Soil organic carbon storage in a mountain permafrost area of Central Asia (High Altai, Russia)
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SIBERIAN ENVIRONMENTAL CHANGE
Soil organic carbon storage in a mountain permafrost area of Central Asia (High Altai, Russia) Didac Pascual
, Peter Kuhry, Tatiana Raudina
Received: 3 June 2020 / Revised: 9 October 2020 / Accepted: 28 October 2020
Abstract The thawing and subsequent decomposition of large stocks of soil organic carbon (SOC) currently stored in the northern circumpolar permafrost region are projected to result in a ‘positive’ feedback on global warming. The magnitude of this feedback can only be assessed with improved knowledge about the total size and geographic distribution of the permafrost SOC pool. This study investigates SOC storage in an under-sampled mountain permafrost area in the Russian High Altai. SOC stocks from 39 soil pits are upscaled using a GIS-based land cover classification. We found that the top 100 cm of soils in Aktru Valley and the adjacent Kuray Basin only holds on average 2.6 ± 0.6 kg C m-2 (95% confidence interval), of which only c. 1% is stored in permafrost. Global warming will result in an upward shift of alpine life zones, with new plant cover and soil development at higher elevations. As a result, this type of mountain permafrost area might act as a net C sink in the future, representing a ‘negative’ feedback on global warming. Keywords Central Asia Climate change impacts and feedbacks Mountain permafrost Soil organic carbon
INTRODUCTION The northern circumpolar permafrost region represents about 16% of the global soil area, stretching from the High Arctic in the north to mid-latitude mountain and continental areas in the south (Tarnocai et al. 2009). At high Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13280-020-01433-6) contains supplementary material, which is available to authorized users.
latitudes, temperatures have increased at a rate of 0.6 °C per decade over the last 30 years, twice as fast as the global average (IPCC 2013), and temperatures have also increased in the mountain permafrost areas to the south (e.g., Zhang et al. 2018). These trends are expected to continue during the 21st Century. Under these warming conditions, nearsurface permafrost areas are expected to decrease by 37 to 81% by the end of the Century (IPCC 2013). Permafrost has been recognized as one of the vulnerable carbon (C) pools in the Earth System (Gruber et al. 2004). The fate of permafrost C in a warming climate has received increased attention, both in the scientific community as well as the public in general. This interest was fueled by a new and high estimate of the total amount of soil organic carbon (SOC) stored in the northern circumpolar permafrost region (Tarnocai et al. 2009). These stocks are susceptible to thawing and decomposition under rising temperatures, resulting in the release of greenhouse gases to the Earth’ atmosphere and leading to even more global warming and permafrost thawing (the so-called ‘positive’ permafrost C feedback). International research on this topic has thus increased exponentially over th
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