Spring rain not enough to save drought-damaged trees

PDF: Recovery From Freeze Damage and Drought Stress

Rather than cut a sprawling elm in his St. Elmo yard, Sean Loftin hired specialists to remove dead branches in an attempt to nurse the tree back to health.

“It is such a beautiful shade tree that I want to try to save it,” he said as he watched a tree service crew work from a bucket truck on the drought-damaged 80-year-old elm.

The one-two punch of a killing frost last April followed by a record-breaking heat wave in August damaged trees already weakened by the 3-year-old Southern drought, experts agree. “Damage is pretty much widespread,” said Jerry Roberts, owner of Roberts Tree Service.

Rainfall this spring will not be enough to save dying trees.

“Some trees that had leaves last year were so stressed they may not have survived the winter or have enough food reserves to last through this season,” said Tom Hudlow, district forester for the Tennessee Division of Forestry. “Trees haven’t leafed out yet so it is difficult to detect mortality either from the ground or the air.”

The ongoing drought may harm the region’s trees for years to come, foresters and arborists said.

“It is the type of damage that doesn’t show up right away,” said Ray Burden, director of the University of Tennessee Extension Service for Hamilton County. “Some may not recover, and for those that do recovery could be a long-term process.”

Mr. Loftin’s tree has “a 50/50 chance of survival,” Mr. Roberts said.

NOT MUCH HELP

Recent rains have provided some drought relief for the Chattanooga area, allowing the National Weather Service to reduce drought conditions from exceptional to extreme on its most recent U.S. Drought Monitor.

The 5.99 inches of rain recorded March 1 through Saturday is slightly above normal for the month but only brings the year-to-date precipitation total to 13.49 inches. That’s a deficit of 2.60 inches from normal precipitation averaged over the past 10 years.

This year’s deficit follows rainfall deficits of 15.9 inches in 2007, the sixth-driest year on record, and followed a 7.85- inch deficit for 2006.

Some trees will recover, particularly if near-normal rainfall continues, but others will not.

Experts say drought damage is similar to starvation; replenishing plant fiber and returning to health depend on several factors, including the degree of damage, the availability of water and nutrients and time to recuperate. “We suspect there will be quite a few trees that will not releaf in the spring,” said Dr. Wayne Clatterbuck, an associate professor of forest management and silviculture at the University of Tennessee. “The trees probably died last fall, but we did not know it because the drought caused many trees to hold their leaves longer than usual.”

How Drought Kills

Effects of the drought are visible in the withered leaves and dead branches of dogwoods and pines growing in area yards and forests.

“Trees can survive a wet/dry cycle, but they are not capable of thriving in a prolonged drought,” Mr. Hudlow said. “We will see reduced growth over the next year or so and dying trees for the next two to five years.”

Several years of below-normal rainfall stress trees large and small, making them susceptible to disease, insect infestation and possibly causing irreversible damage to root systems, according to foresters and biologists.

Trees mobilize stored sugars to put out leaves in the spring, and last year’s Easter frost caused already stressed trees to develop leaves twice, said J. Hill Craddock, associate professor with the biology and environmental sciences department at the University of Tennessee at Chattanooga.

Leaves are food factories that replace the sugar reserves used for leaf production and other plant compounds within the body of the tree, Dr. Craddock said.

“These stored reserves allow trees to battle constant attack by insects and disease,” he said. “When a tree is under stress ... it will grow less and it will have less reserves for its defenses.”

A tree is then more susceptible to problems that include insects, such as pine beetles, that usually are forced from a tree’s bark by secretion of sap, he said.

Dead trees and dry leaves are fuel for forest fires, according to foresters.

“Last year we just about had a year-round wildfire season,” Mr. Hudlow said.

The wildfire season usually lasts from fall until spring, and in some years no forest fires will be reported from June until August. Last year, however, drought caused 12 local and 100 fires statewide reported during a single week in August 2007, state foresters said.

DEAD TREES DENT WALLETS

Forests cover more than half of Tennessee, and trees are a cash crop throughout the region. Woodland trees supply pulp and furniture, and nurseries grow plants for resale.

While it may take several years to assess the full extent of drought-related damage to Tennessee’s farmers, foresters and nurseries, state Commissioner of Agriculture Ken Givens said losses could total $750 million to $1 billion for 2007.

State Agriculture Department spokesman Tom Womack said crop losses could continue in 2008 but rising commodity prices should help farmers weather the drought.

Mr. Roberts said dead and dying trees will increase demand for businesses like his.

“We will be busy for at least the next three years,” he said.

Last year’s combination of freeze and drought has made it necessary for “a lot of people to replace plants,” according to Kim Bonastia, manager of Signal Mountain Nursery.

“The most damaged were Japanese maples, azaleas, mountain laurel, rhododendron and yews,” she said. “There was also a lot of insect damage due to stress from the drought.”

Replacement costs vary according to the size plants — both being removed and replanted — soil preparation and the type plants being used, Ms. Bonastia said.

“You may see more fences than shrubbery and trees for privacy, but I hope not,” she said.

adapting to drought

Dr. Craddock, who is active in the American Chestnut Project to reintroduce the American chestnut tree made nearly extinct by blight, said the remaining pure strains and hybrids of the species thrived during last year’s drought.

He said the native plant sale set for April 11-13 at Reflection Riding is an educational event that also provides an opportunity to add native plants to the home landscape.

“If you choose Tennessee native trees, you have a better chance of getting one that can adapt to our climate,” he said.

But arborists agree even the hardiest of trees are not immune to drought-related distress and possibly death.

“If we get another event, it will be really, really bad,” Mr. Roberts said. “We don’t need a freeze or a drought this year.”