Does Diapirism Influence Greenhouse Gas Production on Patterned Ground in the High Arctic?

Abstract

There are unusual patterns of greenhouse gas (GHG) net production in soil profiles of Arctic polar deserts. These deserts include frost boils that are symptomatic of permafrost‐associated soils. Some frost boils contain diapirs, intrusions of recently thawed, carbon‐ and water‐rich fine material pushed upward into the overlying active layer. Here we identified diapir‐associated frost boils in an Arctic polar desert that we had previously found to have highly variable patterns of GHG net production, and compared patterns of GHG net production in soil profiles between diapir and non‐diapir frost boils. In addition, we tested the repeatability of soil gas probes measurements and if estimates of diffusivity based on bulk density were accurate. Probes were installed in frost boils identified as including or not including diapirs, and measurements were conducted over several days to evaluate net GHG production.Soil gas probes deployed for longer than approximately 3 d showed loss of signal, and the injection of an inert tracer, SF6, validated our estimates of soil diffusivity based on bulk density. Diapir‐associated frost boils showed reduced soil respiration compared with non‐diapir frost boils, despite these diapir‐associated frost boils having increased soil organic matter content. Thus, diapir intrusions in frost boils of the Arctic polar desert simultaneously store greater amounts of organic C and reduce soil respiration compared with non‐diapir frost boils. Differences in soil organic matter quality and/or its interaction with soil texture may be an important control for carbon storage in Arctic soils.

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

“…Our band assignment interpretation agrees with Gillespie et al (), who suggested that cryoturbated organic horizons that had previously lost labile organic matter become resistant to further decomposition. Therefore, diapirism may inject previously decomposed and recalcitrant SOC into the upper soil, which is consistent with both the lower C and N mineralization rates (Figures a and ) and reduced soil respiration (Brummell et al, ) in diapiric frost boils at our study sites. Reduced microbial activity due to recalcitrant SOC (Kaiser et al, ; Wild et al, ) suggests that, despite high levels of soil C in these diapiric injections, this C is comparatively stabilized and therefore not a key driver of soil nitrogen cycling.…”

“…In other arctic regions, C and N mineralization was lower in cryoturbated relative to noncryoturbated horizons (Gillespie et al, ; Kaiser et al, ; Wild et al, ). Therefore, diapiric nutrients may be less bioavailable for microbes due to release of recalcitrant C from plants actively colonizing frost boils (e.g., Betula nana ; Lynch et al, ), or organic detritus may be occluded in the aggregates of Bhy horizons, inhibiting microbial metabolism of soil organic carbon (SOC; Brummell et al, ; sensu Schimel & Schaeffer, ). It may also be that cryoturbated SOC accumulates ketones that increase recalcitrance (i.e., lowers quality), becoming more resistant to biodegradability than SOC of noncryoturbated soils (Gillespie et al, ) despite similar C/N ratios (Ernakovich et al, ).…”

“…How plant and soil biology interacts with diapirism and how this interaction may contribute to GHG production from frost boil systems are not clear. Muller et al (2017) found that Salix arctica (arctic willow) roots actively targeted Bhy horizons for N, though microbial C respiration was lower in diapiric relative to nondiapiric frost boils (Brummell et al, 2015). In other arctic regions, C and N mineralization was lower in cryoturbated relative to noncryoturbated horizons (Gillespie et al, 2014;Kaiser et al, 2007;Wild et al, 2013).…”

Biogeochemical and Ecological Responses to Warming Climate in High Arctic Polar Deserts

“…Diapirism is, however, driven by unstable bulk density caused by differences in water content between the ice-rich layer and the overlying soil layer instead of segregated ice and ice lens formation which leads to frost heave (Ping et al, 2015;Swanson et al, 1999). Until recently, few studies assessed soil properties and the GHG production associated with diapirism in Canadian High Arctic polar desert ecosystems where frost boils dominated the landscape (Brummell et al, 2015;Muller et al, 2017;. Approximately 30% of frost boils have an abrupt increase in SOC (> 0.2 log % SOC)-indicative of diapirism-based on visible near-infrared reflectance at depths ranging from 10-30 cm within the frost-boil profile (Muller et al, 2017).…”

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

“…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).…”