Released April 11, 2008

LITTLE ROCK, Ark. -- For certain Arkansas tree species, just a few hours of flooding can prove fatal, says a forestry expert with the University of Arkansas Division of Agriculture.

"Even after five hours of standing in a couple inches of water, trees start shutting down photosynthesis," said Dr. Tamara Walkingstick, an extension forestry specialist and associate professor for the division of agriculture.

Trees that can’t tolerate flooding include hickories, southern red oak, dogwoods, shortleaf pines and eastern red buds.

Spring is a time when trees are especially vulnerable.

"This is their big time when they are expending a lot of energy blooming and putting out leaves," Walkingstick says.

"The key problem is that the flooding rapidly depletes the oxygen in the soil," she says. "They have to have oxygen in the soil for root respiration."

When the oxygen is shut out, anerobic processes begin. The foul smell is the first clue the process has started.

"That produces toxins in the soil and the absorbing roots begin to die," Walkingstick says. "Everything shuts down."

Some species handle the water better. "They’re adapted to the flooding," she says. "They’ve evolved in wet ecosystems."

These include cypress, willows, sweet gums, green ash and maples. Other species that are somewhat tolerant of flooding include some hackberries, oaks, loblolly pines, birches and elms.

Some trees can tolerate 30 to 80 days of root submergence. In addition to species, how the tree copes with the water depends on age, health and how leaved out the trees are.

"The most critical time is just after the leaves have fully expanded," she says. "That’s when the most potentially dangerous flood damage can occur. We’re borderline now."

Early signs of damage include brown, wilted leaves and branch die-back. The injuries may leave the trees susceptible to insects and disease.

"It could take years for some of them to die," she said. "Unfortunately, there’s not much people can do to help their flooded trees."

The Cooperative Extension Service is part of the U of A Division of Agriculture.

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http://www.uaex.edu/news/april2008/0411floodedtrees.htm

Contact: Mary F. Hightower, (501) 671-2126, mhightower@uaex.edu