Skip navigationDigital Arborist Forest Health Protection, Southern Region

How to Evaluate and Manage Storm-Damaged Forest Areas

[ Digital Arborist home ] [ Contents ] [ Next ] [ Previous ]

Note Types of Damage
and Take Action


Breakage is the most common type of storm damage. The degree of impact depends on the degree and pattern of damage as well as the tree species involved.

Breakage inevitably lowers timber values. Breaks are uneven by their nature and occur randomly along the tree bole. This random breakage lowers commercial value since products are normally cut in specified lengths. Breakage also lowers value because the difficulty of logging in broken timber slows productivity.

Patterns are important when assessing the impact of breakage. When strong galeforce winds break trees, break patterns are simple and limited to the area adjacent to the breakpoint. Hardwood trees are seldom killed by breakage. Many hardwood species can survive severe breakage. Even when tops are nearly gone, new branches will sprout allowing many younger trees to survive. In hardwoods, the major problem is that breaks in the trunk or large branches (over 3 in. diameter) permit entry of stain and decay fungi. Stain will move vertically from the injury at a rate of 6 to 18 inches per year, and decay will follow the stain in 8 to 10 months.

Most species of pine will die if tops are completely broken and no live limbs remain. However, young, otherwise healthy slash and loblolly pines may survive if three or more live limbs remain after the storm. One of the lateral branches in these trees will become the new terminal, and in 8 to 10 years the only sign of breakage will be a sharp crook in the bole at the point where the break occurred. These trees will experience growth loss.


Hardwood trees with broken tops or branches over 3 inches in diameter should be salvaged during the next scheduled harvest. High-value trees, such as those in recreation areas and in yards, should be properly pruned to promote rapid healing.

Pine tree with broken main stem

Pine tree with broken main stem.

Twisted Trunks

The cyclonic winds that are typical of tornadoes, and often accompany hurricanes, cause twisting and separation of wood fibers in the main stem. Logs from trees that have experienced this treatment may fall apart when sawn for lumber products. Hardwoods twisted by cyclonic winds may appear normal. Pines twisted by wind often have pitch flow along the trunk in the area damaged by the twisting.

Wind damage


Trees with evidence of twist injury should be felled. They do not recover and considerable loss may be incurred by carrying this damaged material to harvest.

Internal stain on a previously damaged tree

Internal stain on a previously damaged tree.

Root Damage

If they are not salvaged promptly, uprooted trees probably will be degraded quickly by stains, decays, and secondary insects such as Ips bark beetles, borers, powderpost beetles, and ambrosia beetles. The longer salvage is delayed, the greater the amount of degrade and weight loss from rapid drying. Degrade translates into a stumpage value loss. The amount of degrade that is acceptable to industry depends on the tree species and local markets. Table I shows the probable sequence of invasion by damaging organisms in storm-damaged timber. Root-sprung trees will not die immediately, but may fall later or show decline symptoms over a period of several years. These trees may be invaded by root rot organisms, be subjected to drought stress, or suffer insect attack. Rootsprung pines may be invaded by bark beetles and blue stain fungi. These pines can serve as prime habitat for the southern pine beetle and, if conditions become favorable, an outbreak could occur. They can also harbor high populations of turpentine beetles.

Table 1 - Sequence of invasion of damaging organisms in storm-damaged timber.
Species Year 1 Year 2
Pine Bark beetles, ambrosia beetles, sawyers, blue stain fungi, soft rot funi Decay fungi
Oak and hickory Wood borers, ambrosia beetles, stains, soft rot fungi Sapwood decay fungi
Other hardwoods Wood borers, ambrosia beetles, stains, soft rot fungi Sap and heartwood decay fungi


Trees with major root damage should be salvaged as soon as possible to avoid growth loss, product degrade, bark beetle attacks, and mortality.

Major Wounds

During storms, many trees sustain wounds caused by falling tops, adjacent uprooted trees, and major branch breakage. In hardwoods, wounds that do not penetrate more than 2 inches into the sapwood and have less than 144 square inches of surface area will have only localized stain and little decay. Wounds that exceed these limits will have stains and decay that move at the rates described for broken branches. Pine trees with major wounds to the lower bole and larger roots may be attacked by bark beetles.

Wounds associated with storm damage

Wounds associated with storm damage.


Trees with major wounds should be considered for removal during the next scheduled harvest, or they should be included in the salvage operation.

Bent Trees

Bent hardwoods are not usually attacked by insects or diseases because they are not in a stressed condition. Pine trees that are bent to the extent that cracks and resin flow occur may be invaded by bark beetles and disease-causing organisms.

Trees bent during a hurricane

Trees bent during a hurricane.


Small trees (under 15 feet in height) may straighten even after severe wind. Taller severely bent hardwoods should be removed during the salvage operation or the next scheduled harvest. Be sure to inspect large pine timber for pitch flow. Many large, green, standing trees may not be usable for veneer, poles, or lumber because of internal ring shake, splintering, and separation of the wood fibers caused by the storm. Often the only external evidence of such damage is pitch or sap flow where the injury has broken the bark. These characteristics are often overlooked, and considerable losses are incurred during a later harvest.

Standing Water

In standing water, the dissolved oxygen is quickly depleted, so trees of most species are injured by prolonged flooding, particularly during the growing season. The loss of soil oxygen leads to root mortality and tree death. Trees weakened by standing water are often attacked by insects or affected by diseases.

Trees killed by standing water

Trees killed by standing water.


Forest managers may wish to favor flood-tolerant trees and shrubs in areas subject to intermittent flooding.

Tree species that can tolerate prolonged or intermittent flooding are noted in table 3. Flood tolerant shrubs include: buttonbush, sand plum, deciduous holly, and swamp ironwood.

[ Top of page ]

[ Digital Arborist home ] [ Contents ] [ Next ] [ Previous ]