Volume 6, No. 2
Duke University School of Forestry
The character of any natural place is determined in large part by the shape of the land and the vegetation which it supports. Much of the charm of the Eno Valley is a result of the interaction of these two, its trees and topography, and a third factor—time. Time is required for the trees and shrubs of the valley to respond to the pressures and changes, both subtle and intense, which result from the activities of man and the slower swings of natural cycles.
For example, the presence of pine stands along the river today reflects the intense change brought about by land clearing for agriculture and subsequent abandonment. The rapid invasion of pines followed by the slower, more subtle shift back to the original forest type reflect the slower cycles of nature. The developing young pine forest in the abandoned field creates a new environment beneath its canopy, an environment which is favor- able for the successful establishment of different species of trees and shrubs. These develop and grow to share the canopy with the older pines and eventually to replace them. All the while the environment beneath the canopy continues to change. Additional species of trees and shrubs find these new conditions suitable to their needs, become established, and begin their slow and patient progress upward toward the sun. This shifting of species and groups of species is often called the process of vegetational succession—the movement from disturbance to stability.
As the soils and topography of the valley influence the vegetation through natural processes so they have, over the years, influenced man’s activity and his profound impact upon the trees of the river. Soils and topography dictated the location of fields to be cleared for farming, of roads and mills for commerce, and to a certain extent the trees and groups of trees to be harvested. Man’s activities increased the natural occurrence of fire which, in turn, shaped the character of portions of the forested areas. It is due to man that we find fewer white oak, beech, sugar maple, and black walnut and more pine, tuliptree, and sweetgum than would be expected. Exotic species such as osage orange, privet, and perhaps even honey locust have escaped into the valley from the hedges, fence rows, and pastures of the adjacent farms. During the early and mid-1800’s many of the wealthy landowners of the region had an active interest, and even competed in a friendly fashion, in the planting of foreign species. Many remnants of this vogue exist today in the rich woody flora of Hillsborough.
Species of trees are quite individualistic in their requirements for optimum establishment, survival and development. This fact, together with the topography and soils adjacent to the valley, shapes the character of even the undisturbed forest. Some species require full sunlight to develop normally. These are termed intolerant of shade. Others are well-adapted to develop in light intensities much below full sunlight. These are the tolerant species. A few thrive with their roots in water-saturated soils while others are killed or seriously weakened by relatively brief exposure to such an oxygen-deficient root environment. Some are capable as seedlings of efficiently extracting moisture and nutrients from heavy clay soils while others struggle until some inevitable protracted drought. The seeds of certain species can effectively germinate and survive only on a seedbed of moist mineral soil while others require the protection of humus, litter, and shade. A flexible few can bend and twist their way to the sun while others are programmed by their genes to grow straight upward—or not at all.
The sum of the characteristics above, and many others, are known as the silvical features of a species—its life style. These features determine, to a large extent, the types of soils and sites where a tree is most likely to be found. They are not totally limiting, but given the tremendous amount of seed—potential trees and shrubs—produced and widely distributed by wind, water and animals year after year and considering the constant competition for growing space, probability dictates that a tree is more likely to survive and develop on those sites—in those ecological niches— which best suit its requirements, and where the species has some competitive advantage.
Knowledge of silvical features enhances our enjoyment of learning to identify the trees and shrubs found along the river. To recognize and name a species makes it a speaking acquaintance, but knowledge of its likes and dislikes, its personality quirks or silvical features makes it an old friend.
Our appreciation of the woody vegetation of the Eno can be further enriched by learning about the special uses and lore which have developed over the centuries. To the Indians the rich multiplicity of species provided an abundance of materials for food, fuel, tools and shelter. The European settlers moving into the area adopted many of these uses and, with their more sophisticated tools, added to them. Indeed the techno- logical characteristics of the Eastern North American species amazed and delighted the Europeans. These characteristics were identified, experimented with, and, developed into an amazing variety of products—from clockworks and mill gears to bowls and barn timbers—during a period in our country’s history which can be best described as “The Age of Wood.” An understanding of these contributions, along with the silvical characteristics, not only adds to the enjoyment of seeing and identifying but also creates a link with the past, as we walk along the river.
The following capsular notes on a sample of the species of trees and shrubs along the Eno suggest why looking at trees can become a fascinating hobby. There is a rich literature to be found in the fields of botany, history, and even folklore a few of which are hinted at in the accompanying bibliography.
The various oaks, formally the genus Quercus, are among the most commonly encountered species along the Eno. Oaks are not very tolerant of low light intensity nor are they capable of very rapid growth as seedlings or saplings. This is unusual in that species which are intolerant are usually characterized by rapid height growth. An oak seedling has a unique ability to grow for a few years, die back to the roots and then sprout again. The cycle can be repeated many times, permitting the in- errant species to await an opening in the canopy. Once it has gained the upper levels of the forest canopy an oak is quite enduring, ages of up to 500 years ‘having been recorded. It is this longevity which contributes much to the place of oak in the climax, or ultimate forest within the Piedmont.
An oak’s fruit, the acorn, is its most characteristic feature. Production of acorns is very erratic, ranging at irregular intervals from total failure to incredibly heavy crops. The acorn is sought for as food by a wide variety Of animals, birds, and insects and has always been a source of food for man. The kernel of an acorn is rich in concentrated food value and only the astringent bitterness of tannins deters from its use. The Indians devised numerous ways of extracting the tannins by boiling or leaching to produce a wholesome, albeit somewhat coarse, form of meal. Acorns of the white oak group have less tannin than those of the red oaks, and those of at least one species may be eaten without treatment as an emergency
The wood of the oaks is hard, strong and heavy, yet it is easily split. The feature has been utilized by many cultures to produce long thin flexible strips of wood for weaving into baskets, chair seats and similar items. Hewn or sawn it provided much of the enduring structural timber of the Day. The strong, non-porous wood of certain of the white oak group produced the tight cooperage of the past century as well as today’s whiskey barrels. Furthermore, dyes, inks, preservatives, and tannins for the manufacture of leather are extracted from oak wood and bark. Today the lumber products from the oaks include furniture, flooring, veneers, timbers, railroad crossties; the list is long—so long indeed that it is safe that even today the oaks are the most generally useful group of species.
Birch. The river birch is a frequent tree along the river and with its pinkish, papery bark is certainly one of the most distinctive. It is quite intolerant of shade and capable of rapid growth on moist soils. It is a good example of a species that is phototropic—that is growing toward the light. characteristically its riverside stems bend gracefully out over the channel to seek the sun. The only birch of low elevations in the south, it is a small tree with little of the utility of its more northerly kin. The graceful sweep and the often-forked stem produce lumber of undesirable quality. Though its colorful papery bark has never covered a canoe, it makes easily-ignited tender.
Hickory became an extinct species in Europe prior to stone age cultures. Hence, as a commonly occurring but totally new species, it attracted much attention from the early settlers who soon shaped the tough, heavy, resilient wood into a wide variety of special uses. Weight for weight it can rival steel in strength and elasticity. Boxes from the tough bark, ramrods, tool handles, furniture parts, split rails, hubs for wagon wheels, and mile after mileof railroad crossties were fashioned from this truly American species. Pehaps its greatest utility was then and still is as firewood since, when seasoned, it yields a hot often smokeless fire. Hickory nuts, though mostly ignored today, were a staple food supply for many eastern Indians. The extremely rich fats and oil obtained by crushing and boiling the nuts yield a thick creamy oil known to the Creek Indians as powohiccoria. Hickories range from tolerant to intolerant but all have an enduring capacity to respond quickly to additional growing space with accelerated growth. Even at its best the growth of most species of hickories is quite slow. Seedlings often average three inches per year or less for the first several years of their life.
Beech ranks as one of the most tolerant of all the species along the river. Beech seedlings can grow and develop quite normally in deep shade, and a mature beech in turn creates a very dense shade. It is most frequently found in streamside locations where its very shallow root system can find adequate moisture. Beech was not a new tree to the settlers. In Europe beech had long been a source of both food and lumber. The presence of beech-dominated forests assured the pioneer of fertile soil, and many acres of beech fell to the ax and then to the plow. In fact the reduction of the food and shelter of the vast beech forests of the Ohio Valley contributed much to the extinction of the passenger pigeon. Its shallow roots and very thin bark render beech highly susceptible to damage by both flood and fire. Hard to split and quick to rot, beech was little used by the pioneers. However, because it does not rot or soften in long exposure to water, it was often used in wheels and gears of water-powered mills. Today it is little used.
Sycamore, with its smooth, mottled and almost ghostly looking bark, is certainly one of the most easily recognized of all the trees along the river. Tolerant of moist soils and light shade, the sycamore in our region is largely a tree of the alluvial soils of streams and rivers. It may achieve a greater diameter than any other American hardwood. It is also very prone to heart rot and large trees are frequently hollow. This resulted in a unique occasional use by the pioneer who, arriving late in the season and needing shelter for his family, would cut a door into the butt of a hollow sycamore, a smoke hole high upon the stem and move his family into temporary quarters. Smaller stems, equally hollow, were often used as crude barrels. Though little used today, sycamore may well loom large as an important contributor of energy. Studies are underway leading to the development of large sycamore plantations to be fertilized, irrigated and carefully tended to produce rapid and repeatable crops of wood chips for industrial fuel.
The glimpses presented above are but an abbreviated sample of the sort of interesting information which has accumulated over many years about the species present along the river. It is the sort of knowledge that permits one to really know not just what a tree is called but how it fits into the total web of the Eno. As one stands beside a large rough-barked, narrow-leaved tree arching gracefully out over the river, it is nice to be able to identify it as a black willow. However it is still more wonderful to know that its bouyant cottony seed is so short-lived and its germination requirements so rigid that willow seedlings are rare; to know further that the tree has a unique habit of shedding fine branches so that they float downstream, lodge, strike root, and create a new tree; to know that from its bark and roots come the precursor of aspirin which cooled the fevers of primitive man; to know that its charcoal helped produce the finest gun- powder for the flintlock rifles of the seventeen hundreds; to know that its tough light wood was long chosen to create both artificial limbs and cricket bats; to know that perhaps from the unproductive bogs of Ireland may soon be flowing an ever renewable supply of clean, nonpolluting willow wood chip fuel to Irish generating stations. Then, standing by that willow on the Eno, one is standing by an old friend whose ways are known and through whom one can sense echoes of those long before today, and perhaps even a glimpse of those yet to be.