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Biogeosciences An interactive open-access journal of the European Geosciences Union
Biogeosciences, 14, 4279-4294, 2017
https://doi.org/10.5194/bg-14-4279-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
26 Sep 2017
Variability in above- and belowground carbon stocks in a Siberian larch watershed
Elizabeth E. Webb1, Kathryn Heard2, Susan M. Natali1, Andrew G. Bunn3, Heather D. Alexander4, Logan T. Berner5, Alexander Kholodov6,7, Michael M. Loranty8, John D. Schade1, Valentin Spektor9, and Nikita Zimov10 1Woods Hole Research Center, 149 Woods Hole Road, Falmouth, MA 02540, USA
2Western Washington University, 516 High Street, Bellingham, WA 98225, USA
3Department of Environmental Science, Western Washington University, 516 High Street, Bellingham, WA 98225, USA
4Department of Forestry, Forest and Wildlife Research Center, Mississippi State University, MS 39762, USA
5School of Informatics, Computing, and Cyber Systems, Northern Arizona University, Flagstaff, AZ 86011, USA
6University of Alaska, 903 Koyukuk Dr., Fairbanks, AK 99775, USA
7Institute of Physical-Chemical and Biological Problems of Soil Science RAS, 2 Institutskaya str., Pushchino, Russia
8Department of Geography, Colgate University, 13 Oak Dr, Hamilton, NY 13346, USA
9Melnikov Permafrost Institute, Siberian Branch of the Russian Academy of Sciences, Yakutsk, Russia
10Northeast Science Station, Chersky, Russia
Abstract. Permafrost soils store between 1330 and 1580 Pg carbon (C), which is 3 times the amount of C in global vegetation, almost twice the amount of C in the atmosphere, and half of the global soil organic C pool. Despite the massive amount of C in permafrost, estimates of soil C storage in the high-latitude permafrost region are highly uncertain, primarily due to undersampling at all spatial scales; circumpolar soil C estimates lack sufficient continental spatial diversity, regional intensity, and replication at the field-site level. Siberian forests are particularly undersampled, yet the larch forests that dominate this region may store more than twice as much soil C as all other boreal forest types in the continuous permafrost zone combined. Here we present above- and belowground C stocks from 20 sites representing a gradient of stand age and structure in a larch watershed of the Kolyma River, near Chersky, Sakha Republic, Russia. We found that the majority of C stored in the top 1 m of the watershed was stored belowground (92 %), with 19 % in the top 10 cm of soil and 40 % in the top 30 cm. Carbon was more variable in surface soils (10 cm; coefficient of variation (CV)  =  0.35 between stands) than in the top 30 cm (CV  =  0.14) or soil profile to 1 m (CV  =  0.20). Combined active-layer and deep frozen deposits (surface – 15 m) contained 205 kg C m−2 (yedoma, non-ice wedge) and 331 kg C m−2 (alas), which, even when accounting for landscape-level ice content, is an order of magnitude more C than that stored in the top meter of soil and 2 orders of magnitude more C than in aboveground biomass. Aboveground biomass was composed of primarily larch (53 %) but also included understory vegetation (30 %), woody debris (11 %) and snag (6 %) biomass. While aboveground biomass contained relatively little (8 %) of the C stocks in the watershed, aboveground processes were linked to thaw depth and belowground C storage. Thaw depth was negatively related to stand age, and soil C density (top 10 cm) was positively related to soil moisture and negatively related to moss and lichen cover. These results suggest that, as the climate warms, changes in stand age and structure may be as important as direct climate effects on belowground environmental conditions and permafrost C vulnerability.

Citation: Webb, E. E., Heard, K., Natali, S. M., Bunn, A. G., Alexander, H. D., Berner, L. T., Kholodov, A., Loranty, M. M., Schade, J. D., Spektor, V., and Zimov, N.: Variability in above- and belowground carbon stocks in a Siberian larch watershed, Biogeosciences, 14, 4279-4294, https://doi.org/10.5194/bg-14-4279-2017, 2017.
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Short summary
Permafrost soils store massive amounts of C, yet estimates of soil C storage in this region are highly uncertain, primarily due to undersampling at all spatial scales; circumpolar soil C estimates lack sufficient continental spatial diversity, regional intensity, and replication at the field-site level. We aim to reduce the uncertainty of regional C estimates by providing a comprehensive assessment of vegetation, active-layer, and permafrost C stocks in a watershed in northeast Siberia, Russia.
Permafrost soils store massive amounts of C, yet estimates of soil C storage in this region are...
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