City heat could be beneficial for trees

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NEW YORK, April 24 (UPI) -- Urban "heat islands," chronically elevated city heat levels, are driving some city trees to grow far better than their country cousins, U.S. researchers say.

Scientists at Columbia University's Earth Institute said they found common native red oak seedlings grow as much as eight times faster in New York's Central Park than in more rural, cooler settings in the Hudson Valley and Catskill Mountains.

Since red oaks and their close relatives dominate areas ranging from northern Virginia to southern New England, the finding may have implications for changing climate and forest composition over a wide region, a Columbia release said Tuesday.

Urban "heat islands" are the result of solar energy being absorbed by pavement, buildings and other infrastructure, then radiated back into the air.

While the phenomenon is generally viewed as a threat to public health and a cause for concern, trees actually benefit, researchers say.

"Some organisms may thrive on urban conditions," Columbia tree physiologist Kevin Griffin said.

While a city's hot summer nights can be a trial for humans, they are a boon to trees, he said, allowing them to perform more of the chemical reactions needed for photosynthesis when the sun comes back up.

"Some things about the city are bad for trees. This shows there are at least certain attributes that are beneficial," said lead author Stephanie Y. Searle, a Washington environmental researcher who was a Columbia undergraduate when she participated in the research.