As noted at the beginning of this chapter, oak trees and oak mast influence every aspect of a bear's life. Throughout much of their range, bears are intimately tied to and dependent upon this resource for their food and shelter needs. Loss of this resource can and does have long-term impacts on bear populations. Reproductive rates, survival rates, and ultimately population growth rates all may depend on the year-to-year productivity of acorns and the availability of oak trees as secure den sites. One or two consecutive years of acorn crop failure can affect a bear population for years to come, as the following case illustrates.
In 1984, Great Smoky Mountains National Park, Tennessee, experienced an acorn crop failure. As a result, cub recruitment in 1986 was almost nil (Pelton 1989). This led to synchronized breeding in 1986 (i.e., by females that had failed to reproduce in 1985 plus females that had yearlings in 1985), and a high cub recruitment rate in 1986. By 1989 this bumper crop of young bears dispersed throughout the park and the number of panhandler bears and nuisance complaints rose sharply, as did the harvest rate around the park. This scenario likely played out for several more years until alternate-year breeding returned, with about 50% of adult females producing every year, or until another crop failure caused another spike in the population. In either case, this example illustrates the need for long-term studies of how yearly fluctuations in acorn production drive the dynamics of bear populations.
Because oak trees and oak mast are so important to black bears, it is critical that forest be properly managed to insure a continual supply of mature, mast-producing oak trees, along with buffer species, such as wild grapes, to reduce the severity of periodic acorn crop failures (Eiler et al. 1989). Management practices should be specific to the area or particular habitat conditions. For the southern Appalachians, Pelton (1989) recommended long cutting rotations, to take advantage of the most productive years for oak trees, and careful selection of the configuration and oak regeneration potential for proposed clearcuts. He also noted the importance of maintaining mixed oak-pine forest types rather than converting to pure pine stands, and research to determine the usefulness of shelterwood, seed tree, and group selection methods in maintaining the stability of the oak mast potential of an area. In forested wetlands of the Mississippi Alluvial Valley, where availability of dry, secure den sites is a concern, maintenance of large-cavity trees of overcup oak (Q. lyrata) and bald cypress (Taxodium distichum) is important (White et al. 1996).
In Louisiana, the Black Bear Conservation Committee (BBCC), an organization formed to manage and recover the endangered Louisiana black bear (U. a. luteolus), published a black bear management handbook and a restoration plan specific to that area (Black Bear Conservation Committee 1996, 1997). Their management recommendations for bottomland hardwoods include:
—Maintenance of large tracts of bottomland hardwood forest with a mixture of tree species —Uneven-aged management through group selection and small patch harvest cuts, which research has shown is best for oak regeneration
—Maximization of tree vigor for best hard mast production —70-100 year rotation (minimum 50 years) for best hard mast production
—Intermediate cuts to improve tree species composition, remove poor quality trees, and promote oak regeneration —Identification and maintenance of large-cavity trees with minimum 91 cm dbh
—Bear-friendly harvest strategies, such as small clear cuts, maintenance of travel corridors, maintenance of clumps of hard mast producing trees
—Maintenance of a diverse mixture of mast species to reduce annual fluctuations in mast abundance —Stand improvement for high-graded stands (from which all big trees have been removed) and other poor-quality stands on sites capable of substantially greater mast production
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