Tree mortality predicted from drought-induced vascular damage
Tree mortality predicted from drought-induced vascular damage
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DOI：
10.1038/ngeo2400
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发表时间：
2015-05-01
影响因子：
18.3
通讯作者：
Field, Christopher B.
中科院分区：
文献类型：
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作者：
Anderegg, William R. L.;Flint, Alan;Field, Christopher B.
预计森林生态系统对与21-世纪气候变化相关的变暖和干旱的反应差异很大，从恢复力到广泛的树木死亡率（1-3）。由于造成死亡的机制和阈值的不确定性，目前的植被模型缺乏计算极端干旱期间地上树木死亡率的能力（4、5）。在这里，我们评估树木死亡的原因，使用现场测量的分支导水率在美国西南部的山杨正在进行的死亡率和详细的植物水力学模型。我们确定了一个致命的植物水分胁迫阈值，对应于从空气进入木质部的血管运输能力的损失。然后，我们使用这个基于水力的阈值来模拟历史干旱期间的森林枯梢病，并将预测结果与三个独立的死亡率数据集进行比较。水力阈值预测与75%的准确度区域模式的树木死亡率，发现在野外地块和死亡率地图来自陆地卫星图像。在高排放情景下，气候模型预测，到2050年代，干旱压力将超过美国西南部观察到的死亡率阈值。我们的方法提供了一个强大的和易于处理的方式，将树木死亡率纳入植被模型，以解决森林生态系统在气候变化中的命运的不确定性。
The projected responses of forest ecosystems to warming and drying associated with twenty-first-century climate change vary widely from resiliency to widespread tree mortality(1-3). Current vegetation models lack the ability to account for mortality of overstorey trees during extreme drought owing to uncertainties in mechanisms and thresholds causing mortality(4,5). Here we assess the causes of tree mortality, using field measurements of branch hydraulic conductivity during ongoing mortality in Populus tremuloides in the southwestern United States and a detailed plant hydraulics model. We identify a lethal plant water stress threshold that corresponds with a loss of vascular transport capacity from air entry into the xylem. We then use this hydraulic-based threshold to simulate forest dieback during historical drought, and compare predictions against three independent mortality data sets. The hydraulic threshold predicted with 75% accuracy regional patterns of tree mortality as found in field plots and mortality maps derived from Landsat imagery. In a high-emissions scenario, climate models project that drought stress will exceed the observed mortality threshold in the southwestern United States by the 2050s. Our approach provides a powerful and tractable way of incorporating tree mortality into vegetation models to resolve uncertainty over the fate of forest ecosystems in a changing climate.