Drought's legacy: multiyear hydraulic deterioration underlies widespread aspen forest die-off and portends increased future risk
Drought's legacy: multiyear hydraulic deterioration underlies widespread aspen forest die-off and portends increased future risk
复制标题
DOI：
10.1111/gcb.12100
复制
发表时间：
2013-04-01
影响因子：
11.6
通讯作者：
Field, Christopher B.
中科院分区：
文献类型：
--
作者：
Anderegg, William R. L.;Plavcova, Lenka;Field, Christopher B.
森林死亡率是预测气候对陆地生态系统影响和碳循环反馈的一个主要不确定因素。最近由干旱引起的大范围森林死亡突出表明，气候变化可能会加速森林死亡，对全球碳循环、生态系统服务和生物多样性造成各种可能严重的后果。树木如何在多年干旱期间死亡仍然是未知的，并排除了森林死亡与气候变化的机械建模和预测。在这里，我们研究的生理基础，最近多年来广泛死亡的颤抖白杨（杨树tremuloides）在北美西部大部分地区。从本地树木的观察，而他们正在死亡和降雨排除实验成熟的树木，我们测量水力性能在多个季节和年份，并评估累积水力损害的途径。我们测试了累积水力损伤是否可以预测树木存活超过20年的概率。我们发现，液压损坏持续多年，并在垂死的树木增加，并表现出很少的修复迹象。这种累积的水力恶化主要是由对气蚀的增加的脆弱性介导的，该过程被称为气蚀疲劳。此外，这种水力损害预测的概率，跨年茎死亡。与幸存的树木经受住了严重干旱的预期相反，这里展示的水力恶化表明，由于累积的木质部损伤，这些森林的幸存区域实际上更容易受到未来干旱的影响。作为北美分布最广的树种，这些森林对干旱的脆弱性日益增加，对生态系统稳定性、生物多样性和生态系统碳平衡产生了重要影响。我们的研究结果为将累积干旱影响纳入气候植被模型提供了基础。最后，我们的研究结果强调了干旱胁迫积累和修复胁迫引起的损害，以避免植物死亡的关键作用，提出了一个动态和应急框架干旱对森林生态系统的影响。
Forest mortality constitutes a major uncertainty in projections of climate impacts on terrestrial ecosystems and carbon-cycle feedbacks. Recent drought-induced, widespread forest die-offs highlight that climate change could accelerate forest mortality with its diverse and potentially severe consequences for the global carbon cycle, ecosystem services, and biodiversity. How trees die during drought over multiple years remains largely unknown and precludes mechanistic modeling and prediction of forest die-off with climate change. Here, we examine the physiological basis of a recent multiyear widespread die-off of trembling aspen (Populus tremuloides) across much of western North America. Using observations from both native trees while they are dying and a rainfall exclusion experiment on mature trees, we measure hydraulic performance over multiple seasons and years and assess pathways of accumulated hydraulic damage. We test whether accumulated hydraulic damage can predict the probability of tree survival over 2years. We find that hydraulic damage persisted and increased in dying trees over multiple years and exhibited few signs of repair. This accumulated hydraulic deterioration is largely mediated by increased vulnerability to cavitation, a process known as cavitation fatigue. Furthermore, this hydraulic damage predicts the probability of interyear stem mortality. Contrary to the expectation that surviving trees have weathered severe drought, the hydraulic deterioration demonstrated here reveals that surviving regions of these forests are actually more vulnerable to future droughts due to accumulated xylem damage. As the most widespread tree species in North America, increasing vulnerability to drought in these forests has important ramifications for ecosystem stability, biodiversity, and ecosystem carbon balance. Our results provide a foundation for incorporating accumulated drought impacts into climatevegetation models. Finally, our findings highlight the critical role of drought stress accumulation and repair of stress-induced damage for avoiding plant mortality, presenting a dynamic and contingent framework for drought impacts on forest ecosystems.