The term "Cross Timbers" refers to an ecological region of woodland and forest vegetation in central and eastern Oklahoma. Although Cross Timbers also occur in Kansas and Texas, over half of the estimated 4.8 million hectares of that region are found in Oklahoma, making it the state's most abundant woody vegetation type. Albeit the Cross Timbers are the western most extension of the oak-hickory forest of the eastern United States, it is not accurate to describe Cross Timbers simply as forest. In fact, the Cross Timbers is a mosaic of forest, woodland, and prairie.
Nevertheless, the most important tree species in the Cross Timbers are post oak and blackjack. Both are slow growing, low in stature, intolerant of shade, they reproduce from root sprouts and have limited commercial value. A number of other trees and shrubs are also common, such as black hickory, bitternut hickory, black oak, shumard oak, and red cedar. Grasses found in the Cross Timbers are those of surrounding grasslands: Little bluestem, big bluestem, and Indiangrass. Animal species such as black bear, bison, Carolina parakeet, and passenger pigeons once roamed freely in the Cross Timbers. Presently, the black-capped vireo and least tern are two federally listed endangered species found in the vegetation.
Cross Timbers forests occur on deep, coarse-textured soils derived from sandstone, whereas fine-textured soils derived from shale and limestone support woodland and grassland vegetation. Whether a stand of Cross Timbers vegetation is woodland or forest in aspect depends upon fire. Fire destroys saplings under two inches in diameter, thus reducing the number of trees and favoring the growth of grasses.
The origin of the term "Cross Timbers" has been lost over time, but it may refer to the "timber" that expeditions and settlers "crossed" as they moved west. Many early explorers left vivid accounts of the Cross Timbers. The entrepreneur Josiah Gregg wrote in 1840 that "the celebrated cross timbers, of which frequent mention has been made, . . . vary in width from five to thirty miles, and entirely cut off the communication betwixt the interior prairies and those of the Great Plains." The Ellsworth expedition, accompanied by Washington Irving, entered the cross timbers in 1832. Irving later wrote, "I shall not easily forget the mortal toil, and the vexations of flesh and spirit, that we underwent occasionally, in our wanderings through the Cross Timber. It was like struggling through forests of cast iron."
However, in 1852, passing across southern Oklahoma, Capt. Randolph B. Marcy also reported, "At six different points where I have passed through it [the Cross Timbers], I have found it characterized by these peculiarities; the trees, consisting primarily of post-oak and black-jack, standing at such intervals that wagons can without difficulty pass between them in any direction." Captain Marcy also noted that "in the early days, traders, trappers, and other travelers in the country employed the Cross Timbers as a datum line for location, and measured distances of places from this well known landmark, as in populated parts of the world reference is made to the meridian of Greenwich," thus denoting the cultural importance of the Cross Timbers.
BIBLIOGRAPHY: W. E. Bruner, "The Vegetation of Oklahoma," Ecological Monographs 1 (1931). Carolyn Foreman, The Cross Timbers (Muskogee, Okla.: The Star Printery, 1947). B. W. Hoagland, I. Butler, and F. L. Johnson, "Ecology and Vegetation of the Cross Timbers in Kansas, Oklahoma and Texas," in The Savannas, Barrens, and Rock Outcrop Plant Communities of North America, ed. Roger Anderson, James Fralish, and Jerry Baskin (Cambridge, U.K.: Cambridge University Press, 1999).
Bruce W. Hoagland
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