Wednesday, August 6, 2003

Stressed-out trees create dangers

After years of drought, an abundance of rainfall has caused some area trees to be weakened to the point of collapse. Why? Because of weakened roots. When roots are healthy, the bulk of a tree's root mass is usually about 1 1/2 times the size of the drip line diameter and roots can extend out up to five times from the height of the tree. Typically, tree roots grow within the top 16 inches of soil.

After years of drought, the trees' roots may be much less dense and shallower. Subsequently, rains make the soil more pliable. The trees' roots have weakened holding power which may cause them to collapse. Urban structures such as curbs, sewers and other things can prevent tree roots from spreading evenly, causing instability.

Our area is blessed with stately hardwoods towering over many older neighborhoods. Our big trees provide beauty and charm and shade on hot, summer days. But urban trees also can be deadly hazards, especially after five months of above-average rainfall following years of drought. Naturally there is concern about the safety of the big trees, that tower over homes, streets and parks. Concrete, asphalt, compacted soil and other harsh conditions of urban environments put tremendous amount of stress on trees.

Above-average rainfall this year has caused even greater stress for these trees creating potentially dangerous conditions. The previous drought has shrunk roots, and the recent rains have saturated soils to the point that just a little wind can uproot century-old, 40-ton trees. Normally, healthy trees can easily withstand wind gusts of 40 to 50 miles per hour.

Recent tragedies with falling trees should be a "wake-up call" to homeowners and public officials alike that urban trees need regular maintenance and appropriate care. This includes proper mulching, watering, pruning and fertilizing. Also, big trees should be examined by certified arborists periodically to identify problems not noticeable to the average person.

Our trees are important to us and our environment. They help remove or trap lung-damaging dust, ash, pollen and smoke (particulate matter) from the air. They absorb carbon dioxide and other dangerous gases and, in turn, replenish the atmosphere with oxygen.

For more information on caring for "big" trees contact your local Georgia Forestry Commission office at 770-227-5522 or 770-358-1459. Literature on this and related subjects is available from GFC foresters. Visit our Web site at www.gfc.state.ga.us. Listings for certified arborists are available upon request or can be found by visiting www.isa-arbor.com/arborists/arbsearch.html.

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