High synchrony of tree growth is followed by a uniform pattern of de-synchronization

Aim: Growth asynchrony in trees increases deviation in the average of forest growth and, consequently, brings uncertainty in modeling forest productivity and other functions. Despite recognition of growth variability among trees, the process of asynchronous growth and its ecological implications are poorly understood. Here we used tree-ring data to show that, although forest growth is influenced by climatic factors, inter-annual growth changes of individual trees often do not respond in a synchronous manner. Location: China. Time period: The past five and a half centuries. Major taxa studied: Forest tree growth. Methods: We used tree-ring methods and tree-ring data obtained from increment core samples in 1046 juniper trees at 32 sites and 538 pine trees at 20 sites to explore the implications of growth asynchrony in maintaining forest stability in the face of environmental fluctuations. Results: After highly synchronous growth events, the number of trees keeping continuous growth synchrony declined progressively and, notably, in a relatively uniform pattern. Main conclusions: We argue that diverse rather than synchronized growth spreads the capacity of trees to respond to disturbances and stresses at the individual level, consequently enhances forest resilience to risks of climate uncertainty. This resilience-acquisition strategy is an inherent and an adaptive property of forest tree growth that is similar to maintaining a diversified financial investment portfolio. This new perspective on widespread asynchronous tree growth sheds insight into assessment of forest health risks under future climate change.

研究目的：树木生长异步性会加剧森林生长平均值的偏差，进而增加森林生产力及其他生态功能建模的不确定性。尽管学界已认识到树木间的生长变异，但对异步生长的过程及其生态意义的理解仍较为匮乏。本研究利用树轮（tree-ring）数据证实：尽管森林整体生长受气候因子调控，但单木的年际生长变化往往并不同步。
研究区域：中国。
研究时段：过去550年。
研究类群：森林树木生长。
研究方法：本研究采用树轮分析方法，结合采自32个样地的1046株刺柏（juniper）以及20个样地的538株松属（pine）树木的生长样芯（increment core）数据，探究生长异步性在环境波动下维持森林稳定性的生态学意义。
研究结果：在出现高度同步的生长事件后，维持持续生长同步性的树木数量会逐渐减少，且该过程呈现出相对统一的模式。
主要结论：本研究认为，相较于同步生长，多样化的生长模式可提升单木应对干扰与胁迫的能力，进而增强森林应对气候不确定性风险的恢复力。该恢复力获取策略是森林树木生长的固有且适应性特征，与多元化金融投资组合的逻辑相似。这项针对普遍存在的树木异步生长的新视角，可为未来气候变化下的森林健康风险评估提供新的认知。