There are many species of hardwood trees throughout Virginia. Individual species and groups of species are specifically associated with each region of the State and site. Hardwood forests are very diverse and harbor many benefits including those associated with timber production, game and non-game wildlife, aesthetics and landscape, recreation, quality water production, and soil protection. Biological diversity of flora and fauna is great in the hardwood forest eco-systems.
Like pine forests and agricultural crops, hardwood forests should be managed properly to attain even greater benefits than those solely provided by nature. However, management of hardwood forests is more complex and thus very challenging owing to the various mixtures of tree species. Each different species has inherent needs for sunlight, nutrients, water, and other biological support which affect growth and development. Management in hardwood stands is much different than management in pine stands. Professional forestry assistance should be summoned well in advance of any timber harvesting in hardwood stands. Important differences in site productivity, species composition present or potential, and numerous other distinctions must be defined. Often, damage to the present stand and serious loss of potential, or destruction occurs before technical advice is sought.
Hardwood trees grow on a wide range of sites. Some sites are dry and relatively infertile while others are nutrient rich, and moist. Site differences must be defined early to set production guidelines. Growing quality hardwoods economically over longer rotations will require the best sites. Poorer sites should be chosen for pine conversion (the species are less demanding), or for short rotations of small-size hardwoods (pulpwood, fuelwood, or small sawtimber). Forest management recommendations will vary greatly between hardwood stands. These comments address techniques more associated with growing large, high-quality/high-value hardwood trees on good sites.
Professional foresters should analyze hardwood forest conditions and prescribe necessary practices to meet landowner objectives while retaining biological integrity. Recommended forest management activities and stand prescriptions (with schedules) should be outlined in a detailed forest management plan. Practical balance between timber production and other values can be planned and controlled. Forests are “alive” and constantly evolving; so is all the associated life. Management activities can speed the change for positive benefits. Table I at the end of this section indicates some changes in wildlife benefits and timber associated with various options for timber harvesting.
Activities affecting the management of hardwood forests generally can be combined under three major categories. These are:
Regeneration/Site Preparation includes all activities associated with developing natural reproduction in existing forests or cutover forests, and planting/direct seeding in open fields or harvested forests (artificial reproduction). Also, those activities implemented for establishing site conditions suitable for germination of seed and early survival, early development, or to prepare soil/site conditions for introduced planting stock or seed.
Intermediate Treatments include all the cultural work and thinnings performed in the development of the hardwood stand to maturity. These include many forms of thinnings often referred to as timber stand improvements (TSI).
Harvesting of Mature Timber includes the cutting of the final product (the Crop Trees). No final harvest should be made until advanced regeneration is in place, seed is on site, or other plans are concrete for the establishment of the new forest.
Regeneration/site preparation, intermediate treatments, and harvesting will be briefly discussed later.
Large, high quality, very valuable hardwood trees are more site sensitive than many species of pines. Sensitivity varies considerably between species. For instance, growing tall, large diameter, limb-free black walnut trees will require the deepest, most nutrient rich, moist, but well drained soils. Whereas, chestnut oak can thrive relatively well on shallow, rocky, and dry soils.
Good hardwoods require adequate sunlight, moisture during the growing season, and nutrients. Site factors that are important are soil conditions, topographic position, and seasonal climatic factors.
Good hardwood soils are derived from parent rocks that contain high levels of the basic elements necessary for tree growth. Topsoils should be deep and high in organic content. Soils should be moist, but with good internal drainage for most species. Species composition and tree development will be reflected in the soil quality.
Topography is an important element in site productivity in extremely hilly or mountainous terrain. Generally, along the length of slopes, the top is poorer than the bottom. Coves, benches, drainages, and floodplains are usually productive sites.
Season and climate have important effects on tree growth. Many factors such as length of growing season; length of day; early and late frost dates; season, duration, intensity, and amount of rainfall; prevailing wind direction and velocity; and other factors and extremes have major influences on the establishment and growth of quality hardwoods. Quality hardwoods require long rotations under relatively stable conditions.
The combination of factors contributing to site productivity can be measured and defined in terms for growing trees. The term site index is used and indicates the expected height of dominant trees at a specific age (usually 50 years). Site index can be measured using tree height, soil characteristics, vegetative composition, and others. High site index numbers reflect potentials for growing large volumes of better quality trees; low numbers just the opposite. Several technical sources of site information are available.
Although published soil surveys are useful, they are general. An experienced forester or soil scientist should be consulted for field work to identify specific planting locations and selection of proper hardwood species if they are not presently on site. When timber production is the major objective, select economically important tree species that are best suited to soils and sites. If wildlife, recreation, aesthetics, or other non-timber uses are the objective, select the species accordingly.
Reasons for establishing hardwood forests on suitable sites are three-fold:
When should a hardwood stand be regenerated? (1) If properly managed, hardwood stands should be harvested and regenerated at the end of the planned rotation. These are final cuts and are separate from cuts performed for intermediate stand improvements. Exact timing of the harvest can be flexible to coincide with favorable market conditions. Proper management requires that provisions for establishing the new forest are firmly established before final harvest cutting occurs.
(2) Unfortunately, many hardwood stands are in need of restoration. These are stands dominated by low quality trees and reduced volumes resulting from a history of improper cutting and follow-up, or from incomplete harvesting. The all-too-common practice of “high-grading” has created many such stands. In those stands, provisions must be planned for starting anew in establishing a stand of desirable trees.
When hardwood trees are immature, approximately 35 to 60 firmly established, well-spaced trees per acre of desirable species and quality make management of existing stands practical. Many of these will be final crop trees with other trees being relatively unimportant.
When management of the current hardwood stand is concluded, plans must be firmly established for establishing the new one. Start with consultation of your Virginia Department of Forestry county forester or other professional consultants well in advance (several years at least) of timber harvesting. With landowner objectives considered, the professional will develop and start implementation of a regeneration plan.
Regeneration systems are defined as even-aged or uneven-aged. Systems are matched to the biological requirements of tree species for sunlight, moisture, temperature, and other competitive factors that permit seed germination, survival, and early tree growth. even-aged systems are used to establish species requiring high levels of sunlight, and that are shade intolerant such as yellow poplar and many oaks. Stands established from this method contain trees of the same age. Conversely, UNEVEN-AGED systems are used where favoring shade tolerant species such as maple. In theory, these stands contain trees of many ages, but usually contain two dominant age classes. There are few true uneven-aged stands. Most desirable Virginia hardwoods are shade intolerant and are best suited to even-aged systems. Each of the systems has advantages and disadvantages for timber production and other values.
Hardwood reproduction will originate from natural means (seed, sprouts, root suckers, and advanced reproduction of trees formerly occupying the site). Or, from artificial means (direct seeding or planting). Natural means are most commonly used on sites formerly in forest. Site preparation for hardwood establishment is closely linked to quality and disturbance from harvesting activities. In hardwood plantings on open fields, similar site preparation as used for pines is satisfactory. Young hardwoods should be protected from grass competition.
Timing the harvest cut will have a considerable influence on the composition and quality of the reproduction. Harvesting the original stand from November through March favors coppice development (stump sprouts), and takes advantage of current year seed crops. Summertime cutting has other effects on reproduction and favors different species.
Clearcutting is one of the most successful methods of reproducing hardwood forests, particularly those containing oaks and other desirable shade-intolerant species. For improved results of natural hardwood regeneration as well as maximum wildlife benefits, follow these guidelines:
Additional elements considered in clearcutting that benefit wildlife are:
Seed tree forestry is similar to clearcutting with the exception of leaving trees for seed production or insurance.
Shelterwood cutting for hardwood regeneration involves a series of several cuts to:
Shelterwood cuts result in even-aged stands of natural regeneration of intermediate shade-tolerant species, such as northern red oak. Both economic advantages and disadvantages are associated with shelterwood cutting depending on landowner objectives and finance. Some landowners consider shelterwood cuts more aesthetic than other forms of even-aged management.
The most intensive silvicultural method is individual tree selection. The method can be used to perpetuate high quality, shade-tolerant tree species such as beech or sugar maple. Timber can be harvested at periodic intervals of 10 to 25 years. In theory, new trees are constantly emerging to replace harvested trees. Individual tree selection appeals to many landowners, especially those concerned with aesthetics. Individual tree selection takes very technical application and extremely careful logging, and seldom is perfect.
Too often, landowners contract for diameter-limit cutting (so called selection cutting) which is not individual tree selection. Trees above a specified diameter are cut and nothing else. The biggest and the BEST is not necessarily the oldest, most mature. Diameter-limit cutting (cutting the BEST and leaving the rest) is called high-grading and leads to degradation of stand potential. High-grading should be avoided.
Group selection is also very intensive silviculture. In general, hardwood groups are cut and resemble small-scale clearcuts. Intended to favor intermediate shade tolerant species, nevertheless, often satisfactory tree development occurs only near the center of the opening. It works in reproducing the shade tolerant species.
As with individual tree selection, group selection requires excellent access to all parts of the tract. Financially, the method is feasible where tolerant species are preferred and the dollar value of harvested trees is high.
Group selection cuts provide ideal openings and pockets of young vegetation in hardwood forests for wildlife. Habitat created is excellent for grouse, woodcock, wild turkey, deer, and many songbirds.
Planting and direct seeding of hardwoods involves intensive site preparation, establishment, cultural release, corrective pruning (or optional training with interplanted conifers). Planted hardwoods must receive abundant moisture for survival and early development. Thus, moisture must be available for hardwood seedling, sapling use and not consumed by competing vegetation. Planting and direct seeding of hardwoods should be focused on the most favorable sites, and where sufficient time and finance is available to perform needed work.
Hardwood seedlings account for about one percent of the total seedlings produced in southern nurseries. Of the timber species, highest production is for black locust, sycamore, sweetgum, black walnut, yellow poplar, green ash, white ash, and several oaks. Important factors to consider when planning for the artificial establishment of hardwoods:
Some success has been reported on direct seeding hardwoods, particularly oaks.
Consult technical advice before planting or seeding hardwoods. Site examinations may reveal that the practices are unnecessary. If artificial establishment is needed, sound advice should direct the considerable investment needed in time and finance.
Carefully regulated harvesting techniques to support the regeneration often preclude the need for early cultural practices in natural stands. On the other hand, cultivation and mowing are beneficial in hardwood plantations.
Here are some intermediate practices associated with the development of quality hardwoods of natural origin on good sites:
After new reproduction of desirable species is assured, overtopping residuals from the harvest cut should be removed to release the new growth to full sunlight. Failure to do so results in retardation of the new trees. Sound regeneration/harvest practices can eliminate the need for liberation since it is done through harvest. When liberation cutting is needed, it can be performed by powersaw-felling, or with herbicides on all material above 1 1/2 inches in diameter or about six feet tall. If limited finances are available for hardwood development, liberation cutting should receive priority.
If regeneration harvest is conducted effectively, weeding and cleaning may not be necessary. However, when needed, this TSI (Timber Stand Improvement) practice is used to assure the survival and early growth of desirable trees from competing vegetation such as vines, heavy weeds and grasses, or undesirable trees.
This form of release can be accomplished with chemical herbicides, or “mechanically” by hand or machine. It is important when releasing the selected seedlings that climbing vines be cut or killed. “Climbers” on establishing hardwood reproduction can produce serious consequences during snow and ice storms, and during heavy winds. Foliage from vines also proliferates in the upper tree canopies and “steals” valuable sunlight slowing down growth of developing trees. When vine species are desirable for wildlife, they should be restricted to arbor areas. Weeding and cleaning practices can be excluded from these special areas.
Remember, it is not necessary to release all desirable seedlings in the stand. A few hundred well-distributed free-to-grow seedlings per acre is all that is needed.
Another timber stand improvement practice in young hardwood stands is crop tree release. The practice is performed in sapling stage stands (1-5 inches in diameter) and at least 12 years old. Trees should have started to show height dominance and be about 25 feet tall. The purpose of crop tree release is to maintain survival and growth on the best trees.
Crop trees should be good, healthy trees of desirable species. The trees can be good timber species, desirable for wildlife values, or for aesthetics. Crop trees should be uniformly spaced throughout the stand where practical. Do not select crop trees on poor sites and where no good candidates exist. 50-75 crop trees per acre should suffice in sapling size stands.
Release the young crop trees by eliminating adjacent trees whose crowns are touching that of the crop tree. Also, cut or kill climbing vines on or near the crop tree. Competing trees are usually cut with chainsaws. Released trees should be exposed to full sunlight and free-to-grow overhead and at least three sides (hopefully four).
Remember not to cut non-crop trees if they are not competing. These can be harvested later in commercial thinnings.
Keep the best trees growing. Commercial thinning allows the maintenance of good growth rates on the higher quality crop trees. Essentially, it is crop tree release at a later date, yielding commercial products. Thinning reduces the competition to the good trees for sunlight, soil moisture, and soil nutrients. Inferior species and lesser quality trees are removed.
Thinning is particularly challenging in hardwood stands because of mixed species, the different biological needs of each, and the various growth responses during various life stages. In many cases, larger trees may be the youngest, or certainly not older than smaller trees. Very skilled technicians should designate which trees to be removed in hardwood thinnings. Beware of high-grading in immature hardwood stands on good sites. Several commercial thinnings should be possible during the rotation for good hardwoods. Commercial thinnings should be terminated approximately 25 to 30 years before rotation ends at harvest to prevent possible degrade to valuable sawtimber.
Thinning can be aesthetically pleasing and certainly is advantageous for wildlife. Thinning increases sunlight penetration to the forest floor stimulating understory growth of food and cover for wildlife species, such as quail, rabbits, turkey, deer, and for numerous species of non-game wildlife.
During thinning operations, wildlife habitat should be protected while timber production is enhanced. Den trees should be protected.
Mast production trees should be encouraged during thinnings as well as particularly aesthetic ones. Hardwood species such as hickory, beech, persimmon, black gum, serviceberry, American holly, hawthorn, and dogwood produce both hard or soft mast favored for wildlife. Grapevines are particularly important for wildlife, but they should be restrained and managed in arbor areas.
Numerous options for harvest are available to meet landowner objectives and biological needs of trees. Sound forestry on good hardwood sites expands options and enhances financial opportunities.
Provide for the regeneration of new hardwood forests BEFORE harvest. Carefully regulate timber harvest through detailed timber sale contracts.
The list below shows the relation of Management Method, Timber Benefits, and Wildlife Benefits.