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Rare Forest Communities

Primary Question (chapter 1): What are the history, status, and projected future of terrestrial wildlife habitat types and species in the South?

Related Question (chapter 17): How have biological agents, including insects and disease, influenced the overall health of the South’s forests, and how will they likely affect it in the future?

Several forest communities have become limited to only a tiny portion of their original range and thus may be disproportionately impacted by future changes. There are 14 critically endangered communities (where losses of more than 98 percent of their area have occurred since European settlement) and 25 endangered communities in the South (losses between 85 and 98 percent of area). Most of these communities are in the following seven classes (see chapter 1):

• Old-growth—Less than 586,000 acres of forest area (0.3 percent) in the South is in an old-growth condition. Old-growth assemblages are diverse, and they exhibit unique structural characteristics such as multilayered canopies and large accumulations of woody debris. The largest tracts of these remnant forests are limited to a few ecological provinces. Most are on public land such as the Great Smoky Mountains National Park and the region’s national forests. Some very small tracts occur on private land. While most publicly owned old-growth forest is administratively protected, factors such as air pollution and forest pests will continue to alter them.

• Spruce-fir forests—They are limited to high elevations in the Blue Ridge Mountains. These are very scarce ecosystems containing unique assemblages of species with a high degree of endemism. They are threatened by a combination of exotic pests and environmental factors. The exotic insect having substantial impacts on these forests is the balsam woolly adelgid, which has already eliminated 95 percent of the mature Fraser fir from high elevation forests of the Southern Appalachians. A significant restructuring of this type of forest is anticipated. Additionally, soils in this community predispose the area to changes in stream chemistry and other ecosystem damage from increased acid deposition derived from nitrous oxides (chapter 18).

• Wetlands, bog complexes, and pocosins—They have been reduced in total area by land use conversions and changes in hydrologic regimes. Bogs and pocosins provide habitat for many rare herpetofauna and birds. They also provide important refuges for species in landscapes that are dominated by agriculture and intensive silviculture. Fire regimes are crucial to the sustainability of many of these forests, and the exclusion of fire has substantially altered them.

• Bottomland and floodplain forests—Because they often occur on rich alluvial soils, a large share of these forests has been converted to agricultural uses, especially in the Lower Mississippi Alluvial Valley. Such forests, therefore, occupy only 20 percent of their original area. Certain forest pests can affect these forests. For example, the baldcypress leafroller, which defoliates and kills baldcypress, is prevalent in Louisiana swamps (chapter 17). Hydrologic alterations also alter the condition and structure of these forests.

• Glades, barrens, and prairies—They are naturally treeless areas in Piedmont, Interior Plateau, Ridge and Valley, and Coastal Plain ecoregions of the South. These areas evolved under extensive fire regimes, and fire exclusion has caused substantial ecological modification and continues to impact remnants of these systems.

• Longleaf pine ecosystems—They once covered much of the South’s Coastal Plain. They now occupy only 2 percent of their original range. The herb layer of these forests is one of the most diverse in the world. They are home to several threatened or endangered species, such as the red-cockaded woodpecker, and several species with high rates of endemism. Decline in these systems is attributable to several factors, including removal of original stands followed by fire exclusion, conversion to other pine species, conversion to other land uses, and the introduction of livestock. Brown-spot needle disease infects longleaf pine seedlings and therefore hampers efforts to restore the longleaf ecosystems across the South. Current concerns include continued urban development and difficulty in reestablishing fire regimes.

• Atlantic white cedar swamps–They have been reduced to 10 percent of their original range. They persist only in isolated small stands. As with pocosins, they provide for diverse wildlife refuges in intensively managed forest and agricultural landscapes.

Several increasingly rare types of wetlands—Atlantic white cedar swamps, bottomland forests, wetlands, bog complexes, and pocosins—are concentrated on private land, so their future condition is dependent on the decisions of their numerous owners. The spruce-fir and old-growth ecosystems are found mainly on public land. Old-growth is protected but is susceptible to invasion by exotic species, damage from air pollution, and restructuring due to fire suppression. Among rare forest communities, the spruce-fir ecosystem is currently under the most stress due to a combination of exotic insects and environmental stressors. Most remnant longleaf pine forests occur on private land and may be impacted by development, both directly through their conversion and indirectly due to the difficulty of providing the necessary fire regimes in areas of mixed ownership and high population density. Restoration efforts are underway, but challenges to restoring the longleaf pine ecosystem are great.