Environmental effects on cryoturbation along bioclimatic gradients in subarctic Sweden : The importance of soil disturbance proxy, spatial scale and mesoclimatic regime

Abstract: Cryoturbation is a fundamental soil forming process with large importance for ecosystem functioning in the Arctic. Recent investigations have emphasized the effect of climate change on cryoturbation, but contrast in their predictions on cryoturbation under future climate warming. This study analyzed to what extent conclusions on the response of cryoturbation to environmental conditions depend on: 1) the proxy of cryogenic activity used; 2) the spatial scale of environmental predictor variables; and 3) the mesoclimatic regime of the study site. As an example of cryoturbated soil, 48 non-sorted patterned-ground features were sampled at eight sites along an elevational and a precipitation gradient and vegetation gradients nested within each site in the Abisko area, northernmost Sweden. To quantify cryogenic activity, eight proxies of cryogenic activity were used. In addition, environmental data were obtained at two spatial scales from field surveys and existing geodata. The results suggest a significant correlation between most activity proxies. Cryogenic activity increased along the precipitation gradient and peaked at intermediate elevations, while within-site variation was similar to between-site variation. The response of cryogenic activity to environmental factors was largly independent of the proxy used but varied with the spatial scale of predictor variables and across mesoclimatic regimes, with precipitation and vegetation cover being the most important predictors. The study indicates that spatial scale and mesoclimate should be considered when assessing the sensitivity of cryoturbation to climate changes. The results therefore provide possible explanations for contrasting previous predictions on the fate of cryoturbated patterned-ground ecosystems under future climate warming.