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Climate Affects Arctic Tree Growth

By studying the growth of trees in Siberia, Alaska and the Northwest territories, scientists have learned that warming in recent decades has had large, and often negative, effects on high-latitude trees. Growth of the northernmost tree species--spruce in North America and larch in Siberia--has slowed in many locations.

Trees provide the foundation for entire ecosystems: Increased stress revealed in tree-ring data may herald changes in the very makeup of these forests. Changes in the species composition of trees are likely to have a ripple effect on other species, changing the resources provided by a forest. Moreover, the boreal forest has a significant effect on the climate system. Declines in productivity would reduce the amount of carbon dioxide being absorbed by high-latitude ecosystems and could act as positive feedback on climate, enhancing the amount of warming.

By comparing tree growth to historical climate data, scientists Andrea Lloyd and Logan Berner of Middlebury College and Andy Bunn of Huxley College showed that declines in growth were related to warming--with trees growing significantly slower in warm years than in cool years. The team found that the productivity of the boreal forest has declined across broad areas. The slower growth seen in tree rings is not isolated to single trees here and there, but instead is a more widespread phenomenon.

In Siberia, for example, the researchers found that the places where productivity (measured from satellite data) has declined in recent years were the same places where tree-ring data revealed signs of stress. The boreal forest is thus changing on a large scale, and those changes have implications for the climate system and for human use of the resources it provides.  

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  • researcher cores a larch tree near the arctic circle
Andrea Lloyd cores a larch near the Arctic Circle.
Alexander Zhulidov

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