Impact of Enhanced Tempertature and Snowfall on Soil Methane Dynamics in High Arctic Tundra
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Authors
Caspi, Noa
Date
2025-10-03
Type
thesis
Language
eng
Keyword
Biogeochemistry , Soil science , Methane , High Arctic
Alternative Title
Abstract
The Arctic is warming at four times the global rate, leading to changes in precipitation and permafrost thaw with consequences for soil biogeochemistry, including methane (CH4) dynamics. Research has primarily focused on CH4-emitting wetlands, with little attention to upland ecosystems covering around 80% of the Arctic landscape. These soils contain CH4-consuming bacteria, methanotrophs, which comprise the only biological CH4 sink, globally consuming 35Tg CH4 yr-1 from the atmosphere. This thesis explores environmental controls on soil CH4 dynamics in a High Arctic upland tundra and responses to enhanced snowfall and warming through field experiments and laboratory incubations, with data and samples collected from the Cape Bounty Arctic Watershed Observatory (Melville Island, NU) located in the Canadian High Arctic.
The first study examines the effects of experimental winter snow enhancement and summer warming treatments on summer CH4 fluxes. Contrary to expectations, plots that received more snow accumulation exhibited stronger net CH4 uptake, with a significant relationship between snow depth and cumulative seasonal flux (R2=0.30, p<0.001). Continuous soil temperature data showed increased snowpack insulated plots in winter (p<0.001). These findings suggest that increased snow accumulation during the winter may strengthen the Arctic upland soil CH4 sink capacity emphasizing the effects of changing precipitation patterns on soil thermal regimes controlling CH4 sink-source capacity.
The second study focused on depth-resolved laboratory incubations examining CH4 dynamics across the soil profile and assessing the effects of a long-term field experiment on soil characteristics. Incubations created ideal environments targeting different functional groups of CH4-cycling microbes. Results showed high-affinity CH4 oxidation potential was highest between 0-15cm, suggesting high-affinity methanotroph abundance is greatest near the soil’s surface. The CH4 production potential incubation, which included both acetate and CO2 amendments showed net CO2 uptake. This may suggest the hydrogenotrophic pathway which consumes CO2 was favored over the acetoclastic pathway which produces it. There was no observed effect of long-term enhanced snow or warming on soil characteristics or CH4 incubation results. Warming treatments did had no effect on soil temperatures which is most likely responsible for the observed lack of effect, alongside a small sample size compromised by high variability.