Nearly eight million acres, or 30%, of Ohio’s land area are forested. These forests provide a variety of benefits including timber, pulpwood, and veneer products; wildlife habitat; a high-quality water supply; clean air; recreational experiences; carbon sequestration; aesthetics; and others.
The mix of benefits and products produced by a particular forest depends on the characteristics of the forest and how it has been managed. Ninety-six percent of Ohio’s forests are classified as timberland. Four percent are public lands set aside as reserved forest land.
Ohio's forests are quite diverse. They vary in acreage, species composition, age, size structure, and past uses. Eighty-five percent of Ohio's forest land is privately owned, and the goals of ownership and intensity of management vary greatly. Except where strict preservation is the primary ownership objective, the periodic harvest of trees can play an important and often necessary role in accomplishing many ownership objectives.
The theory and practice of controlling the establishment, composition, growth, and quality of forest stands to achieve management objectives is termed silviculture. Various kinds of management practices are used by foresters, including timber harvesting, tree planting, prescribed burning, and the use of specific chemicals such as pesticides and fertilizers. Timber harvesting is the most common practice used by land managers to manipulate existing forest stands to meet their objectives.
There are two types of treatments that involve timber harvesting. Intermediate treatments are conducted with the objective of improving the quality and growth potential of the remaining stand (residual stand) to meet ownership objectives. If, for example, objectives include the production of high-value timber products, some of the poorer, less-desirable trees may be harvested to improve the stand's overall species composition and quality. If wildlife habitat is an important objective, an intermediate treatment might consist of removing competing trees in the vicinity of good, mast-producing trees. This allows mast-producing trees to expand their crowns, thereby increasing the amount of mast produced.
In contrast to intermediate treatments, the primary objective of harvesting in a mature stand is to regenerate or reproduce a new forest stand. Depending on the regeneration method used, large or small openings may be created in the stand. If the stand is regenerated using one to three harvests spaced over a short period of time, the new stand will consist of one age class of trees. Such a stand is uneven-aged. If the stand is regenerated using a series of harvests spaced over many years, the new stand will consist of trees of many age classes. Such a stand is uneven-aged. The remainder of this article discusses regeneration methods commonly used in Ohio.
Choosing a Regeneration/Harvest Method
Selection, clearcutting, and shelterwood are the regeneration methods commonly used in Ohio. All three methods are not equally applicable to every forest. The appropriateness of a particular regeneration method depends on the forest ownership’s objectives and the forest’s characteristics, particularly its species composition, age structure, and overall quality.
It is essential that ownership objectives be identified before considering whether trees are to be harvested, and if so, by which method. Ownership objectives define the goals of management and therefore the type of forest that best satisfies the owner's desires. Each regeneration method produces a forest with distinctly different characteristics, varying in species composition, age and size structure, appearance, etc. If, for example, grouse habitat is an important management objective, small clearcuts or large group selection openings might be needed to create required habitat. If periodic income is an important ownership objective for an uneven-aged maple-beech woodland, individual-tree selection or small group selection might be the appropriate method.
From an ecological perspective, the predominant tree species present or desired in a forest is a major factor in the choice of method. Tree species differ in their ability to establish and grow successfully in different environments. Some species, such as sugar maple and beech, reproduce and grow in almost complete shade under a dense forest canopy. Such species are termed shade-tolerant because of their ability to establish and grow in the shade of larger trees. Other species, such as yellow-poplar and aspens, are shade intolerant, requiring essentially full sunlight to survive and continue growing. Still other species, including many oaks, are intermediate in shade tolerance, which allows them to establish and grow in partially shaded conditions. Shade tolerance ratings of some common Ohio tree species are indicated in Table 1.
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Different regeneration methods create unique environments which best fit the environmental requirements of different tree species. Clearcutting creates the open conditions required for species that require full sunlight, like yellow-poplar and aspens. Species that thrive in essentially full shade, like sugar maple and American beech, may be managed using any of the regeneration methods. Species with intermediate light requirements, such as white oak or northern red oak, are commonly managed using group selection, shelterwood, or clearcutting. Again, other considerations determine the choice of regeneration method. Other factors, such as the stand-age structure, economic criteria, or aesthetic considerations, also inform the choice.
The overall quality of the trees in a forest may also influence the regeneration method chosen. Some ownership objectives, such as the desire for an undisturbed woodland for recreational activities, may be satisfied by a forest containing any species of tree in almost any condition. Most ownership objectives, however, are enhanced by the presence of healthy, vigorous, high-quality trees of desired species, which is a result of properly applying one of the three main regeneration methods. When a forest consists mostly of less-desirable species, or trees of low vigor or poor quality, harvests may need to be prescribed that reduce the number of less-desirable species. This creates the conditions needed for the establishment and growth of more desirable species.
Regeneration Methods
Clearcutting Method
As the name suggests, clearcutting is the removal of all trees from a forested area at one time, without regard to species, quality, age, or spacing (Figure 1). Clearcutting may be prescribed for a variety of reasons:
- to reproduce even-aged stands of intermediate or shade intolerant tree species
- to create openings and early successional vegetation for wildlife habitat
- to create vistas, campsites, roads, etc.
- to clear the area for tree planting or seeding
Clearcutting is the most dramatic regeneration method. Some people object to it because it creates temporarily unattractive areas. However, the initial visual impact of clearcutting is quickly reduced in Ohio. The rapid establishment and growth of vegetation, including tree seedlings and sprouts, causes the harvested site to look like a young forest in a relatively short time. A number of strategies can be used to lessen the visual impact of clearcuts:
- exercising care in their location
- leaving borders of uncut trees as visual buffers where appropriate
- planning harvest areas that conform to the natural topography
- designing irregular-shaped areas in a range of sizes, up to some acceptable maximum.
Some commonly cited advantages and disadvantages of clearcutting are available in Table 2.
Where necessary to accomplish ownership objectives, clearcutting is an important and valuable regeneration method. As with all harvesting, care must be exercised so that it is properly prescribed and carried out. One form of clearcutting, called commercial clearcutting, is rarely appropriate. In a commercial clearcut, all merchantable trees are cut and removed, while the rest are left standing. Such a cut usually does not create the type of full-sunlight environment desired when a clearcut is prescribed. Further, the trees remaining after a commercial clearcut do not commonly develop into a desirable forest stand. The only situation where a commercial clearcut would commonly be appropriate is where forest land is being converted to some other land use.
Shelterwood Method
The shelterwood method also produces an even-aged stand, but in contrast to clearcutting, this method commonly consists of a series of two or more partial cuts spaced over several years (Figure 2). The major ecological objective of a shelterwood is to create a partially shaded and protected environment in the understory where young trees can become established and grow. This is particularly beneficial for species that initially do not compete well with other trees and shrubs such as oak and hickory. Once the desired reproduction is well-established, the remaining larger trees are harvested. One advantage of the shelterwood method is that it greatly reduces the negative visual impact of a clearcut because the harvested area is dominated by trees, and the debris (branches, tops, etc.) generated by the harvest is less visible.
Throughout the United States, two- or three-cut shelterwoods have been used to reproduce a variety of coniferous and hardwood species. In a three-cut system, the first cut removes enough of the stand to stimulate the crowns to increase seed production, hastens the decomposition of soil surface organic matter to form a suitable seedbed, and allows new seedlings to develop on the forest floor. Several years later (commonly five to 20), a second cut removes approximately half of the remaining stand to create conditions suitable for the establishment and early growth of young trees. The largest and highest quality trees are retained in the stand after the second harvest to create ideal growing conditions the largest and highest quality trees in the area. Finally, several years later when adequate regeneration has become established, the remaining trees are harvested. Some care is necessary during the final harvest to minimize damage to the development of the young, even-aged stand.
Most shelterwoods in Ohio use a two-cut rather than a three-cut system. In a two-cut system, 40%–70% of the stand (depending on the species) is removed; several years (perhaps five to 20) pass until adequate reproduction is achieved; and then the remaining trees are harvested. An increasingly used option that helps shape a desired regeneration layer of oak and hickory is to use a prescribed fire between the two harvests.
Although suitable for most Ohio forests, the shelterwood method is uncommon for several reasons. First, the short-term planning horizons and brief land tenure of many Ohio forest landowners does not lend itself to a harvesting method that extends over several years. Second, use of the shelterwood method requires a market for the relatively small amounts of lower-quality trees removed in the first cutting—something that has not been common in Ohio. However, with increasing public concern over widespread use of clearcutting, the shelterwood method may become more common in situations where it can successfully achieve landowner objectives. Table 2 summarizes some of the commonly cited advantages and disadvantages of the shelterwood cutting method.
Selection Method
Selection is a regeneration method in which individual trees or small groups of trees are periodically (usually every 10–15 years) harvested based on their size, species, quality, condition, and spacing. Selection is used to create and maintain an uneven-aged stand. Using the selection method to convert an even-aged stand to an uneven-aged stand is difficult, can result in economic loss, and often causes a major change in species composition.
When individual trees are selected for harvest (individual-tree selection), they are replaced either by new seedlings or by small trees already present (Figure 3). Individual-tree selection is best suited for shade-tolerant species such as sugar maple and American beech. When small groups of trees are selected for harvest at the same time (group selection), a larger opening in the forest canopy is created (Figure 4). Depending on the size of the opening, group selection areas may favor the successful reproduction of intermediate or shade-intolerant tree species.
Aesthetically, the selection method has the least visual impact of any regeneration method. Using this method, trees approximately equal in volume to the growth of the stand since the last harvest are periodically selected for harvest. The openings created by the removal of individual trees or small groups of trees are small and scattered throughout the forest. The overall integrity and appearance of the forest is only slightly modified, and after a few years much of the residue from the harvest will have decomposed.
Selection can also be economically attractive to many private woodland owners with small acreage. Most uneven-aged forests managed with selection can be economically harvested every 10–15 years. There are many advantages and some disadvantages to the selection method (Table 2).
Two important cautions must be kept in mind when using the selection method. First, extreme care must be exercised in selecting the logging company to perform the harvest. One of the strong advantages of the selection method is that a forest remains after the harvest. It is important, however, that the harvest be carried out by a professional logger with the skills to minimize damage to the remaining trees.
The second caution involves the need to work with a professional forester to determine the need for and extent of a selection harvest. Two all-too-common and undesirable cutting practices encountered in Ohio are high grading and diameter limit cutting. In high grading, all the trees with economic value are removed from the stand. In diameter limit cutting, all the trees above a certain diameter, usually specified at stump height, are cut. While both high grading and diameter limit cutting are often promoted as acceptable forms of "selective harvesting," they are not. Both cutting methods as commonly applied ignore the sound ecological principles on which the selection method is based. Both practices will generally leave a forest composed of poor-quality, low-vigor trees with very little value or limited ability to meet most landowner objectives.
An Important Concern
Protecting soil and water resources is an important concern during forest regeneration activities. Removing trees typically requires heavy equipment that disturbs the porous organic layer of the forest floor. The mineral soil is then exposed to the erosive forces of raindrops and surface runoff. Soil may move downslope off the area and become sediment in streams, rivers, and lakes. The implementation of best management practices (BMPs) can substantially reduce soil erosion and its negative effects. BMPs include many activities and considerations:
- properly locating and constructing skid trails and logging roads
- preserving forested buffer strips along streams
- diverting runoff into the forest from roads and trails
- seeding trails, landings, and roads, upon completion of the harvest
Landowners should discuss best management practices with their professional forester and with the logger who will perform the harvest. To promote discussion with the logging operator and to avoid future disagreements, the best management practices for harvesting should be specified in the timber sale contract.
Conclusion
Forests can provide many long-term benefits, and many of these benefits can be created and enhanced by properly harvesting trees. A close working relationship between the woodland owner, a professionally trained forester, and the logger is critical. Personal assistance in planning for the regeneration of a stand can be obtained from many sources, including an ODNR Division of Forestry Service forester, a self-employed consulting forester who will not only plan but also supervise a timber harvest, or a forester employed by a forest products company. The Ohio Society of American Foresters (osafdirectory.com) maintains a list of these foresters. The Ohio Call Before You Cut program is a great place to start when considering a regeneration harvest.
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Acknowledgments
The authors would like to thank former Ohio State University Extension Specialists Randall B. Heiligmann and Eric R. Norland, along with former Ohio State University Associate Professor David M. Hix, for all their work on previous versions of this fact sheet.
Originally written in 2001 by Randall B. Heiligmann, State Forestry Specialist, Ohio State University Extension; Eric R. Norland, State Natural Resources Specialist, Ohio State University Extension; and David M. Hix, Associate Professor, Forestry, The Ohio State University.