Earth and Environmental Science Department, Lehigh University, Bethlehem, PA, 18015, USA.
Columbia Basin Groundwater Management Area, Kennewick, WA, 99366, USA.
New Phytol. 2013 Oct;200(2):413-421. doi: 10.1111/nph.12362. Epub 2013 Jun 17.
Recent regional tree die-off events appear to have been triggered by a combination of drought and heat - referred to as 'global-change-type drought'. To complement experiments focused on resolving mechanisms of drought-induced tree mortality, an evaluation of how patterns of tree die-off relate to highly spatially variable precipitation is needed. Here, we explore precipitation relationships with a die-off event of pinyon pine (Pinus edulis Engelm.) in southwestern North America during the 2002-2003 global-change-type drought. Pinyon die-off and its relationship with precipitation was quantified spatially along a precipitation gradient in north-central New Mexico with standard field plot measurements of die-off combined with canopy cover derived from normalized burn ratio (NBR) from Landsat imagery. Pinyon die-off patterns revealed threshold responses to precipitation (cumulative 2002-2003) and vapor pressure deficit (VPD), with little to no mortality (< 10%) above 600 mm and below warm season VPD of c. 1.7 kPa. [Correction added after online publication 17 June 2013; in the preceding sentence, the word 'below' has been inserted.] Our results refine how precipitation patterns within a region influence pinyon die-off, revealing a precipitation and VPD threshold for tree mortality and its uncertainty band where other factors probably come into play - a response type that influences stand demography and landscape heterogeneity and is of general interest, yet has not been documented.
最近发生的区域性树木死亡事件似乎是由干旱和高温共同引发的，这种情况被称为“全球变化型干旱”。为了补充专注于解决干旱导致树木死亡机制的实验，需要评估树木死亡模式与高度空间变化的降水之间的关系。在这里，我们探讨了 2002-2003 年全球变化型干旱期间美国西南部辐射松（Pinus edulis Engelm.）死亡事件与降水的关系。通过在新墨西哥州中北部的降水梯度上进行标准实地调查测量，结合归一化植被比（NBR）从 Landsat 图像中得出的树冠覆盖度，对辐射松死亡及其与降水的关系进行了空间量化。辐射松死亡模式揭示了对降水（2002-2003 年累计）和水汽压亏缺（VPD）的阈值响应，在 600 毫米以上和温暖季节 VPD 低于约 1.7 kPa 的情况下，死亡率几乎没有（<10%）。[在线出版后于 2013 年 6 月 17 日更正；在前面的句子中，“below”一词已被插入。]我们的结果细化了一个区域内的降水模式如何影响辐射松死亡，揭示了树木死亡率的降水和 VPD 阈值及其不确定性范围，在这个范围内，其他因素可能会发挥作用——这是一种影响林分动态和景观异质性的反应类型，具有普遍意义，但尚未有记录。
