Northeastern North America as a potential refugium for boreal forests in a warming climate

A future for boreal forests Conservation under climate change presents the challenge of predicting where will be suitable for particular organisms and ecological communities in the future. D'Orangeville et al. assess the probable future range for boreal forests in eastern North America, which are expected to be subject to large temperature increases in their natural range. Using tree-ring data from many thousands of forest stands, they delineate the geographical extent of the region where tree growth responds favorably to higher temperatures and where the forest should persist at least until 2070. Science, this issue p. 1452 Tree-ring data from black spruce indicate increased growth in response to increased temperatures. High precipitation in boreal northeastern North America could help forests withstand the expected temperature-driven increase in evaporative demand, but definitive evidence is lacking. Using a network of tree-ring collections from 16,450 stands across 583,000 km2 of boreal forests in Québec, Canada, we observe a latitudinal shift in the correlation of black spruce growth with temperature and reduced precipitation, from negative south of 49°N to largely positive to the north of that latitude. Our results suggest that the positive effect of a warmer climate on growth rates and growing season length north of 49°N outweighs the potential negative effect of lower water availability. Unlike the central and western portions of the continent’s boreal forest, northeastern North America may act as a climatic refugium in a warmer climate.

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