Competition amplifies drought stress in forests across broad climatic and compositional gradients
Competition amplifies drought stress in forests across broad climatic and compositional gradients
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DOI：
10.1002/ecs2.1849
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发表时间：
2017-07-01
期刊：
影响因子：
2.7
通讯作者：
Kern, Christel C.
中科院分区：
文献类型：
--
作者：
Gleason, Kelly E.;Bradford, John B.;Kern, Christel C.
由于树木密度的增加，世界各地的森林正在经历日益严重的干旱和竞争强度的增加。然而，干旱和竞争之间的相互作用对森林生长的影响仍然知之甚少。使用从6405棵树上采样的独特的林分尺度年代学数据集，我们量化了整个树木种群的年生长如何对干旱和竞争做出反应，在8个长期(数十年)的实验中，利用分布在广泛气候和成分梯度上的重复密度水平(例如，竞争强度)。森林生长(林内单木累积生长)在干旱期间下降，特别是在气候较干燥的更严重的干旱期间。除一个地点外，所有地点的高密度都加剧了森林增长的下降，特别是在更严重的干旱期间。令人惊讶的是，森林密度的影响总体上是持续的，但这些密度的影响在潮湿的地点比在干旱的地点更大。显著的密度影响发生在更极端的干旱期间，以及在半干旱地点温度较暖但在潮湿地点温度较低的时期。由于竞争对生长对干旱的反应有持续的影响，因此保持较低的森林密度可能会增强所有气候条件下对干旱的适应能力。
Forests around the world are experiencing increasingly severe droughts and elevated competitive intensity due to increased tree density. However, the influence of interactions between drought and competition on forest growth remains poorly understood. Using a unique dataset of stand-scale den-drochronology sampled from 6405 trees, we quantified how annual growth of entire tree populations responds to drought and competition in eight, long-term (multi-decadal), experiments with replicated levels of density (e.g., competitive intensity) arrayed across a broad climatic and compositional gradient. Forest growth (cumulative individual tree growth within a stand) declined during drought, especially during more severe drought in drier climates. Forest growth declines were exacerbated by high density at all sites but one, particularly during periods of more severe drought. Surprisingly, the influence of forest density was persistent overall, but these density impacts were greater in the humid sites than in more arid sites. Significant density impacts occurred during periods of more extreme drought, and during warmer temperatures in the semi-arid sites but during periods of cooler temperatures in the humid sites. Because competition has a consistent influence over growth response to drought, maintaining forests at lower density may enhance resilience to drought in all climates.