Could Cryoturbic Diapirs Be Key for Understanding Ecological Feedbacks to Climate Change in High Arctic Polar Deserts?. Issue 3 (14th March 2020)

• Record Type: Journal Article
• Authors: Ota, Mitsuaki; Mamet, Steven D.; Muller, Amanda L.; Lamb, Eric G.; Dhillon, Gurbir; Peak, Derek; Siciliano, Steven D.
• Is Part Of: Journal of geophysical research. Volume 125:Issue 3(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-03-14
• Subjects: permafrost -- patterned ground -- soil viscosity -- frost boils -- soil organic carbon -- polysaccharides; Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1029/2019JG005263
• Languages: English
• ISSNs: 2169-8953

Abstract

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. Plain Language Summary: Arctic ecology and climate are intricately interconnected. During short summers, the upper soil layers thaw, allowing biological activities. Recent warming in polar deserts has influenced key thaw processes and plant‐microbe interactions with soil nutrients. Polar desert ecosystems cover 26% of the Arctic and are expected to transform dramatically with further warming, with important implications for climate‐ecology feedbacks. To evaluate feedbacks in polar deserts, we focused on cryoturbic diapirism (buoyant nutrient patches above the permafrost), which is expected to increase with warming. We investigated soil properties and microbial activities in frost boils (density‐driven circulations of sediments above the permafrost). We found that diapirism increased recalcitrant soil organic carbon, which decreased microbial activities. Interestingly, we found that microbes and/or plants may augment diapirism by enhanced polysaccharide production increasing soil viscosity. Despite low organic carbon quality, the dominant vascular plant species, Salix arctica, increased root biomass and nitrogen uptake from diapirs, suggesting a mutualistic relationship between S. arctica and microbes. Under warming air temperatures, permafrost degradation releases stored organic matter, which may enhance nutrient cycling via diapirism. Therefore, our study suggests that diapirism may represent ecological change in High Arctic polar deserts in response to global warming. Key Points: Diapirism increased soil organic carbon in both dolomitic and granitic deserts, and total dissolved nitrogen in the dolomitic desert Diapirism decreased carbon and nitrogen mineralization Diapirism increased recalcitrant organic carbon and increased polysaccharides, which suggests microbes may cause diapirism through soil viscosity