New research demonstrated a warmer and dried California climate is changing the forest structure throughout the state.
Researchers compared forest surveys collected during the 1920s and 1930s with recent U.S. Forest Service data and found a decline of large trees and increase in the density of smaller trees across the entire region, as opposed to exclusively in the Sierra Nevada as has been previously suggested, UC Berkeley reported.
"Older, larger trees are declining because of disease, drought, logging and other factors, but what stands out is that this decline is statewide," said study leader Patrick McIntyre, who began the research while a postdoctoral fellow at UC Berkeley and now manages biodiversity data for the California Department of Fish and Wildlife. "Forests are becoming dominated by smaller, more densely packed trees, and oaks are becoming more dominant as pines decline."
The researchers believe the stressed forests and large tree loss could influence the global carbon situation, especially because scientists have been hoping to rely on forests to soak up a large portion of these greenhouse gases.
"There's no question that if you are losing large trees, you are losing the standing carbon in the forest," said co-author David Ackerly, a professor of integrative biology. "Loss of these big trees and the impact of drought stress become a big concern going forward in terms of its impact on the carbon cycle; they can turn a carbon sink into a source of carbon released to the atmosphere."
The findings could help researchers determine how forests will respond to future climate change, suggesting large-scale changes in temperature and water availability could have a significant impact on their composition.
The study was published online this week in the early edition of the Proceedings of the National Academy of Sciences.
