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Glossary of Forestry Terms

Acceptable Growing Stock (AGS) Living trees of commercially viable species that meet specific quality standards and the landowner’s objectives. These may include the potential to produce logs of specified minimum lengths.

Access Road An entry road to a stand or forested road, whether permanent or temporary.

Acid Soil A term descriptive of a soil, which has a pH less than 6.6. This is typical of soils found in coniferous forests. pH values are based on a scale of 1 to 14 in which 7.0 is neutral, values lower than 7.0 reflect degrees of acidity, and values greater than 7.0 represent degrees of alkalinity. Grass does not grow well in acid soil. The presence of moss is an indication of an acid soil. See also Alkaline Soil, pH, Soil.

Acre A commonly used unit of land area. It is equal in area to 43,560 square feet or, alternatively, 4,840 square yards, 160 square rods, 10 square chains, 10,000 square links, or 0.405 hectares. An acre is an area equal to a tract of land measuring 208.71 feet by 208.71 feet. The acre originated as the amount of land, which a yoke of oxen could plow in one day. A section is comprised of 640 acres. See also Hectare.

Adaptation The process by which living things change in order to adjust to changes in their environment, or to a special situation. Also, the changes that were made in order to adapt.

Afforestation The process of converting that which has lacked forest cover for a long time into forest or woodland. The establishment of trees on a long unforested area.

Age Class Any age range of trees, typically intervals of 10-20 years, into which the trees of a forest, stand, or forest type are grouped for purposes of classification.

Agroforestry The integration of the growing of trees for production of forest products and other agricultural pursuits. The intercropping of woody and non-woody plants.

Air-Dried Lumber Lumber that has been left to dry naturally in yards or sheds for any period of time. The minimum moisture content of thoroughly air-dried lumber in the United States is 12 to 15 percent with an average that is somewhat higher. See also Green, Seasoning.

Alkaline Soil A soil having a pH greater than 7.3. Alkaline soil is found in many arid regions and is usually poorly drained. pH values are based on a scale of 1 to 14 with 7.0 being neutral. Values lower than 7.0 reflect degrees of acidity. Values greater than 7.0 represent degrees of alkalinity. See Acid Soil, pH.

All-Aged Stand See Uneven-Aged Stand

All-Aged Management Another term for uneven-aged management. See Uneven-Aged Management.

Amgiosperm A plant whose seeds develop in fruits. One for which flowers are the reproductive structure. Examples include oaks, maples, birches, and willows.

Annual Rings See Growth Rings.

Artificial Regeneration The growth of new trees as a result of direct seeding or planting, rather than natural regeneration.

Aspect The compass direction towards which something (building, slope, etc.) faces. The exposure or view commanded.

Backfire A fire deliberately set in front of an advancing forest fire in order to deprive the wildfire of its fuel supply.

Bare-Root Seedling A seedling ready for transplanting that has its roots exposed, in contrast to container or plug seedlings. When seedlings are grown in nursery seedbeds, they are removed from the soil in which they have grown before being transplanted.

Bark The external covering of the woody stem, branches and roots of a tree that protects it from insects, animals, disease and fire.

Basal Area The cross-sectional area of the trunk of a tree at a height of 4½ feet above the ground and expressed in square feet.

The basal area per acre is the sum of the basal areas of all trees on an acre and provides a measure of stand stocking or forest density. For example, poorly stocked stands might have a basal area 20 to 70 square feet of basal area per acre, whereas it might be more than 200 square feet per acre for dense stands.

Bedding The land that has been prepared for seeding by gathering the surface soil into small mounds or ridges that are 6 to 10 inches in height. When forest seedlings are planted in this, their roots will be higher than the level of any temporary standing water.

Biltmore Stick A graduated stick that resembles a yardstick, but is about 25 inches in length. It is used to measure the diameter of a tree at breast height. To do so, one holds the stick against the tree at right angles to the direction of the trunk and reads the gradations on the scale that correspond to both outside edges of the trunk.

Biodiversity The diversity of plants, animals, and other life forms within and between ecosystems, as well as the variety of ecosystems. Biodiversity is life in all its forms within an area. It can be classified by the number of species, the genetic variability of the plants or animals, or a combination of both. Biodiversity is also called biological diversity.

Biofuel The primary and secondary organic fuel derived from biomass. Any fuel produced from organic matter, whether directly, or indirectly as through fermentation or burning. This includes wood, wood waste, peat, wood alcohol, soybean oil, black liquor from the papermaking process, landfill gases, and agricultural waste.

Bioindicator Species Any biological species or group of species that are so sensitive to a particular pollutant that they serve to warn of the presence of that pollutant.

Biological Control The use of living organisms, such as insects, fungi, and viruses, to control weeds and other pests.

Biological Diversity See Biodiversity.

Biological Herbicide Any naturally occurring substance or organism that can be used to kill weeds, brush or other competing or undesirable vegetation. They are less toxic to the environment than chemicals. See also Herbicide.

Biomass The total mass of living matter within a habitat. It can be expressed as either the weight of organisms per unit of area or the volume of organisms per unit volume of habitat. Also, all plant material that can be burned as fuel, such as wood and forest residues, or all harvestable vegetation in a stand.

Biota The collective animal and plant life of a region or period.

Bleed To exude sap, gum, or other substance from lumber. See also Fat Pine.

Blemish In carpentry, any physical defect marring the appearance of wood. See Knot

Blight Rapid and extensive discoloration, wilting and death of plant tissues. A common term for such a disease.

Blowdown An alternative term for windthrow, the uprooting of trees by excessive wind, or the trees so felled. See Windthrow.

Board A piece of timber which has been sawed thin and is considerably longer than broad. Boards are one inch thick (in nominal size) and up to 12” wide. However, in actual size, they are ¾” thick and up to 11 ½” wide. That is because any board is really ¾” thick and ½” less in width than its nominal width. A large board, such as a 2” by 4,” 2” by 6,” or 2” by 10,” is termed dimension lumber. Again, its actual size is less than what is specified. For example, a 2” by 4” really measures 1 ½” by 3 ½.” See also Dimension Lumber.

Board Foot A unit of measurement of standing or felled timber, but usually saw logs and lumber. The price of lumber is set at so much per thousand board feet. One board foot is equal to the amount (volume) of wood in a square piece of lumber measuring one foot by one foot by one inch in thickness. This is equal to 144 cubic inches. However, these dimensions are nominal. Thus, the price of lumber is based on nominal dimensions. See also Board, Lumber, Nominal dimensions.

Bog A wetland identifiable by sphagnum mosses and heaths. In contrast to bogs, swamps are dominated by trees and marshes are dominated by grasses. Bogs are found in moist, depressed land formed by the retreat of glaciers and having poor drainage. Precipitation provides their only source of water. (Bogs fed by springs or other waters are known as fens.) The low oxygen level in a bog retards plant decay. Dead vegetation, which settles to the bottom, becomes peat, a forerunner of coal. Although swamps and some marshes produce peat, the accumulation of peat is greatest in bogs. There, sphagnum mosses excrete antibiotics and raise the water acidity.

Bole The stem or trunk of a tree.

Breast Height A standard height in forestry for determination of diameter and circumference of trees. Breast height is a height of 4½ feet above ground level. See Diameter At Breast Height.

Bridgemat A heavy panel-like section constructed of steel panels or wooden timbers for use in spanning streams, ditches or other small waterways. It provides a temporary crossing during logging operations. A bridgemat is also known as a skidder bridge, pontoon bridge, or dragline mat.

Broadcast Burning Controlled burning, slash burning, or prescribed burning. See Prescribed Burning.

Broadleaf A reference to plants that have broad, flat leaves. Most broadleaf trees are deciduous, also termed hardwood. Oak, ash, and maple are examples of broad-leaved trees.

Browse The buds, leaves, twigs, shrubs, herbs, and parts of seedlings, and saplings that serve as food resource for forest animals. Also, to feed on such vegetation.

Brushing An operation conducted to control competing vegetation and reduce competition with seedlings or trees for nutrients, light, and space. It may by undertaken manually, mechanically, or by chemicals.

Brush Rake A blade that is attached to a tractor or skidder to use in mechanical site preparation. The teeth at the bottom of the blade cut through the soil and roots.

Buck To cut felled trees into shorter lengths for yarding and hauling, whether as specified lengths of logs or cordwood. Also, to make any bucking cut on logs.

Buffer Strip A narrow strip of land, trees, or vegetation that borders an area to preserve aesthetic values or to mitigate the impact of actions on adjacent lands. Buffers may also be used as firebreaks.

Cable Logging A method of skidding logs to a landing by means of winches, blocks, and wire ropes. In this system, one or both ends of the log is lifted free of the ground.

Caliper An instrument used to measure the diameter of logs and trees.

Cambium A single layer of cells between the bark and the woody interior of a tree trunk. These cells divide to create new inner bark cells (phloem) and new sapwood cells (xylem), thereby causing growth in diameter and circumference.

Canker: A plant disease. It is characterized by a well defined area of diseased tissue in the bark and cambium of a trunk, branch, or root, often sunken below the bark's surface and with an overgrowth of surrounding tissue.

Canopy The continuous forest cover or roof created by the contiguous grouping of tree crowns and foliage of approximately the same height in a forest. It is the layer of branches and foliage at the top of a forest.

Closed Canopy A term that describes the canopy of a stand of trees when the crowns of the trees that form the canopy are touching and intermingled, thereby preventing direct sunlight from reaching the forest floor.

Canopy Cover The percentage coverage of a specified area of a stand or wooded area that the canopy provides. Also, the percentage coverage provided by a particular species of trees.

Cellulose An inert carbohydrate, the chief constituent of the cell walls of plants.The scientific name for wood fiber.

Chain A unit of linear measurement used in surveying. A chain was the instrument, which surveyors historically laid down over the surface of the ground in order to measure distances. It was constructed from a series of metal bars and links. Strong wire bars were connected, one to the other, by three oval links or rings. The distance from the middle ring, which connects two bars to the next middle ring, is known as one link and is 7.92 inches in length (twelve inches for an Engineer's Chain).

A surveyor's chain is 66 feet in length. This is equal to 100 links, four rods, 20 meters, or 22 yards. A distance of 80 chains is equal to one mile. Ten square chains comprise an area equal to one acre. Land Office Maps still show distances in chains and links. The chain used in the early U.S. public land surveys is known as Gunther's Chain. In contrast, an Engineer's Chain (Ramden's Chain) is 100 feet in length.

The term also applies to a tape, often nylon, that is 50 m. or 75 m. in length and used to measure distances. .

Chlorosis The yellowing of normally green plant tissue due to nutrient deficiency or inadequate light and a consequent reduction in the production of chlorophyll. Chlorosis is sometimes a symptom of other problems, such as stem or root girdling, attack by sucking insects, or disease. See also Girdling.

Choker A length of wire rope with attachments with which to encircle the end of a log to be skidded or yarded.

Clay Loam Any soil comprised of sand particles and clay particles in proportions of twenty to fifty percent and twenty to thirty percent respectively, with silt particles making up the balance. See Loam, Sandy Loam, Soil.

Clear Without obstructions or restrictions. In the case of lumber, clear indicates that the wood is free from defects, such as knots. Also, to remove competing vegetation to provide optimal conditions for growth. See also Knot

Clearcutting The removal of all trees and vegetation from a designated area of land in one cutting operation. Ground material, along with stumps and leftover woody debris, are left in place. It differs from clearing operations, in which stumps are removed and all material scraped from the ground to facilitate a change in land use to non-forestry purposes. This management system is usually used to regenerate shade-intolerant tree species, trees that require full exposure to direct sunlight. Patch-cutting and strip clearcutting are variations. Clearcutting is also called clearfelling. See also Timber.

Clearfelling See Clearcutting.

Clinometer A hand-carried instrument used to measure vertical angles or slopes. When these angles are correlated with the distances from which tree tops are sighted through the instrument, one can estimate the heights of the standing timber. The difference between readings at 50 and 66 feet from the base of the tree is the height.

Co-Dominant Tree A tree whose crown extends into the forest canopy. It receives direct sunlight from above, although relatively little from the sides due to crowding by the dominant trees. A co-dominant is a fairly large tree that has above average growth in height. See also Dominant Trees.

Commercial Thinning A partial thinning of a stocked stand for economic gain, and to improve the health and accelerate the growth of the remaining crop trees. See also Thinning.

Competing Vegetation Adjacent or nearby vegetation that provides competition for the direct sunlight, water, nutrients, and space available at a particular location in a stand or forest.

Competition The competition among trees for adequate sunlight, water, nutrients, and space in which to grow. This competition involves all parts of a tree, from the uppermost branches and foliage the roots.

Composition The percentage contribution of each species of tree in a stand to the total number of trees, the total basal area of all trees, or the volume of all trees in the stand.

Cone rake A device lowered from a helicopter over the crown of a standing tree for the purpose of collecting cones.

Conifer A coniferous tree. See Coniferous Tree

Coniferous Tree A resinous group of trees having cone-like fruits and needle-like or scaly leaves. Conifers are generally evergreen. They range in variety from shrubs to giant trees. Examples of coniferous trees include pine, hemlock, cedar and cypress. Conifers help to anchor the soil in steep or deeply terraced soil. Some can tolerate shade. They grow in woodland or sandy, rocky sites. Conifers are virtually pest and disease-free and can tolerate pollution. They need no special care if properly planted. Sticky, wet clay is not suitable. See also Softwood.

Conk See Fruiting Body.

Conservation The management of resources in a manner that will yield the greatest sustainable benefit, whether economic or social, from the resource, while maintaining its quality and potential for future generations.

Consulting Forester A professional forester who manages forests and markets forest products on behalf of private or public woodland owners. Consulting foresters act as agents of woodland owners and have no ties to firms that buy wood products.

Controlled Burn See Prescribed Burning.

Conventional Logging Any combination of felling and skidding, whether by hand or mechanical means, except cable logging.

Cord A standard unit of volume for stacked fuel wood, whole or split, with or without bark. It is a unit of volume equal to 128 cubic feet. It is normally expressed as a stack of wood that measures 4 feet in width by 4 feet in height by 8 feet in length.

Cordwood Any low quality or small diameter wood that is not suitable for lumber. Cordwood is suitable only for pulp or firewood.

Crook: An abrupt bend in a tree or log. It may have been caused by insect-induced topkill and a recovery by a lateral branch. See also Fork and Shepherd's Crook.

Crop tree Any tree in a plantation or young stand that has been selected for growth to maturity, or to a predetermined size, before harvesting. The choice of crop trees is based on species, size, quality, and timber potential.

Crop Tree Release The freeing of a tree or group of trees from other closely surrounding or overtopping trees that compete with the former for nutrients, sunlight, and space. Natural stands of trees begin with thousands of trees per acre. At maturity, there may be only 50 to 70 per acre. Crop tree release is the practice of deciding which trees will stay to maturity and then removing their competition.

Crown The leaves and living branches of a tree, especially the uppermost parts.

Crown Class A tree classification system based on the tree's relative height, density of density and ability to intercept direct sunlight. The classification brings attention to trees that would benefit from future thinning and harvesting operations. The four classifications are dominant, co-dominant, intermediate, and suppressed. See Dominant, Co-dominant, Intermediate, Suppressed.

Crown Closure If the crowns of trees touch and prevent direct sunlight from reaching the forest floor, the situation is termed crown closure.

Crown Dominance A term used in reference to the position of the crown of a living tree relative to those nearby. A crown may be (1) dominant (above adjacent crowns and receiving direct sunlight on all sides), (2) co-dominant (at the same level as one or more adjacent crowns; the top of the crown receives direct sunlight, (3) intermediate (the crown is below the level of two or more of the adjacent crowns; it receives direct sunlight only when the sun is directly overhead, or (4) suppressed (the crown is below most adjacent crowns and receives no direct sunlight).

Crown Fire A fire that spreads from treetop to treetop. It jumps from the top of one shrub or tree to the top of the next, rather than slowly advancing along the ground.

Cruise A systematic survey of a forested area to locate marketable timber and estimate its volume by species, quality, or other characteristics. Also, the actual estimate so obtained.

Cull A tree or log of saw log size that is marketable only as firewood or pulpwood because of defects. The defects may be shape or result from insects, disease, or injury.

Cut-and-Fill The process by which the surface of land is altered by excavating portions of a site and filling others with the fill, the material removed by excavation. This includes the process of constructing benches on hill slopes to create road rights-of-way and landings by excavating convex slopes and filling concave slopes (gullies).

Cut Period See Cutting Cycle.

Cutting Contract A written contract for the sale of standing timber. The cutting contract spells out the provisions that address the needs of buyer and seller.

Cutting Cycle The planned time interval between successive major harvesting operations in the same stand, woodlot, or forest, normally within uneven-aged stands. See Uneven-Aged Stand.

Cut-to-Length (Short Wood) Logging Method Trees are felled with a stump height of less than one-half butt diameter remaining, delimbed, and bucked to various uses (e.g., pulpwood, saw log, veneer bolt) in the stump area. The cut-to-length method is used for all needs (e.g., clear felling, thinning, individual tree selection logging). All processing is done in the cut-over. This method permits better sorting and storage. Because the wood is carried off the ground, there is less risk of breakage and dirt contamination.

Decay The deterioration or disintegration of wood or other substances by the action of fungi. Certain fungi use wood as food. This causes the wood to soften and eventually shrink, crack, and crumble. A discoloration of the wood appears during the early stages of decay.

Decay fungi require air, warmth, food, and moisture for growth. Temperatures of approximately 70 to 85 degrees F are ideal for growth. High temperatures, as used in kiln-drying lumber, kill fungi. Decay fungi become dormant at low and very low temperatures. Wood, which is wet for only very brief periods, will not decay. However, wood is susceptible to decay, if kept wet for long periods in temperatures favorable to the growth of decay fungi. If the surrounding air is very damp, fungi may appear on the surface of the wood as white or brownish growths in patches or strands. However, the primary sources of water for fungi are condensation, rain, ground water, and leaks. See also Dry Rot, Durable Species, Fungi, Preservative

Decidous A term used to describe those trees, which shed their leaves each autumn (or at some other period during the year). The trees may be cold-deciduous and shed their leaves when the weather becomes cool or drought-deciduous and drop them when the water supply becomes low. Examples of deciduous trees include oak, ash, elm, birch, and poplar. See also Hardwood.

Deck See Landing.

Decomposer An organism, such as a bacterium or fungus, which feeds on dead plant or animal matter, thereby making organic nutrients available to the ecosystem.

Decomposition The process of decomposing or disintegrating. The process by which material, such as leaves, twigs, and bark are broken down by bacteria, fungi, and other life forms that live in the soil.

Deficit Forest A forest that cannot sustain its present level of harvest volumes over the long term until the new stands created will be available for harvesting. Before that time arrives, the existing ones will have all been cut down, See also Surplus Forest.

Defect Any disease or injury to an individual tree that reduces the usable quantity of wood from it.

Defoliator An insect or chemical that damages trees by destroying leaves or causing them to be shed.

Deforestation The removal of trees from land without an intention to reforest it.

Dendrology The branch of botany that is concerned with trees and shrubs.

Den Tree Any tree that contains one or more cavities, which are suitable for use as dens or nests for animals or birds.

Desertification The advance of desert conditions into an arid or semi-arid region due to climactic change, human influence, or both. The characteristics of desertification include a decrease in surface water, a lowering of the water table, salinization of topsoil and water, rising erosion, and a decline in native vegetation. The life-supporting capabilities of the land dwindle.

Detritus Small particles of dead and decomposing organic matter, including leaves, twigs, and animals. Also, any disintegrated material.

Diameter at Breast Height (DBH) A standard measurement in inches of a tree's diameter, including its bark. It is usually determined at a height of 4½ feet above the ground.

Diameter Inside Bark (DIB) The measurement or estimate of the diameter of a tree or log, excluding the thickness of its bark. The volume of a log can be obtained from a log scale table, using the length of the log and its DIB. See also DOB, Doyle Rule.

Diameter-Limit Cutting The cutting and removal of trees from a stand that are greater in diameter than a predetermined amount. The remaining trees are left uncut. However, because the fastest growing trees are removed first, leaving smaller, slower growing trees of tolerant species, it results in a loss of stand vigor. In turn, this leads to irregular harvests and long cutting cycles. Diameter-limit cutting is also known as Diameter-Limit and Diameter-Limit Scale.

Diameter Tape A cloth or steel tape that is wrapped around a tree trunk in order to measure its diameter at breast height. The tape's scale shows both diameter and circumference. It assumes that there are 3.1416 inches of circumference for each inch of diameter. (based on 2p r, the formula for the perimeter of a circle)

Dibble A pointed gardening tool that one uses to make holes in the soil to receive seeds, seedlings, or bulbs. Also, to make holes in the soil with this tool, or to plant seeds or seedlings with the help of this tool.

Dieback: The gradual dying of shoots, twigs, tops, branches or roots, which begins at their tips, due to disease or climatic conditions.

Difficult Site A term used to describe a forest site that has environmental conditions that are unfavorable to the establishment and growth of trees.

Dimension lumber Yard lumber that has a thickness of at least two inches, but less than five inches, and a width of two inches or more. If softwood, such lumber is used as joists, rafters, studs, plank, and small timbers. If hardwood, the lumber is used in the manufacture of furniture and other products.

Direct Seeding The landowner, or someone acting on his behalf, sows seeds of commercially valuable species from the air or on the ground in the areas where tree regeneration is sought. The seeds germinate in these denuded areas, send up shoots, and grow to become saplings. Direct seeding involves no transplanting. Direct seeding is also called Broadcast Seeding.

DOB An acronym for diameter outside bark. The diameter of a log or tree, including its bark.

Dominant Trees Larger than average trees that have broad, well developed crowns, which extend above surrounding trees and receive direct sunlight from above and from the side. Dominant trees contribute more cover or basal area to the community than do other trees.

Doyle Rule A formula for the calculation of the volume of logs. However, it underestimates the board feet that can be obtained from small logs and overestimates that of large logs.

Dragline Mat See Bridgemat.

Dressed Size Lumber mills dry their newly cut wood in order to remove most of its moisture. This is accomplished through the use of a kiln or by leaving the lumber in the open air for a period of time. The drying causes shrinkage in the wood. This shrinkage varies from one type of wood to another and from one batch to another. Consequently, the dried lumber is subjected to a dressing process (planing) after the drying. This ensures consistent sizing and gives the lumber a smoother finish than that created when the timber was first cut at the sawmill. Naturally, the new dressed size is somewhat smaller than the size of the lumber when it was first cut (its nominal size). Nevertheless, lumber is sold by its nominal (original) size, rather than its actual (dressed) size. See also Nominal Dimensions.

Dry Rot The decay of dry or seasoned wood, which changes it to a fine powder. The cause of dry rot is a brown-black fungus, which takes advantage of moisture in, or near, the wood. See also Decay, Fungi.

Duff Organic matter in various stages of decomposition that is lying on the floor of the forest beneath the litter of leaves, twigs, and needles and just above the soil. Its upper surface is immediately below the green of any moss present.

Durable Species A term applicable to certain species of trees, including varieties of redwood, cedar, and cypress, which naturally resist decay and attack by insects. The term is occasionally used to describe other woods, which have been pressure treated with chemicals in order to resist decay. See also Decay, Preservative, and Pressure Treatment

Earlywood Wood cells that are produced early in the growing season, a time of more rapid growth. The cells of the walls are thin and less dense. The wood is generally light in color. Earlywood is also called springwood.

Eco-Friendly A term meaning earth friendly or environmentally friendly. For example, a decision to preserve existing mature trees during the development of a subdivision would be considered to be eco-friendly.

Ecology The science that studies the relationships and interactions between organisms and their environment.

Ecosystem A community of living things and the environment in which they live. The plants and animals of a given habitat and all physical factors that surround them. An ecosystem can be a log or pond, a forest, or something of even greater size, but which functions as a complete unit.

Edge The line of demarcation between areas of differing vegetation, such as a field and a wooded area. The band or area of transition between the two types.

Endemic Indigenous. See Indigenous.

Environmental Protection Agency (EPA) An independent agency established within the executive branch of the federal government in 1970. It was created in order to coordinate governmental action to protect and enhance the environment. Its mission is to control and abate pollution in air, water, and the soil and to deal with solid waste, pesticides, radiation, and toxic substances. The EPA coordinates and supports research and antipollution activities conducted by state and local governments, private and public groups, individuals, and educational institutions. It prepares environmental assessments of proposals, which are potentially detrimental to the health or welfare of the public or environment. It develops national programs, technical policies, and regulations concerning air, water, radiation, pesticides, and toxic substances and enforces adherence to standards. The Environmental Protection Agency serves as the public's advocate for a livable environment.

Epicormic Branching Branches that grow from the main trunk of a tree, rather than from the crown. Pronounced epicormic branching increases the number of knots and reduces the quality of the lumber. Branches sprout from buds on the bole of a tree usually as a result of stress.

Evapotranspiration The evaporation of water from the soil and the leaves of plants. Evapotranspiration returns an estimated one-quarter of all rainfall received by forests.

Even-Aged Management The management of forested land in a manner to produce or maintain even-aged stands. All trees are harvested at the same time in one or several cuttings to produce stands of trees that have approximately the same age. This management method is often used for hardwoods and shade-intolerant conifers.

Even-Aged Stand A stand of trees that is populated by one or two age classes. Within an age class, the age differences among trees are relatively small. Even-aged stands are perpetuated by cutting all trees at the same time. They are often brought about by fire or a harvesting method, such as clearcutting seed trees, or shelterwood. The three methods used to achieve even-ages stands are seed trees, clearcutting, and shelterwood. See Clearcutting, Seed Trees, Shelterwood.

Evergreen A term used to denote woody plants, which retain their foliage throughout the year, as do most conifers and some broad-leaved plants. Instead of losing all of their leaves every year, they drop only their oldest leaves each year. As a result, evergreens serve as excellent windbreaks, if planted in the path of prevailing (wintry) winds. See also Conifer, Softwood.

Fabric Land Timberland. Land given to a cathedral or church to provide an income or the materials necessary to repair and maintain the church. Land provided to maintain the fabric or structure of a church.

Fat Pine Lumber or timber cut from pine that is high in resin. See also Bleed.

Feller-Buncher A tractor-mounted harvesting machine that uses a large set of cutting shears, a heavy-duty chainsaw bar, or a large circular saw to cut trees. The steam-shovel-like machine is available with rubber tires or caterpillar tracks and a rotating platform or a fixed chassis. A felling head, which consists of grappling devices and saw, is attached to an articulating extensible arm. The machine approaches the tree, grips the tree, and severs it from the stump. It then takes the severed vertical tree and lowers it onto a pile of trees on the ground.

Fell To cut standing trees.

Fertilizer Any material, natural or chemical which, when added to soil, supplies one or more of the nutrients essential for plant or tree growth. Fertilizer is often used to improve the vigor of crop trees following commercial thinning or juvenile spacing. Three elements essential to plant growth are nitrogen, phosphorous and potassium. Chemical fertilizers are sold on the basis of their relative proportions of these elements. See also Soil.

Firebreak A strategically located wide strip of land that is created manually or mechanically, or simply maintained, as an open corridor in order to retard or prevent the spread of wildfires. It is often selected or constructed in order to protect a high-value area from fire. Trails, roads, rivers, or utility rights-of-way can be useful as firebreaks during an emergency.

Fire Hazard The potential for fire that the fuel on the ground of a forested area, including slash, represents.

Fire Line Any cleared trail or pathway that has been created to prevent a fire from spreading in a certain direction or beyond a designated area. A fire line should expose the bare mineral soil to ensure that no debris will ignite and help the fire to spread. Fire lines are used to contain prescribed burns and control wildfires. Tractor blades, specially-designed fire-plows, or hand tools, such as shovels and rakes, are used to create fire lines.

Fire Season The period(s) of the year during which the risk of forest fires is greatest. This is the period when the probability of damage and loss from fires are enough to justify a concerted approach to fire preventions and control.

Fixed Area Plot Sampling Method A method in which small plots of specific size in a forest area are used as representative samples of an entire forest area in order to obtain information, such as wood volume, about the entire area.

Flagging The Marking of boundaries by the use of colored plastic ribbons attached to trees or stakes.

Foliage The leaves of a plant or tree.

Foliar Analysis Chemical analysis of the leaves or needles of plants to determine the state of their nutrients or the requirements of soil for plant-nutrients.

Forb Any herb that is not a grass or grass-like.

Forest A dense growth of trees, plants, and underbrush that covers a large area. A biological community that resembles a large, dense growth of trees

Forester A person who has been educated in forestry and is engaged in the profession of forestry and forest management. Depending on the jurisdiction, the forester may be required to be registered with the province or state.

Forest Fire Any fire, whether wild or prescribed, that takes place in grass, forest, or other vegetation.

Forest Floor The layer of organic material lying on the surface of the forest soil. It consists of accumulated matter, such as partially or fully decomposed leaves, seedlings, needles, grasses, ferns, flowers, fungi, twigs, branches, and logs.

Forest Inventory A survey of a forest to accumulate data on its location, nature of its cover, composition by species and age, and timber volume, as well as soils, wildlife, etc.

Forestland A section of land that is covered with forest or set aside for the cultivation of forest.

Forest Management The application of scientific, economic and social principles to the management and care of a forest in order that it remains healthy and vigorous while enabling stated objectives to be achieved.

Forest Practice Any activities undertaken on forestland that facilitate the use of its resources. These relate to growing, harvesting, or processing timber, but do not include such preparatory work as surveying, tree marking, road flagging. It also excludes the harvesting or removal of incidental vegetation, such as berries, ferns, or mushrooms, which normally will not cause damage to forest soils or timber. However, specific activities included are: road and trail construction, thinning, harvesting, reforestation, planting, fertilization, suppression of insects and diseases, control of vegetation, and salvage operations.

Forest Renewal The renewal of trees in a forest area or stand by natural or artificial means.

Forestry The science concerned with the study and optimal management of forestlands for the continuing use of their resources.

Forest Type A natural group of different species of trees that commonly are occur together over a large area. They grow in the same forest or stand because they have similar environmental requirements. The forest type is defined by one or more of its dominant species of trees. Common northeastern forest types include beech-birch-maple, beech-red maple, and mixed wood. Common forest types in another area might be pine and mixed hardwood, oak and hickory, and oak-pine.

Fork A tree defect caused by the division of a bole or main stem into two or more stems, possibly caused by loss of a leader or apical shoot due to terminal weevils. See also Crook, Shepherd's Crook.

Fragmentation The transformation of large continuous forest patches into smaller patches by such natural means as windthrow, insect attack, landslide, and fire. Harvesting and ancillary activities are the main causes of disturbance in managed forestlands.

Free-Growing Stand A stand of healthy trees of a commercially valuable species, which are not hindered by competition from other trees, plants, or shrubs for nutrients, light, and space.

Frilling A method of girding trees to kill undesirable trees or reduce stand density. It is performed by making a cut around the trunk and applying a herbicide to the open cut.

Fruiting Body The hard fruiting structure of a wood-decaying fungus that is seen on tree trunks, branches, and stumps. The reproductive part of a fungus that contains or bears spores. Also called a conk.

Fuel Any dry grass, leaves, needles, twigs, branches, trees, or shrubs that are easily consumed by fire. The more fuel that is available, the faster and more intensely will a fire burn.

Fuelbreak See Firebreak.

Fuel-Loading The accumulation on the forest floor of easily ignitable fuels, such as leaves, pine straw, twigs, branches, and trees.

Fuelwood Trees (or logs) that are suitable in size and quality for the production of firewood or some other fuel.

Full Crown Release The removal of all other tree crowns that compete with the crown of a particular tree for sunlight. The extent of crown release is decided by the spacing between the

crown of the particular tree and those around it.

Full Tree-Logging Method Trees are felled and transported to roadside with branches and top intact. The full trees are processed at roadside or hauled as full trees to central processing yards or the mill. Roadside processing of full trees can include any of the following: delimbing, topping, bucking, debarking, chipping. This logging method is most applicable to clear felling operations, and in some cases to first commercial thinning.

Fusiform Rust A disease that degrades stem quality and often leads to breakage and disfigurement. It can lead to the tree's death. Fusiform rust appears as a swollen area on the trunk or limbs of a tree.

Gall An abnormal swelling or lump of plant tissue caused by an insect, disease, or injury.

Girdle To cut or sever the bark of a tree in a ring around it, thereby severing the cambium layer and disrupting the flow of sap within the tree. This interruption of the flow of food between the leaves and the rest of the tree may cause the roots to die, followed by the death of other parts of the tree. Girdling may be caused by humans using a hatchet or special tool, rodents, fungal infections, bark beetles, or weevils. Many deciduous trees are able to repair the damage and survive.

Gout Formation of excessive swellings of a branch or shoot at the nodes or the base of buds.

Grading Classifying logs, timber, or lumber according to use or quality.

Grapple A set of large hinged jaws or arms that are used to grip logs or trees during skidding or loading operations. The driver of the skidder, on which the grapple is mounted, operates the device from inside his cab.

Green A term used in reference to freshly sawed lumber or wood, which has not been intentionally subjected to drying. Such wood may warp as it ages. The term, green, does not apply to lumber, which may have become waterlogged. See Warp.

Greenbelt An area of parks or recreational or undeveloped land, which surrounds a planned community or other residential area. It is normally land that has been set aside to contain development and preserve the character of the countryside and community and provide open space. It is usually zoned as such.

Green tree Retention The act of holding a particular species of tree or size from harvesting for a specific reason.

Ground The layer of solid substances, such as soil or sand, which form the surface of the Earth. The term also is used to denote an area or tract of land, particularly one reserved or used for a specific purpose. In addition, ground may be used to describe the private land surrounding a dwelling or other building. See also Soil.

Ground Cover Any natural vegetation or manmade material that protects the soil surface against the impact of rainfall impact and rapid erosion. Also, any grasses, ferns, or other plants of that grow in height from a few inches to a few feet, protect the soil from the impact of rain drops, and hold the soil in place.

Ground Fire An uncontrolled spreading surface fire, generally with low flame. It burns the humus and may not appear on the surface. A ground fire will sometimes burn for an extended period of time before being detected.

Group Selection An uneven-aged harvesting method that favors shade-intolerant species. Openings are created in the stand by removing groups of trees to regenerate shade-intolerant trees. The size of opening depends on the area being managed (usually 1/2 to 5 acres). A type of selective cutting. See Uneven-Aged Management

Growing Stock All trees in a forest or a designated part of it.

Growth Rings Trees in climates, where growth stops or slows during a portion of the year, form annual rings, which can be read to determine tree age and rate of growth. The rings are layers of wood added in successive growing seasons. Trees form wider annual rings during seasons when growing conditions are favorable and narrow rings when not. The rings are visible in a cross-section of the tree or log. The early wood layer is light colored whereas the late wood layer is dark colored. In tropical species, growth seldom stops and rings may not be apparent. Growth rings are also called annual rings.

Gymnosperm A plant whose seeds are not enclosed in flowers. The seeds are usually produced on the scales of female cones. Conifers are the most common gymnosperms. See also Angiosperm.

Habitat The area or environment in which a plant or animal (or community of plants and animals) lives and reproduces, including soil, vegetation, food, and water.

Hardwood Wood provided by broad leafed, deciduous trees, such as oak, maple, and ash, which shed their leaves each year. Hardwood trees bear flowers each year and belong to the group of trees known as angiosperms. Wood hardness varies within the hardwood species, with some varieties being softer than certain softwoods. Flooring for homes and furniture are two uses of hardwood. See also Conifer, Deciduous.

Harvesting The felling and gathering of forest timber.

Harvesting Method The form in which wood is delivered to the logging access road. This depends on the amount of processing (e.g., delimbing, bucking, barking, chipping). The different harvesting methods are: (1) cut-to-length logging (2) tree-length (3) full tree logging and (4) whole tree.

Harvesting System The tools, equipment, and machines used to harvest a wooded area. A typical cut-to-length logging system could employ a harvester, which fells, delimbs and bucks the trees in the stump area, and a forwarder to carry the pulpwood and logs to roadside. With the tree-length method a common system includes chain saws, delimbing and topping, tree-length skidding to roadside, and roadside slashing. A typical full tree harvesting system would include a buncher, grapple skidder, delimber and slasher.

Hauling The transportation of logs, usually from a landing to a mill or shipping point.

Hazard Reduction Burning The intentional burning of accumulated fuel under controlled conditions in order to reduce the fuel in an area, thereby reducing the risk of damage from wildfires.

Heartwood The inner core of a tree's trunk that is composed of dead cells, which no longer produce sap. It is darker in color than the outer layer of wood (sapwood). Heartwood contributes strength to the tree.

Hectare A measure of land area in the metric system equal to 10,000 square meters or 100 ares. It is also equal to 2.471 acres in British Imperial and U.S. customary measure. Hectare derives from hect, a contraction of the Greek word for hundred, and from the Latin word, area. A hectare is an area of 100 ×100 meters or one hundredth of a square kilometer.

Height/diameter Curve A graph indicating the relationship between tree diameters and heights. It is used to estimate the wood volumes of trees.

Herbaceous Vegetation Non-woody plants. These include grasses, flowers, and ferns.

Herbicide Any compound or mixture of chemicals used as a weed killer or to prevent the growth of weeds. Weeds are any woody or non-woody undesirable vegetation. Many herbicides are available to kill broad-leafed weeds such as dandelions. Compounds containing a high proportion of 2,4-D are able to kill trees, shrubs, and flowers. Weed killers may be classified as selective (affecting only certain plant species) or non-selective (affecting plants in general). They may be further classified as foliage-applied or soil herbicides. The EPA believes that 60 percent of all herbicides are carcinogenic.

High Grading The process of cutting and removing all mature, good quality trees from a stand and leaving all inferior trees and species uncut. High grading is a shortsighted harvesting approach, as it provides high returns at the expense of future growth potential. The natural regeneration will likely produce a poor-quality stand. High grading should not be confused with even-aged management in which both mature and immature trees are removed in order to aid regeneration.

Hoe-Chucking The use of an excavator or hoe to yard logs to the landing.

Humus A term that describes the dark material in soils produced by the decomposition of plant or animal matter.

Hydroseeding A method of seeding prepared land with a spray containing seed, fertilizer, water and a binder. It is useful in seeding banks or other places having significant gradients, which inhibit the use of conventional seeding methods.

Immature Timber A description of any stand in which the age of the main species is less than the designated age for harvesting. Conifers, with the exceptions of lodgepole pine and whitebark pine, are considered to be immature if less than 121 years in age.

Improvement Cut An intermediate cut to improve the quality of a stand. This may consist of removing undesirable tree species or poor quality and low-value trees in order to provide more space in which the best trees can grow.

Increment The increase during a particular period of the diameter, basal area, height, volume, quality or other attribute of an individual tree or stand.

Increment Borer An auger-like tool that has a hollow bit. It is used to extract cores of wood from living trees in order to study the annual growth rings of trees. It provides a non-destructive way to determine the ages and condition of trees. However, it can facilitate the entry of insects and disease to the wood. The cores that are extracted are called increment cores.

Indicator Species A species of plants that has a narrow range of ecological tolerance and suffers under certain conditions, such as pollution or stress. As a result, its presence (or health) serves to indicate whether a site's characteristics are favorable or unfavorable.

Indigenous Originating by natural means in the region or location where it was found.

Individual Tree Selection An uneven-aged harvesting method designed to favor tolerant species. Trees are removed individually to provide sufficient area and light for tree regeneration. Also referred to as single tree selection.

Industrial Forester A professional forester who is employed by a forest-based industry. He may be responsible for purchasing timber for a sawmill, managing woodlands, or helping to improve forest management practices, etc.

Inoperable Land Land that is unsuitable for the production of timber due to its elevation, inaccessibility, topography, soil, or other characteristics.

Interdependence A reciprocal relation between interdependent objects, groups, or individuals. Dependence on each other for resources, information, or services.

Intermediate Trees Medium sized trees whose crowns extend to the general level of the canopy, but receive little direct light from above and almost none from the sides. Their crowns are usually small and crowded on all sides.

Intermediate Cutting A cutting undertaken to modify or shape the development of standing trees, rather than for regeneration.

Intolerant Species Trees that do not thrive in the shade of other larger trees. They require full exposure to direct sunlight. Also termed shade-intolerant trees (or species).

J-Root A seedling that assumes a j-shaped configuration in the soil because it was improperly planted. Seedlings with J-roots grow poorly and are susceptible too windthrow. J-root is also known as L-root.

Juvenile Spacing A cutting undertaken to reduce the number of trees in a young stand, often while the main stems are too thin to be saleable. This action improves growing conditions for the trees remaining. Juvenile spacing is also called precommercial thinning. See also Precommercial Operation.

KG Blade A specialized bulldozer-mounted blade used to shear, or split apart, leftover stumps at their bases to help clear land for tree regeneration.

Kiln-Dried Lumber Lumber that has been dried in a kiln to a moisture level of 6 to 12 percent. Some varieties of softwood lumber are dried to a somewhat higher percentage. See also Air-Dried lumber.

Knot The hard cross section of wood, which is visible in a plank or other piece of wood, that previously was the junction of a branch or limb of a tree with the tree trunk. See also Blemish, Clear.

Knuckleboom Loader A self-propelled, hydraulically-operated loading boom that is used to load logs onto a truck. There are also smaller versions, which can be mounted directly onto trucks.

Laminar Decay A term applicable to decayed wood that separaties easily along its growth rings. Laminar decay is also called delamination.

Landing A cleared area in a logging operation where logs are accumulated prior to being loaded on trucks for transport to a sawmill or other facility. Also called deck, ramp, or set-out.

Landing Pile A pile of slash, logging residue, and stumps in the landing area, that is created by harvesting operations and preparing logs for transport to the mill. Also called a cull pile.

Laps See Slash.

Latewood See Summerwood.

Liquidation Cutting The harvesting of all merchantable products from a stand or wooded area without regard to regeneration or improvement, normally in advance of a sale of the land.

Litter Layer The surface layer of organic debris on the forest floor that has not yet decomposed. This consists of leaves, needles, bark, stems, twigs, and fruits.

Loam A loose textured soil of high fertility. Loam is largely a mixture of clay, sand, and decomposed vegetable matter. The word is often used in reference to any good topsoil. See also Clay Loam, Loam, Sandy Loam, Soil, Topsoil.

Log A portion or length of the log, or of a large limb, of a tree. A log should be a section of at least 8 feet in length and not contain a fork.

Logger A person who earns his livelihood by cutting standing timber and delivering logs for processing.

Logging The process of harvesting trees, sawing them to desired lengths, and transporting them to a sawmill. See also Timber.

Logging Trail A narrow path for temporary use in transporting equipment for harvesting.

Log rule See Volume Table.

Logging Debris The unused and relatively unmarketable accumulation of woody material and residue that remains after timber harvesting. This includes tops, stumps, large limbs, and cull logs.

Longwood Pulpwood logs that exceed 15 feet in length.

Lopping Cutting off branches and the tops of trees after felling trees into lengths. Also, that which has been cut off.

Lowboy A type of flatbed trailer used to haul heavy machinery or off road equipment, such as a skidder. See also SKIDDER.

Lumber Timbers sawed into planks, boards, etc., at a sawmill and not further processed, except by sawing, resawing, passing lengthwise through a planing machine, and cutting to length. Wood suitable for use in construction. All lumber is graded for quality. Generally, higher quality lumber costs more. In addition, hardwood lumber costs more than softwood lumber. See also Board, Timber.

Lump-Sum Sale A timber sale where all marked standing trees are sold to the highest acceptable bidder for a single price before the wood is cut and removed. See also Unit Sale.

Marking Timber The process of marking trees to cut in a harvesting operation, or to be left. The marking is normally done by spraying a spot of bright paint on the tree at eye level.

Mast The fruits or nuts of trees that serve as food for wildlife. Examples include hard mast, such as beechnuts, chestnuts, acorns, walnuts, hickory nuts, and pecans, as well as soft mast, such as cherries, persimmon, and dogwood seed.

Mat (Logging) See Bridgemat, Road Mats.

Mature Tree A tree that is ready to be harvested. It has achieved the desired size or reached the age for its intended use. This varies with the species and intended uses of the trees.

MBF The abbreviation for one thousand board feet, a standard unit of trade for lumber. See also Board Foot.

Mean Annual Increment (MAI) The average annual increase in the volume of individual trees or stands until a designated time has been reached. This varies by growth phase of the tree. The highest increments are experienced during middle years after which the MAI begins to decline. When the MAI value peaks, the stand is considered to be mature and ready for harvesting.

Mean Stand Diameter (MSD) The arithmetic mean of tree diameters in a stand.

Merchantable Height The height of a tree trunk, above which the wood is not saleable. The minimum acceptable diameter of a trunk is normally 4, 6, 8, or 10 inches, measured inside the bark. Trunks that have diameters less than this are not saleable. Similarly, wood beyond a point on a tree where any defect, which cannot be processed out, is found may not be saleable. Merchantable heights are determined by local markets.

Mill Site Any area where logs or trees are stored, altered, or processed.

Mineral Soil A soil that is composed primarily of mineral matter. Organic matter normally accounts for less than 20% of its mass.

Mixed Hardwoods A stand in which there is a mixture of hardwood species.

Mixed Stand A stand in which there are two or more species of trees. No species accounts for more than 80% of the trees in the main canopy.

Monoculture In agriculture, the farming of only one crop (e.g., wheat). In forestry, monoculture is the cultivation of an even-aged, single-species of tree.

Mulch Any loose material or mixture of materials, such as wet straw, leaves, grass clippings, peat moss, bark, wood chips, straw, etc., which are deposited on the ground around the trunks of newly planted trees or the stalks of other plants in order to protect their roots from drying or freezing.

A loosely added mulch of two to three inches in depth prevents the upper surface of the soil from packing and scaling off and enables more water to soak into the ground. Mulch retards evaporation, thereby improving water retention. Further, it helps to prevent growth of weeds and grasses, reserving water for use by the tree or shrub. It also insulates the soil from the sun, resulting in lower soil temperatures. This aids root growth. It also protects soil against the adverse effects of the wind. Mulch, when mixed into the soil, introduces nutrients which promote root growth. However, an excess buildup of mulch around the trunk of trees and shrubs can harm the plants.

Natural Regeneration Forest renewal brought about by natural replacement without human assistance. Nature's means are natural seeding, seeds carried on the wind or by animals, and sprouts growing from stumps.

Natural Stand A stand of trees that regenerated by natural means. The trees are the result of natural seed fall or sprouting.

Nominal Dimensions A reference to lumber’s dimensions when first cut, rather than after drying and subsequent “dressing.” For example, if the nominal thickness of dressed lumber is 1,” the actual thickness will be ¾.” If the nominal thickness of dressed lumber is 2,” the actual thickness will be 1 ½.” If the nominal width of dressed lumber, which is 2” thick or less, is under 8,” the actual width will be ½” less. If the nominal width of dressed lumber, which is 2” thick or less, is 8” or more, the actual width will be ¾” less. See also Board, Lumber.

Non-Renewable Any resource that can be used only once. Its quantity is finite.

Nurse Log A large fallen log, which is in the process of decomposing, in a forest or wooded area. Because it provides moisture and nutrients to a variety of insects and plants, it is called a nurse log.

Nutrients Elements necessary for plant growth and reproduction that are naturally present in the forest environment. The primary nutrients required are nitrogen, phosphorous, and potassium. They are also available in commercial fertilizers.

Old Growth Forest A forest that has not been significantly changed or harvested by humans. It contains large individual trees, a wide variation in tree sizes, and accumulations of large dead trees, both standing and fallen. The old growth forest has many canopy layers; gaps in the canopies, understory patchiness, and elements of decay, such as broken or deformed tree tops or trunks and root decay.

On The Stump A descriptive term for standing timber, uncut timber.

Organic Soil Any soil in which organic matter accounts for more than 20 or 30 percent of the content.

Overmature A term that is applicable to any tree that has declined in growth rate because of age and loss of vigor. Also, any stand of trees, which are older than the normal rotation age for the species.

Overstocked A very dense stand or wooded area. The trees are so closely spaced that they compete for resources and do not attain full growth potential. See Stocking.

Overstory The uppermost level of the forest canopy. It consists of the crowns of the dominant, codominant, and intermediate trees.

Overtopped Trees that receive little direct sunlight because their crowns are completely below the general level of the canopy of the forest. Overtopped trees that are intolerant to shade lose vigor and die.

Overtopping Vegetation that is higher than a favored species. The shading and suppressing of coniferous trees by brush would be an example.

Partial Cut A harvest that removes only part of a stand.

Partial Cutting See Thinning

Patch cut To clear-cut a small area. See also Clearcutting.

Pathogen Any disease-producing microorganism, often microscopic, such as bacteria, fungi, and viruses.

Pedology The field of study concerned with the origin, nature, properties, formation, and classification of soils. See Soil.

Perennial A plant which normally grows for more than two growing seasons. Typically, a perennial blossoms and bears fruit during each growing season.

Pesticide A chemical or other substance used to destroy plant and animal pests. Many insects and other organisms are harmful to plant life, including fungi, weeds, and other forms of plant or animal life. Pesticides must be applied in strict accordance with federal, state, and local government regulations.

The EPA approved many pesticides for use long before research had established a link between those chemicals and cancer, birth defects, and other diseases. Today it appears that 30 percent of all insecticides are carcinogenic. Further, it has been estimated that pesticides contaminate the groundwater in 38 states, polluting the primary source of drinking water for much of America's population.

pH A measure of the relative acidity or alkalinity of a substance, whether water, soil, or anything else. pH values range from acidic to alkaline on a scale of 0 to 14 on which 7 is neutral. A soil of pH less than 6.6 is considered to be acidic. A soil of pH greater than 7.3 is considered to be alkaline. The pH scale is logarithmic. Consequently, a soil having a pH of 5 is ten times more acidic than one having a pH of 6. Soils, which have a pH in the range of 6.6 to 7.3 can be considered to be neutral and usually provide a good medium for plants. However, plants grow well in mildly acidic soils of pH 5.5 to 6.5. Many plants have a tolerance to acidity of only a range of two or three on the scale. Consequently, limestone is sometimes added to a soil in order to increase its pH and make it more alkaline. Aluminum sulfate, powdered sulfur, or peat moss causes soil to become more acidic and lowers the pH. See Acid Soil, Alkaline Soil.

Phloem The layer of tree tissue just beneath the bark that carries sap from the leaves to the stem and roots. The phloem is also called inner bark. See Cambium, Heartwood.

Photosynthesis The synthesis of glucose and oxygen in plants from water and carbon dioxide, using sunlight as the energy source.

Pioneer Plants A term applicable to plants that are the first trees to develop in an area following its abandonment or a disturbance that exposes the soil. Paper birch and aspen are examples of pioneer species. A pioneer plant remains there until supplanted later by another species.

Plank A long flat piece of timber thicker than a board, typically two inches or more, and approximately five inches or more in width. See also Board.

Plantation A planted stand of trees, typically in equally spaced rows.

Pole Stand A stand of trees that has an average diameter at breast height between 4 and 10 inches. Also called pole timber.

Precommercial Operation The cutting of wood that is too small to be marketed. This is an intermediate harvesting operation in a young stand to improve the species composition and increase the rate of growth, quality and vitality of the trees that remain. It is also called precommercial thinning. See also Juvenile Spacing

Prescribed Burning The intentional and controlled use of fire in a specific area of land in order to achieve predetermined resource management goals. Fire is used under supervision and specified weather conditions to enable it to be confined to a predetermined area. The practice is undertaken in order to reduce the accumulation of fuels on the forest floor, to reduce competing vegetation, or to prepare the seedbed. Also called controlled burning.

Prescription A planned action, or series of actions, designed to effect changes to a stand in order to fulfill management goals, such as planting, harvesting, or timber stand improvement, etc.

Preservative Any chemical substance that, if used, will help to preserve the condition of something. Typically, the term is used in reference to chemicals, which will prevent the action of wood-destroying fungi and borers of various kinds on wood, if the wood has been adequately coated or impregnated with it..

Commonly used wood preservatives include pentachlorophenol or creosote (for wood to be buried underground); chromated copper arsenate (CCA) for wood, buried or above ground; and paint or stain for wood exposed above ground.

Pentachlorophenol and creosote are used mainly to protect heavy timbers, such as railroad ties and telephone or utility poles. CCA is used for the treated lumber available from lumberyards or home centers. It imparts a greenish tinge to the lumber.

Pressure Treatment The process of impregnating wood with chemical preservatives, which are toxic to insects and fungi and will remain in the wood. Chromated copper arsenate (CCA) is a commonly used preservative. It gives a greenish tinge to the wood. Pressure-treated wood can be painted or stained. Like untreated wood, it will also warp, swell, and crack. The use of pressure-treated wood is particularly appropriate for framing and supporting posts, which will be in contact with the ground.

Primary Logging Road A road that is constructed for a great deal of use. It usually has ditches on both sides, a surface of gravel or clay, and can be used during most weather conditions. It is normally part of a larger, permanent road system. A primary logging road is also called a haul road or truck road.

Prospectus A document that is prepared to supply information about standing timber to be sold. It gives the property location, the number of trees that have been marked for cutting by diameter class and a volume estimate for each species. The prospectus advises that the timber will be sold in accordance with the terms of a suitable contact.

Pruning The act of sawing or cutting side branches of live trees, usually plantation-grown trees. Pruning is undertaken in order to improve to encourage the growth of clear, valuable wood on the tree trunk. This is also called side limb pruning. The market value of the final wood product is greater if the wood is knot-free. The side branches of young trees are also trimmed in order to develop straight, central trunks. Then, the pruning is called corrective pruning

Pulp The fibrous raw material used in papermaking. It consists of a slurry of beaten and refined plant fibers to which chemicals and fillers are added. Pulp is 99.5% water. In the papermaking process, pulp forms a matted or felted sheet on a moving screen as moisture is removed.

With the exception of some special papers, such as asbestos paper, all papers are made from cellulose fibers. Trees are the most abundant source of cellulose. The raw materials are separated into fibers by mechanical or chemical means. Mechanical pulp, also called groundwood pulp, is normally produced by a mechanical grinding process. Chemical pulps are classified as bleached sulfite, unbleached sulfite, bleached and unbleached sulfate, and soda.

Pulpwood Wood that is suitable for use in the manufacture of paper. Pulpwood trees are those, which are unsuitable for lumber. However, they usually have a diameter of at least 4 to 6 inches.

Pup Trailer A trailer that is used to carry logs, often by a tri-axle log truck. A pup trailer is also known as a tag-along trailer. See also Tri-Axle Log Truck.

Pure Stand A stand in which a single species accounts for 80% or more of the trees in the main canopy area.

Ramp Another term for landing. See Landing.

Reforestation The natural or artificial restocking of a forest area with trees. Also called forest regeneration. The planting, seeding of a forest area.

Regeneration The renewal of tree cover by the establishment of young trees naturally or artificially. Also, the process by which an area of land is reseeded and renewed.

Regeneration Cut A timber harvest of old trees in order to ensure the maintenance of favorable conditions for the establishment of a new stand of seedlings.

Regrowth Forest A forest that has grown back after the area has been burned, logged, or subjected to some other disturbance. A forest in which most mature trees have been cut.

Reserves The retention of live or standing, pole size or larger, on the site following harvest for purposes other than regeneration. They may be uniformly distributed as single trees or left in small groups.

Residual Trees that are left intact to grow further in a stand after any harvesting operation. They form what is called a residual stand or residual trees.

Resin A semi-viscous liquid that is exuded by certain trees and plants. It appears on the external surface of the plant, if wounded.

Resinosis The excessive flow of resin or pitch in a conifer, in response to injury or disease.

Road Mat Large wooden pallets that are laid end to end on the ground to form a temporary road surface into and out of the woods. Road mats are normally used on flat terrain in wet or soft ground conditions. They are also useful in creating a stable loading area for trucks.

Root Ball The clump of soil and intact network of roots of a tree or any other plant, often balled and burlapped.

Root Collar That part of a tree or seedling where the trunk joins the main roots. This is typically at or near ground level.

Roots The portion of the tree that is underground. The roots reach out to absorb water and nutrients from the soil, and also anchor the tree.

Rot: In forestry, a state of decay in a log or standing tree caused by fungi. See also Decay.

Rotation The period required to establish and grow trees to a desired size or maturity. Rotation is the planned number of years between regeneration of a stand and its final cutting at a designated maturity. Pine rotation can be as short as 20 years for pulpwood and more than 60 years for saw logs.

Roundwood Wood products that are cut to length, but otherwise used in their original form, with or without bark. Examples include posts, poles, pulpwood, and firewood.

Royalty In forestry, payment for the right to extract forest products from an owner's land. Land owners, who lease their rights to others, receive royalty payments, which are negotiated in advance.

Sale, Lump Sum (Boundary) The sale of specified timber growing in a specified stand or area. It is the buyer's responsibility to determine the correct volume of wood The seller may or may not publish an estimate. This seller only guarantees the ownership and boundaries of the area.

Sale, Unit A timber sales agreement in which the amount paid depends on the quantity of forest products removed. The quantity is verified by scale sticks, mill tally, and computation by buyer or seller. The units of measurement may be cords, board feet, or pounds.

Salvage Cut The harvesting of dead or damaged trees, or trees for which there is a risk of loss due to disease, flooding, or insects, etc. The cutting is undertaken to secure the present value of the trees and avoid a possible loss. It may also be undertaken as a salvage operation following an infestation, windthrow, or other natural disaster.

Sandy Loam Soil comprised of sand, silt, and clay in proportions of 50 to 80 percent, less than 50 percent, and less than 20 percent respectively. See also Clay Loam, Loam, Soil.

Sapling An imprecise term used to describe a young tree that is no longer a seedling, but not yet a pole. A sapling has a diameter at breast height of 2 to 4 inches and a height of more than 4 or 5 feet.

Sapwood See Xylem.

Saw Log A log or tree that is large enough (usually 10 to 12 inches in diameter at breast height) and of suitable quality to be sawed economically into lumber. The minimum log length is normally eight feet. Also called sawtimber.

Scaling The process of measuring the lengths and diameters of logs, and using the customary calculations to determine the gross and net volume.

Scalping Site preparation work that involves removing small plants and duff or ashes from the area where a tree seedling will be planted in order to expose the soil. This is usually done by hand with a blade, rather than by machine.

Scarification A loosening of the soil surface by mechanical action in order to prepare the ground for seeding.

Screefing Another term for scalping. See Scalping.

Sealed Bid Sale A sale in which interested parties must submit their bids in writing at a specified time and place.

Season To dry green lumber (remove its moisture) by the passage of time to prevent later shrinking or warping. Also, to otherwise treat lumber to prevent shrinkage or warpage. See also Air-Dried Lumber, Green, Kiln-Dried Lumber.

Secondary Logging Road An unimproved road. Secondary logging roads are often bare dirt or grassed soil, which can be used only during dry weather. They normally have no additional surface. A secondary logging road is also known as a woods road, dim road, or 2-trail road.

Second Growth Timber, which has grown to replace a previous stand of timber, or portion thereof, which has been removed or otherwise eliminated. See also Timber.

Secondary Logging Road A road designed for relatively little use and only during dry weather. A secondary logging road is normally a dirt road. No gravel is involved.

Section One of the 36 equal parcels of land forming a township. The section provides an important reference in legal descriptions of land. Each section is a one-mile square having an area of 640 acres. In all townships, section number 1 is located in the extreme northeast corner of the township. The numbers, which identify sections, rise consecutively from east to west across the northernmost row of sections to number six. The second horizontal row begins directly under number six and proceeds from west to east from 7 through 12. Sections in the third row are numbered from east to west, etc. Sections may be subdivided into half sections and quarter sections. Quarter sections are identified as corners, such as the Northwest Corner of Section 11 (NW ¼ of Sec.11). See also Acre.

Seedbed An area that has been prepared to receive seeds by natural or artificial means. In the case of natural regeneration, it might be an area of soil or forest floor, which has been cleared of plants and duff, in order that the natural seed fall can establish a new forest. In the case of artificial regeneration, it will be a prepared (nursery) area in which seed will be sown.

Seedlings A tree, usually less than two inches in diameter at breast height, if grown from seed, rather than from sprouts. Also, nursery-grown trees that have not been transplanted yet.

Seed Lot The designation for a group of cones or seeds that have a common factor, such as the stand where they were collected, the year in which they were collected, or some other factor.

Seed Orchard A plantation operated for the production of seeds of specific tree species or new varieties.

Seed Tree Cut A method of harvesting that leaves a few scattered trees to provide a source of seeds for natural regrowth of the stand. Only trees that have good growth rates, form, seeding ability, wind firmness, and an absence of serious damage from disease should be selected. This will produce an even-aged stand or forest. After successful regeneration has begun, the seed trees can be removed.

Selective Logging The removal of specific trees in a stand that fit predetermined criteria (e.g., species, diameter at breast height, height, form). Selective logging should not be confused with the selection method.

Selection Method A harvesting method in which mature timber, usually the oldest and largest trees, whether scattered individual trees or in small groups, is cut at short intervals, repeated and indefinitely, to ensure the maintenance of uneven-aged stands and a sustained yield. Deformed and undesirable trees are also removed in order to provide space for the uncut trees. The selection method is used in the management of shade-tolerant species. It is also called Selection Silvicultural System, Selection Cutting, Selective Cutting, and Selection Harvest. See also Clear Cutting, Timber.

Set-out See Landing.

Shade-Intolerant Trees See Intolerant Species.

Shade-Tolerance The ability of a tree to maintain vigor, grow, and reproduce, in the shade of other trees. Species, such as cottonwood, black walnut, red and white oak, sycamore, and pin oak are intolerant to shade. The ratings of shade-tolerance are: very tolerant, tolerant, intermediate, intolerant, and very intolerant.

Shade-Tolerant Species Trees that are able to grow and thrive in the shade of other trees. Examples include beech, hemlock, red spruce, and sugar maple. See also Intolerant Species.

Shearing The process of cutting or slicing trees or stumps at ground level. This may be done during harvesting, or with a KG blade, a type of specialized bulldozer blade, during site preparation.

Shelterwood Cut The removal of all mature trees in the harvested area in a series of two or more cuttings over the period of the rotation. This ensures that that new seedlings can grow from the seeds of older trees and that there are mature trees to produce adequate shade to protect the young seedlings growing beneath them.

Half to three-fourths of the stand is cut on the first cut, enabling direct sunshine to penetrate the upper canopy. This encourages the growth of sprouts and new seedlings. When the lower story is fully stocked, the remainder of the old overstory is harvested. This helps both shade tolerant and shade intolerant species to develop. This harvesting method produces an even-aged forest. A shelterwood cut is also called shelterwood, shelterwood harvest, and shelterwood silvicultural system.

Shepherd's Crook A branch that has a tip curved down in the shape of a shepherd's crook. It is the result of an attack by certain insects or pathogens. See also Crook and Fork.

Shot Holes A series of small holes in a leaf that suggests shotgun damage, but which are the result of feeding activity.

Shrub A woody, perennial plant that is smaller than a tree and usually has permanent stems, which branch from, or near, the ground. It has little or no central stem.

Silvics The study of the characteristics and history of forest trees and stands in relation to environment factors.

Silviculture The art and science of the cultivation of forest trees. It involves establishing, tending, controlling, and reproducing forest stands and woodlands that have the characteristics desired.

Silvicultural Practices The maintenance of forest productivity, restocking of denuded forestland with commercial tree species, and protection against damage by fire, insects and diseases. Silviculture activities encompass all forest management activities, including seed collecting, site preparation, artificial and natural regeneration, brushing, spacing and stand tending, tendering, harvesting, logging, log transport, forest roads, and replacing forest trees.

Single Tree Selection See Individual Tree Selection..

Site Index(SI) A measure of the relative productivity capacity of a wooded area based on the height (in feet) of the dominant trees at a specific age (usually 25 or 50 years), depending on the rotation period. The site index is the average height of a particular species of tree of age 50 (or 25) years. The index varies by species. It helps to estimate future land productivity.

Site Preparation The preparation of an area of land for planting of trees, whether by natural reproduction or direct seeding. The various operations undertaken may include any of the following: mechanical clearing, burning, piling unusable woody debris, burning excess material, disking, bedding or furrowing, applying chemicals. Site preparation differs from land clearing operations undertaken to assist in a change of land use to a non-forestry purpose. In the latter instance, all material is scraped from the ground to expose the soil and stumps are removed.

Skidder A tractor-like machine available in a rubber-tired, 4-wheel drive model, which is articulated in the middle for greater maneuverability, or a caterpillar track-mounted model. A skidder is used to bring logs or whole trees to the landing after they have been felled. It pulls the logs by cables or chains attached to a winch at the rear of the tractor, or seizes them in a grapple also mounted in the machine.

Skidder Bridge See Bridgemat

Skidding The process of dragging trees from where they fell to a landing. Tractors, horses, or specialized equipment may be used. However, the term is usually associated with ground-based methods, rather than a high lead operation. The various skidding methods vary in their impact on the remaining stands.

Skid Trail Any temporary pathway in the woods along which logs are dragged to the landing.

Skyline A type of cable logging system in which a cable is suspended between two points. A carriage, traveling along it, carries logs high above the ground from the felling site to the landing.

Slab An outside, rounded piece side of a log that is removed when squaring the log for lumber.

Slash Tree tops, branches, bark, or other residue left on the ground as a result of logging or other forestry operations. Also, the tree debris left after a storm, fire, or other natural catastrophe. Slash is also known as laps.

Slope A measure of the steepness of the ground. The degree of deviation of a surface from the horizontal. It is expressed as a numerical ratio, a percentage, or in degrees. When expressed as a ratio, the first number is the horizontal distance (run) and the second is the vertical distance (rise), as 2:1. A slope of 2.1 is a 50 percent slope. When expressed in degrees, the slope is the angle from the horizontal plane, with a 90-degree slope being vertical (maximum) and a 45-degree slope being a 1:1 slope.

Snag A standing dead tree. Snags can often provide good habitat to a variety of birds and small animals. Consequently, if they do not constitute a safety hazard, they can be left in place.

Soft Wood The wood from a coniferous (cone bearing) tree, such as pine, spruce, fir, and cedar. The term, softwood, has no direct relationship to the hardness of the wood. Instead, the term soft wood denotes wood from trees, which belong to the botanical group of trees known as gymnosperms. Such trees are coniferous, except for cypress, larch, and tamarack. Examples of softwoods include pine, cedar, and fir. See also Conifer, Deciduous, Hard Wood.

Soil The ground or upper layer of the Earth in which plants grow and which consists of disintegrated rock, usually with vegetable or animal matter and mold. Soil is a source of plant nutrients, including water and oxygen, for growth and reproduction. A soil's most important chemical characteristic for plant growth is its degree of acidity or alkalinity. This affects its suitability as a growing medium. Texture, structure and porosity of a soil also affect plant growth.

Texture refers to the feel of a soil. Sandy soils are coarse and gritty, whereas clay soils are smooth and sticky. Soil texture is defined by the relative proportions of sand, silt and clay particles. Soils having a high content of sand or gravel are porous and have a low water-holding capacity, but afford good drainage. Conversely, soils having a high proportion of silt possess greater water-holding capacity. In addition, they contain a variety of minerals. Particularly important is the clay content of a soil. Clay particles influence the water retention capacity of soil, in addition to providing nutrients. The proportion of clay particles also affect the capacity of a soil to swell and shrink and the stickiness of the soil. Sand particles are approximately 100 times larger than clay particles. Silt particles are intermediate in size.

Soil structure refers to the physical arrangements of mineral and organic particles and determines the shapes, sizes and porosities of different aggregates. A good soil structure permits movement of air and water and increases the soil's resistance to erosion.

Soil porosity refers to the total space of pores filled with either air or water. It determines soil drainage, the volume of water or air, which the soil can hold, and the depth to which roots may penetrate. Compaction of soil during construction may remove good soil porosity.

Soil names are based on the sizes of particles, which comprise them. Examples include silty clays and sandy clays. Loam describes a soil, which has approximately equal parts of clay, silt, and sand. Organic matter comprises only a small percent of most soils. The micro-organisms in soil contain millions of individual microbes, primarily bacteria, fungi, algae, and protozoa, which serve to decompose plant residues leaving nutrients behind for roots to absorb. See also Acid soil, Alkaline soil, Loam, Sandy Loam, Soils Map, Subsoil, Topsoil.

Soil Productivity The capacity and suitability of a soil to support the growth of a specific plant species.

Soils Map A map depicting the different soils of a specific region. A soils map helps one to select the type of vegetation best suited to the specific area. Different species of plants do better or worse in differing soil conditions. For example, some plants grow better in wet ground whereas others thrive in dry soils. Also, the map enables one to determine the nature of the vegetation of an area not yet visited. See Soil.

Soil Texture See Soil.

Soil Type See Soil.

Species A group of related organisms that have common characteristics and can interbreed freely with each other, but not with members of other species.

A subspecies is a subdivision of a species. Endemic species are species that originated in, or belong to, a particular region. In contrast, exotic species are species, which have been introduced to a region unintentionally.

Springwood See Earlywood.

Sprout A shoot of a plant, such as a tree, that begins to grow from a recently cut stump or from an already established system of roots.

Stand An area of forest that is easy to define geographically and is sufficiently uniform in tree species composition or age that it can be considered to be homogeneous and managed as a single unit. A stand may be a pure stand (composed mostly of a single species of trees) or a mixed stand (composed of a mixture of tree species). A stand is also known as a stand treatment unit.

Stand Density A relative measure of the total stocking of a stand of trees. It is usually expressed in square feet of basal area per acre. See Basal Area.

Standing Timber Timber that is still on the stump. Unharvested timber. See also Stumpage, Timber.

Stand Structure A description of the composition of the stand in terms of tree species, size, age, or any other factors or combination of factors that are considered to be important.

Stand Type See Forest Type.

Stocking A measure of the area occupied by living trees. It may be expressed as the number of trees per acre or hectare, or the basal area per acre or hectare. A forest stand is often described as being over-stocked, well-stocked, or understocked.

Stocking Class A numerical designation that indicates a range of stems per hectare applicable to a particular stand or wooded area. Stocking class #1 refers to land that has 76 or more mature stems (BDM in excess of 27.5 cms.) per hectare. Class #2 has less than 76 mature stems per acre. Class #0 has no mature trees.

Stocking Level The number of trees in a specific area compared to the desired number for best results. The stocking level is calculated by comparing the basal area or number of trees that could be supported if the land's growth potential was fully utilized to the actual area or number at present.

Stumpage A term referring to standing timber when considering its value for cutting. That is, the value or volume of a tree or trees as they stand in the woods uncut (on the stump). Loggers usually bid on timber based on its stumpage value. The term is sometimes used to denote the price paid for the timber or the right to cut such timber. See also Standing Timber, Timber, Timber Operation.

Stump Height The vertical distance from the top of the stump to the ground on the uphill side of the stump. Stump heights of less than 12 inches are recommended in order to reduce waste and minimize their negative visual impact.

Subsoil The layer of earth immediately below the surface soil. Subsoil is known also as undersoil. See also Soil, Topsoil.

Succession The natural replacement over time of one plant community by another in the absence any factor that would disrupt this. The cycle begins with bare ground and ends when a climax forest has been reached. The process is known as a sere. Each stage in the process is a seral.

Summerwood A term that describes the wood cells that are produced near the end of the growing season and are found in the darker section of the annual growth ring. Also called latewood.

Suppressed A class of small trees that have crowns, which are entirely below the general level of the forest canopy. Because they receive no direct sunlight, they experience low vigor and growth rates. See Overtopped.

Surplus Forest A forest that can more than sustain its present level of harvest volumes over the long term until the new stands created, when the existing ones have all been cut down, will be available for harvesting. See also Deficit Forest.

Sustainability The ability to be maintained indefinitely. In particular, the term applies to the ability of an ecosystem to maintain over time its ecological processes, biodiversity, and productivity.

Sustainable Forest Management The management of forestland in a manner designed to sustain the yield of wood harvested while maintaining indefinitely its productive capacity.

Sustained Yield An approach to forest management that seeks to produce a constant amount of wood for a long time. This requires balancing the net growth of standing timber with the volume of wood harvested.

Sweep A gradual curve in the main stem of a standing tree, pole, or log.

Tag-Along Trailer See Pup Trailer.

Thinning A partial cutting undertaken in an immature, overstocked stand to reduce tree density and competition among trees in the stand. By suitable selection, it corrects overcrowding and concentrates growth on fewer, high-quality trees. This enhances tree vigor and subsequent growth in diameter to improve the average of the uncut trees.

Commercial thinning is the harvesting of trees for sale or use. Non-Commercial Thinning is necessary stand improvement work that is undertaken, although no marketable product can be salvaged from the trees to be removed.

Timber Growing or standing trees of commercial size or felled trees or logs, which are suitable for sawing. Also, wood prepared for structural or building purposes and measuring five inches or more in its smallest dimension. The term, timber, also describes wooded land. Timber forms part of the land until cut. See also Clearcutting, Logging, Second Growth.

Timbered Wooded or forested. Blanketed with growing trees.

Timberland Forestland. Land covered with forest. See also Second Growth, Timberline, Undergrowth.

Timberline The line of demarcation on mountains and in arctic regions above which no trees grow. The term, timberline, also refers to the boundary of an expanse of timber. See also Timber.

Timber Management The act of managing a forest resource to continuously grow taller quality trees in shorter periods of time. This requires a knowledge of the timber inventory, its rate of growth, and the maximum potential of the site. The use of management practices normally improves growth rates.

Timber Operation A term used to describe the planting, cultivating, caring for, or cutting of trees, or other operations, excluding milling, to prepare them for market. See also Logging, Stumpage, Timber.

Timber Rights A profit à prendre, which permits its owner to cut and remove timber from another person's land. See Timber.

Timber Stand Improvement (T.S.I.) Any practice carried on in a stand or forest that improves the trees for any purpose, particularly if it makes them grow more quickly or improves their quality, or improves the composition of the stand or forested area. TSI includes pruning and thinning activities, the removal of undesirable species, and the elimination of competing vines and weeds.

Timber Supply The timber available classified by species or end-use.

Tolerance A term used to describe the ability of a tree species to grow in shade.

Tolerant Species See Shade-Tolerant Species.

Topsoil The surface soil of land. That upper portion of the soil which is rich in organic matter and particularly suited to plant growth. It has been estimated that more than three billion tons of topsoil are eroded from America's croplands each year. This is much greater than the topsoil that is replaced by natural means. See also Loam, Soil.

Toxicity The extent to which a substance is poisonous.

Total Maximum Daily Load (TMDL) The maximum amount of a pollutant that is permitted by government regulations to be discharged into a water body from all sources. It may be expressed in terms of toxicity, percentage concentration, or some other appropriate measure.

Transpiration The process in which water is absorbed by plants through their roots, moves through the plants, and is lost to the atmosphere through small openings on the underside of leaves called stomata.

Tree A large, woody, perennial plant that has a distinct, elongated, main trunk and secondary branches supported by the trunk. There are few branches on the lower part of its trunk. Trees are long-living compared to other plants. They usually attain heights of at least 20 feet by maturity.

Tree Caliper A device used to measure the diameter of a tree. It consists of one arm with a graduated scale and two prongs, one of which is fixed and one that is free to move along the scale.

Tree farm A privately owned stand or woodland devoted to timber production.

Tree-length Logging Method Trees are felled, delimbed and topped in the cut-over. Trees are skidded to roadside. The tree-lengths are bucked to pulpwood and logs at roadside, or can be left as tree-lengths for tree-length hauling to the mill. The tree-length method is most suited to clear felling.

Tree Spacing The distance between trees. Like stand density, spacing affects understory vegetation, growth rates, and production of seeds.

Tri-axle Log Truck A short type of log truck that carries the logs on a rack, which is attached directly to the truck frame. The truck is also called a bobtail or a 10-wheeler. Some tri-axle trucks pull a pup trailer, a short trailer used to carry logs.

Trunk The main stem of a tree, as distinct from its branches or roots..

Turpentine Any of various oleoresins derived from the sap of coniferous trees, particularly the longleaf pine.

Two-Aged Stand A stand that has two intermixed, but distinct, size classes of trees. One is an overstory of larger trees. They are dominant and noticeably taller than the trees of the second group, an understory of small trees.

Undergrowth The growth of smaller plants or bushes among, or below, larger ones.

Underplanting The planting of young trees under an existing stand.

Understory All plants and trees that are growing beneath the forest canopy. This includes small trees, shrubs, and snags. Many of these plants tolerate shade and will remain part of the understory, whereas others will grow and replace older trees that fall.

Uneven-Aged Management Forest management that produces a stand consisting of a variety of age classes and size classes - old, young, and mature. The harvesting methods used in this approach include individual tree and group selection. Uneven-aged management is also called All-aged management and Uneven-aged silvicultural system.

Uneven-Aged Stand A stand that consists of trees of all sizes and ages. More specifically, it has at least three distinct age classes of trees. In a balanced uneven-aged stand, the different age classes use approximately equal areas of land. An uneven-aged stand is created by means of intermediate cutting and regeneration harvests. Also called all-aged stand. See also Intermediate Cutting.

Unit Sale An arrangement for the purchase of timber in which the amount that the buyer pays for logs taken away depends on the number of units removed (e.g., cords, MBF, units of weight). The number of units for which payment must be made is determined by mill tally, scale tickets, and buyer or seller tally.

Unmerchantable Unsalable. The term describes any tree that does not meet the minimum size or quality standards necessary to make it acceptable to buyers and therefore suitable for harvesting.

Variable Area Plot Sampling Method A sampling method used in cruising for industrial timber. In this method, the sample area varies with tree diameter.

Veneer A thin layer of material, which is applied as an exterior finish to a less expensive and attractive material. Wall veneers are available in a variety of finishes including oak, maple, etc. In these cases, a thin veneer of the desired finish has been glued to a less attractive sheet of chipboard or other cheap composite material. Wood veneers are manufactured by peeling layers of wood from a rotating log by the use of a large cutting blade.

Veneer Log A large, straight, round log of minimum taper and desirable species that is without defects. It will be peeled, sliced, and stamped or sawn for later use in a variety of products

Vigor The overall health of a plant and capacity to grow and resist physiological stress. It is best assessed by observing the density, width and color of its foliage and percentage represented by its live crown.

Virgin Timber Timber from an original forest that has never been harvested.

Volume Table A table prepared that is used to estimate the volume of wood, usually in board feet, of a log based on its diameter and length. There are three different log tables in use. One is commonly used for pine and another for hardwood. The third is less used, but estimates best mill output. They are based on assumptions (log rules) concerning the processing of logs into boards. The term, log rule and log scale is often used in place of volume table.

Warp A term frequently used in reference to lumber. It denotes any variation from a true or plane surface. See Green.

Weed Herbaceous plant not valued for is use or beauty, but which propagates easily and competes with other plants for water, nutrients, and space.

Whole Tree Logging Method This method is often confused for the full tree logging. However, in the whole tree method, full trees including their stump are removed to the roadside for processing and utilization.

Wildfire Control Any actions taken to enclose and smother uncontrolled fires.

Wildfire Any unplanned and ucontrolled fire, such as a forest fire, a grass fire, or a fire in brushland.

Windrow An accumulation of slash, branchwood, etc., on harvested land resulting from work undertaken to clear it for regeneration.

Windthrow A tree that has been uprooted by excessive wind. Shallow-rooted trees, such as birch or white pine, are usually the ones affected. In addition, blowdowns are common in areas of shallow soils, or where cutting has reduced stand density, depriving the trees remaining of support.

Witch's Broom A term to describe dense clusters of small shoots or stems appearing on otherwise normal branches.

Wolf Tree A large, rough, older tree that has many limbs and a spreading crown, but little value for lumber. It is a dominant tree that occupies too much growing space for its merchantable volume. It is often a remnant from a previous stand.

Wood The hard, fibrous substance comprising most of the trunk and branches of a tree and lying below the bark.

Wood Chemicals Chemicals that occur naturally in various parts of a tree. Methyl alcohol (wood alcohol) is one chemical that is obtained by destructive distillation of wood.

Wood Chipping The process of grinding of logs harvested for pulpwood into small pieces of wood. This is the first stage in the production of pulp.

Woodland Land that is covered with trees and shrubs.

Woodlot A small forested area. Also, a wooded portion of privately owned property on which a small timber operation is conducted, or a tract set apart for trees

Xylem The layer of cells in the trunk of a tree that carries water and nutrients from the roots to the leaves and branches. The xylem is located between the heartwood and the cambium, the thin membrane located just below the bark. It is the light-colored wood that appears on the outer portion of a cross-section of a log or tree. Old xylem cells become part of the heartwood. The xylem is also called sapwood. See also Cambium, Heartwood.

Yard A cleared area in which logs or felled trees are accumulated for subsequent handling or processing. Also, to transport logs or trees from the woods to a loading area.

Yarder A highly specialized logging machine on wheels, tracks, or skids and on which are mounted a vertical tower or boom and power-operated winches. The machine is used to haul logs from the stump to a landing.

Science Glossaries

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