Shrub expansion may reduce summer permafrost thaw in Siberian tundra

Climate change is expected to cause extensive vegetation changes in the Arctic: deciduous shrubs are already expanding, in response to climate warming. The results from transect studies suggest that increasing shrub cover will impact significantly on the surface energy balance. However, little is kn...

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Bibliographic Details
Published in:Global change biology 2010-04, Vol.16 (4), p.1296-1305
Main Authors: BLOK, D, HEIJMANS, M.M.P.D, SCHAEPMAN-STRUB, G, KONONOV, A.V, MAXIMOV, T.C, BERENDSE, F
Format: Article
Language:English
Subjects:
active layer thickness
alaskan tussock tundra
arctic tundra
Betula nana
boreal forest
Climate change
climate warming
energy-exchange
ground heat flux
litter decomposition rates
northern alaska
permafrost degradation
Plant growth
responses
soil-thaw
Taiga & tundra
Temperature effects
tundra vegetation
Vegetation
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Summary:Climate change is expected to cause extensive vegetation changes in the Arctic: deciduous shrubs are already expanding, in response to climate warming. The results from transect studies suggest that increasing shrub cover will impact significantly on the surface energy balance. However, little is known about the direct effects of shrub cover on permafrost thaw during summer. We experimentally quantified the influence of Betula nana cover on permafrost thaw in a moist tundra site in northeast Siberia with continuous permafrost. We measured the thaw depth of the soil, also called the active layer thickness (ALT), ground heat flux and net radiation in 10 m diameter plots with natural B. nana cover (control plots) and in plots in which B. nana was removed (removal plots). Removal of B. nana increased ALT by 9% on average late in the growing season, compared with control plots. Differences in ALT correlated well with differences in ground heat flux between the control plots and B. nana removal plots. In the undisturbed control plots, we found an inverse correlation between B. nana cover and late growing season ALT. These results suggest that the expected expansion of deciduous shrubs in the Arctic region, triggered by climate warming, may reduce summer permafrost thaw. Increased shrub growth may thus partially offset further permafrost degradation by future temperature increases. Permafrost models need to include a dynamic vegetation component to accurately predict future permafrost thaw.
ISSN:1354-1013
1365-2486
DOI:10.1111/j.1365-2486.2009.02110.x