Trees in the upper canopy layer provide important ecosystem functions, such as a higher carbon sequestration rate and a better cooling effect on the understory. Photo of a mixed forest in Indiana. Image credit: Tsun Fung Au.
Key Points:
- Old-growth trees are more drought resistant than younger trees
- The new study sampled more than 20, 000 trees on five continents
- Preservation of forest cover remains one of the best strategies for combating climate change.
A new study by University of Michigan researchers reveals that old-growth trees play a role in the battle against climate change. The new study on five continents and singling out more than 20,000 trees showed that old-growth trees in forests’ upper canopy are more likely to be drought-resistant than younger tree species.
The study, published in Nature Climate Change, was carried out by analyzing tree rings from 21,194 trees from 119 drought-sensitive species during and after droughts in the past. The researchers used trees in the upper canopy of forests and classified them into young, intermediate, and old.
According to the data, researchers saw a 28% reduction in the growth of young hardwoods and a 21% reduction in old hardwoods during drought conditions. Additionally, there were differences in data obtained from conifers and hardwoods with needle-bearing trees, mainly conifers, showing more resilience since such trees inhabit arid environments.
While those age-related differences may appear fairly minor, when applied at the global scale they could have "huge impacts" on regional carbon storage and the global carbon budget, according to the study authors. That's especially true in temperate forests that are among the largest carbon sinks worldwide.
"These results imply that in the short term, drought's impact on forests may be severe due to the prevalence of younger trees and their greater sensitivity to drought. But in the long run, those younger trees have a greater ability to recover from drought, which could be beneficial to the carbon stock,” said University of Michigan forest ecologist Tsun Fung (Tom) Au, a postdoctoral fellow at the Institute for Global Change Biology.
Researchers predict that as old-growth trees such as hardwoods decline, droughts will severely affect forests in the short term as younger trees adapt to drought resiliency and are key in carbon sequestration.
“Our findings suggest that managing forests for their ability to store carbon and be resilient to drought could be an important tool in responding to climate change, and thinking about the age of the forest is an important aspect of how the forest will respond to drought,” said Indiana University’s Justin Maxwell, author of the study.