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Native American Burning Was Key Factor In Shaping Eastern US Forests

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North American burning caused fire-resistant trees such as oak and pine to dominate forests in the eastern United States. However, when the practice stopped, fire-resistant trees started to lose ground.   ( Pixabay )

Researchers from Pennsylvania State University found that Native Americans had a bigger influence in shaping the forests of the eastern United States.

In a new study, the team revealed that the use of fire to manage vegetation affected the forest composition in the region way more than climate change.

"I believe Native Americans were excellent vegetation managers and we can learn a lot from them about how to best manage forests of the U.S." stated.Marc Abrams, a professor of ecology and physiology.

Changing Forest Composition

Abrams, who is one of the authors of the study published in the journal Annals of Forest Science, has been studying the qualities of the forests in the eastern United States. He said that, for the past 2,000 years, the widespread use of fire has caused fire-adapted trees to dominate forests. However, as burning became less frequent, species such as oak and hickory start to be driven out.

To analyze the changes in forest composition, the researchers used the pollen and charcoal fossil records as well as tree-census studies from forests in eastern North American. They also looked at seven forest types in the north and central regions of the eastern United States.

They found that there was a significant decline in beech, pine, hemlock, and larches in the northernmost forests based on the present-day pollen and tree-survey data. Meanwhile, the same records revealed an increase in maple, poplar, ash, oak, and fir.

Forests in the south, on the other hand, saw the domination of oak and pine, while maple and birch lost ground.

The researcher noted, however, that the same could not be said about the condition of forests in the western United States. Because the east gets more precipitation that offsets the warming, the effects of climate change in the region are not as pronounced as in the west where more drought occurs.

Native American Forest Management

The researchers checked the human population data from the region in the last 2,000 years. They reported that after hundreds of years of steady burning, the activity escalated following the increase of population with the arrival of the European settlement. Then, in the 1940s, the use of fire was mostly shut down across the county.

Abrams stated that the study proves that there is something to be learned from Native Americans. They knew that to regrow plants that give them food, they had to burn forest understory regularly.

He noted that there were abrupt shifts from a moderate amount of burning to too much burning and then to almost zero burning in the past 2,000 years.

"Modern forests are dominated by tree species that are increasingly cool-adapted, shade-tolerant, drought-intolerant pyrophobes — trees that are reduced when exposed to repeated forest burning," explained Abrams. "Species such as oak are largely promoted by low-to moderate-level forest fires. Furthermore, this change in forest composition is making eastern forests more vulnerable to future fire and drought."

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