Fire Regimes of Oak Hickory Forests

The fire regime of the oak-hickory forest has varied spatially and temporally because of changing cultural influences before, during, and after Euro-American settlement.  Before such influence, the fire regime for oak-hickory forests was dictated by the activity of Native Americans because they were the primary ignition source (Abrams 1992, Buckner 1983, Denevan 1992, Pyne 1997). Lightning fires are uncommon in many of these regions because thunderstorms occur primarily during the growing season, usually accompanied by rain (Barden and Woods 1974; Ruffner and Abrams 1998). 

Numerous authors (DeViro 1991, Patterson and Sassamen 1988, Stewart 1951, 1963, Van Lear and Waldrop 1989) have discussed the vast extent to which Native Americans used fire.  Native Americans in the Central Hardwoods Region (Delcourt and Delcourt 1997, 1998, Olson 1996), the Appalachians and Piedmont (Van Lear and Johnson 1983), and the Northeast (Buell and others 1954, Day 1953) commonly used fire for numerous reasons throughout the year. Surface fires predominated and burned over large areas; only natural barriers or unfavorable weather stopped them. Hough (1877) thought the “oak openings,” “barrens,” and prairies east of the Mississippi resulted from Native American use of fire to promote grass growth and attract game (see Oak Savannas). He stated, “Scarcely a year passes without the occurrence of fires of sufficient extent to attract public notice.”  One historian (Russell 1983) agreed that fire frequency was greater near camps and villages than would be expected by lightning, but found no strong evidence that Native Americans burned large areas in the Northeast.

While ecologists and historians generally agree that anthropogenic fires were common in oak-hickory forests, exact presettlement fire frequencies are not known. Delcourt and Delcourt (1997, 1998) believe they varied considerably depending on closeness to Native American habitation. Other references point out that Native Americans maintained an extensive trail system throughout the East that was kept open with fire. Euro-American explorers reported many areas treated with annual and biennial fires (Barden 1997, Buckner 1983, Day 1953). Dendrochronological studies, which give conservative estimates, suggest fire return intervals of 7 to 14 years in the mid-Atlantic and Ozark regions (Buell and others 1954, Guyette and Day 1997). Cutter and Guyette (1994) reported a fire-return- interval of 2.8 years during 1740 to 1850 on a ridgetop in the Mark Twain National Forest. Pre-settlement fires in southern New England generally occurred during the spring and summer (Bromley 1935, Christianson 1969). Brown (1960) believes the prevalence of oak in Rhode Island is the result of a long history of fire. The fire regime was probably more pronounced in Southern areas than in Northern areas due to more favorable climatic conditions for ignition and spread, greater populations of Native Americans, and vegetation more conducive to burning.

The frequency and extent of Indian burning decreased substantially after European contact, which introduced new diseases and decimated their population by 90% or more over the next 100 to 150 years (Denevan 1992, Dobyns 1983, MacCleery 1993). As a result grasslands, savannas, and woodlands succeeded to closed forest (Buckner 1983, Denevan 1992, Dobyns 1983, MacCleery 1993, 1995, Pyne 1997). Subsequent settlement of the oak-hickory forests by Euro-Americans, who used fire for many of the same reasons as the Native Americans, increased the frequency and extent of burning (Abrams 1992, Pyne 1997, Van Lear and Waldrop 1989). Fire return intervals were shortened to 2 to 10 years with many sites burning annually (Cutter and Guyette 1994, Guyette and Day 1997, Holmes 1911, Sutherland and others 1995, Sutherland 1997). For example, the barrens of Pennsylvania and Maryland were burned annually at least through 1731 (Tyndall 1992).

Presently, the fire regime of oak-hickory forests is characterized by infrequent, low-intensity surface fires that occur during the spring and fall. They are caused almost exclusively by humans, and burn small areas (Pyne and others 1996). Lightning is a minor ignition source (Barden and Woods 1974, Ruffner and Abrams 1998). Fire return intervals have lengthened from a few years to several millennia (Harmon 1982), the longest fire-free intervals in the history of the Central Hardwoods Region (Ladd 1991).