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Regular version of the site

Article

Diverse growth trends and climate responses across Eurasia's boreal forest

Environmental Research Letters. 2016. Vol. 11. No. 7. P. 074021-1-074021-13.
Hellman L., Agafonov L., Ljungqvist F., Churakova (Sidorova) O., Duthorn E., Esper J., Hulsmann L., Kirdyanov A., Moiseev P., Myglan V., Nikolayev A., Reinig F., Schweingruber F., Solomina O., Tegel W., Buntgen U.

The area covered by boreal forests accounts for ∼16%of the global and 22% of theNorthern
Hemisphere landmass. Changes in the productivity and functioning of this circumpolar biome not
only have strong effects on species composition and diversity at regional to larger scales, but also on
the Earth’s carbon cycle. Although temporal inconsistency in the response of tree growth to
temperature has been reported from some locations at the higher northern latitudes, a systematic
dendroecological network assessment is stillmissing formost of the boreal zone.Here, we analyze
the geographical patterns of changes in summer temperature and precipitation across northern
Eurasia>60 °Nsince 1951 AD, aswell as the growth trends and climate responses of 445 Pinus,
Larix and Picea ring width chronologies in the same area and period. In contrast to widespread
summer warming, fluctuations in precipitation and tree growth are spatially more diverse and
overall less distinct. Although the influence of summer temperature on ring formation is increasing
with latitude and distinctmoisture effects are restricted to a fewsouthern locations, growth
sensitivity to June–July temperature variability is only significant at 16.6% of all sites (p„0.01). By
revealing complex climate constraints on the productivity of Eurasia’s northern forests, our
results question the a priori suitability of boreal tree-ring width chronologies for reconstructing
summer temperatures. This study further emphasizes regional climate differences and their role on
the dynamics of boreal ecosystems, and also underlines the importance of free data access to
facilitate the compilation and evaluation ofmassively replicated and updated dendroecological
networks.