Eastern Trees Move North & West

Evergreen & deciduous species respond to climatic changes

Red oak
The distribution of 13 red oak species shifted west during the study period. Photo by David Stephens, Bugwood.org.

After analyzing extensive data collected on 86 tree species in the eastern U.S., researchers found that most trees have been shifting their ranges westward or northward in response to temperature and precipitation changes.

Scientists from Purdue University, North Carolina State University, and the U.S. Forest Service collaborated on the study, which was recently published in Science Advances

“Trees are shifting partially because of climate change, but their responses are species specific,” said Songlin Fei, a Purdue University scientist and professor who led the study. “Deciduous trees like oak and maple are primarily moving westward. Evergreens are responding in a different way. They’re moving northwards.”

The researchers used Forest Service Forest Inventory and Analysis data on tree abundance between 1980 and 2015. Study collaborators include Purdue scientists Johanna Desprez, Insu Jo, and Jonathan Knott; NCSU scientist Kevin Potter, a cooperator with the Eastern Forest Environmental Threat Assessment Center; and Southern Research Station research forester Chris Oswalt.

During the past 30 years, the mean annual temperature in the eastern U.S. has increased by 0.29 degree Fahrenheit. The northern areas of this region have among the highest temperature increases.

Precipitation patterns have also changed during the past 30 years, with increasing temperatures resulting in widespread droughts in the south. Some western areas of the study region have experienced increasing precipitation patterns.

Changes in temperature and precipitation
Changes in average temperature (left) and precipitation (right) between 1951-1980 and 1981-2014. Image courtesy of Science Advances.

The study, which outlined species-by-species responses to climate change, revealed that precipitation can significantly impact biodiversity and ecosystem sustainability. Many previous studies have generally shown a strong correlation between changes in temperature and tree shifting.

“We did see some northward shift as we had anticipated,” Fei said. However, “Precipitation has a stronger near-term impact on species shift than temperature,” said Fei, who also noted the westward shift following moisture changes was one of the most surprising findings of the study.

Fei said that the research shows the clear impact of climate change based on big data, not just modeling. “It is not future predictions,” he said. “Empirical data reveals the impact of climate change is happening on the ground now. It’s in action.”

Further research will focus on communities of trees, and the impact climate change can have on the sustainability of diverse ecosystems. “We want to know if there is a community breakdown among groups of species resulting from climate changes,” said Fei.

Read the full text of the article.

For more information, email Kevin Potter at kevinpotter@fs.fed.us.

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