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The Cross Timbers: The Ancient Forest at America’s Crossroads

By John Gifford

An example of the Cross Timbers' unique, irregularly shaped tree structure

An example of the Cross Timbers’ unique, irregularly shaped tree structure. Credit: John Gifford.

Imagine for a moment that it is Autumn 1832. Imagine, too, that your name is Washington Irving. You’re one of America’s most famous writers, and by virtue of this, and mere chance, you’ve been invited to join U.S. Indian Commissioner Henry Ellsworth and a party of mounted rangers on an expedition to the frontier lands of Indian Territory (present-day Oklahoma). Setting out on horseback from Fort Gibson, you head into the wild landscape of the southern Great Plains, crossing rolling hills, fording sandy rivers and picking your way through canebrakes and plum thickets. Your party hunts for food. At night, you sleep beneath starry skies so clear and bright that, weeks later, after you return to civilization’s comforts and security, you’ll find it difficult to sleep indoors.

Despite the roving bears and the marauding packs of wolves, what you most dread out on the plains are the dense forests of low-growing, rough-barked trees, which your expeditionary party can’t quite avoid and which seem to flank you everywhere you go until, at last, confrontation inevitable; you have no choice but to meet them head on. These mysterious forests and their gnarled, clothes-catching, skinscuffing, limbs, and the blankets of thick, prickly vines and underbrush, test you. They disorient you. And, they so torment you that weeks, months, even years later you’ll recall them in the book you’re destined to write, the future American classic, “A Tour on the Prairies:”

“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,” Irving writes.

Even at the time of Irving’s visit to the southern plains in 1832, this seemingly impenetrable forest was known as the “Cross Timber,” or, more appropriately, as the “Cross Timbers,” for it’s comprised not of a singular, continuous band of trees, but rather a mosaic of forests interspersed with prairies, stretching from southeast Kansas, through central and eastern Oklahoma and into central Texas. Post oaks and blackjack oaks dominate the Cross Timbers, growing so closely together that their canopies often encroach on one another. These rugged, drought-stressed oaks are accented in places with hickory, elm and hackberry trees, while tangles of vines, briars and shrubs clutter the understory, as Irving well knew.

Long before the Cross Timbers provided settlers with firewood and building materials, it acted as a natural, and often dreaded, barrier and a general obstruction to our nation’s westward expansion.
“The Cross Timbers vary in width from five to thirty miles,” wrote Santa Fe trader, Josiah Gregg, in his 1844 book, “Commerce of the Prairies,” “and entirely cut off the communication betwixt the interior prairies and those of the great plains.” [sic]

Perhaps not surprisingly, these dense forests once served as a distinguishing point of reference for Native Americans and, later, European explorers, traders and, eventually, settlers. In this sense they were little different than a prominent mountain range or one of the West’s great rivers, as the Cross Timbers appeared on most early maps of the region, not only as a curious point of reference, but also as a demarcation point separating the more established East from the wild western frontier. Indeed, even today, the Cross Timbers represent a stark transition zone, marking the westernmost limit of the Eastern deciduous forests, and the eastern border of the Great Western Plains. These short, rugged forests of post oaks and blackjacks serve as a buffer between these two very different landscapes, and also as an ecotone in which species from both geographical areas — such as the eastern bluebird and the greater roadrunner, for example — coexist as they have for millennia.

PHYSICAL FEATURES

Cross Timbers landscapes are mosaics that include both forest and the surrounding prairies, which make up much of what people believe the landscape of Oklahoma to look like.

Cross Timbers landscapes are mosaics that include both forest and the surrounding prairies, which make up much of what people believe the landscape of Oklahoma to look like. Credit: John Gifford.

When considered as a singular geographical feature, the Cross Timbers are characterized by coarse, sandy soils supporting post oak (Quercus stellata) and blackjack oak (Q. marilandica) forests over a sandstone substrate. As Richard V. Francaviglia writes in “The Cast-Iron Forest,” these post oaks and blackjacks are uniquely suited to the area’s harsh environment, as their “well-developed, strong roots work down into the bedrock.” This provides anchorage for the trees, as well as moisture, which seeps up from subterranean aquifers through crevices in the rocks, producing, as Francavigilia writes, “remarkably tenacious” trees that are able to endure the region’s strong winds, ice storms, frequent hail and searing summer temperatures with “seeming impunity.”

Perhaps the best description of these trees is the one Francaviglia recounts from an Oklahoma rancher, who said, “Them old post oaks on the ridges are tough as nails.”

They have to be in order to survive this extreme climate, where temperatures can plummet to near 0 degrees Fahrenheit in winter and regularly soar to 100 degrees Fahrenheit or more during summer. But survive, these drought-stressed, slow-growing trees certainly do. According to the University of Arkansas Tree Ring Laboratory, the Cross Timbers contain millions of 200- to 400-year-old post oaks, trees predating the birth of our nation and which had already lived for a century or more at the time of Washington Irving’s visit to Indian Territory. Surprisingly, however, these trees conceal their age very well. Even a 200-year-old post oak might grow to be only 30 feet in height, and for this reason many residents of the region even fail to recognize their significance. After all, when we think of ancient forests, many envision giant sequoias or towering pines rather than dense growths of short, gnarled, rough-barked oaks.

A LIVING NATURAL HISTORY MUSEUM

The author’s son, Jackson, on a hike in the Oklahoma Cross Timbers.

The author’s son, Jackson, on a hike in the Oklahoma Cross Timbers. credit: John Gifford.

Not long after moving to Edmond, Okla., in 2006, my son, Jackson, and I were fascinated to discover an urban Cross Timbers forest in the city’s E.C. Hafer Park, near our home. Jackson was still in elementary school then, and we visited the park often. He loved the swings and the rock climbing wall, while I enjoyed the walking trail skirting the park’s perimeter and the abundant trees. The 121- acre park was commissioned in 1979, and appears to have been carved out of Cross Timbers forest, for there are scattered blackjack and post oaks throughout the property, as well as a large woodlot on the east side of the park. While some areas of Hafer Park have been cleared to make space for playground equipment, roadways and parking lots, this isolated forest appeared untouched. I wondered why. Was this space earmarked for some future development? Was the forest simply awaiting its day with the bulldozer? Or, was this dense stand of post oaks and blackjacks serving some purpose, beyond that of a home for the park’s resident coyotes, raccoons and squirrels?

One day not long ago, Jackson and I decided to investigate this urban forest. Veering from the paved walking path, we followed one of the twisting dirt trails into the trees and moments later found ourselves ensconced in the Oklahoma Cross Timbers, suddenly separated from civilization and the development that surrounded the park on every side.

We could hear children’s voices in the distance, and the roar of traffic out on the street. But, we couldn’t see anything beyond the trees that surrounded us. In some places they grew in such dense concentrations that their limbs covered the canopy, shading the understory, while in other places it was open to the sunshine. Soon, our trail crisscrossed another path, and a short distance later twisted into yet another. Blue jays and cardinals fluttered through the branches and brambles. Somewhere nearby, a woodpecker hammered a tree. We spotted bobcat tracks and the knobby-tire pattern of a mountain bike. Then, the trail diverged into two separate paths.

Sometime later, I realized I could no longer hear the children playing in the distance. The breeze had picked up, rattling the leaves and tree limbs, and buffering the sounds of traffic out on the street. I realized we were lost.

“How can we get lost in our own city park?” I wondered. But, as I began to reflect on the situation, I felt strangely liberated. After all, in our modern, technologically dependent culture, getting lost is something that’s getting harder and harder to do. And, thankfully, my son had left his cell phone in the car, which meant I could embrace our predicament and use it as an opportunity to show Jackson how to find his way out of the woods — at least these woods.

We positioned ourselves so that the sun was over our right shoulders and headed east, toward the side of the forest from which we’d entered. As we threaded our way along the narrow, twisting trails, through the monotonous and disorienting Cross Timbers landscape, I told Jackson to scan the treetops for a landmark we could use to find our way out. With the fading sun, growing shade and the often-crowded forest canopy, this wasn’t easy.

Eventually, we spotted an electric tower, and not long thereafter we emerged from the trees. It was then that I realized the value of this urban forest. Though it was undeveloped and unimproved save for the primitive trails, it constituted as much an attraction as the playground or rock-climbing wall. It was, in every sense, a feature of the park.

But, was this intentional or incidental?

I was delighted to learn, a few days later, that the City of Edmond has no plans to raze or otherwise develop this forest. This meant that, like Jackson and me, others have the opportunity to lose themselves in the trees for a little while, which may be one of the greatest benefits of our urban forests.

A FOREST IN TRANSITION

The paved walking trail through the Cross Timbers forest at E.C. Hafer Park in Edmond, Okla.

The paved walking trail through the Cross Timbers forest at E.C. Hafer Park in Edmond, Okla. Credit: John Gifford.

Though large tracts of the original Cross Timbers remain intact today, much of the area abounds in second-growth oak forests, reflecting the millions of trees that were cleared during European settlement of the southern plains in the 19th century.

In the early decades of the 20th century, the boll weevil, falling cotton prices and the Great Depression proved to be insurmountable challenges for many
area settlers, and, as a result, hundreds of farms were abandoned, allowing for the eventual regeneration of the native post oak and blackjack forests. Only now, as urban areas like Oklahoma City, Okla., Tulsa, Okla., and Fort Worth, Texas, were growing up around these forests, so too was society’s desire to suppress the naturally occurring wildfires which had shaped this land over millennia.

Today, a century of fire deprivation is evident in the proliferation of the eastern red cedar (Juniperus virginiana), which has invaded the southern plains while, ironically, significantly increasing the fire hazard both to human dwellings and native trees. Deprived of the very fire that helped maintain the forest’s vigor for thousands of years, some areas of the Cross Timbers are being inundated by other invasive species, such as Chinese privet, a shrub which forms a dense understory, severely limiting or preventing new growth of sunlight-dependent oaks while allowing for the proliferation of shade-tolerant species. It’s not hard to imagine that with continued neglect, the Cross Timbers may look very different in 50 or 100 years.

To help educate the public about these and other issues, the Ancient Cross Timbers Consortium for Research, Conservation and Education has established several research natural areas (RNAs) — a cooperative network of ancient Cross Timbers sites, primarily in Oklahoma and Texas. Using these sites, the consortium teaches landowners how to restore the ecological integrity of compromised Cross Timbers landscapes, while offering best practices for preserving those precious, pre-settlement tracts of undisturbed forest, which are threatened by suburban and exurban development, oil and gas activity and, increasingly, apathy.

“People continue to remove native forest that’s never been cut before, examples of pre-settlement vegetation that are extremely rare around the world,” said Dr. David Stahle of the Department of Geosciences at the University of Arkansas. “This is people not understanding what they have.”

What we have with the Cross Timbers, according to Dr. Stahle, is something truly special.

“Eastern Oklahoma has some of the most extensive examples of unlogged forests in the eastern United States,” Dr. Stahle said. “These trees have a beautiful sculpted architecture reflecting centuries of life in Oklahoma’s hills.”

Imagine: forests that have survived hundreds of years of Oklahoma summers, ice storms and tornadoes, trees that once shaded and tormented Washington Irving.

The Cross Timbers are certainly worth preserving.

John Gifford is a writer from Oklahoma.

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