Historical Origin of Existing Oak Stands

Oaks have dominated much of the central hardwood region of North America for over 6,000 years (Lorimer 1993). At the end of the glacial episode, much of central hardwood region was occupied by a boreal forest of spruce and pine. About 6,000-9,000 years ago, this boreal forest was replaced by an oak-pine-mixed hardwood forest, which has retained dominance ever since (Craig 1969, Watts 1979, Delcourt and Delcourt 1985).

This evidence from the pollen record is supported by independent historical evidence on the presettlement forest (ca. 1600-1850) from early travelers and government land survey records. For example, species of oaks comprised 40-80% of the witness trees in sizable areas of New Jersey, Pennsylvania, Virginia, Kentucky, and Illinois (Spurr 1951, Russell 1981, Leitner and Jackson 1981, Bryant and Martin 1988, Abrams and Downs 1990). Thus, while disturbances that accompanied European settlement may have increased oak dominance in some places, particularly at the margins of its range (Whitney 1987, Nowacki et al. 1990), oak was already dominant over large sections of the landscape and maintained by natural regeneration as influenced by more of less frequent and extensive fires set by native Americans long before European settlement (Lorimer 1993).

If oak regeneration on mesic sites is so difficult, how did the existing stands originate? Historical events have played a major role in the establishment of the presently mature oak stands in the Central Appalachians. Crow (1988) refers to the present abundance of oak in eastern forests as "an artifact of disturbance regimes that are no longer common." Although our existing oak forests on mesic sites have clearly originated in a variety of ways, the common denominator in all of these scenarios is that historical events resulted in a "low competition" environment in which sizable understory trees were either absent, sparse, or periodically eradicated. The present stands were born out of very harsh efforts to either convert forest lands to agriculture through fire and grazing or to mine them of timber with little or no concern for future crops. Repeated fires, death of the American chestnut, probable changes in wildlife and insect populations, and perhaps climatic conditions related to flowering are some of the factors that may have influenced availability of acorns and oak seedling development (Lorimer 1993).

Todays existing oak stands originated after 50-100 years of influence by European settlers (fires, logging, and grazing), and in a number of different ways (Lorimer 1993):

1. Some of our existing oak stands on mesic sites originated after intense fire and are even-aged (Brown 1960, Ward and Stephens 1989, Nowacki et al. 1990) From a historical perspective, it may be more accurate to regard the absence of fire as unnatural rather than natural. But just as burning had its social and ecological consequences, the permanent cessation of burning also produced its consequences. For oak, the cessation of burning was not an entirely positive event (Johnson 1993).
2. Some eastern oak stands apparently originated in a manner similar to those in the Midwest, after the cessation of repeated fires. In the southeastern Piedmont, Hammond (1880) noted that "since the discontinuation of spring and autumn fires, [a deer] could not be seen at fifteen paces, because of the thick growth of oak and hickory that has taken over the land." Grazing was also widespread at the time (Greeley and Ashe 1907) and may have had an effect similar to fire (Lorimer 1993).
3. Detailed stand records rarely go back as far as 70 or 80 years, but comments by contemporary observers, supplemented by field evidence on stand history, can give us a general idea of stand origins (Lorimer 1993). The most thorough evidence comes from the Midwest, because it was the last part of the central hardwood region to be settled and has the best records. Many Midwestern oak stands occur on sites that supported oak savannas at the time of settlement. These savannas were usually dominated by the more fire-resistant species such as bur oak (Q. macrocarpa), white oak, and black oak, and were "covered with trees about as far apart as in a common orchard" (Bayley 1954). Oak savannas are estimated to have covered between 13-32 million acres in eight states (Nuzzo 1986). Based on 19th century land survey records, Curtis (1959) estimated that southern Wisconsin at that time was approximately 45 percent oak savannas, 20 percent prairie and sedge meadow, 25 percent maple and floodplain forest, and 10 percent oak forest. There is little question that these oak savannas were fire-maintained and fire-dependent (Gleason 1913, Muir 1913, Curtis 1959, Grimm 1984). For example, in 1750, Father Vivier wrote that in the Ozark region, "trees are almost as thinly scattered as in our public promenades. This is partly due to the fact that the savages set fire to the prairies toward the end of autumn, when the grass is dry; the fire spreads everywhere and destroys most of the young trees" (Johnson 1992). In Wisconsin, the more fire-sensitive northern red oak was often present only as brushy sprouts or "grubs" among the prairie grasses (Curtis 1959). When the fires ceased, "the grubs grew up into trees, and formed tall thickets so dense that it was difficult to walk through them and every trace of the sunny openings vanished" (Muir 1913). Many of the red oak stands being harvested today appear to be the first and only generation of closed-canopy oak forest to follow the savannas. Stands harvested in recent decades have been displaced by the shade-tolerant species that quickly developed as an understory beneath the oaks (Johnson 1976, Jokela and Sawtelle 1985, Hix and Lorimer 1991, Lorimer 1993).
4. Liming and Johnson (1944) described oak reproduction in the Missouri Ozarks in 1933 when fire protection started on the new National Forests. Reproduction appeared to be sparse and in poor condition. But within a few years sprout stands emerged from existing roots. Seedling numbers also increased. The authors predicted that with time and protection the forests would improve. And so they have. As the Ozark forests grew so did the concerns that the next generation of forest stands might be different. A similar "sudden" appearance of oak advance regeneration took place in the late 1800s in southern Wisconsin with the cessation of wildfire as described by Curtis (1959). Crow (1988) provides an excellent historical review and bibliography on oak forests and savannas before European settlement. He cites numerous authors to show how fire and logging favored oak in many parts of the East (Clark 1993).
5. Probably millions of acres of existing oak forest, both in the Northeast and Southeast, originated as an understory beneath a pine canopy (Hammond 1880, Oosting 1942). In central New England, 65-70 percent of the land had been cleared for agriculture at some point, but much was subsequently abandoned. Much of this land reverted to "old-field" pine. As can be seen today, old field pine stands usually have a relatively sparse understory, but oak saplings 3-15 ft. tall are common. Data gathered by McKinnon et al. (1935) in central New England show an average of 578 saplings per acre released after the harvest of old-field pine on good sites, of which 215 were oak. The oaks typically became the dominant species in the subsequent stands (Oosting 1942, Lutz and Cline 1947, Lorimer 1993).
6. Many oak stands in the mid-Atlantic region appear to have originated after repeated, intensive clearcutting to produce charcoal for the iron and brick industries. Because stem quality was not an important consideration, small stems as well as large could be utilized, and clearcutting was often done at short intervals of 30-40 years (Schnur 1937, Raup 1938, Abrams and Nowacki 1992). Approximately 300 acres of forest had to be cleared each year to supply a single iron furnace (Stout 1933). Fires often followed. All of these factors would have favored vigorous sprouters such as oaks and hickories. The coppice nature of most stands was such a prominent feature of the landscape that Hawley and Hawes (1912) mapped a large area of southern New England, New York, and New Jersey as the "Sprout Hardwoods Region." These historical circumstances are much different from the prevailing situation today, when small trees are in little demand, and both logging and natural blowdown remove only the larger overstory trees and leave the small tree layer largely intact (Lorimer 1993).

Oak regeneration failures appear to have been a widespread problem only in the last 50 years or so (Lorimer 1993). There were few references to oak management problems in American forest literature until after the 1930s. There are a number of plausible reasons for this lack of concern:

1. Historically much of the hardwood forest was an unwanted barrier to agricultural development;
2. After several hundred years of harsh treatment and neglect oak trees were still plentiful and there were no serious timber supply problems;
3. Protection and re-establishment were the primary early forestry concerns; and
4. The very practices of indiscriminate burning and overcutting that fostered the forest conservation movement favored oak.

Therefore, it was not so much that we ignored oak regeneration problems in the United States; we are following historical precedence of abundance (Clark 1993).

On the other hand, one of the most noted naturalists in the history of our country, Henry David Thoreau, made detailed observations and notes about the difficulties of obtaining desired oak reproduction (primarily northern red and scarlet) following removal of the parent stand in which good quantities of oak were present. He concluded:

"The time will soon come when we shall have to take special pains to secure and encourage the growth of white oaks, as we already must that of chestnuts for the most part. The oaks will be so scattered that there will not be enough to seed the ground rapidly and completely" (Torrey and Allen 1962, page 1698).

The time was in the late 1850s, and the area was the environs of Waldens Pond, Massachusetts (Kellison 1993).

See: Effects of fire on oak