Preprints
https://doi.org/10.5194/bg-2023-117
https://doi.org/10.5194/bg-2023-117
04 Sep 2023
 | 04 Sep 2023
Status: this preprint is currently under review for the journal BG.

Environmental and vegetation control on active layer and soil temperature in an Arctic tundra ecosystem in Alaska

Kevin J. Gonzalez Martinez, Donatella Zona, Trent Biggs, Kristine Bernabe, Danielle Sirivat, Francia Tenorio, and Walter Oechel

Abstract. Permafrost soils contain approximately twice the amount of carbon than the atmosphere, which could be released as global warming continues. Increasing global temperatures have in fact the potential to result in increased permafrost degradation, and carbon loss into the atmosphere. To properly understand the potential release of the carbon stored in permafrost soils, it is critical to understand the environmental and vegetation control on the development of active layer, the upper soil layer that thaw during the growing season in the Arctic. Arctic tundra ecosystems are dominated by mosses, which compose approximately 40 % of the vegetation, and have a critical role in regulating the heat condition into the soil. Given their importance, the role that mosses play on permafrost degradation should be investigated in more details. This study measured soil temperature together with thaw depth, a range of environmental variables, and moss thickness, to identify the most important controls on the development of the active layer across 124 plots in continuous permafrost tundra ecosystems. We found that a thicker moss layer insulated the soil and resulted in cooler temperatures deeper in the soil, despite warmer surface temperatures. A thicker moss layer was associated with a deeper depth of thaw, likely for the higher growth of mosses in the drier and warmer topographically higher elevation areas. The protective role of mosses was only relevant for the first ~3 cm of the green moss layer, suggesting that the living moss layer was more important in regulating soil temperature, possibly through a higher ability to retain water. Soil moisture was in fact an important control on surface and deeper soil temperatures, with wetter soils been associated with cooler surface temperatures because of the higher evaporative cooling, and warmer deeper temperatures likely because of the larger heat conduction to deeper soils. Overall, this study highlights the importance of a green living moss layer on soil temperature and thaw depth. Mosses are among the most vulnerable vegetation to hydrological changes, given their lack of a rooting system, and their sensitivity to climate change should be considered when predicting the response of permafrost thaw to climate change.

Kevin J. Gonzalez Martinez et al.

Status: open (until 30 Oct 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Kevin J. Gonzalez Martinez et al.

Kevin J. Gonzalez Martinez et al.

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Short summary
Permafrost soils contain twice the amount of carbon than the atmosphere, and its release could majorly affect global temperatures. This study found that a thicker moss layer resulted in cooler temperatures deeper in the soil, despite warmer surface temperatures. The top green living moss layer was the most important in regulating the soil temperatures and should be considered when predicting the response of permafrost thaw to climate change.
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