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How to Evaluate and Manage Storm-Damaged Forest Areas

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Manage to Reduce
Hurricane Damage

Tree species vary in their ability to withstand hurricane winds and salt damage. Wind resistance depends on the interaction of five factors: strength of the wood; shape and size of the crown; extent and depth of the root system; previous moisture conditions; and shape of the bole.

No tree species has perfect wind resistance, but live oak, palm, pondcypress, and baldcypress are among the best, as shown in table 3. These trees combine deep root systems with buttressed trunks (low center of gravity). The wood of live oak is exceedingly strong and resilient. The crown is usually widespread, but this does not seem to negate its strong points. Cypress has relatively weak wood, but its crown is so sparse and its foliage so limber that it is also extremely windfirm. Shallow-rooted trees are easily uprooted, especially after the soil is saturated by heavy rains or if the tree is suffering from root disease.

Common shallow-rooted trees along the coast are dogwood, water oak, pecan, sweetbay, and red maple. Common deeprooted trees are live oak, longleaf pine, pondcypress, and baldeypress.

Trees growing in sandy soils are more deeply rooted than trees growing in soils with an inhibiting clay layer or a high water table. Although rooting habits vary according to the soil profile, each species has a characteristic pattern.

Another factor to be considered is the height of the tree. The taller the tree, the greater is its chance of breaking, especially if the bole has little taper. For this reason, tall slim slash and longleaf pines are extremely vulnerable.

Open-crowned and lacy-foliaged trees, like cypress and mimosa, offer less resistance to the wind, and thus are better able to survive. On the other hand, magnolia trees with their heavy, wind-catching foliage are windthrown more than their root system and bole structure would indicate. Palm trees offer little surface to the wind because they have almost no laterally extended crown and branches. This characteristic makes them fairly windfirm, despite their limited root systems.

Based on these observations, the following preventive measures are recommended to forest managers in hurricane-risk areas:

  1. Keep a balanced mixture of size and age classes to prevent a complete loss. Young trees are rarely damaged, because they tend to bend with the wind: old trees tend to break or uproot.
  2. Where feasible, stagger thinnings to limit exposure of recently thinned areas. (During Hurricane Camille, recentlythinned stands of pine with little taper were mostly broken, while in open stands and stands thinned several years earlier less damage occurred.)
  3. Manage for well-spaced, thrifty trees and, as much as possible, develop a spread of age classes to distribute the risk of wind damage.
  4. Consider planting longleaf pine in deep sandy soils because longleaf has a deep taproot.
  5. When planting slash and loblolly, use an 8- by 8-foot (or wider) spacing.

Winds often carry saltwater inland for a considerable distance. The leaves on trees saturated with saltwater turn brown and give the appearance of being burned. Most of these trees will not die and should not be cut. See table 3 for resistance to salt damage among tree species. The trees may lose their leaves and some growth, but most of them will grow new leaves and recover. Check trees closely in the spring after salt damage for adequate recovery or possible bark beetle attack. Trees should be harvested if they have been attacked by bark beetles or if they have not put on new growth in the first full growing season after the damage occurred.


Table 3 -- Resistance of tree species to hurricane-related damage (in descending order of resistance).

Flood tolerant Breakage Uprooting Salt Deterioration by insect and disease

baldcypress

pondcypress

tupelo-gum

sweetbay willow

sweetgum

sycamore river

birch cottonwood

green ash red maple

pecan mulberry

American elm

persimmon

silver maple

water oak

swamp chestnut oak

magnolia

hickory

live oak palm

baldcypress

pondcypress

sweetgurn

tupelo-gum

mimosa

dogwood

magnolia

sweetbay

southern red oak

water oak

sycamore

longleaf pine

slash pine

loblolly pine

redcedar

hickory

red maple

pecan

live oak

palm

baldcypress

pondcypress

tupelo-gum

redcedar

sweetgum

sycamore

longleaf pine

mimosa

southern red oak

magnolia

slash pine

loblolly pine

sweetbay

water oak

red maple

dogwood

hickory


pecan

live oak

palm

slash pine

longleaf pine

pondcypress

loblolly pine

redcedar

tupelo-gum

baldcypress

sweetgum

water oak

sycamore

sweetbay

southern red oak

hickory

mimosa

pecan

magnolia

red maple

dogwood

live oak

palm

sweetgum

water oak

sycamore

baldcypress

pondcypress

southern red oak

magnolia

tupelo-gum

sweetbay

hickory

pecan

redcedar

red maple

mimosa

dogwood

longleaf pine

slash pine

loblolly pine


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