The Fate of Arkansas’s Upland Forests as seen from Hawksbill Crag

Many naturalists throughout the range of the eastern deciduous forest biome have wondered what the undisturbed forest experienced by the first colonists in North America might have looked like. This question is closely tied to the desire by many ranging from the likes of Henry Thoreau to modern landscape architects to have the spiritual experience of the “forest primeval”. Sort of like returning to the Creator’s Garden of Eden. It would seem that all one needs to do is nothing – just let nature take its course and the forest will recover according to nature’s own plan. It has been more than a century since many parts of the Ozark plateau have been logged. To the consternation of ecologists nothing like a return to the admittedly poorly-documented pre-settlement forests seems to be happening.

How do we even know what the pre-settlement forests were like? The best measurable answer comes from the original land office survey of ranges and townships starting from the famous Louisiana Purchase benchmark (tri-point intersection of Lee, Monroe, and Phillips Counties, Arkansas). Townships were marked by corners identified by witness trees. Surveyors recognized that corner markers might not remain in place – or be displaced by land speculators. So, they recorded the distance (in survey chain links), compass heading and species identity of several trees around each corner. That formed a deeply rooted and recognizable geometric pattern that would be hard to tamper with. Assuming we can trust the botanical ability of surveyors, witness trees give an effective sample of trees growing in the Ozarks around 1820 when the forest was largely uncleared. This data shows clearly that the forest was mostly of oak – 70% divided equally into red and white varieties. Pine and hickory were another 5% each and then maple, ash and chinquapin comprising much of the rest. Not too different from the oak-dominated forests we see when driving through the Ozarks.

The problem with this information is that ongoing monitoring of Ozark forests repeatedly shows that so-called mesic species are actively replacing oaks and hickory in our local forests – and in most locations with oak-hickory forests throughout the southern Appalachians. Mesic species are those varieties that are found in protected ravines and stream bottoms where moisture conditions act to favor their reproduction. They replace themselves with the ability to grow in deep shade so as to come up beneath established trees of the same variety such as maple and beech that cast deep shade. Oaks cannot compete in that environment because they are adapted to more abundant light and expect to replace older trees when they are felled by disease or wind. To the consternation of foresters, mesic tree seedlings are seen to expand out of their ravine strongholds to become established under more commercially valuable oaks, hickories and pines. These trees are ready to shade out oak seedlings when the existing trees are removed by loggers or windstorm.

This “mesification” process has been a real concern to the timber industry. But just as much a concern to ecologists who see this as an unnatural change in the trajectory of future Ozark forest ecosystems.

The oak replacement problem has been a major driving force behind the movement to return fire to our ecosystem. The idea is that light ground fires will destroy thin-barked mesic seedlings while the thicker bark and resprouting ability of oaks and hickories let them survive. Some worry that the effect of long-term fire suppression cannot be reversed. Once beech, maple and cucumber tree saplings become big enough they can survive light fires and then serve as additional outlying seed sources for further spread away from their natural enclaves. Forestry research stations in Arkansas and beyond are actively investigating management techniques such as selective harvest regimes or creation of patchwork openings to favor oaks over mesic species. Environmentally concerned citizens need to be aware of that so called “mesification” problem and how well-intentioned programs to address the issue will someday influence the forests we all enjoy.

One of the most important things a concerned outdoors enthusiast can do is get some first-hand experience of the mesification problem. This can be done at familiar overlooks such as Magnolia Falls near Jasper and Hawksbill Crag in the Upper Buffalo Wilderness. These are locations where deep mesic ravines meet the upland oak, hickory and pine dominated forest. You can stand on these overlooks and gaze over uninterrupted forest for a view essentially identical with what the first visitors to the Ozarks (such as Henry Schoolcraft in 1812) saw when they came through the area. We know that is so because the forest overstory today is composed of the same oaks and accessory species as documented by witness tree surveys (see chapter 5 in Ozark Forest Forensics for a more in-depth discussion of pre-settlement forests in Arkansas). It’s certainly worthwhile to look out from such a crag over uninterrupted woodland to get the feel of what the view was like for early Ozark explorers. But take the time to examine the forest as you walk down to the actual overlook. Look to see how much beech and maple is growing under the oaks and hickories. The mesic species are especially easy to spot in the winter when they retain nearly all of their shriveled and brown leaves while the branches overhead become bare. How far away from their natural home have they expanded? How likely are they to succumb to a low-intensity ground fire consuming fallen leaves and small woody material? What can possibly be done to reverse this process? Does it matter (apart from the economics of the forestry industry) what kind of trees compose a naturally functioning ecosystem? In doing so you will be matching wits with some of the most learned forest ecologists in the world.

Illustration in Ozark Forest Forensics showing the appearance of oak and pine upland forest some distance from Magnolia Falls where mesic tree saplings – beech (a), sugar maple (b), and cucumber tree (c) – are infiltrating the understory and ready to take control of the landscape when the overstory eventually gives way.