Research press release


Nature Geoscience

A threshold for drought-induced forest diebacks



William Andereggたちは、2010年、2011年および2013年の夏に得られた野外観測を用いてポプラの枝中の水流を調べ、それ以上の干ばつ条件下で木の中の水流が減少し、木に死をもたらす重要な閾値を見つけた。彼らはこの閾値を詳細な植物の水文学的モデルに取り込み、75%の精度で過去のポプラ森林の立ち枯れを予測し、この閾値が木の死亡率予測に有用であることを示した。彼らは6個の大循環モデルから得られた気候データを用いてこのモデルを実行させ、温室効果ガス放出が高くなると2050年代までに米国南西部の大部分でこの閾値を超える干ばつ条件が作り出されることを見いだした。

Increasing drought stress in the southwestern United States could lead to widespread diebacks of aspen forests by the mid-twenty-first century, according to a study published online in Nature Geoscience.

During droughts, as plant demand for water outstrips supply, bubbles of air can be introduced into plant vessels, severely reducing the flow of water and ultimately leading to mortality. While droughts are expected to become more intense and frequent in response to a warming climate, current models are not able to predict forest dieback.

William Anderegg and colleagues used field measurements taken during the summers of 2010, 2011, and 2013 to test water flow in the branches of aspens, and discovered a critical threshold above which drought conditions reduced water flow in the trees enough to cause mortality. They incorporated this threshold into a detailed plant hydraulics model and were able to predict historical aspen forest die-offs with 75% accuracy, supporting the utility of the threshold for predicting tree mortality. Running this model using climate data from six general circulation models, they find that high greenhouse-gas emissions could create drought conditions that exceed the threshold throughout much of the southwestern United States by the 2050s.

doi: 10.1038/ngeo2400


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