Sammendrag
Climate warming is expected to positively alter upward and poleward treelines which
are controlled by low temperature and a short growing season. Despite the importance
of treelines as a bioassay of climate change, a global field assessment and posterior
forecasting of tree growth at annual scales is lacking. Using annually resolved tree-ring
data located across Eurasia and the Americas, we quantified and modeled the
relationship between temperature and radial growth at treeline during the 20th century.
We then tested whether this temperature–growth
association will remain stable
during the 21st century using a forward model under two climate scenarios (RCP 4.5
and 8.5). During the 20th century, growth enhancements were common in most sites,
and temperature and growth showed positive trends. Interestingly, the relationship
between temperature and growth trends was contingent on tree age suggesting biogeographic
patterns in treeline growth are contingent on local factors besides climate
warming. Simulations forecast temperature–growth
decoupling during the 21st century.
The growing season at treeline is projected to lengthen and growth rates would
increase and become less dependent on temperature rise. These forecasts illustrate
how growth may decouple from climate warming in cold regions and near the margins
of tree existence. Such projected temperature–growth
decoupling could impact ecosystem
processes in mountain and polar biomes, with feedbacks on climate warming.
climate warming, forest limit, growth model, mountain ecosystems, tree rings
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