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When wet Arctic tundra soils begin to freeze in the fall, an unfrozen layer remains between the frozen surface and deeper permafrost layers. This period is known as the zero curtain, as liquid water keeps the temperature of this soil layer near 0 Celsius (C) while latent heat is gradually dissipated. This experiment compares the temperature response of the methanogenic community in the zero curtain period with that of the summer community to test whether the zero curtain methanogenic community is especially cold adapted. This dataset includes methane production rates measured in anaerobic laboratory incubations of soils collected from two dates (July and Nov 2018) at temperatures around 0, 4 and 10C.
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Dissolved methane concentrations in Arctic tundra soil profiles in Utqiagvik, Alaska during Fall 2019 and Spring 2021
When wet Arctic tundra soils begin to freeze in the fall, an unfrozen layer remains between the frozen surface and deeper permafrost layers. This period is known as the zero curtain, as liquid water keeps the temperature of this soil layer near 0 Celsius (C) while latent heat is gradually dissipated. Significant methane emissions have been observed during this period but the role of concurrent biological production vs escape of stored methane requires more study. This dataset includes dissolved methane concentrations from the active layer (upper 35 centimeters (cm)) of Arctic tundra soils during the fall zero curtain period and in the spring, at the beginning of the thaw period. These data help address the question of biological methane production and storage during the fall.
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- Award ID(s):
- 1702797
- PAR ID:
- 10310645
- Publisher / Repository:
- NSF Arctic Data Center
- Date Published:
- Format(s):
- Medium: X Other: text/xml
- Sponsoring Org:
- National Science Foundation
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When wet Arctic tundra soils begin to freeze in the fall, an unfrozen layer remains between the frozen surface and deeper permafrost layers. This period is known as the zero curtain, as liquid water keeps the temperature of this soil layer near 0 Celsius (C) while latent heat is gradually dissipated. This project investigates the microbes that are metabolically active in the unfrozen layer during the fall zero curtain period and compares this community to that which is active in the late summer at the same depth (10-20 centimeters (cm)). This dataset contains the abundance and taxonomic designation of distinct 16S ribosomal ribonucleic acid (16S rRNA) sequences (operational taxonomic units, OTU's) associated with samples in this study. These data complement the sequences and metadata deposited in GenBank Bioproject PRJNA780202.more » « less
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When wet Arctic tundra soils begin to freeze in the fall, an unfrozen layer remains between the frozen surface and deeper permafrost layers. This period is known as the zero curtain, as liquid water keeps the temperature of this soil layer near 0 Celsius (C) while latent heat is gradually dissipated. This project investigates the methanogenic Archaea that are metabolically active in the unfrozen layer during the fall zero curtain period and compares this community to that which is active in the late summer at the same depth (10-20 centimeters (cm)). This dataset contains the abundance of distinct partial mcrA (Methyl-coenzyme M reductase alpha subunit) gene sequences (operational taxonomic units, OTU's defined at 16% similarity) amplified from messenger ribonucleic acid (mRNA) extracted from soil samples in this study. These data complement the sequences deposited in GenBank (accession numbers OL505703-OL505708).more » « less
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Abstract The atmospheric methane (CH4) concentration, a potent greenhouse gas, is on the rise once again, making it critical to understand the controls on CH4emissions. In Arctic tundra ecosystems, a substantial part of the CH4budget originates from the cold season, particularly during the “zero curtain” (ZC), when soil remains unfrozen around 0 °C. Due to the sparse data available at this time, the controls on cold season CH4emissions are poorly understood. This study investigates the relationship between the fall ZC and CH4emissions using long‐term soil temperature measurements and CH4fluxes from four eddy covariance (EC) towers in northern Alaska. To identify the large‐scale implication of the EC results, we investigated the temporal change of terrestrial CH4enhancements from the National Oceanic and Atmospheric Administration monitoring station in Utqiaġvik, AK, from 2001 to 2017 and their association with the ZC. We found that the ZC is extending later into winter (2.6 ± 0.5 days/year from 2001 to 2017) and that terrestrial fall CH4enhancements are correlated with later soil freezing (0.79 ± 0.18‐ppb CH4day−1unfrozen soil). ZC conditions were associated with consistently higher CH4fluxes than after soil freezing across all EC towers during the measuring period (2013–2017). Unfrozen soil persisted after air temperature was well below 0 °C suggesting that air temperature has poor predictive power on CH4fluxes relative to soil temperature. These results imply that later soil freezing can increase CH4loss and that soil temperature should be used to model CH4emissions during the fall.more » « less
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Soil anoxia is common in the annually thawed surface (‘active’) layer of permafrost soils, particularly when soils are saturated, and supports anaerobic microbial metabolism and methane (CH4) production. Rainfall contributes to soil saturation, but can also introduce oxygen, causing soil oxidation and altering anoxic conditions. We simulated a rainfall event in soil mesocosms from two dominant tundra types, tussock tundra and wet sedge tundra, to test the impacts of rainfall‐induced soil oxidation on microbial communities and their metabolic capacity for anaerobic CH4 production and aerobic respiration following soil oxidation. In both types, rainfall increased total soil O2 concentration, but in tussock tundra there was a 2.5‐fold greater increase in soil O2 compared to wet sedge tundra due to differences in soil drainage. Metagenomic and metatranscriptomic analyses found divergent microbial responses to rainfall between tundra types. Active microbial taxa in the tussock tundra community, including bacteria and fungi, responded to rainfall with a decline in gene expression for anaerobic metabolism and a concurrent increase in gene expression for cellular growth. In contrast, the wet sedge tundra community showed no significant changes in microbial gene expression from anaerobic metabolism, fermentation, or methanogenesis following rainfall, despite an initial increase in soil O2 concentration. These results suggest that rainfall induces soil oxidation and enhances aerobic microbial respiration in tussock tundra communities but may not accumulate or remain in wet sedge tundra soils long enough to induce a community‐wide shift from anaerobic metabolism. Thus, rainfall may serve only to maintain saturated soil conditions that promote CH4 production in low‐lying wet sedge tundra soils across the Arctic.more » « less
