美国印第安纳大学Au, Tsun Fung等研究人员认为树冠层上层的幼龄乔木应对环境变化时更为敏感，也更能适应干旱。这一研究成果于2022年12月1日发表在国际顶尖学术期刊《自然—气候变化》上。

该课题组研究了五大洲超过2万棵树木的年龄相关的干旱敏感性，研究表明，干旱地区的树冠层上层的年轻树木有更大幅度的生长减速。被子植物比裸子植物表现出更大的年龄差异，同时与干旱地区相比，年龄相关的敏感性在潮湿的气候中更为明显。

然而，幼龄的树冠优势乔木也能更快地从干旱中恢复。未来干旱事件增加和幼龄树冠优势乔木比例增加表明，短期内对碳储量的不利影响更大，而幼龄树冠状优势乔木具有更高的复原力，可能会随着时间的推移对碳储量产生积极影响。

据介绍，全球古树的数量减少和重新造林的努力改变了改变了森林的树木统计结构，预计幼树将对固碳和森林生态系统功能产生越来越重要的影响。然而，人们对这些幼树抵抗气候变化压力的相对恢复力知之甚少。

附：英文原文

Title: Younger trees in the upper canopy are more sensitive but also more resilient to drought

Author: Au, Tsun Fung, Maxwell, Justin T., Robeson, Scott M., Li, Jinbao, Siani, Sacha M. O., Novick, Kimberly A., Dannenberg, Matthew P., Phillips, Richard P., Li, Teng, Chen, Zhenju, Lenoir, Jonathan

Issue&Volume: 2022-12-01

Abstract: As forest demographics are altered by the global decline of old trees and reforestation efforts, younger trees are expected to have an increasingly important influence on carbon sequestration and forest ecosystem functioning. However, the relative resilience of these younger trees to climate change stressors is poorly understood. Here we examine age-dependent drought sensitivity of over 20,000 individual trees across five continents and show that younger trees in the upper canopy layer have larger growth reductions during drought. Angiosperms show greater age differences than gymnosperms, and age-dependent sensitivity is more pronounced in humid climates compared with more arid regions. However, younger canopy-dominant trees also recover more quickly from drought. The future combination of increased drought events and an increased proportion of younger canopy-dominant trees suggests a larger adverse impact on carbon stocks in the short term, while the higher resilience of younger canopy-dominant trees could positively affect carbon stocks over time.

DOI: 10.1038/s41558-022-01528-w

Source: https://www.nature.com/articles/s41558-022-01528-w