Could Cryoturbic Diapirs Be Key for Understanding Ecological Feedbacks to Climate Change in High Arctic Polar Deserts?

Abstract

High Arctic polar deserts cover 26% of the Arctic. Increasing temperatures are predicted to significantly alter polar desert freeze‐thaw and biogeochemical cycles, with important implications for greenhouse gas emissions. However, the mechanisms underlying these changing cycles are still highly uncertain. Cryoturbic, carbon‐rich Bhy horizons (diapirs) in frost boils are key nutrient sources for Salix arctica. We hypothesized that diapirism leads to organic carbon characteristics that alter microbial pathways, which then control root foraging and greenhouse gas production. During July and August 2013, we characterized soil properties and examined gross nitrogen transformation rates in frost boils both with and without diapirs in two High Arctic polar deserts (dolomite and granite) near Alexandra Fjord (78°51′N 75°54′W), Ellesmere Island, Nunavut, Canada. Diapiric frost boils had 18% higher soil organic carbon in the dolomitic and 9% higher in the granitic deserts, and 29% higher total dissolved nitrogen in the dolomitic desert. However, diapirs decreased gross nitrogen mineralization rates by 30% in the dolomitic and by 48% in the granitic deserts. Attenuated total reflectance Fourier transformed mid‐infrared spectroscopy revealed greater concentrations of polysaccharides and recalcitrant carbon in diapiric versus nondiapiric frost boils. These increased polysaccharide concentrations likely facilitate diapirism as soil viscosity increases with polysaccharides. Lower microbial activity or ectomycorrhizae that are known to colonize S. arctica may accumulate total dissolved nitrogen in diapirs. Our results suggest geomorphologic‐plant‐microbe interactions may underlie important patterns of geochemical cycling in arctic systems. Thus, polar desert frost boils should represent a key focus of future investigations of climate change in arctic systems.

Positron‐emitting radiotracers spatially resolve unexpected biogeochemical relationships linked with methane oxidation in Arctic soils

“…Soils were collected from a High Arctic desert plateau 5 km southwest of Alexandra Fjord (78°51′N, 75°54′W) on Ellesmere Island, Nunavut (Bliss et al, 1994; Ota et al, 2020). Annual precipitation averages <50 mm and mean annual temperature ranges from −16 to −19°C (Bliss et al, 1994; Ota et al, 2020).…”

“…Soils were collected from a High Arctic desert plateau 5 km southwest of Alexandra Fjord (78°51′N, 75°54′W) on Ellesmere Island, Nunavut (Bliss et al, 1994; Ota et al, 2020). Annual precipitation averages <50 mm and mean annual temperature ranges from −16 to −19°C (Bliss et al, 1994; Ota et al, 2020). Soils are classified as Regosolic Turbic Cryosols, reflecting weak horizon development, low SOC content, and cryoturbic frost boils across the field site (Brummell et al, 2012).…”

“…Within the context of Arctic desert soils, all these factors are influenced by widespread cryoturbic features, which locally alter soil moisture and nutrient, SOC, and DOC speciation. This results from freeze‐thaw processes, which can lead to concentric size‐sorted features known as frost boils (i.e., frost heaving) as well as upward injection of DOC and nutrients from subsoils into higher soil horizons (i.e., diapirism), which may influence GHG dynamics (Brummell et al, 2015; Ota et al, 2020; Walker et al, 2004). For example, reduction in CH 4 fluxes by cryoturbic diapirism have been linked to lower substrate availability and reduced SOC degradability (Ota, 2021).…”

“…Taxa labelled in bold were >10-fold more abundant in [ 11 C]CH 4 hotspots relative to background (bulk) soil. Ralstonia pickettii relative abundance is highlighted [Colour figure can be viewed at wileyonlinelibrary.com]boils, which showed relative enrichment of polysaccharide and aromatic-rich SOC constituents in diapiric frost boils(Ota et al, 2020). SOC speciation is similar within active [ 11 C]CH 4 uptake regions compared with background regions, even under more constrained comparison (FigureS5b), indicating SOC speciation does not spatially relate with CH 4 uptake across these Arctic desert soils at spatial scales probed, regardless of diapirism (FigureS5c).…”

Rocks, lichens, and woody litter influenced the soil invertebrate density in upland tundra heath

“…The Arctic tundra is characterized as a very cold biome with low precipitation, short growing seasons of approximately 50 to 60 days, and poor soil nutrient conditions [ 1 ]. Due to these harsh conditions, biodiversity in the Arctic tundra tends to be lower than other biomes [ 2 , 3 ].…”