Even-aged management is defined as the type of forest management that results in forest stands composed of trees having no, or relatively small, differences in age. By convention the maximum difference admissible is generally 10 to 20 years, though with rotations of 100 years or less, differences up to 30% of the rotation may be admissible. The most widely used forest management technique for creating even-aged stands is clearcutting. The shelterwood and seed-tree systems are also even-aged methods but information on their effects on wildlife is limited.
Clearcutting in this report means the harvest of all commercially valuable trees in a stand for the purpose of establishing a new stand of trees. Unmerchantable trees may or may not be removed after the commercial harvest. To achieve the ecological conditions of a clearcut, the minimum area harvested must be at least 2 ac, the smallest opening likely to have at its center temperature and light regimes like that prevailing within large forest openings (Smith 1986, Patric and Schell 1990). Sources of regeneration in clearcuts include the following: seedlings from planting or natural seeding, stump or root sprouts, or advance reproduction in the cut area prior to harvest, (Ford-Robertson 1971). Since regeneration occurs over a short period of time, clearcutting leads to even-aged stands. Once the canopy closes in the cut area it is no longer regarded to be in the clearcut stage (Kimmins 1992).
Related Glossary Terms
Agricultural Cropping - Use of land for growing agricultural crops (Strayer et al. 1986).
Bayhead - A plant association dominated by broad-leaved evergreen trees that grows in very acid, saturated soils subject to periodic flooding. They characteristically occur in depressions in the flatwoods or as marginal growths about flatwood ponds that are not subject to excessive variations in water level (Laessle 1942).
Best Management Practices (BMP’s) - Standard, well-defined methods for harvesting and managing forested lands in compliance with federal and state regulations regarding conservation of soil, water, plants, and animal habitats (Hook et al. 1991).
Cable Logging - A system for transporting logs along, and/or by means of, steel cables, the load being lifted partly or wholly off the ground.
Canopy - The branches and foliage formed collectively by the crowns of adjacent trees and other woody growth.
Cleaning - The elimination or suppression, in stands not past the sapling stage, of weeds, vines, sod-forming grasses, and undesired woody species.
Diversity - There are at least six expressions of relative abundance and variety that apply to mixtures of animal species, vertical layers of vegetation, horizontal distribution of cover types, and other phenomena that are commonly called simply "diversity." These express a range of relationships from simple counts of the number of species (species richness) to measures of the uniformity of abundance of the species, layers, etc. present (Raw index of diversity). Several expressions combine abundance and uniformity (Wenger 1984). The reader should consult the original research reports to obtain details of the expressions used.
Equitability - Raw index of diversity (RID) is another measure of the “evenness” of specific densities. "Maximum equitability" (RID=O) is defined as the condition where all species are equally abundant (Wenger 1984).
Forb - Any herbaceous plant except grasses and grass-likes.
Forest Fragmentation - Islands of forest habitat that persist on the land when the intervening forest has been removed (Hunter 1990).
Forest Patches - Contiguous areas composing adjacent stands of mid - to late - successional forest (>20 ft in height, >50% canopy closure; <50% canopy closure if 39 ft in height (Chapin et al. 1995).
Forest Type - Forest types are named after predominant tree species. A category of forest defined by its vegetation.
Fuelwood Harvesting - Generally refuse material cut into short lengths for burning.
Ground Cover - Herbaceous plants (including grasses and ferns) and the lowest shrubs occupying an area.
Ground Skidding - A loose term for hauling loads of logs by sliding, not on wheels.
Group Selection - An uneven-aged system in which trees are removed in small groups. Habitat - The abode, natural or otherwise, of a plant or animal, considered particularly in relation to all the environmental influences affecting it.
Herps - A common contraction of the word “herpetofauna,” specifically toads, frogs, salamanders, lizards, snakes, and turtles.
Improvement Cutting - The elimination of less valuable trees in favor of more valuable tree growth, typically in mixed uneven-aged forest.
Litter - The uppermost layer of organic debris on a forest floor, i.e., essentially the freshly fallen or slightly decomposed vegetable material, mainly leaf litter, bark fragments, twigs, flowers, and fruits.
Mast - The fruit of trees, shrubs, herbaceous flowering plants, grasses, and grass-likes.
Mature Forest - A loose term for the stage at which most forest components have attained full development, particularly in height and seed production.
Mechanical methods of site preparation - Discing, terracing, bedding, chopping, crushing, shear and chop, KG blading, chain-saw; the use of machines or equipment to prepare a seed bed and/or remove competing vegetation.
Microhabitat - Localized areas within a community occupied by certain organisms because of microdifferences in moisture, light, and other conditions (Smith 1966).
Midstory - That portion of the trees, in a forest of more than one vertical layer or canopy, forming the middle layer. A loose term.
Old-Growth - According to Hunter (1989) it is probably neither possible nor desirable to craft a universal definition of old-growth. Hunter suggests that forest ecologists outline a broad, conceptual definition of old-growth forests from which specific definitions for each forest type can be derived. The core of such a conceptual definition would be, "Old-growth forests are relatively old and relatively undisturbed by humans."
Overstory - That portion of the trees forming the upper canopy.
Plant Succession - The orderly and gradual supplanting of one plant community by another.
Pocosin - Evergreen shrub bogs composed of poorly drained, mostly organic soil found on the southeastern Coastal Plain of the United States (particularly North Carolina). With recent developments in technology, a large percentage of these wetlands are currently managed for pine timber, agriculture, and energy products (Mitchell 1992).
Poletimber - Young trees, from the time their lower branches begin to die, up to the time when the rate of height growth begins to slow down and crown expansion becomes marked.
Pulpwood - Wood primarily for manufacture into pulp for use in making products such as paper and textiles.
Regeneration - The renewal of a tree crop, whether by natural or artificial means.
Regeneration cutting - Any removal of trees intended to assist regeneration.
Residual - A general term for trees remaining after merchantable trees have been removed.
Sapling stand - A loose term for young trees no longer in the seedling stage but not yet in the pole stage, i.e., a few feet high and an inch or so in diameter.
Sawtimber - Trees fit to yield saw logs.
Seedling stand - Trees originating in situ from seed, naturally fallen or sown, as distinct from those planted or arisen from coppice or root suckers.
Seed-tree harvest - A few good seed-producing trees are left per acre when the mature stand is logged. The seed trees usually are harvested after the crop of new young trees has become established (Soc. of Am. For. 1981).
Second-growth forest - Forest growth that has arisen naturally after some drastic interference such as wholesale cutting, serious fire, or insect attack.
Selective cutting - A loose term for the periodic removal of trees (particularly the mature) individually or in small groups.
Selection cutting - The annual or periodic removal of trees (particularly the mature), individually or in small groups.
Seral stage - The term for each successional stage is referred to as a seral stage.
Shelterwood harvest- Any regeneration cutting under the protection (overhead or side) of some old trees.
Site preparation - Any treatment that modifies existing vegetation of physical site conditions to improve germination, survival, and subsequent growth of desired seedlings (Nyland, 1996).
Site quality - A loose term denoting the relative productivity of a site for a particular tree species.
Slash - Woody debris accumulating on the ground as a result of a storm, fire, girdling, harvesting or poisoning.
Snags - A standing dead tree from which the leaves and most of the branches have fallen and/or a standing section of the stem of a tree broken off at a height of £20 ft.
Community composition - The assortment of species that comprises a community (Hunter 1990).
Species richness - The total number of species present. It expresses variety but not relative abundance (Wenger 1984).
Stand density - A quantitative measure of tree stocking usually expressed in terms of the absolute number of trees, basal area, volume, or other criteria on a per unit area basis (Wenger 1984).
Stand - A group of trees reasonably similar in age structure and species composition, usually occupying at least 5 acres (Hunter 1990).
Streamside Management Zone (SMZs) - Strips of forest vegetation maintained along waterways for many reasons, including enhancement of wildlife habitat (Wigley and Melchiors 1993).
Sustainable Forestry Initiative (SFISM) - SFISM is an initiative by participating forest products companies to practice a land stewardship ethic that integrates the managing, growing, nurturing, and harvesting of trees for useful products with the conservation of soil, air, and water quality, wildlife, and fish habitat and aesthetics (American Forest and Paper Association 1995).
Sustainable forestry - The practice of forestry in a manner which meets the needs of the present without jeopardizing the ability of future generations to meet their own needs (American Forest and Paper Association 1995).
Thinning - Partial cuttings designed to improve future growth of residual trees by regulating stand density.
Two-age timber management - A type of deferred timber removal. After a deferment cutting, the residual stand resembles a seed-tree cut with 15 to 20 trees per acre remaining; however, residual trees are not cut when the regenerated stand becomes established (Wood and Nichols 1995).
Understory - Any plants, particularly shrubs, growing under a tree canopy.
Uneven-aged management - A management system that maintains 3 or more distinctly different age classes in a stand.
Whole-tree harvesting - A form of clearcutting, removes essentially all the tops of harvested trees and leaves little coarse woody debris, an essential component of habitat for many groups of wildlife in eastern forests (McMinn and Crossley 1996). Conversely, commercial clearcuts in many high-graded hardwood stands remove only the central stem, less than half the woody biomass, leaving many standing snags and much logging slash.