Tree Survival Depends on Root Cycle

First posted on 02-02-2011

By Mary Hightower, U of A Division of Agriculture

The ability of a tree to survive a dry year depends very much on the condition of the root system, according to Jon Barry, extension forester for the University of Arkansas Division of Agriculture.

With the National Weather Service projecting a prolonged dry period driven by a strong La Niña, the going may be tough for trees this year.

“The result of a spring drought will be smaller-than-normal leaves and less leaf area for photosynthesis,” said Barr, who is based at the Southwest Extension and Research Center in Hope. “That means the tree is going to make and store less food through the summer.”

Barry said that’s not a problem if it happens once in a while.

“However, when trees have been under stress for several years, a dry spring adds one more stress to the pile,” he said. “For some trees, a dry spring could be the last straw.”

“Trees constantly shed and replace roots,” he said. “During any given year, they grow enough root system to extract the water they need to survive.”

Dry years like 2010 are tougher on trees when they follow wet years like 2009.

“During a wet year, a tree may shed roots; but won’t replace all of them because it doesn’t need an extensive system that summer,” Barry said. “If the following year is dry, the tree is going to suffer because it doesn’t have enough root system to extract sufficient water.”

Whether a tree survives a drought depends on a few factors such as age, species, site, soil volume available for rooting, and recent history.

“All of those factors interact with each other to determine how well any individual tree can deal with drought stress,” he said.

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