Department of Biology, 1 University of New Mexico, MSC03 2020, Albuquerque, NM, 87131-0001, USA.
Department of Statistics, Rice University, MS 138, PO Box 1892, Houston, TX, 77251, USA.
New Phytol. 2013 Oct;200(2):375-387. doi: 10.1111/nph.12392. Epub 2013 Jul 12.
Global climate change is predicted to alter the intensity and duration of droughts, but the effects of changing precipitation patterns on vegetation mortality are difficult to predict. Our objective was to determine whether prolonged drought or above-average precipitation altered the capacity to respond to the individual precipitation pulses that drive productivity and survival. We analyzed 5 yr of data from a rainfall manipulation experiment in piñon-juniper (Pinus edulis-Juniperus monosperma) woodland using mixed effects models of transpiration response to event size, antecedent soil moisture, and post-event vapor pressure deficit. Replicated treatments included irrigation, drought, ambient control and infrastructure control. Mortality was highest under drought, and the reduced post-pulse transpiration in the droughted trees that died was attributable to treatment effects beyond drier antecedent conditions and reduced event size. In particular, trees that died were nearly unresponsive to antecedent shallow soil moisture, suggesting reduced shallow absorbing root area. Irrigated trees showed an enhanced response to precipitation pulses. Prolonged drought initiates a downward spiral whereby trees are increasingly unable to utilize pulsed soil moisture. Thus, the additive effects of future, more frequent droughts may increase drought-related mortality.
全球气候变化预计会改变干旱的强度和持续时间，但降水模式变化对植被死亡率的影响很难预测。我们的目的是确定长期干旱或高于平均水平的降水是否改变了对驱动生产力和生存的个别降水脉冲的响应能力。我们使用蒸腾作用对事件大小、前期土壤湿度和后期蒸气压亏缺的混合效应模型，分析了在派恩-杜松（Pinus edulis-Juniperus monosperma）林地进行的为期 5 年的降雨处理实验的数据。重复处理包括灌溉、干旱、环境对照和基础设施对照。在干旱条件下死亡率最高，死亡树木在脉冲后蒸腾作用的减少归因于除了更干燥的前期条件和减少的事件大小之外的处理效应。特别是，死亡的树木几乎对浅层土壤湿度没有反应，这表明浅层吸收根区减少。灌溉树木对降水脉冲的响应增强。长期干旱引发了一个恶性循环，树木越来越无法利用脉冲土壤水分。因此，未来更频繁的干旱的附加效应可能会增加与干旱相关的死亡率。
