Katrina Comes A Shore On The Mississippi Coast-LSU Hurricane Center Image

Trees And The Storm - Katrina 2005
Coastal communities are not the same today as they once were. They do not exist by the sea to harvest its resources. Rather they exist in part to allow exploitation of scenic and recreational resources. Coastal communities today are diverse combinations of service businesses, resort housing and recreational marinas. Most coastal development is vulnerable to hurricanes and so are the trees that are planted in garden parks, And along public roads and streets.

New residents have moved to the Gulf Coast of Mississippi have never experienced hurricanes. People are now living on the coast which has flooded at some point in time or been visited by a hurricane such as Katrina.. Coastal residents have homes on lots that were once wooded, which provided some protection from wind. Trees once filtered, slowed and deflected the wind. These coastal trees are gone and any protection they provided for low category hurricanes no longer exists.

A tree for instance, growing in a coastal zone is a marvel of structural integrity. By itself, it offers several methods of protection. First, a tree will shed its leaves to reduce wind load and therefore look like it is dead. The root zone of a tree is composed of a network of fibrous and structural water channels that anchor solidly into the soil, oftentimes at great depth. The root systems of native species are well adapted to the native soils of a coastal community. When trees up-root, it is because exotic or non-native species with shallow root systems are unable to penetrate deeply into native soils and high water table conditions. Shallow roots are ineffective structural devises to anchor trees.

Limbs on trees were designed for bending. Limbs, branches and twigs that bend offer less resistance to wind and there by increase their effectiveness in filtering and slowing the wind. Solid structural pieces do not bend and therefore offer a better opportunity for structural failure from splintering or breaking. The most effective urban forest is one that is planted with limbs that are flexible and arranged on a trunk in a descending pattern of size, with smaller limbs above and more sturdy, larger heavier limbs below. The fact that most limbs are circular in cross section like the boles make them even more able to resist wind loads. The little twists, turns and irregular directions seen in limbs and branches caused by their growth pattern reaching for light make them even more efficient in storm winds.

Trees with fewer branches are better than those with more. Trees with more limbs but fewer branches are better still. Trees with more branches but fewer twigs are even better. The perfect storm resistant tree would be one with layered limbs, short flexible branches and twigs that easily break away in wind storms and torrential rains. Trees such as palms, cypress, live oak, locust, ash, holly and red maple seem to fit this description. But best of all are our coastal live oaks that can take heavy wind and occasional flooding and can survive hurricane attacks for over one hundred years.

Trees with weak wood will often twist and snap in high winds. Pines do this often. Small trees some times will overturn their root ball and can easily be up-righted and replanted by a horticulturist that knows how to save a wind bashed trees. Crape myrtles, river birch or Bradford pears in our area will often overturn but can be put back in place to live again. Others overturn but can not be reset. They must be sectioned and carried off to the recycler. Still other trees in hurricane zones simply break apart and facture. After this happens the tree is so disfigured it must be removed. Some species of trees can be severely damaged yet with a little selective pruning by a qualified arborist can live for years. We see these types of trees all around. They are called ‘survivor trees.’ The carry the scars of past storms and add so much to our community. Home owners and gardens should not be too quick in removing a damaged tree. Many will rebound by re-leafing days after the storm has past.

No engineer, or computer could design a structure to be as efficient as a tree in dealing with wind. When planted in masses as they are in the urban forest, within public open spaces, in parks, along streets and in private preserves, trees become effective structures that can modify the impacts of low level hurricanes, their winds and tides.

Communities, gardeners and highway department contractors should not be to quick to remove trees in hurricane zones. Trees in areas subject to tropical weather can offer subtle services that will protect life and property if the proper tree is planted in the right place. Citizens and communities should replant native trees following hurricanes to reap the protection and provide the beauty that well selected trees can give.

Wind Resistant Trees
Native trees, particularly those with wide spreading branches, low centers of gravity, strong deep penetrating root systems, and small leaf size seem to hold up better in tropical storms! Especially those trees found growing in mixed groves of layered trees. Lone growing solitary specimens have less wind resistance than massed trees. Layered forests consisting of mixed species of native trees are much more wind resistant that single species plantations with no under-story of layers. Trees like live oak, cypress, crape myrtle, winged elm, magnolia, tulip tree, red oak, American holly, sweetgum, and sycamore hold up to tropical storms better than most.

The coastal live oak tree, Quercus virginiana, is Mississippi’s premier storm resistant tree! This is largely due to their low profile, strong trunks, branches, fine leaf pattern, well tapered and balanced central leader, minimal branch pattern and broadly balanced root system that anchors the tree to the ground. Live oaks along the Mississippi coast will live for hundreds of years and weather many hurricanes and tropical storms.

Preparing Trees to Withstand Hurricanes.
What to do to prepare for a future storm? There are some things that can be done to the community trees prior to a projected storm that will reduce post storm clean up operations and costs and may save the life of the tree. Pre-storm maintenance is the key..

Remove weak and diseased trees as well as any large trees within one hundred feet of homes or cars or other valuable property. Prune and thin trees to give them a lower center of gravity and to lessen leaf mass. Sculpting a tree will allow wind resistance to increase. Adding under story planting to layer the forest also helps. Lightly fertilize annually and be sure that all trees are growing where their root zones are covered with a good organic mass of healthy forest floor material. Watering during the drought periods of summer will allow the roots of the plants to maintain their turgid state and therefore their holding power. Plant trees in groves and add ample shrub mass to deflect wind upwards. This places what is called the point of overturning pressure farther from the root zone into the area of the tree with more flexibility.

It should be noted however that very large and tall trees standing along near buildings represent a substantial threat for overturning or trunk snapping. Tall trees, those in excess of forty (40) feet, should be considered for removal within the ‘drop line’ or the area within reach of a building. The length of the drop line is based upon the height of the nearest tree and the height of a building. Use this rule of thumb for trees near buildings. Trees should never exceed the height of a building within the drop zone by more by the height of the building. For instance, if the building is twenty five (25) feet tall, there should not be a tree taller than fifty (50) feet within the within a fifty (50) foot drop line. Small or medium sized trees and large shrubs masses with low centers of gravity and many branches and stems near buildings actually do a better job of protecting the building than tall over-towering trees.

One further action to protect the urban forest, remove non-native over story vegetation, keeping in mind that canopy trees in any community are composed of native trees that have withstood coastal storms in the past and will do so in the future. Tall exotic trees are not conditioned for coastal survival so they should be removed.

Survivor trees can vary from region to region. To determine which trees are survivor trees, trees that can strengthen the urban forest one merely has to look carefully at the tree canopy in a coastal community and look for three characteristic which generally will tell you which are the survivor trees. Look for dominate species. This is surely a sign that the particular plant is successful in an exposed location. Also look for the oldest trees. Survivor trees have a tendency to live longer. Older trees are often the very tallest trees in a forest as well. Finally, look for unusual and grotesquely shaped trees throughout the forest that show the battering of many former hurricanes. Many people think these specimens should be removed because they are not perfect trees. To landscape architects these trees are always the most picturesque because of some of the unusual shapes they assume as a result of hurricane damage. Often they will lean, they may have broken parts and their branch structure is often open telling of many past storms. But a gnarled old tree is proof that the tree can survive wind, rain and storm. These are all signs of hurricane resistant trees to experienced foresters. Mississippi residents who have suffered damages to favorite trees are encouraged to follow three simple steps. First survey the damage to your trees. Which are damaged, which can be repaired and which should be replanted. Can any of them be up-righted and staked? Second determine which trees should be pruned and treated by a licensed arborist. Third, trees that have been removed should be replanted using a more hurricane resistant native tree more suitable for growing along Mississippi’s coast. Good selections include several oaks, especially live oaks, swamp oaks, cypress, cabbage palm, windmill palm, pindo palm, canary island date palm, crape myrtle, magnolia, American holly, iron wood, hop hornbeam, sugar hackberry, winged elm, beech and red maple.

Help With Your Trees
Help is available locally for people who have questions about damaged, dying or dead trees. The following contacts can provide you answers or professional help in understanding how to repair, remove or replant damaged trees caused as a result of Katrina’s high winds, tides and salty water.

Brion Capo, City Forester for Gulfport, Mississippi
Mississippi Forestry Commission at 601-359-1386, Walter Passmore
Mississippi Urban Forest Council, Donna Yowell at 601-672-0755
Steve Dickie with Ms State University Extension Service