Abstract
Abstract. This study investigates the soil organic carbon (SOC) storage in Tarfala Valley, northern Sweden. Field inventories, upscaled based on land cover, show that this alpine permafrost environment does not store large amounts of SOC, with an estimate mean of 0.9 ± 0.2 kg C m−2 for the upper meter of soil. This is 1 to 2 orders of magnitude lower than what has been reported for lowland permafrost terrain. The SOC storage varies for different land cover classes and ranges from 0.05 kg C m−2 for stone-dominated to 8.4 kg C m−2 for grass-dominated areas. No signs of organic matter burial through cryoturbation or slope processes were found, and radiocarbon-dated SOC is generally of recent origin (<2000 cal yr BP). An inventory of permafrost distribution in Tarfala Valley, based on the bottom temperature of snow measurements and a logistic regression model, showed that at an altitude where permafrost is probable the SOC storage is very low. In the high-altitude permafrost zones (above 1500 m), soils store only ca. 0.1 kg C m−2. Under future climate warming, an upward shift of vegetation zones may lead to a net ecosystem C uptake from increased biomass and soil development. As a consequence, alpine permafrost environments could act as a net carbon sink in the future, as there is no loss of older or deeper SOC from thawing permafrost.
Highlights
The permafrost-affected soil area in the northern circumpolar region is widespread, occupying about 17.8 million km2 (Hugelius et al, 2014)
A Mean soil organic carbon (SOC) storage is based on the land cover classification upscaling
The second number in each column is not the standard deviation like in the land cover classes but the 95 %-confidence interval which is based on the SOC variance and areal extent of each land cover classification (LCC). b Only the vegetated area is considered
Summary
The permafrost-affected soil area in the northern circumpolar region is widespread, occupying about 17.8 million km (Hugelius et al, 2014). With a warming climate, which is expected to be most pronounced in northern high latitudes, thawing permafrost soils may cause remobilization of soil organic matter (SOM) previously protected in permafrost (Gruber et al, 2004; Schuur et al, 2008). This can lead to an increased microbial decomposition of SOM and a release of carbon dioxide (CO2) and methane (CH4) into the atmosphere. The total storage of SOC within the northern permafrost region and the amount of greenhouse gases that can be released into the atmosphere and trigger accelerated climate warming are still uncertain (Schuur et al, 2009, 2013; Kuhry et al, 2010; McGuire et al, 2010)
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