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Effects of Forest Management

Primary Question (chapter 4): What are the historical and projected future impacts of forest management and access on terrestrial ecosystems in the South?

Related Question (chapter 16): What are the history, status, and projected future of southern forests?

Forest management, by definition, affects the structure and distribution of forest conditions. Forest types have been dynamic in the South, with upland hardwood types increasing between the 1950s and the 1990s, lowland hardwood types essentially stable since the 1970s, and pine types in considerable flux. Net changes in forest are the result of several offsetting changes. For example, natural pine types are reclassified to upland hardwoods as a result of succession, while some upland hardwoods are converted to planted pine. All forest types are converted to urban uses, and agricultural fields are converted to planted pine (“Broad Forest Types” and chapter 16).

Silvicultural treatments can have important implications for wildlife. Timber harvesting, especially clearcutting, as well as afforestion of agricultural fields restarts successional processes. Young stands, especially those that follow timber harvesting, exhibit an increase in species richness and species diversity. Many wildlife species thrive in these early successional communities. After canopy closure, plant diversity generally decreases and wildlife use declines. Uneven-aged management that encourages several age classes of trees can sustain benefits for many but not all wildlife species due to the resulting stratified forest canopy. However, these benefits may lessen somewhat if stand entries are more frequent (chapter 4).

Planted pines, while sometimes characterized as monocultures, vary considerably in their composition. Wildlife species that thrive in early successional habitats use plantations heavily during the first few years after planting, although habitat values decline with heavy stocking, application of herbicides, and other intensive management practices. Browse is abundant, and several mammals graze these stands. Small mammals are abundant, thus raptor use is high. Many priority neotropical migrants use pine plantations after the first thinning or use lower stocked areas where hardwoods are allowed to thrive in the understory (usually stands managed for sawtimber). Several neotropical migratory birds use plantations early on, when insects and seeds are abundant. After canopy closure, plant diversity decreases and wildlife use declines.

Forest management can be augmented with techniques to directly enhance wildlife habitat. These include leaving mature trees in a stand to enhance structural diversity, application of streamside management zones to retain landscape diversity, and retention of snags to provide nesting habitat (chapter 4). Additional wildlife benefits may be obtained with natural regeneration techniques such as seed-tree cuts and shelterwoods, and with management practices such as midrotation thinning and prescribed burning.

Gauging the effects of forest management on mobile wildlife populations requires more than an understanding of stand-level dynamics. It requires insights into the overall landscape structure of forests within the region. Although this type of analysis is relatively new, several studies have examined the effects of forest fragmentation on wildlife species, especially birds. We found that (chapter 4):

• Studies have documented declines in migratory bird species from isolated forest patches, especially where agricultural and urban uses represent substantial components of the landscape. However, in heavily forested areas—70 percent or more forest—these negative effects do not occur. Accordingly, in large portions of the southern landscape, these fragmentation effects are not a substantial concern. They include the Southern Blue Ridge, Cumberland Plateau and Mountains, and Ozark and Ouachita Mountains.

• Forest fragmentation and negative edge effects are most prevalent in Ridge and Valley, Piedmont, Interior Low Plateau, and the Mississippi Alluvial Plain where agriculture and development dominate the landscape. In these areas, forest operations may impact fragmentation effects on wildlife.

• In heavily forested areas, forestry practices may provide important benefits for forest-breeding bird species through provision of early successional habitats. This is especially true for areas where existing hardwood forest structure is dominated by closed canopy stands and sparse understories or where dense pine stands and fire suppression exclude pine specialists.

Landscape configuration and fragmentation at fine scales may be critical for some species, especially amphibians, even in heavily forested areas. For example, persistence of pond-breeding salamanders requires access between terrestrial habitat and vernal ponds or Carolina bays. Roads and certain kinds of management practices can isolate these two habitat components. Spatial configuration of forest habitat is also an important factor in the recovery of federally listed subspecies of black bears in Louisiana and the black bear subspecies of conservation concern in Florida (chapter 4).

Across the South, more threatened and endangered species are affected by increased isolation of shrub-scrub and grassland habitats than are affected by scarcity or fragmentation of mature forests. The ultimate challenge for forest management then is to provide habitat conditions that support the array of grassland, shrub-scrub, and mature forest species occurring within the same landscape.