, suggesting that using static temperature relations to predict CH4 emissions is mechanistically flawed. Our model results indicate that such intra-seasonal variability is driven by substrate-mediated microbial and abiotic interactions: seasonal cycles in substrate availability favors CH4 production later in the season, leading to hysteretic temperature sensitivity of CH4 production and emission. Our findings demonstrate the uncertainty of inferring CH4 emission or production rates from temperature alone and highlight the need to represent microbial and abiotic interactions in wetland biogeochemical models.

  • 15. Chang, Kuang-Yu
    et al.
    Riley, William J.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Grant, Robert F.
    Rich, Virginia I.
    Saleska, Scott R.
    Large carbon cycle sensitivities to climate across a permafrost thaw gradient in subarctic Sweden2019Ingår i: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 13, nr 2, s. 647-663Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Permafrost peatlands store large amounts of carbon potentially vulnerable to decomposition. However, the fate of that carbon in a changing climate remains uncertain in models due to complex interactions among hydrological, biogeochemical, microbial, and plant processes. In this study, we estimated effects of climate forcing biases present in global climate reanalysis products on carbon cycle predictions at a thawing permafrost peatland in subarctic Sweden. The analysis was conducted with a comprehensive biogeochemical model (ecosys) across a permafrost thaw gradient encompassing intact permafrost palsa with an ice core and a shallow active layer, partly thawed bog with a deeper active layer and a variable water table, and fen with a water table close to the surface, each with distinct vegetation and microbiota. Using in situ observations to correct local cold and wet biases found in the Global Soil Wetness Project Phase 3 (GSWP3) climate reanalysis forcing, we demonstrate good model performance by comparing predicted and observed carbon dioxide (CO2) and methane (CH4) exchanges, thaw depth, and water table depth. The simulations driven by the bias-corrected climate suggest that the three peatland types currently accumulate carbon from the atmosphere, although the bog and fen sites can have annual positive radiative forcing impacts due to their higher CH4 emissions. Our simulations indicate that projected precipitation increases could accelerate CH4 emissions from the palsa area, even without further degradation of palsa permafrost. The GSWP3 cold and wet biases for this site significantly alter simulation results and lead to erroneous active layer depth (ALD) and carbon budget estimates. Biases in simulated CO2 and CH4 exchanges from biased climate forcing are as large as those among the thaw stages themselves at a landscape scale across the examined permafrost thaw gradient. Future studies should thus not only focus on changes in carbon budget associated with morphological changes in thawing permafrost, but also recognize the effects of climate forcing uncertainty on carbon cycling.

  • 16. Christensen, T
    et al.
    Johansson, T
    Olsrud, M
    Ström, L
    Lindroth, A
    Mastepanov, M
    Malmer, N
    Friborg, T
    Crill, P
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Callaghan, T
    A catchment scale carbon and greenhouse gas budget of a subarctic landscape2007Ingår i: Philosophical Transactions of the Royal Society A, Vol. 365, s. 1643-1656Artikel i tidskrift (Refereegranskat)
  • 17. Christensen, Torben R.
    et al.
    Jackowicz-Korczynski, Marcin
    Aurela, Mika
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Heliasz, Michal
    Mastepanov, Mikhail
    Friborg, Thomas
    Monitoring the multi year carbon balance of a subarctic palsa mire with micrometeorological techniques2012Ingår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 41, s. 207-217Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This article reports a dataset on 8 years of monitoring carbon fluxes in a subarctic palsa mire based on micrometeorological eddy covariance measurements. The mire is a complex with wet minerotrophic areas and elevated dry palsa as well as intermediate sub-ecosystems. The measurements document primarily the emission originating from the wet parts of the mire dominated by a rather homogenous cover of Eriophorum angustifolium. The CO2/CH4 flux measurements performed during the years 2001-2008 showed that the areas represented in the measurements were a relatively stable sink of carbon with an average annual rate of uptake amounting to on average -46 g C m(-2) y(-1) including an equally stable loss through CH4 emissions (18-22 g CH4-C m(-2) y(-1)). This consistent carbon sink combined with substantial CH4 emissions is most likely what is to be expected as the permafrost under palsa mires degrades in response to climate warming.

  • 18.
    Christensen, T.R.
    et al.
    Lund Univ.
    Johansson, T.J.
    Copenhagen Univ.
    Olsrud, M.
    Lund Univ.
    Ström, L.
    Lund Univ.
    Lindroth, A.
    Lund Univ.
    Mastepanov, M
    Lund Univ.
    Malmer, N.
    Lund Univ.
    Friborg, T.
    Copenhagen Univ.
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Callaghan, T.
    KVA-ANS.
    A catchment scale process study of carbon and greenhouse gas exchange in a subarctic landscape.2009Ingår i: Climate Change Impacts on Sub-arctic Palsa mires and Greenhouse Gas Feedbacks / [ed] S. Fronzek et al., 2009, s. 41-43Konferensbidrag (Refereegranskat)
  • 19.
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Fluxes and budgets, GHG feedbacks of palsa mires.2009Ingår i: Climate Change Impacts on Sub-arctic Palsa mires and Greenhouse Gas Feedbacks, / [ed] S. Fronzek et al., 2009, s. 27-29Konferensbidrag (Refereegranskat)
  • 20.
    Crill, Patrick
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Riise, A.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Assessment of local sources of methane from biomass burning in Lycksele town.2005Rapport (Övrigt vetenskapligt)
  • 21. Deng, J.
    et al.
    Li, C.
    Frolking, S.
    Zhang, Y.
    Bäckstrand, Kristina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Assessing effects of permafrost thaw on C fluxes based on multiyear modeling across a permafrost thaw gradient at Stordalen, Sweden2014Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 11, nr 17, s. 4753-4770Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Northern peatlands in permafrost regions contain a large amount of organic carbon (C) in the soil. Climate warming and associated permafrost degradation are expected to have significant impacts on the C balance of these ecosystems, but the magnitude is uncertain. We incorporated a permafrost model, Northern Ecosystem Soil Temperature (NEST), into a biogeochemical model, DeNitrification-DeComposition (DNDC), to model C dynamics in high-latitude peatland ecosystems. The enhanced model was applied to assess effects of permafrost thaw on C fluxes of a subarctic peatland at Stordalen, Sweden. DNDC simulated soil freeze-thaw dynamics, net ecosystem exchange of CO2 (NEE), and CH4 fluxes across three typical land cover types, which represent a gradient in the process of ongoing permafrost thaw at Stordalen. Model results were compared with multiyear field measurements, and the validation indicates that DNDC was able to simulate observed differences in seasonal soil thaw, NEE, and CH4 fluxes across the three land cover types. Consistent with the results from field studies, the modeled C fluxes across the permafrost thaw gradient demonstrate that permafrost thaw and the associated changes in soil hydrology and vegetation not only increase net uptake of C from the atmosphere but also increase the annual to decadal radiative forcing impacts on climate due to increased CH4 emissions. This study indicates the potential of utilizing biogeochemical models, such as DNDC, to predict the soil thermal regime in permafrost areas and to investigate impacts of permafrost thaw on ecosystem C fluxes after incorporating a permafrost component into the model framework.

  • 22. Deng, Jia
    et al.
    McCalley, Carmody K.
    Frolking, Steve
    Chanton, Jeff
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Varner, Ruth
    Tyson, Gene
    Rich, Virginia
    Hines, Mark
    Saleska, Scott R.
    Li, Changsheng
    Adding stable carbon isotopes improves model representation of the role of microbial communities in peatland methane cycling2017Ingår i: Journal of Advances in Modeling Earth Systems, ISSN 1942-2466, Vol. 9, nr 2, s. 1412-1430Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Climate change is expected to have significant and uncertain impacts on methane (CH4) emissions from northern peatlands. Biogeochemical models can extrapolate site-specificCH(4) measurements to larger scales and predict responses of CH4 emissions to environmental changes. However, these models include considerable uncertainties and limitations in representing CH4 production, consumption, and transport processes. To improve predictions of CH4 transformations, we incorporated acetate and stable carbon (C) isotopic dynamics associated with CH4 cycling into a biogeochemistry model, DNDC. By including these new features, DNDC explicitly simulates acetate dynamics and the relative contribution of acetotrophic and hydro-genotrophic methanogenesis (AM and HM) to CH4 production, and predicts the C isotopic signature (delta C-13) in soil C pools and emitted gases. When tested against biogeochemical and microbial community observations at two sites in a zone of thawing permafrost in a subarctic peatland in Sweden, the new formulation substantially improved agreement with CH4 production pathways and delta C-13 in emitted CH4 (delta C-13-CH4), a measure of the integrated effects of microbial production and consumption, and of physical transport. We also investigated the sensitivity of simulated delta C-13-CH4 to C isotopic composition of substrates and, to fractionation factors for CH4 production (alpha(AM) and alpha(HM)), CH4 oxidation (alpha(MO)), and plant-mediated CH4 transport (alpha(TP)). The sensitivity analysis indicated that the delta C-13-CH4 is highly sensitive to the factors associated with microbial metabolism (alpha(AM), alpha(HM), and alpha(MO)). The model framework simulating stable C isotopic dynamics provides a robust basis for better constraining and testing microbial mechanisms in predicting CH4 cycling in peatlands.

  • 23.
    do Carmo, J.B:
    et al.
    Univ Sao Paulo.
    Keller, M.
    USDA Forest Service.
    Dias, J.D.
    Univ Sao Paulo.
    de Carmago, P.B:
    Univ Sao Paulo.
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    A source of methane from upland forests in the Brazilian Amazon.2006Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 33, nr L04809Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We sampled air in the canopy layer of undisturbed upland forests during wet and dry seasons at three sites in the Brazilian Amazon region and found that both methane (CH4) and carbon dioxide (CO2) mixing ratios increased at night. Such increases were consistent across sites and seasons. A canopy layer budget model based on measured soil-atmosphere fluxes of CO2 was constructed to estimate ecosystem CH4 emission. We estimate that net CH4 emission in upland forests ranged from 2 to 21 mg CH4 m−2 d−1. While the origin of this CH4 source is unknown, these ground based measurements are consistent with recent findings based on satellite observations that indicate a large, unidentified source of CH4 in tropical forest regions.

  • 24. Douglas, P. M. J.
    et al.
    Stolper, D. A.
    Smith, D. A.
    Anthony, K. M. Walter
    Paull, C. K.
    Dallimore, S.
    Wik, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Winterdahl, Mathias
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Eiler, J. M.
    Sessions, A. L.
    Diverse origins of Arctic and Subarctic methane point source emissions identified with multiply-substituted isotopologues2016Ingår i: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 188, s. 163-188Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Methane is a potent greenhouse gas, and there are concerns that its natural emissions from the Arctic could act as a substantial positive feedback to anthropogenic global warming. Determining the sources of methane emissions and the biogeochemical processes controlling them is important for understanding present and future Arctic contributions to atmospheric methane budgets. Here we apply measurements of multiply-substituted isotopologues, or clumped isotopes, of methane as a new tool to identify the origins of ebullitive fluxes in Alaska, Sweden and the Arctic Ocean. When methane forms in isotopic equilibrium, clumped isotope measurements indicate the formation temperature. In some microbial methane, however, non-equilibrium isotope effects, probably related to the kinetics of methanogenesis, lead to low clumped isotope values. We identify four categories of emissions in the studied samples: thermogenic methane, deep subsurface or marine microbial methane formed in isotopic equilibrium, freshwater microbial methane with non-equilibrium clumped isotope values, and mixtures of deep and shallow methane (i.e., combinations of the first three end members). Mixing between deep and shallow methane sources produces a non-linear variation in clumped isotope values with mixing proportion that provides new constraints for the formation environment of the mixing end-members. Analyses of microbial methane emitted from lakes, as well as a methanol-consuming methanogen pure culture, support the hypothesis that non-equilibrium clumped isotope values are controlled, in part, by kinetic isotope effects induced during enzymatic reactions involved in methanogenesis. Our results indicate that these kinetic isotope effects vary widely in microbial methane produced in Arctic lake sediments, with non-equilibrium Delta(18) values spanning a range of more than 5 parts per thousand.

  • 25. Douglas, Peter M. J.
    et al.
    Moguel, Regina Gonzalez
    Anthony, Katey M. Walter
    Wik, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Dawson, Katherine S.
    Smith, Derek A.
    Yanay, Ella
    Lloyd, Max K.
    Stolper, Daniel A.
    Eiler, John M.
    Sessions, Alex L.
    Clumped Isotopes Link Older Carbon Substrates With Slower Rates of Methanogenesis in Northern Lakes2020Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 47, nr 6, artikel-id e2019GL086756Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The release of long-stored carbon from thawed permafrost could fuel increased methanogenesis in northern lakes, but it remains unclear whether old carbon substrates released from permafrost are metabolized as rapidly by methanogenic microbial communities as recently produced organic carbon. Here, we apply methane (CH4) clumped isotope (Delta(18)) and C-14 measurements to test whether rates of methanogenesis are related to carbon substrate age. Results from culture experiments indicate that Delta(18) values are negatively correlated with CH4 production rate. Measurements of ebullition samples from thermokarst lakes in Alaska and glacial lakes in Sweden indicate strong negative correlations between CH4 Delta(18) and the fraction modern carbon. These correlations imply that CH4 derived from older carbon substrates is produced relatively slowly. Relative rates of methanogenesis, as inferred from Delta(18) values, are not positively correlated with CH4 flux estimates, highlighting the likely importance of environmental variables other than CH4 production rates in controlling ebullition fluxes. Plain Language Summary There is concern that carbon from thawed permafrost will be emitted to the atmosphere as methane (CH4). It is currently uncertain whether old organic carbon from thawed permafrost can be converted to CH4 as rapidly as organic carbon recently fixed by primary producers. We address this question by combining radiocarbon and clumped isotope measurements of CH4 from lakes in permafrost landscapes. Radiocarbon (C-14) measurements indicate the age of CH4 carbon sources. We present data from culture experiments that support the hypothesis that clumped isotope values are dependent on microbial CH4 production rate. In lake bubble samples, we observe a strong correlation between these two measurements, which implies that CH4 formed from older carbon is produced relatively slowly. We also find that higher rates of CH4 production, as inferred from clumped isotopes, are not linked to higher rates of CH4 emissions, implying that variables other than CH4 production rate strongly influence emission rates.

  • 26.
    Duc, Nguyen Thanh
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Crill, Patrick, M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Bastviken, David
    Implications of temperature and sediment characteristics on methane formation and oxidation in lake sediments2010Ingår i: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 100, nr 1-3, s. 185-196Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Methane emissions from aquatic environments depend on methane formation (MF) and methane oxidation (MO) rates. One important question is to what extent increased temperatures will affect the balance between MF and MO. We measured potential MF and MO rates simultaneously at 4, 10, 20 and 30A degrees C in sediment from eight different lakes representing typical boreal and northern temperate lake types. Potential MF rates ranged between 0.002 and 3.99 mu mol CH4 g(d.w.) (-1) day(-1), potential MO rates ranged from 0.01 to 0.39 CH4 g(d.w.) (-1) day(-1). The potential MF rates were sensitive to temperature and increased 10 to 100 fold over the temperature interval studied. MF also differed between lakes and was correlated to sediment water content, percent of organic material and C:N ratio. Potential MO did not depend on temperature or sediment characteristics but was instead well explained by MF rates at the in situ temperature. It implies that elevated temperatures will enhance MF rates which may cause increased methane release from sediments until MO increases as well, as a response to higher methane levels.

  • 27. Duc, Nguyen Thanh
    et al.
    Silverstein, Samuel B.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Lundmark, Lars
    Reyier, Henrik
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Bastviken, David
    Automated Flux Chamber for Investigating Gas Flux at Water-Air Interfaces2013Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 47, nr 2, s. 968-975Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aquatic ecosystems are major sources of greenhouse gases (GHG). Representative measurements of GHG fluxes from aquatic ecosystems to the atmosphere are vital for quantitative understanding of relationships between biogeochemistry and climate. Fluxes occur at high temporal variability at diet or longer scales, which are not captured by traditional short-term deployments (often in the order of 30 min) of floating flux chambers. High temporal frequency measurements are necessary but also extremely labor intensive if manual flux chamber based methods are used. Therefore, we designed an inexpensive and easily mobile automated flux chamber (AFC) for extended deployments. The AFC was designed to measure in situ accumulation of gas in the chamber and also to collect gas samples in an array of sample bottles for subsequent analysis in the laboratory, providing two independent ways of CH4 concentration measurements. We here present the AFC design and function together with data from initial laboratory tests and from a field deployment.

  • 28.
    Duc, Nguyen Thanh
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Silverstein, Samuel
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Lundmark, Lars
    Reyier, Henrik
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Bastviken, David
    An automatic flux chamber for investigating gas flux at water – air interfacesManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Aquatic ecosystems are major sources of greenhouse gases (GHG).  Representative measurements of GHG fluxes from aquatic ecosystems to the atmosphere are vital for quantitative understanding of climate related biogeochemistry. Fluxes occur at high temporal variability at diel or longer scales which are not captured by traditional short term deployments (typically on the order of 30 minutes) of floating flux chambers. High temporal frequency measurements are necessary but are extremely labor intensive if manual flux chamber based methods are used. Eddy correlation methods require expensive equipment and lead to uncertain results because of the high spatial variability of fluxes from restricted areas. Therefore we designed an inexpensive and easily mobile automatic flux chamber system (AFC) for extended deployments. This device includes a flux chamber and a box with the controller/datalogger, valves, a pump, a 12 V battery and a solar cell. Sensors tested in this study recorded CH4 concentration in the chamber headspace, temperature in the water and air and barometric pressure, but other sensors for CO2 and weather variables can also be attached to the system. The unit was designed to measure in situ accumulation of gas in the chamber and also to collect gas samples in an array of sample bottles for subsequent analysis in the laboratory, providing two independent ways of CH4 concentration measurements.  We here present the AFC design and function together with data from initial laboratory tests and from a field deployment.

  • 29. Ellenbogen, Jared B.
    et al.
    Borton, Mikayla A.
    McGivern, Bridget B.
    Cronin, Dylan R.
    Hoyt, David W.
    Freire-Zapata, Viviana
    McCalley, Carmody K.
    Varner, Ruth K.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper. Stockholms universitet, Naturvetenskapliga fakulteten, Bolincentret för klimatforskning (tills m KTH & SMHI).
    Wehr, Richard A.
    Chanton, Jeffrey P.
    Woodcroft, Ben J.
    Tfaily, Malak M.
    Tyson, Gene W.
    Rich, Virginia I.
    Wrighton, Kelly C.
    Methylotrophy in the Mire: direct and indirect routes for methane production in thawing permafrost2024Ingår i: mSystems, E-ISSN 2379-5077, Vol. 9, nr 1, artikel-id e00698-23Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    While wetlands are major sources of biogenic methane (CH4), our understanding of resident microbial metabolism is incomplete, which compromises the prediction of CH4 emissions under ongoing climate change. Here, we employed genome-resolved multi-omics to expand our understanding of methanogenesis in the thawing permafrost peatland of Stordalen Mire in Arctic Sweden. In quadrupling the genomic representation of the site’s methanogens and examining their encoded metabolism, we revealed that nearly 20% of the metagenome-assembled genomes (MAGs) encoded the potential for methylotrophic methanogenesis. Further, 27% of the transcriptionally active methanogens expressed methylotrophic genes; for Methanosarcinales and Methanobacteriales MAGs, these data indicated the use of methylated oxygen compounds (e.g., methanol), while for Methanomassiliicoccales, they primarily implicated methyl sulfides and methylamines. In addition to methanogenic methylotrophy, >1,700 bacterial MAGs across 19 phyla encoded anaerobic methylotrophic potential, with expression across 12 phyla. Metabolomic analyses revealed the presence of diverse methylated compounds in the Mire, including some known methylotrophic substrates. Active methylotrophy was observed across all stages of a permafrost thaw gradient in Stordalen, with the most frozen non-methanogenic palsa found to host bacterial methylotrophy and the partially thawed bog and fully thawed fen seen to house both methanogenic and bacterial methylotrophic activities. Methanogenesis across increasing permafrost thaw is thus revised from the sole dominance of hydrogenotrophic production and the appearance of acetoclastic at full thaw to consider the co-occurrence of methylotrophy throughout. Collectively, these findings indicate that methanogenic and bacterial methylotrophy may be an important and previously underappreciated component of carbon cycling and emissions in these rapidly changing wetland habitats.

  • 30. Emerson, Joanne B.
    et al.
    Roux, Simon
    Brum, Jennifer R.
    Bolduc, Benjamin
    Woodcroft, Ben J.
    Jang, Ho Bin
    Singleton, Caitlin M.
    Soden, Lindsey M.
    Naas, Adrian E.
    Boyd, Joel A.
    Hodgkins, Suzanne B.
    Wilson, Rachel M.
    Trubl, Gareth
    Li, Changsheng
    Frokings, Steve
    Pope, Phillip B.
    Wrighton, Kelly C.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Chanton, Jeffrey P.
    Saleska, Scott R.
    Tyson, Gene W.
    Rich, Virginia
    Sullivan, Matthew B.
    Host-linked soil viral ecology along a permafrost thaw gradient2018Ingår i: Nature Microbiology, E-ISSN 2058-5276, Vol. 3, nr 8, s. 870-880Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Climate change threatens to release abundant carbon that is sequestered at high latitudes, but the constraints on microbial metabolisms that mediate the release of methane and carbon dioxide are poorly understood(1-7). The role of viruses, which are known to affect microbial dynamics, metabolism and biogeochemistry in the oceans(8-10), remains largely unexplored in soil. Here, we aimed to investigate how viruses influence microbial ecology and carbon metabolism in peatland soils along a permafrost thaw gradient in Sweden. We recovered 1,907 viral populations (genomes and large genome fragments) from 197 bulk soil and size-fractionated metagenomes, 58% of which were detected in metatranscriptomes and presumed to be active. In silico predictions linked 35% of the viruses to microbial host populations, highlighting likely viral predators of key carbon-cycling microorganisms, including methanogens and methanotrophs. Lineage-specific virus/host ratios varied, suggesting that viral infection dynamics may differentially impact microbial responses to a changing climate. Virus-encoded glycoside hydrolases, including an endomannanase with confirmed functional activity, indicated that viruses influence complex carbon degradation and that viral abundances were significant predictors of methane dynamics. These findings suggest that viruses may impact ecosystem function in climate-critical, terrestrial habitats and identify multiple potential viral contributions to soil carbon cycling.

  • 31. Emerson, Joanne B.
    et al.
    Varner, Ruth K.
    Wik, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Parks, Donovan H.
    Neumann, Rebecca B.
    Johnson, Joel E.
    Singleton, Caitlin M.
    Woodcroft, Ben J.
    Tollerson II, Rodney
    Owusu-Dommey, Akosua
    Binder, Morgan
    Freitas, Nancy L.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Saleska, Scott R.
    Tyson, Gene W.
    Rich, Virginia I.
    Diverse sediment microbiota shape methane emission temperature sensitivity in Arctic lakes2021Ingår i: Nature Communications, E-ISSN 2041-1723, Vol. 12, artikel-id 5815Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Northern post-glacial lakes are significant, increasing sources of atmospheric carbon through ebullition (bubbling) of microbially-produced methane (CH4) from sediments. Ebullitive CH4 flux correlates strongly with temperature, reflecting that solar radiation drives emissions. However, here we show that the slope of the temperature-CH4 flux relationship differs spatially across two post-glacial lakes in Sweden. We compared these CH4 emission patterns with sediment microbial (metagenomic and amplicon), isotopic, and geochemical data. The temperature-associated increase in CH4 emissions was greater in lake middles—where methanogens were more abundant—than edges, and sediment communities were distinct between edges and middles. Microbial abundances, including those of CH4-cycling microorganisms and syntrophs, were predictive of porewater CH4 concentrations. Results suggest that deeper lake regions, which currently emit less CH4 than shallower edges, could add substantially to CH4 emissions in a warmer Arctic and that CH4 emission predictions may be improved by accounting for spatial variations in sediment microbiota.

  • 32.
    Enrich-Prast, A.
    et al.
    Univ Fed Rio de Janeiro.
    Bastviken,
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Chemosynthesis2009Ingår i: Encyclopedia of Inland Waters. / [ed] edited by Gene E. Likens...[et al.], Amsterdam: Elsevier/Academic Press , 2009Kapitel i bok, del av antologi (Övrig (populärvetenskap, debatt, mm))
  • 33. Fahnestock, M. F.
    et al.
    Bryce, J. G.
    McCalley, C. K.
    Montesdeoca, M.
    Bai, S.
    Li, Y.
    Driscoll, C. T.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Rich, V.
    Varner, R. K.
    Mercury reallocation in thawing subarctic peatlands2019Ingår i: Geochemical perspectives letters, ISSN 2410-339X, Vol. 11, s. 33-38Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Warming Arctic temperatures have led to permafrost thaw that threatens to release previously sequestered mercury (Hg) back into the environment. Mobilisation of Hg in permafrost waters is of concern, as Hg methylation produced under water-saturated conditions results in the neurotoxin, methyl Hg (MeHg). Thawing permafrost may enhance Hg export, but the magnitude and mechanisms of this mobilisation within Arctic ecosystems remain poorly understood. Such uncertainty limits prognostic modelling of Hg mobilisation and impedes a comprehensive assessment of its threat to Arctic ecosystems and peoples. Here, we address this knowledge gap through an assessment of Hg dynamics across a well-studied permafrost thaw sequence at the peak of the growing season in biologically active peat overlying permafrost, quantifying total gaseous mercury (TGM) fluxes, total mercury (Hg-Tot) in the active layer peat, porewater MeHg concentrations, and identifying microbes with the potential to methylate Hg. During the initial thaw, TGM is liberated, likely by photoreduction from permafrost where it was previously stored for decades to centuries. As thawing proceeds, TGM is largely driven by hydrologic changes as evidenced by Hg accumulation in water-logged, organic-rich peat sediments in fen sites. MeHg in porewaters increase across the thaw gradient, a pattern coincident with increases in the relative abundance of microbes possibly containing genes allowing for methylation of ionic Hg. Findings suggest that under changing climate, frozen, well-drained habitats will thaw and collapse into saturated landscapes, increasing the production of MeHg and providing a significant source of the toxic, bioaccumulative contaminant.

  • 34. Fisher, Rebecca E.
    et al.
    France, James L.
    Lowry, David
    Lanoisellé, Mathias
    Brownlow, Rebecca
    Pyle, John A.
    Cain, Michelle
    Warwick, Nicola
    Skiba, Ute M.
    Drewer, Julia
    Dinsmore, Kerry J.
    Leeson, Sarah R.
    Bauguitte, Stéphane J. -B.
    Wellpott, Axel
    O'Shea, Sebastian J.
    Allen, Grant
    Gallagher, Martin W.
    Pitt, Joseph
    Percival, Carl J.
    Bower, Keith
    George, Charles
    Hayman, Garry D.
    Aalto, Tuula
    Lohila, Annalea
    Aurela, Mika
    Laurila, Tuomas
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    McCalley, Carmody K.
    Nisbet, Euan G.
    Measurement of the C-13 isotopic signature of methane emissions from northern European wetlands2017Ingår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 31, nr 3, s. 605-623Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Isotopic data provide powerful constraints on regional and global methane emissions and their source profiles. However, inverse modeling of spatially resolved methane flux is currently constrained by a lack of information on the variability of source isotopic signatures. In this study, isotopic signatures of emissions in the Fennoscandian Arctic have been determined in chambers over wetland, in the air 0.3 to 3m above the wetland surface and by aircraft sampling from 100m above wetlands up to the stratosphere. Overall, the methane flux to atmosphere has a coherent delta C-13 isotopic signature of -71 +/- 1%, measured in situ on the ground in wetlands. This is in close agreement with delta C-13 isotopic signatures of local and regional methane increments measured by aircraft campaigns flying through air masses containing elevated methane mole fractions. In contrast, results from wetlands in Canadian boreal forest farther south gave isotopic signatures of -67 +/- 1%. Wetland emissions dominate the local methane source measured over the European Arctic in summer. Chamber measurements demonstrate a highly variable methane flux and isotopic signature, but the results from air sampling within wetland areas show that emissions mix rapidly immediately above the wetland surface and methane emissions reaching the wider atmosphere do indeed have strongly coherent C isotope signatures. The study suggests that for boreal wetlands (>60 degrees N) global and regional modeling can use an isotopic signature of -71 parts per thousand to apportion sources more accurately, but there is much need for further measurements over other wetlands regions to verify this.

  • 35. Fofana, Aminata
    et al.
    Anderson, Darya
    McCalley, Carmody K.
    Hodgkins, Suzanne
    Wilson, Rachel M.
    Cronin, Dylan
    Raab, Nicole
    Torabi, Mohammad
    Varner, Ruth K.
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Saleska, Scott R.
    Chanton, Jeffrey P.
    Tfaily, Malak M.
    Rich, Virginia I.
    Mapping substrate use across a permafrost thaw gradient2022Ingår i: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 175, artikel-id 108809Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Permafrost thaw in northern peatlands is likely to create a positive feedback to climate change, as microbes transform soil carbon (C) into carbon dioxide (CO2) or methane (CH4). While the microbiome's encoded C-processing potential changes with thaw, the impact on substrate utilization and gas emissions is less well characterized. We therefore examined microbial C-cycling dynamics from a partially thawed Sphagnum-dominated bog to a fully thawed sedge-dominated fen in Stordalen Mire (68.35°N, 19.05°E), Sweden. We profiled C substrate utilization diversity and extent by Biolog Ecoplates™, then tested substrate-specific hypotheses by targeted additions (of glucose, the short chain fatty acids (SCFAs) acetate and butyrate, and the organic acids galacturonic acid and p-hydroxybenzoic acid, all at field-relevant concentrations) under anaerobic conditions at 15 °C. In parallel we characterized microbiomes (via 16S rRNA amplicon sequencing and quantitative polymerase chain reaction) and C gas emissions. The fen exhibited a higher substrate use diversity and faster rate of overall substrate utilization than in the bog, based on Biolog Ecoplate™ incubations. Simple glucose additions (akin to a positive control) to peat microcosms fueled fermentation as expected (reflected in enriched fermenter lineages, their inferred metabolisms, and CO2 production), but also showed potential priming of anaerobic phenol degradation in the bog. Addition of SCFAs to bog and fen produced the least change in lineages and in CO2, and modest suppression of CH4 primarily in the fen, attributed to inhibition. Addition of both organic acids greatly increased the CO2:CH4 ratio in the deep peats but had distinct individual gas dynamics and impacts on microbiota. Both organic acids appeared to act as both C source and as a microbial inhibitor, with galacturonic acid also likely playing a role in electron transfer or acceptance. Collectively, these results support the importance of aboveground-belowground linkages - and in particular the role of Sphagnum spp.- in supplying substrates and inhibitors that drive microbiome assembly and C processing in these dynamically changing systems. In addition, they highlight an important temporal dynamic: responses on the short time scale of incubations (which would reflect transition conditions in the field) differ from those evident at the longer scales of habitat transition, in ways consequential to C gas emissions. In the short term, substrate addition response reflected microbiome legacy (e.g., bog communities were slower to process C and better tolerated inhibitors than fen communities) but led to little overall increase in C gas production (and a high skew to CO2). At the longer time scale of bog and fen thaw stages (which are used to represent these systems in models) the concomitant shifts in plants, hydrology and microbiota attenuate microbiome legacy impacts on substrate processing and C gas emissions over time. As habitat transition areas expand under accelerating change, we hypothesize an increased role of microbiome legacy in the landscape overall, leading to a lag in the increase of CH4 emissions expected from fen expansion.

  • 36. Franz, Daniela
    et al.
    Acosta, Manuel
    Altimir, Núria
    Arriga, Nicola
    Arrouays, Dominique
    Aubinet, Marc
    Aurela, Mika
    Ayres, Edward
    López-Ballesteros, Ana
    Barbaste, Mireille
    Berveiller, Daniel
    Biraud, Sébastien
    Boukir, Hakima
    Brown, Timothy
    Brümmer, Christian
    Buchmann, Nina
    Burba, George
    Carrara, Arnaud
    Cescatti, Allessandro
    Ceschia, Eric
    Clement, Robert
    Cremonese, Edoardo
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Darenova, Eva
    Dengel, Sigrid
    D'Odorico, Petra
    Filippa, Gianluca
    Fleck, Stefan
    Fratini, Gerardo
    Fuss, Roland
    Gielen, Bert
    Gogo, Sébastien
    Grace, John
    Graf, Alexander
    Grelle, Achim
    Gross, Patrick
    Grünwald, Thomas
    Haapanala, Sami
    Hehn, Markus
    Heinesch, Bernard
    Heiskanen, Jouni
    Herbst, Mathias
    Herschlein, Christine
    Hörtnagl, Lukas
    Hufkens, Koen
    Ibrom, Andreas
    Jolivet, Claudy
    Joly, Lilian
    Jones, Michael
    Kiese, Ralf
    Klemedtsson, Leif
    Kljun, Natascha
    Klumpp, Katja
    Kolari, Pasi
    Kolle, Olaf
    Kowalski, Andrew
    Kutsch, Werner
    Laurila, Tuomas
    de Ligne, Anne
    Linder, Sune
    Lindroth, Anders
    Lohila, Annalea
    Longdoz, Bernhard
    Mammarella, Ivan
    Manise, Tanguy
    Maraňón Jiménez, Sara
    Matteucci, Giorgio
    Mauder, Matthias
    Meier, Philip
    Merbold, Lutz
    Mereu, Simone
    Metzger, Stefan
    Migliavacca, Mirco
    Mölder, Meelis
    Montagnani, Leonardo
    Moureaux, Christine
    Nelson, David
    Nemitz, Eiko
    Nicolini, Giacomo
    Nilsson, Mats B.
    Op de Beeck, Maarten
    Osborne, Bruce
    Ottosson Löfvenius, Mikaell
    Pavelka, Marian
    Peichl, Matthias
    Peltola, Olli
    Pihlatie, Mari
    Pitacco, Andrea
    Pokorny, Radek
    Pumpanen, Jukka
    Ratié, Céline
    Rebmann, Corinna
    Roland, Marilyn
    Sabbatini, Simone
    Saby, Nicolas P. A.
    Saunders, Matthew
    Schmid, Hans Peter
    Schrumpf, Marion
    Sedlák, Pavel
    Serrano Ortiz, Penelope
    Siebicke, Lukas
    Šigut, Ladislav
    Silvennoinen, Hanna
    Simioni, Guillaume
    Skiba, Ute
    Sonnentag, Oliver
    Soudani, Kamel
    Soule, Patricé
    Steinbrecher, Rainer
    Tallec, Tiphaine
    Thimonier, Anne
    Tuittila, Eeva-Stiina
    Tuovinen, Juha-Pekka
    Vestin, Patrik
    Vincent, Gaëlle
    Vincke, Caroline
    Vitale, Domenico
    Waldner, Peter
    Weslien, Per
    Wingate, Lisa
    Wohlfahrt, Georg
    Zahniser, Mark
    Vesala, Timo
    Towards long-term standardised carbon and greenhouse gas observations for monitoring Europe's terrestrial ecosystems: a review2018Ingår i: International Agrophysics, ISSN 0236-8722, Vol. 32, nr 4, s. 439-+Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Research infrastructures play a key role in launching a new generation of integrated long-term, geographically distributed observation programmes designed to monitor climate change, better understand its impacts on global ecosystems, and evaluate possible mitigation and adaptation strategies. The pan-European Integrated Carbon Observation System combines carbon and greenhouse gas (GHG; CO2, CH4, N2O, H2O) observations within the atmosphere, terrestrial ecosystems and oceans. High-precision measurements are obtained using standardised methodologies, are centrally processed and openly available in a traceable and verifiable fashion in combination with detailed metadata. The Integrated Carbon Observation System ecosystem station network aims to sample climate and land-cover variability across Europe. In addition to GHG flux measurements, a large set of complementary data (including management practices, vegetation and soil characteristics) is collected to support the interpretation, spatial upscaling and modelling of observed ecosystem carbon and GHG dynamics. The applied sampling design was developed and formulated in protocols by the scientific community, representing a trade-off between an ideal dataset and practical feasibility. The use of open-access, high-quality and multi-level data products by different user communities is crucial for the Integrated Carbon Observation System in order to achieve its scientific potential and societal value.

  • 37.
    Friborg, T.
    et al.
    Copenhagen Univ.
    Johansson, T.J.
    Copenhagen Univ.
    Jackowicz-Korczyński, M.
    Lund Univ.
    Christensen, T.R.
    Lund Univ.
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologi och geokemi.
    Palsa mires – CO2 exchange from Stordalen Mire.2009Ingår i: Climate Change Impacts on Sub-arctic Palsa mires and Greenhouse Gas Feedbacks, / [ed] S. Fronzek et al., 2009, s. 36-40Konferensbidrag (Refereegranskat)
  • 38. Galfalk, Magnus
    et al.
    Olofsson, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för astronomi.
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Bastviken, David
    Making methane visible2016Ingår i: Nature Climate Change, ISSN 1758-678X, E-ISSN 1758-6798, Vol. 6, nr 4, s. 426-430Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Methane (CH4) is one of the most important greenhouse gases, and an important energy carrier in biogas and natural gas. Its large-scale emission patterns have been unpredictable and the source and sink distributions are poorly constrained. Remote assessment of CH4 with high sensitivity at a m(2) spatial resolution would allow detailed mapping of the near-ground distribution and anthropogenic sources in landscapes but has hitherto not been possible. Here we show that CH4 gradients can be imaged on the <m(2) scale at ambient levels (similar to 1.8 ppm) and filmed using optimized infrared (IR) hyperspectral imaging. Our approach allows both spectroscopic confirmation and quantification for all pixels in an imaged scene simultaneously. It also has the ability to map fluxes for dynamic scenes. This approach to mapping boundary layer CH4 offers a unique potential way to improve knowledge about greenhouse gases in landscapes and a step towards resolving source-sink attribution and scaling issues.

  • 39. Giasson, M-A
    et al.
    Ellison, A. M.
    Bowden, R. D.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Davidson, E. A.
    Drake, J. E.
    Frey, S. D.
    Hadley, J. L.
    Lavine, M.
    Melillo, J. M.
    Munger, J. W.
    Nadelhoffer, K. J.
    Nicoll, L.
    Ollinger, S. V.
    Savage, K. E.
    Steudler, P. A.
    Tang, J.
    Varner, R. K.
    Wofsy, S. C.
    Foster, D. R.
    Finzi, A. C.
    Soil respiration in a northeastern US temperate forest: a 22-year synthesis2013Ingår i: Ecosphere, ISSN 2150-8925, E-ISSN 2150-8925, Vol. 4, nr 11, s. UNSP 140-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To better understand how forest management, phenology, vegetation type, and actual and simulated climatic change affect seasonal and inter-annual variations in soil respiration (R-s), we analyzed more than 100,000 individual measurements of soil respiration from 23 studies conducted over 22 years at the Harvard Forest in Petersham, Massachusetts, USA. We also used 24 site-years of eddy-covariance measurements from two Harvard Forest sites to examine the relationship between soil and ecosystem respiration (R-e). R-s was highly variable at all spatial (respiration collar to forest stand) and temporal (minutes to years) scales of measurement. The response of R-s to experimental manipulations mimicking aspects of global change or aimed at partitioning R-s into component fluxes ranged from similar to 70% to +52%. The response appears to arise from variations in substrate availability induced by changes in the size of soil C pools and of belowground C fluxes or in environmental conditions. In some cases (e.g., logging, warming), the effect of experimental manipulations on R-s was transient, but in other cases the time series were not long enough to rule out long-term changes in respiration rates. Inter-annual variations in weather and phenology induced variation among annual R-s estimates of a magnitude similar to that of other drivers of global change (i.e., invasive insects, forest management practices, N deposition). At both eddy-covariance sites, aboveground respiration dominated R-e early in the growing season, whereas belowground respiration dominated later. Unusual aboveground respiration patterns-high apparent rates of respiration during winter and very low rates in mid-to-late summer-at the Environmental Measurement Site suggest either bias in R-s and R-e estimates caused by differences in the spatial scale of processes influencing fluxes, or that additional research on the hard-to-measure fluxes (e.g., wintertime R-s, unaccounted losses of CO2 from eddy covariance sites), daytime and nighttime canopy respiration and its impacts on estimates of R-e, and independent measurements of flux partitioning (e.g., aboveground plant respiration, isotopic partitioning) may yield insight into the unusually high and low fluxes. Overall, however, this data-rich analysis identifies important seasonal and experimental variations in R-s and R-e and in the partitioning of R-e above-vs. belowground.

  • 40. Goodrich, Jordan P.
    et al.
    Varner, Ruth K.
    Frolking, Steve
    Duncan, Bryan N.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    High-frequency measurements of methane ebullition over a growing season at a temperate peatland site2011Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 38, s. L07404-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bubbles can contribute a significant fraction of methane emissions from wetlands; however the range of reported fractions is very large and accurate characterization of this pathway has proven difficult. Here we show that continuous automated flux chambers combined with an integrated cavity output spectroscopy (ICOS) instrument allow us to quantify both CH(4) ebullition rate and magnitude. For a temperate poor fen in 2009, ebullition rate varied on hourly to seasonal time scales. A diel pattern in ebullition was identified with peak release occurring between 20:00 and 06:00 local time, though steady fluxes (i.e., those with a linear increase in chamber headspace CH(4) concentration) did not exhibit diel variability. Seasonal mean ebullition rates peaked at 843.5 +/- 384.2 events m(-2) d(-1) during the summer, with a mean magnitude of 0.19 mg CH(4) released in each event.

  • 41. Gålfalk, Magnus
    et al.
    Karlson, Martin
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Bousquet, Philippe
    Bastviken, David
    Technical note: A simple approach for efficient collection of field reference data for calibrating remote sensing mapping of northern wetlands2018Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 15, nr 5, s. 1549-1557Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The calibration and validation of remote sensing land cover products are highly dependent on accurate field reference data, which are costly and practically challenging to collect. We describe an optical method for collection of field reference data that is a fast, cost-efficient, and robust alternative to field surveys and UAV imaging. A lightweight, waterproof, remote-controlled RGB camera (GoPro HERO4 Silver, GoPro Inc.) was used to take wide-angle images from 3.1 to 4.5 m in altitude using an extendable monopod, as well as representative near-ground (< 1 m) images to identify spectral and structural features that correspond to various land covers in present lighting conditions. A semi-automatic classification was made based on six surface types (graminoids, water, shrubs, dry moss, wet moss, and rock). The method enables collection of detailed field reference data, which is critical in many remote sensing applications, such as satellite-based wetland mapping. The method uses common non-expensive equipment, does not require special skills or training, and is facilitated by a step-by-step manual that is included in the Supplement. Over time a global ground cover database can be built that can be used as reference data for studies of non-forested wetlands from satellites such as Sentinel 1 and 2 (10 m pixel size).

  • 42. Hodgkins, Suzanne B.
    et al.
    Chanton, Jeffrey P.
    Langford, Lauren C.
    McCalley, Carmody K.
    Saleska, Scott R.
    Rich, Virginia I.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Cooper, William T.
    Soil incubations reproduce field methane dynamics in a subarctic wetland2015Ingår i: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 126, nr 1-2, s. 241-249Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A major challenge in peatland carbon cycle modeling is the estimation of subsurface methane (CH4) and carbon dioxide (CO2) production and consumption rates and pathways. The most common methods for modeling these processes are soil incubations and stable isotope modeling, both of which may involve departures from field conditions. To explore the impacts of these departures, we measured CH4/CO2 concentration ratios and C-13 fractionation factors (alpha(C), indicating CH4 production pathways) in field pore water from a thawing subarctic peatland, and compared these values to those observed in incubations of corresponding peat samples. Incubation CH4/CO2 production ratios were significantly and positively correlated with observed field CH4/CO2 concentration ratios, though observed field ratios were similar to 20 % of those in incubations due to CH4's lower solubility in pore water. After correcting the field ratios for CH4 loss with an isotope mass balance model, the incubation CH4/CO2 ratios and alpha(C) were both significantly positively correlated with field ratios and alpha(C) (respectively), both with slopes indistinguishable from 1. Although CH4/CO2 ratios and alpha(C) were slightly higher in the incubations, these shifts were consistent along the thaw progression, indicating that ex situ incubations can replicate trends in in situ CH4 production.

  • 43. Hodgkins, Suzanne B.
    et al.
    Tfaily, Malak M.
    McCalley, Carmody K.
    Logan, Tyler A.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Saleska, Scott R.
    Rich, Virginia I.
    Chanton, Jeffrey P.
    Changes in peat chemistry associated with permafrost thaw increase greenhouse gas production2014Ingår i: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 111, nr 16, s. 5819-5824Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Carbon release due to permafrost thaw represents a potentially major positive climate change feedback. The magnitude of carbon loss and the proportion lost as methane (CH4) vs. carbon dioxide (CO2) depend on factors including temperature, mobilization of previously frozen carbon, hydrology, and changes in organic matter chemistry associated with environmental responses to thaw. While the first three of these effects are relatively well understood, the effect of organic matter chemistry remains largely un-studied. To address this gap, we examined the biogeochemistry of peat and dissolved organic matter (DOM) along a similar to 40-y permafrost thaw progression from recently- to fully thawed sites in Stordalen Mire (68.35 degrees N, 19.05 degrees E), a thawing peat plateau in northern Sweden. Thaw-induced subsidence and the resulting inundation along this progression led to succession in vegetation types accompanied by an evolution in organic matter chemistry. Peat C/N ratios decreased whereas humification rates increased, and DOM shifted toward lower molecular weight compounds with lower aromaticity, lower organic oxygen content, and more abundant microbially produced compounds. Corresponding changes in decomposition along this gradient included increasing CH4 and CO2 production potentials, higher relative CH4/CO2 ratios, and a shift in CH4 production pathway from CO2 reduction to acetate cleavage. These results imply that subsidence and thermokarst-associated increases in organic matter lability cause shifts in biogeochemical processes toward faster decomposition with an increasing proportion of carbon released as CH4. This impact of permafrost thaw on organic matter chemistry could intensify the predicted climate feedbacks of increasing temperatures, permafrost carbon mobilization, and hydrologic changes.

  • 44. Hodgkins, Suzanne B.
    et al.
    Tfaily, Malak M.
    Podgorski, David C.
    McCalley, Carmody K.
    Saleska, Scott R.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Rich, Virginia I.
    Chanton, Jeffrey P.
    Cooper, William T.
    Elemental composition and optical properties reveal changes in dissolved organic matter along a permafrost thaw chronosequence in a subarctic peatland2016Ingår i: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 187, s. 123-140Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The fate of carbon stored in permafrost-zone peatlands represents a significant uncertainty in global climate modeling. Given that the breakdown of dissolved organic matter (DOM) is often a major pathway for decomposition in peatlands, knowledge of DOM reactivity under different permafrost regimes is critical for determining future climate feedbacks. To explore the effects of permafrost thaw and resultant plant succession on DOM reactivity, we used a combination of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), UV/Vis absorbance, and excitation-emission matrix spectroscopy (EEMS) to examine the DOM elemental composition and optical properties of 27 pore water samples gathered from various sites along a permafrost thaw sequence in Stordalen Mire, a thawing subarctic peatland in northern Sweden. The presence of dense Sphagnum moss, a feature that is dominant in the intermediate thaw stages, appeared to be the main driver of variation in DOM elemental composition and optical properties at Stordalen. Specifically, DOM from sites with Sphagnum had greater aromaticity, higher average molecular weights, and greater O/C, consistent with a higher abundance of phenolic compounds that likely inhibit decomposition. These compounds are released by Sphagnum and may accumulate due to inhibition of phenol oxidase activity by the acidic pH at these sites. In contrast, sites without Sphagnum, specifically fully-thawed rich fens, had more saturated, more reduced compounds, which were high in N and S. Optical properties at rich fens indicated the presence of microbially-derived DOM, consistent with the higher decomposition rates previously measured at these sites. These results indicate that Sphagnum acts as an inhibitor of rapid decomposition and CH4 release in thawing subarctic peatlands, consistent with lower rates of CO2 and CH4 production previously observed at these sites. However, this inhibitory effect may disappear if Sphagnum-dominated bogs transition to more waterlogged rich fens that contain very little to no living Sphagnum. Release of this inhibition allows for higher levels of microbial activity and potentially greater CH4 release, as has been observed in these fen sites.

  • 45. Holmes, M. E.
    et al.
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Burnett, W. C.
    McCalley, C. K.
    Wilson, R. M.
    Frolking, S.
    Chang, K-Y
    Riley, W. J.
    Varner, R. K.
    Hodgkins, S. B.
    McNichol, A. P.
    Saleska, S. R.
    Rich, V.
    Chanton, J. P.
    Carbon Accumulation, Flux, and Fate in Stordalen Mire, a Permafrost Peatland in Transition2022Ingår i: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 36, nr 1, artikel-id e2021GB007113Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Stordalen Mire is a peatland in the discontinuous permafrost zone in arctic Sweden that exhibits a habitat gradient from permafrost palsa, to Sphagnum bog underlain by permafrost, to Eriophorum-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 CO2 and CH4 exchange, and 21 core profiles for 210Pb and 14C peat dating. Year-round chamber measurements indicated net carbon balance of −13 ± 8, −49 ± 15, and −91 ± 43 g C m−2 y−1 for the years 2012–2018 in palsa, bog, and fen, respectively. Methane emission offset 2%, 7%, and 17% of the CO2 uptake rate across this gradient. Recent aCAR indicates higher C accumulation rates in surface peats in the palsa and bog compared to current CO2 fluxes, 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 CO2 sink, but this CO2 sink is increasingly offset by rising CH4 emissions, dominated by modern carbon as determined by 14C. The higher CH4 emissions result in higher net CO2-equivalent emissions, indicating that radiative forcing of this mire and similar permafrost ecosystems will exert a warming influence on future climate.

  • 46. Holst, T.
    et al.
    Arneth, A.
    Hayward, S.
    Ekberg, A.
    Mastepanov, M.
    Jackowicz-Korczynski, M.
    Friborg, T.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Bäckstrand, Kristina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    BVOC ecosystem flux measurements at a high latitude wetland site2010Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 10, nr 4, s. 1617-1634Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, we present summertime concentrations and fluxes of biogenic volatile organic compounds (BVOCs) measured at a sub-arctic wetland in northern Sweden using a disjunct eddy-covariance (DEC) technique based on a proton transfer reaction mass spectrometer (PTR-MS). The vegetation at the site was dominated by Sphagnum, Carex and Eriophorum spp. The measurements reported here cover a period of 50 days (1 August to 19 September 2006), approximately one half of the growing season at the site, and allowed to investigate the effect of day-to-day variation in weather as well as of vegetation senescence on daily BVOC fluxes, and on their temperature and light responses. The sensitivity drift of the DEC system was assessed by comparing H3O+-ion cluster formed with water molecules (H3O+(H2O) at m37) with water vapour concentration measurements made using an adjacent humidity sensor, and the applicability of the DEC method was analysed by a comparison of sensible heat fluxes for high frequency and DEC data obtained from the sonic anemometer. These analyses showed no significant PTR-MS sensor drift over a period of several weeks and only a small flux-loss due to high-frequency spectrum omissions. This loss was within the range expected from other studies and the theoretical considerations. Standardised (20 degrees C and 1000 mu mol m(-2) s(-1) PAR) summer isoprene emission rates found in this study of 329 mu g Cm-2 (ground area) h(-1) were comparable with findings from more southern boreal forests, and fen-like ecosystems. On a diel scale, measured fluxes indicated a stronger temperature dependence than emissions from temperate or (sub) tropical ecosystems. For the first time, to our knowledge, we report ecosystem methanol fluxes from a sub-arctic ecosystem. Maximum daytime emission fluxes were around 270 mu g m(-2) h(-1) (ca. 100 mu g Cm-2 h(-1)), and during most nights small negative fluxes directed from the atmosphere to the surface were observed.

  • 47.
    Horst, Axel
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Thornton, Brett F.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Holmstrand, Henry
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Andersson, Per
    Laboratory for Isotope Geology, Swedish Museum of Natural History, Stockholm.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Gustafsson, Örjan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Stable bromine isotopic composition of atmospheric CH3BrArtikel i tidskrift (Refereegranskat)
  • 48.
    Horst, Axel
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Thornton, Brett F.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Holmstrand, Henry
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Andersson, Per
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Gustafsson, Örjan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Stable bromine isotopic composition of atmospheric CH3Br2013Ingår i: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 65, s. 21040-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tropospheric methyl bromide (CH3Br) is the largest source of bromine to the stratosphere and plays an important role in ozone depletion. Here, the first stable bromine isotope composition (delta Br-81) of atmospheric CH3Br is presented. The delta Br-81 of higher concentration Stockholm samples and free air subarctic Abisko samples suggest a source/background value of -0.04 +/- 0.28 parts per thousand ranging up to +1.75 +/- 0.12 parts per thousand. The Stockholm delta Br-81 versus concentration relationship corresponds to an apparent isotope enrichment factor of -4.7 +/- 3.7 parts per thousand, representing the combined reaction sink. This study demonstrates the scientific potential of atmospheric delta Br-81 measurements, which in the future may be combined with other isotope systems in a top-down inverse approach to further understand key source and sink processes of methyl bromide.

  • 49. Hough, Moira
    et al.
    McCabe, Samantha
    Vining, S. Rose
    Pickering Pedersen, Emily
    Wilson, Rachel M.
    Lawrence, Ryan
    Chang, Kuang-Yu
    Bohrer, Gil
    The IsoGenie Coordinators,
    Riley, William J.
    Crill, Patrick M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Varner, Ruth K.
    Blazewicz, Steven J.
    Dorrepaal, Ellen
    Tfaily, Malak M.
    Saleska, Scott R.
    Rich, Virginia I.
    Coupling plant litter quantity to a novel metric for litter quality explains C storage changes in a thawing permafrost peatland2022Ingår i: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 28, nr 3, s. 950-968Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Permafrost thaw is a major potential feedback source to climate change as it can drive the increased release of greenhouse gases carbon dioxide (CO2) and methane (CH4). This carbon release from the decomposition of thawing soil organic material can be mitigated by increased net primary productivity (NPP) caused by warming, increasing atmospheric CO2, and plant community transition. However, the net effect on C storage also depends on how these plant community changes alter plant litter quantity, quality, and decomposition rates. Predicting decomposition rates based on litter quality remains challenging, but a promising new way forward is to incorporate measures of the energetic favorability to soil microbes of plant biomass decomposition. We asked how the variation in one such measure, the nominal oxidation state of carbon (NOSC), interacts with changing quantities of plant material inputs to influence the net C balance of a thawing permafrost peatland. We found: (1) Plant productivity (NPP) increased post-thaw, but instead of contributing to increased standing biomass, it increased plant biomass turnover via increased litter inputs to soil; (2) Plant litter thermodynamic favorability (NOSC) and decomposition rate both increased post-thaw, despite limited changes in bulk C:N ratios; (3) these increases caused the higher NPP to cycle more rapidly through both plants and soil, contributing to higher CO2 and CH4 fluxes from decomposition. Thus, the increased C-storage expected from higher productivity was limited and the high global warming potential of CH4 contributed a net positive warming effect. Although post-thaw peatlands are currently C sinks due to high NPP offsetting high CO2 release, this status is very sensitive to the plant community's litter input rate and quality. Integration of novel bioavailability metrics based on litter chemistry, including NOSC, into studies of ecosystem dynamics, is needed to improve the understanding of controls on arctic C stocks under continued ecosystem transition. 

  • 50.
    Hugelius, Gustaf
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Routh, Joyanto
    Kuhry, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
    Crill, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Mapping the degree of decomposition and thaw remobilization potential of soil organic matter in discontinuous permafrost terrain2012Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117, s. G02030-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Soil organic matter (SOM) stored in permafrost terrain is a key component in the global carbon cycle, but its composition and lability are largely unknown. We characterize and assess the degree of decomposition of SOM at nine sites representing major land-cover and soil types (including peat deposits) in an area of discontinuous permafrost in the European Russian Arctic. We analyze the elemental and stable isotopic composition of bulk SOM, and the degree of humification and elemental composition of humic acids (HA). The degree of decomposition is low in the O-horizons of mineral soils and peat deposits. In the permafrost free non-peatland soils there is enrichment of C-13 and N-15, and decrease in bulk C/N ratios indicating more decomposed material with depth. Spectral characterization of HA indicates low humification in O-horizons and peat deposits, but increase in humification in the deeper soil horizons of non-peatland soils, and in mineral horizons underlying peat deposits. GIS based maps indicate that less decomposed OM characteristic of the O-horizon and permafrost peat deposits constitute the bulk of landscape SOM (>70% of landscape soil C). We conclude, however, that permafrost has not been the key environmental factor controlling the current degree of decomposition of SOM in this landscape due to relatively recent permafrost aggradation. In this century, active layer deepening will mainly affect SOM with a relatively high degree of decomposition in deeper mineral soil horizons. Additionally, thawing permafrost in peat plateaus may cause rapid remobilization of less decomposed SOM through thermokarst expansion.

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