Prescribed Fire Use in Oak-hickory Forests

Until recently, foresters failed to appreciate the role of prescribed fire in maintaining open oak-hickory forests and in facilitating regeneration of these species (Lorimer 1993). Regeneration of oak was attempted only with timber harvesting and herbicides, which generally hastened the successional replacement of oaks by mixed mesophytic species (Abrams and Scott 1989). Research indicates that fire can be used in hardwood stands to establish and release oak-hickory regeneration (Barnes and Van Lear 1998, Brose and Van Lear 1998, 1999, Christianson 1969).

Understory burning of mature, uncut hardwood stands can help establish oak and hickory regeneration by preparing seedbeds (Barnes and Van Lear 1998). Acorns and hickory nuts are often buried by wildlife, particularly squirrels and blue jays, which prefer burned areas because of the thin root mat. The fires also top-kill or eliminate many of the shrubs and small trees that shade the forest floor. In a less shaded environment, the acorns and hickory nuts germinate and the new seedlings begin developing their root systems. Eventually, the regeneration replaces canopy trees.

In this approach, fires are initially applied at a frequent interval (annual or biennial) depending on season of burn and severity of the shade. Once oak seedlings are established, fire is withheld for a few years (Cottam 1949), and then periodically reapplied once or twice a decade. This minimizes mortality of the oak regeneration by allowing time for root systems to develop. This approach may take 15 to 20 years for results to be apparent.

If oak and hickory regeneration is present in the understory, a two-step shelterwood harvest combined with a prescribed fire can be used for release (Brose and others 1999a,b). This shelterwood-burn technique appears to be a reasonable mimic to the disturbance regime of oak-hickory forests before Euro-American influence. It has considerable value as a silvicultural method, a wildlife management tool, and a means for restoring habitats such as oak savannas and open woodlands.  This method, and other methods of using fire in combination with silvicultural treatments are explained in the section: Using Prescribed Fire for Oak Management.