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

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.

Automated summary

With the global decline of old trees and reforestation efforts, younger trees are becoming increasingly important for carbon sequestration and forest ecosystem functioning. This study finds that younger trees in the upper canopy layer are more sensitive to drought and experience larger growth reductions. However, they also recover more quickly from drought, suggesting a potential positive impact on carbon stocks over time.