Variability in above- and belowground carbon stocks in a Siberian larch watershed
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-la...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-09-01
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| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/14/4279/2017/bg-14-4279-2017.pdf |
| Summary: | 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<sup>−2</sup> (yedoma, non-ice wedge) and 331 kg C m<sup>−2</sup> (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. |
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| ISSN: | 1726-4170 1726-4189 |