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The Health of Southern Forests, USDA Forest Service, Forest Health Protection, Southern Region

The Southern Forests

The forests in the southern United States are the most diverse and complex in all of North America. More tree species are found in the Great Smoky Mountains National Park than in all of Europe. Ranging from the subtropical cucumber tree to ancient palms to species such as the balsam fir that are more commonly thought of as typically Canadian, the highly varied southern forest ecosystems serve as hosts for an equally diverse assemblage of insects, diseases, and anthropogenic impacts.

Into this complex but delicately balanced system, several important arrivals have been added recently, including the gypsy moth, balsam woolly adelgid, butternut decline, and dogwood anthracnose. Complicated by man's activities, this "living laboratory" has experienced - and continues to experience - changes that compress eons of evolution into just a few years.

In the broadest terms, southern forests can be classed into four categories: hardwood, pine, mixed hardwood and pine, and spruce-fir. These four are sometimes further subdivided into still more classifications. Examples are southern bottomland hardwood versus upland hardwood and eastern white pine versus loblolly-shortleaf pine. Figure 2 shows one classification system, based on data from the Society of American Foresters.

Figure 2. Forest types in the south.

Figure 2. Forest types in the south.

The present publication focuses on three of the four broad categories and on the insects, diseases, and other problems typically associated with these types.

Except for the spruce-fir type, which is highly limited and confined to only the highest peaks in the southern Appalachian Mountains, southern forest types can be found spread across much of the region. Still, foresters typically associate the hardwood types with more mountainous areas (both the Ozarks and the Appalachian Mountains) or with rich bottomland sites such as the alluvial soils of the Mississippi delta. Pine and pine-hardwood types are most prominent in the Piedmont, coastal plains, and deep Gulf South.

Although each of the following sections of this publication discusses a particular forest stressor found in the South, the reader should realize that insects, diseases, and other forest and tree anomalies are often found in concert. For example, southern pine beetle is often associated with littleleaf disease. Man's activities, such as air pollution or soil degradation, can predispose forests and trees to a variety of insect and disease conditions.