Forest Health Protection, Southern Region
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:
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.
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