Researchers study American forests' response to climate change
Credit: Fotolia
Younger, smaller trees, which cover most of the eastern forests of North America, have increased seed production under the influence of climate change, but older, larger trees that dominate the forests of the American West have suffered, a new study shows.
Knowledge about and understanding the different responses of forests to climate change will help scientists more accurately predict future changes in North American forests and develop conservation and management strategies to mitigate these changes.
Dr. Michał Bogdziewicz from the Faculty of Biology of Adam Mickiewicz University was involved in the research into the American forests' response to climate change conducted at Duke University in the US. The research results have been published in Nature Communications.
According to the research project leader Prof. James S. Clark of Duke University, fecundity is the only major demographic process that lacks field-based estimates in models of vegetation change.
To solve this problem, the team built a network of decades of primary data on size, height, canopy spread and resource access for nearly 100,000 individual trees at long-term North American research sites and in experimental forests.
The data revealed what previous meta-analyses based on average measurements had missed. On a continental scale, fecundity increases as the tree grows, up to a point. And then it starts to drop.
Dr. Bogdziewicz said: “This explains the difference in trends we have seen between East and West. Most trees in the East are young, growing rapidly and entering the size class where fecundity is increasing, so any indirect climate effects that stimulates their growth also increases seed production.”
The opposite is true for older, larger trees in the West. Of course, there are small and large trees in both regions, but the regions are sufficiently different in average size to react differently.
Bogdziewicz said: “Now that we understand how it all works, the next step is to use new knowledge to predict future changes in forests, including species migration in response to climate change.”
In his opinion, the decline in the fecundity of trees may limit the ability of forests to regenerate, for example after large-scale dieback associated with rising temperatures and increasing droughts.
He added that seed production varies over time depending on changes in tree size, growth rate, access to light, water and other resources. It is also driven by two indirect climate effects. On the one hand, the fecundity of trees depends on the size of the trees, and their increments depend on the climate. On the other hand, the direct influence of weather on the fecundity of trees depends on their size.
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