Tree losses in South Mississippi from Hurricane Katrina are still rising 11 months and counting after the devastating storm made landfall.
Glenn Hughes, Mississippi State University Extension Service forestry specialist in Lamar County, said the extent of the damage is still being assessed and more trees continue dying from affects of the storm.
"Live oaks faired very well in the hurricane, especially compared to a lot of the pines that just snapped," Hughes said. "The damage to the oaks was not necessarily that the trees were blown over, but from the loss of the leaves and many branches. It will take several years for the canopy to build back."
While many of the oaks that beautified areas are still standing and can rebound in time, they remain in harm's way from reconstruction.
"When we get into rebuilding and heavy machinery passes over the root systems, we will lose some live oaks that survived the storm," Hughes said.
Tiny roots feed the trees, supplying the nutrients and water the massive trees must have to survive. Hughes said the majority of these feeder roots are concentrated within a foot of the surface and fill the area beneath the tree's previous canopy. Roots do go beyond the canopy and some extend much deeper than one foot deep.
"When you drive a piece of big machinery over the soil around an oak tree, you crush and compact the soil, damaging the roots and making it impossible for them to penetrate the compacted soil and get water," Hughes said. "Crushing the roots is like strangling the tree."
To protect these trees from death by construction equipment, Hughes said to fence off the entire area around the drip line. The drip line is the line encircling a tree reaching out to the furthest extension of where the branches once were.
"These trees are stressed because of Katrina and the subsequent drought; we don't need to stress them further, causing them to die on us," Hughes said.
While heavy machinery is an obvious threat, smaller vehicles like cars and pickup trucks can compact the soil and crush roots, too.
"Wheeled vehicles have greater ground pressure per square inch than does the same or heavier piece of equipment with tracks," Hughes said. "If you run over a site three times, you've compacted it 85 percent of what is possible, so just a few passes by a piece of equipment can significantly damage the roots of a tree."
When it is impossible to keep vehicles safely away from a tree, try to minimize the damage by staying only on one side of the tree.
Katrina devastated pine plantations south of Hattiesburg, and those that survived face another challenge. The drought following Hurricane Katrina last year and this summer's drought are stressing pine trees, making them susceptible to pine bark beetles.
Southern pine bark beetles, the most destructive of the bark beetles, have not been a major problem this year, but the Ips or Engraver beetles have. Hughes said these beetles infest downed and damaged trees first, but then attack stressed, living trees. Landowners should be vigilant in their battle against these pests.
While many trees are still struggling, Scott Roberts, associate professor of forest ecology in MSU's Department of Forestry, said forest ecosystems are very resilient and can recover from significant damage.
"You look at what we as a nation did to our forests in the late 1800s and early 1900s. We abused our forests with mineral development and timber harvests without replanting, and the forests came back anyway," Roberts said. "Today, they look pristine and unencumbered by human impacts, yet many people would be surprised to see how abused these same areas were 100 years ago."
Given time, timber and landscapes in coastal areas can recover as well, but the aesthetic damage will linger for a while.
Trees can re-grow lost leaves quickly, but it can take a few years to re-grow branches that were lost. Roberts said oaks and other hardwoods re-grow branches more easily than do pines. Where hardwoods may regain much of their pre-damage appearance in two or three years, pine trees may take four or five to regain their appearance.
"You don't reestablish a mature landscape in a short period of time," Roberts said.