Dam: Barrier built across a stream, river, or estuary to conserve water for such uses as human consumption, irrigation, flood control, and electric power generation. The earliest recorded dam is believed to be a masonry structure 49 ft (15 m) high built across the Nile River in Egypt c. 2900 BC. Modern dams are generally built of earth fill, rock fill, masonry, or monolithic concrete. Earth-fill (or embankment) dams, such as Egypt’s Aswan High Dam, are usually used across broad rivers to retain water. The profile of an earth-fill dam is a broad-based triangle. Concrete dams may take various forms. The gravity dam uses its own dead weight to resist the horizontal force of the water. Concrete-buttress dams reduce material in the wall itself by using support buttresses around the outside base. An arch dam, such as Hoover Dam, is built in a convex arch facing the reservoir, and owes its strength essentially to its shape, which is particularly efficient in transferring hydraulic forces to supports.
Damselfly: Any of numerous predaceous insects of the suborder Zygoptera (order Odonata) having eyes that project to each side. When at rest, the damselfly holds its narrow, membranous, net-veined wings vertically rather than horizontally, unlike Dragonflies. Damselflies are more delicate and weak-flying than dragonflies but are similar in having male copulatory organs at the front part of the abdomen. They commonly fly in tandem during mating. (Pic)
Damp course: (Syn: Damp proof course) Waterproof layer in a brick wall: a layer of waterproof material near the ground in a brick wall that prevents damp from rising
Dampness: The access or penetration of moisture content inside a building through its walls, floors, or roofs.
Dandelion: Any of the weedy perennial herbaceous plants that make up the genus Taraxacum, in the Composite Family, native to Eurasia but widespread in much of temperate North America. The most familiar species, T. offıcinale, has a rosette of leaves at the base of the plant; a deep taproot; a smooth, hollow stem; and a solitary yellow flower head composed only of ray flowers (no disk flowers). The fruit is a ball-shaped cluster of many small, tufted, one-seeded fruits. The young leaves are edible; the roots can be used as a coffee substitute.
Darwinism: Theory of the evolutionary mechanism proposed by Charles Darwin as an explanation of organic change. It denotes Darwin’s specific view of how Evolution works. Darwin developed the concept that evolution is brought about by the interplay of three principles: variation (present in all forms of life), heredity (the force that transmits similar organic form from one generation to another), and the struggle for existence (which determines the variations that will be advantageous in a given environment, thus altering the species through selective reproduction). Present knowledge of the genetic basis of inheritance has contributed to scientists’ understanding of the mechanisms behind Darwin’s ideas, in a theory known as neo-Darwinism.
Darwin, Charles (Robert): (b. Feb. 12, 1809, Shrewsbury, Shropshire, Eng.—d. April 19, 1882, Downe, Kent) British naturalist. The grandson of Erasmus Darwin and Josiah Wedgwood, he studied medicine at the University of Edinburgh and biology at Cambridge. He was recommended as a naturalist on HMS Beagle, which was bound on a long scientific survey expedition to South America and the South Seas (1831– 36). His zoological and geological discoveries on the voyage resulted in numerous important publications and formed the basis of his theories of evolution. Seeing competition between individuals of a single species, he recognized that within a local population the individual bird, for example, with the sharper beak might have a better chance to survive and reproduce and that if such traits were passed on to new generations, they would be predominant in future populations. He saw this Natural Selection as the mechanism by which advantageous variations were passed on to later generations and less advantageous traits gradually disappeared. He worked on his theory for more than 20 years before publishing it in his famous On the Origin of Species by Means of Natural Selection (1859). The book was immediately in great demand, and Darwin’s intensely controversial theory was accepted quickly in most scientific circles; most opposition came from religious leaders. Though Darwin’s ideas were modified by later developments in genetics and molecular biology, his work remains central to modern evolutionary theory. His many other important works included Variation in Animals and Plants Under Domestication (1868) and The Descent of Man… (1871). He was buried in Westminster Abbey.
Date palm: Tree (Phoenix dactylifera) of the Palm family, found in the Canary Islands and northern Africa, the Middle East, Pakistan, India, and California. The trunk, strongly marked with the pruned stubs of old leaf bases, ends in a crown of long, graceful, shining, pinnate leaves. The fruit, called the date, is a usually oblong brown berry. Dates have long been an important food in desert regions, and are the source of syrup, alcohol, vinegar, and strong liquor. All parts of the tree yield products of economic value, being used variously for timber, furniture, basketry, fuel, rope, and packing material. The seeds are sometimes used as stock feed. The tree is grown as an ornamental along the Mediterranean shores of Europe. Its leaves are used for the celebration of Palm Sunday (among Christians) and the Feast of Tabernacles (among Jews). Date sugar, a product of India, is obtained from the sap of a closely related species, P. sylvestris.
Dating: In geology and archaeology, the process of determining an object’s or event’s place within a chronological scheme. Scientists may use either relative dating, in which items are sequenced on the basis of stratigraphic clues or a presumed evolution in form or structure, or absolute dating, in which items are assigned a date independent of context. The latter type includes Potassium-argon and Carbon-14 dating (See C-14 dating); both are based on the measurement of radioactive decay. The record of changes in polarity of the Earth’s magnetic field has provided a timescale for Seafloor Spreading and long-term marine sedimentation. Dendrochronology has proved useful in archaeology and climatology.
Daylighting: A practice in which trees shading an access road is removed to increase the sunlight on the roadway and along its periphery. This relatively inexpensive practice maximizes forest edge and cover for wildlife and maintains passable roads year- round.
Dead load: intrinsic weight of structure: the permanent weight of a structure such as a bridge, exclusive of its load (See also: Live load)
Deadwood: Timber produced from dead standing trees. More commonly, timber in dead standing trees.
Decapods: Any of more than 8,000 species (order Decapoda) of Crustaceans having five pairs of legs attached to the thorax. The shrimps and shrimplike species, which can be as small as 0.5 in. (12 mm) long, have a slender body with a long abdomen, a well-developed fantail, and, often, long, slender legs. The crabs and crablike species, whose claw span can measure 13 ft (4 m), have a flattened body and, frequently, stout short legs and a reduced tail fan. Decapods are primarily marine and are most abundant in shallow tropical waters, but they are commercially valuable throughout the world. Some species (e.g., Hermit and Fiddler crabs) are adapted to terrestrial environments.
Deciduous or deciduous tree: Broad-leaved tree that sheds all its leaves during one season. Deciduous forests are found in three middle-latitude regions with a temperate climate characterized by a winter season and year-round precipitation: eastern North America, western Eurasia, and northeastern Asia. They also extend into more arid regions along stream banks and around bodies of water. Oaks, Beeches, Birches, Chestnuts, Aspens, Elms, Maples, and Basswoods (or Lindens) are the dominant trees in mid-latitude deciduous forests. Other plants that shed their leaves seasonally may also be called deciduous. (See also Conifer, Evergreen).
Deck: Sometimes applied to stacks of logs. (Syn. log deck).
Decompound: Having divisions that are also compound.
Decumbent: Lying on the ground but having an ascending tip.
Decurrent: Descriptive of leaves whose edges run down onto the stem.
Deep chiseling: A surface treatment that loosens compacted soils.
Deer: Any of the Ruminants in the family Cervidae, which have two large and two small hooves on each foot and antlers on the males of most species and on the females of some species. Deer live mainly in forests but may be found in deserts, tundra, and swamps and on high mountainsides. They are native to Europe, Asia, North America, South America, and northern Africa and have been introduced widely elsewhere. Females are usually called does, and males bucks. Deer range in shoulder height from the 12-in. (30-cm) pudu (genus Pudu) to the 6.5-ft (2-m) Moose. They typically have a compact body, short tail, and long, slender ears. They shed their antlers each year, and new ones grow in. The general form of the antler varies among species. Deer feed on grass, twigs, bark, and shoots. They are hunted for their meat, hides, and antlers.
Defect: Any irregularity or imperfection in a tree, log, piece, product, or lumber that reduces the volume of sound wood or lowers its durability, strength, or utility value
Deficit financing: In government, the practice of spending more money than is received as revenue, the difference being made up by borrowing or minting new funds. The term usually refers to a conscious attempt to stimulate the economy by lowering tax rates or increasing government expenditures. Critics of deficit financing regularly denounce it as an example of shortsighted government policy. Advocates argue that it can be used successfully in response to a Recession or Depression, proposing that the ideal of an annually balanced budget should give way to that of a budget balanced over the span of a Business cycle.
Deflation: Contraction in the volume of available money or credit that results in a general decline in prices. A less extreme condition is known as disinflation. Attempts are sometimes made to bring on deflation (through raising interest rates and tightening the Money Supply) in order to combat Inflation and slow the economy. Deflation is characteristic of Depressions and Recessions.
Defoliant: Chemical dust or spray applied to plants to cause their leaves to drop off prematurely. Defoliants sometimes are applied to Crop plants such as Cotton to facilitate harvesting. They have also been used in warfare to eliminate enemy food crops and potential areas of concealment (as in the Vietnam War).
Defoliate: [Late 18th century Latin folium “leaf, page”] strip or lose leaves: to strip trees and plants of their leaves, e.g. by using chemicals or through pollution or attack by pests, or lose leaves in any of these ways
Defoliator: Any chewing insect that consumes the leaves or needles of plants.
Deforestation: Process of clearing forests. Rates of deforestation are particularly high in the tropics, where the poor quality of the soil has led to the practice of routine clear-cutting to make new soil available for agricultural use. Deforestation can lead to erosion, drought, loss of biodiversity through extinction of plant and animal species, and increased atmospheric carbon dioxide. Many nations have undertaken afforestation or reforestation projects to reverse the effects of deforestation, or to increase available timber. (See also Greenhouse effect).
Dehydration: Loss of water, almost always along with Salt, from the body, caused by restricted water intake or excessive water loss. Early symptoms of water deprivation are thirst, decreased saliva, and impaired swallowing. (When more Electrolytes than water are lost, osmosis pulls water into cells, and there is no thirst.) Later, tissues shrink, including the skin and eyes. Mild fever rises as Plasma volume and cardiac output decrease, and perspiration decreases or stops, greatly reducing heat loss. Urine output falls, and the Kidneys cannot filter wastes from the blood. Irreversible Shock can occur at this point. The cause of dehydration is treated first; then water and electrolytes must be given in the correct proportions.
Delinquency: Criminal behaviour carried out by a juvenile. Young males make up the bulk of the delinquent population (about 80% in the U.S.) in all countries in which the behaviour is reported. Theories regarding delinquency’s causes focus on the social and economic characteristics of the offender’s family, the values communicated by the parents, and the nature of youth and criminal subcultures, including gangs. In general, both “push” and “pull” factors are involved. Most delinquents apparently do not continue criminal behaviour into their adult lives but rather adjust to societal standards. The most common punishment for delinquent offenders is probation, whereby the delinquent is given a suspended sentence and in return must live by a prescribed set of rules under the supervision of a probation officer.
Deliquescent: A type of branching that is exhibited by an oak or maple tree. There is a short main trunk with irregular branching above the short main trunk. This is also known as Sympodial Branching. e.g., witches’ broom development.
Delta: Low-lying plain composed of stream-borne sediments deposited by a river at its mouth. Deltas have been important to humankind since prehistoric times. Sands, silts, and clays deposited by floodwaters were extremely productive agriculturally; and major civilizations flourished in the deltaic plains of the Nile and Tigris-Euphrates rivers. In recent years geologists have discovered that much of the world’s petroleum resources are found in ancient deltaic rocks. Deltas vary widely in size, structure, composition, and origin, though many are triangular (the shape of the Greek letter delta).
Demarcated Forest: (See: Riparian Forest)
Demestid: Beetle that eats organic materials: a beetle with clubbed antennae that eats organic materials, e.g. cabinet and carpet beetles. Family: Dermestidae
Democracy: Form of government in which supreme power is vested in the people and exercised by them directly or indirectly through a system of representation usually involving periodic free elections. In a direct democracy, the public participates in government directly (as in some ancient Greek City-States, some New England Town Meetings, and some Cantons in modern Switzerland). Most democracies today are representative. The concept of representative democracy arose largely from ideas and institutions that developed during the European Middle Ages and the Enlightenment and in the American and French Revolutions. Democracy has come to imply universal suffrage, competition for office, freedom of speech and the press, and the rule of law.
Demography: Statistical study of human populations, especially with reference to size and density, distribution, and vital statistics. Contemporary demographic concerns include the global birth rates, the interplay between population and economic development, the effects of Birth Control, urban congestion, illegal immigration, and labour force statistics. The basis for most demographic research lies in population Censuses and the registration of vital statistics.
Denaturation: Biochemical process modifying a protein’s natural configuration. It involves breaking many weak (hydrogen and hydrophobic) bonds that maintain the protein’s highly ordered structure. This usually results in loss of biological activity (e.g., loss of an enzyme’s ability to catalyze reactions). Denaturation can be brought about by heating; treatment with Alkalis, Acids, urea, or Detergents; or even vigorous shaking of the protein solution. It can be reversed in some cases (e.g., serum albumin, hemoglobin), if conditions favourable to the protein are restored, but not in others. The term is also used to describe the process of rendering ethanol unfit to drink.
Dendrochronology: Method of scientific Dating based on the analysis of tree rings. Because the width of annular rings varies with climatic conditions, laboratory analysis of timber core samples allows scientists to reconstruct the conditions that existed when a tree’s rings developed. By taking thousands of samples from different sites and different strata within a particular region, researchers can build a comprehensive historical sequence that becomes a part of the scientific record. Such master chronologies are used by archaeologists, climatologists, and others.
Dendrology: The identification and systematic classification of trees and shrubs.
Denitrifying bacteria: Soil microorganisms whose action results in the conversion of nitrates in soil to free atmospheric nitrogen, thus exhausting soil fertility and reducing agricultural productivity. Without denitrification, earth’s nitrogen supply would eventually accumulate in the oceans, since nitrates are highly soluble and are continuously leached from the soil into nearby bodies of water. (See also Nitrifying bacteria).
Density: 1. A quantitative measurement of tree cover on an area in terms of biomass, crown closure, number of trees, basal area, volume or weight. In this context, A tree cover includes seedlings and saplings, hence the concept carries no connection of a particular age. Expressed on a per hectare basis. 2. Mass of a unit volume of a material substance. It is calculated by dividing an object’s mass by its volume. In the International System of units, and depending on the units of measurement used, density can be expressed in grams per cubic centimeter (g/cm3) or kilograms per cubic metre (kg/m3). The expression “particle density” refers to the number of particles per unit volume, not to the density of a single particle. (See also Specific gravity).
Dentate: Sharply toothed, with the teeth pointing straight out from the margin.
Den tree: A tree with cavities suitable for birds or mammals to nest in.
Depreciation: Accounting charge for the decline in value of an asset spread over its economic life. Depreciation includes deterioration from use, age, and exposure to the elements, as well as decline in value caused by obsolescence, loss of usefulness, and the availability of newer and more efficient means of serving the same purpose. It does not include sudden losses caused by fire, accident, or disaster. Depreciation is often used in assessing the value of property (e.g., buildings, machinery) or other assets of limited life (e.g., a leasehold or copyright) for tax purposes.
Depression: In economics, a major downswing in the Business cycle characterized by sharply reduced industrial production, widespread unemployment, a serious decline or cessation of growth in construction, and great reductions in international trade and capital movements. Unlike Recessions, which may be limited to a single country, severe depressions such as the great depression encompass many nations. (See also Deflation; Inflation).
Desalination or desalting: Removal of dissolved salts from Seawater and from the salty waters of inland seas, highly mineralized groundwaters, and municipal wastewaters. Desalination makes such otherwise unusable waters fit for human consumption, irrigation, industrial applications, and other purposes. Distillation is the most widely used desalination process; freezing and thawing, electrodialysis, and reverse osmosis are also used. All are energy-intensive and therefore expensive. Currently, more than 2 billion gallons (8 million cu m) of fresh water are produced each day by several thousand desalination plants throughout the world, the largest plants being in the Arabian Peninsula.
Desert: Large, extremely dry area of land with fairly sparse vegetation. It is one of the Earth’s major types of ecosystems. Areas with a mean annual precipitation of 10 in. (250 mm) or less are generally considered deserts. They include the high-latitude circumpolar areas as well as the more familiar hot, arid regions of the low and mid-latitudes. Desert terrain may consist of rugged mountains, high plateaus, or plains; many occupy broad mountain-rimmed basins. Surface materials include bare bedrock, plains of gravel and boulders, and vast tracts of shifting sand. Wind-blown sands, commonly thought to be typical of deserts, make up only about 2% of North American deserts, 10% of the Sahara, and 30% of the Arabian Desert.
Desertification: Spread of a desert environment into arid or semiarid regions, caused by climatic changes, human influence, or both. Climatic factors include periods of temporary but severe drought and long-term climatic changes toward dryness. Human factors include artificial climatic alteration, as through the removal of vegetation (which can lead to unnaturally high erosion), excessive cultivation, and the exhaustion of water supplies. Desertification drains an arid or semiarid land of its life supporting capabilities. It is characterized by a declining groundwater table, salt accumulation in topsoil and water, and a decrease in surface water, increasing erosion, and the disappearance of native vegetation.
Desirable plant species: Species that contribute to management objectives.
Devaluation: Reduction in the exchange value of a country’s monetary unit in terms of gold, silver, or foreign Currency. By decreasing the price of the home country’s exports abroad and increasing the price of imports in the home country, devaluation encourages the home country’s export sales and discourages expenditures on imports, thus improving its Balance of Payments.
Development, biological: Gradual changes in size, shape, and function during an organism’s life that translate its genetic potentials (Genotype) into functioning mature systems (Phenotype). It includes growth but not repetitive chemical changes (metabolism) or changes over more than one lifetime (evolution). DNA directs the development of a fertilized egg so that cells become specialized structures that carry out specific functions. In humans, development progresses through the Embryo and Fetus stages before birth and continues during childhood. Other mammals follow a similar course. Amphibians and insects go through distinctive stages that are quite different. In plants, the basic pattern is determined by the arrangement of lateral buds around a central growing stem. Different rates of growth of the plant’s component elements then determine its shape and that of various parts. In both animals and plants, growth is greatly influenced by hormones; factors within individual cells probably also play a role.
Dew: Deposit of water droplets formed at night by the condensation of water vapour from the air onto the surfaces of exposed objects. Dew forms on clear nights, when exposed surfaces lose heat by radiation and are thus usually colder than the air. The cold surface cools the air in its vicinity, and, if the air is humid enough, it may cool below its dew point, the temperature at which water vapour condenses out of the air onto the surface. (See also Frost)
Diameter: The longest distance at right angles, across any circle or cylinder. In standing trees, estimate diameter by dividing the circumference (length of a line taken completely around the outside of a tree) by 3.1416. (Pic) (See Exploitable diameter, mean diameter, Mid diameter, Top diameter)
Diameter at stump height (dsh): The stem diameter of a tree measured at stump height. Stump height may be the actual height of a cut stump, or some arbitrarily selected standard.
Diameter at breast high (dbh): (See: Breast height)
Diameter class: One of the intervals into which the range of diameters of trees in a forest is divided for purposes of classification and use. Generally, this is done in 12in, even increments (12 in class would contain trees from 11 to 13 in).
Diameter inside bark (dib): The diameter of a tree or log excluding double bark thickness.
Diameter limit: The smallest (occasionally the largest), size to which trees or logs are to be measured, cut, or used. The points to which the limit usually refers to are stump, breast height, or top.
Diameter-limit cutting: A system of selection harvest based on cutting all trees in the stand over a specified diameter. This eliminates marking individual trees
Diamond: Mineral composed of pure Carbon, the hardest naturally occurring substance known and a valuable gemstone. Diamonds are formed deep in the Earth by tremendous pressures and temperatures over long periods of time. In the crystal structure of diamond, each carbon atom is linked to four other, equidistant, carbon atoms. This tight crystal structure results in properties that are very different from those of Graphite, the other common form of pure carbon. Diamonds vary from colourless to black and may be transparent, translucent, or opaque. Most gem diamonds are transparent and colourless or nearly so. Colourless or pale blue stones are most valued, but most gem diamonds are tinged with yellow. Because of their extreme hardness, diamonds have important industrial applications. Most industrial diamonds are gray or brown and are translucent or opaque. In the symbolism of gemstones, the diamond represents steadfast love and is the birthstone for April
Diapause: 1. Slow-down of animal’s metabolism. 2. A period during which the metabolism of some animals or insects slows down, temporarily suspending their bodily development and growth. Such periods are linked to seasonal or environmental changes.
Diastrophism or tectonism: Large-scale deformation of the Earth’s Crust by natural processes, which leads to the formation of continents and ocean basins, mountain systems and rift valleys, and other features by mechanisms such as lithospheric plate movement (see Plate tectonics), volcanic loading, or folding. The study of diastrophism, or tectonic processes, is the central unifying principle in modern geology and geophysics.
Diatom: Any member of the algal division or phylum Bacillariophyta (about 16,000 species), tiny planktonic, unicellular or colonial Algae found floating in all the waters of the earth. The intricate and delicate markings of the silicified cell wall are useful in testing the resolving power of microscope lenses. The beautiful symmetry and design of diatoms justify their title “jewels of the sea.” Among the most important and prolific sea organisms, diatoms serve directly or indirectly as food for many animals. Diatomaceous earth, composed of fossil diatoms, is used in filters, insulation, abrasives, paints, and varnishes, and as an insecticide. (Pic)
d.i.b.: Abbreviation for “diameter inside bark.”
Dibble: A flat or round metal tool used to make a hole for planting containerized seedlings. Direct seeding. Sowing tree seed to regenerate a forest.
Dibble planting: Sowing seeds or setting out seedlings in rough holes made with a stick or peg. Also termed dibbling if done with a specially adapted tool such as a dibble.
Dichotomous: Dichotomous branching is where the stem repeatedly forks. It forks into to branches, and then each of those two branches fork, etc. This is quite common in the lower tracheophyte plants such as Psilotum, Selaginella, and Lycopodium.
Digitate: Compound, with the elements growing from a single point.
Dike: Bank, usually of earth, constructed to control or confine water. Dikes were purely defensive at first but later became a means to acquire polders (tracts of land reclaimed from a body of water through the construction of offshore dikes roughly parallel to the shoreline). After a dike is built, the polder is drained by pumping out the water. Where the land surface is above low-tide level, tide gates discharge water into the sea at low tide and automatically close to prevent reentry of seawater at high tide. To reclaim lands that are below low-tide level, the water must be pumped over the dikes. The most notable example of polder construction is the system adjacent to Holland’s Ijsselmeer (Zuider Zee) barrier dam. If The Netherlands were to lose the protection of its dikes, its most densely populated portion would be inundated by the sea and rivers.
Dilated: Expanded, broadened, flaring.
Dimension: In mathematics, a number indicating the fewest coordinates necessary to identify a point in a geometric space; more generally, a number indicating a measurement of length. One-dimensional space can be represented by a numbered line, on which a single number identifies a point. In two-dimensional space, a Coordinate system may be superimposed, requiring only two numbers to identify a point. Three numbers suffice in three-dimensional space, and so on.
Dimension lumber: Hardwood dimension lumber is processed to be used whole in the manufacture of furniture or other products. Softwood dimension lumber consists of boards more than 2 inches thick but less than 5 inches thick. This wood is used in construction and is sold as 2 by 4s, 4 by 8s, or 2 by 10s.
Diminishing returns, law of: Economic law stating that if one input used in the manufacture of a product is increased while all other inputs remain fixed, a point will eventually be reached at which the input yields progressively smaller increases in output. For example, a farmer will find that a certain number of farm labourers will yield the maximum output per worker. If that number is exceeded, the output per worker will fall.
Diorite: Medium- to coarse-grained igneous rock that commonly is composed of about two-thirds plagioclase feldspar and one-third dark-coloured minerals, such as hornblende or biotite. Diorite has about the same structural properties as granite but, perhaps because of its darker colour and more limited supply, is rarely used as an ornamental building material. It is one of the dark gray stones that is sold commercially as “black granite.”
Dipping: The immersion of seedling roots in a solution or water prior to planting.
Direct or Broadcast Seeding: (a) Sowing seed for broad coverage from the air or on the ground. (b) Seeding of forest stands, roadways, or specified plots for wildlife.
Disease: Harmful deviation from the normal functioning of physiological processes, generally pathogenic or environmental in origin.
Disk flower: One of the tubular flowers or florets in the center of the flower head of a composite flower such as the daisy (See also Ray flower).
Display behaviour: Ritualized activity by which an animal conveys specific information. The best-known displays are visual, but others rely on sound, smell, or touch. Agonistic (aggressive) displays make it unnecessary to chase intruders from a territory or for animals to injure each other in competition for mates. One type of defensive display deceives predators or lures them away from vulnerable young.
Disposable income: Portion of an individual’s income over which the recipient has complete discretion. To assess disposable income, it is necessary to determine total income, including not only wages and salaries, interest and dividend payments, and business profits, but also transfer income such as social-security benefits, pensions, and alimony. Obligatory payments, including personal income taxes and compulsory social insurance contributions, must be subtracted. Disposable income may be used for consumption or saving.
Distemper: The paint consisting of powdered chalk, some coloring pigment, and mixed in water.
Distempering: “The art of applying tow or three coats of distemper on the plastered or whitewashed surface.”
Distillation: Vaporization of a liquid and subsequent condensation of the resultant gas back to liquid form. It is used to separate liquids from nonvolatile solids or solutes (e.g., water from salt and other components of seawater) or to separate two or more liquids with different boiling points (e.g., alcohol from fermented beers and wines). Many variations have been devised for industrial applications. An important one is a fractional distillation, in which vapour from a heated liquid mixture is contacted by a series of trays and condensed liquid as it rises through a vertical column. The most volatile fraction of the mixture emerges from the top of the column, while less volatile fractions are withdrawn at lower points. In petroleum refining, this method is very efficient for removing naphtha, kerosene, and gas oils from crude oil. (Pic)
Distributive law: One of the laws relating to number operations. In symbols, it is stated: a(b + c) = ab + ac. The monomial factor a is distributed, or separately applied, to each term of the polynomial factor b + c, resulting in the product ab + ac. It can also be stated in words: The result of first adding several numbers and then multiplying the sum by some number is the same as first multiplying each separately by the number and then adding the products.
Disturbance: Any removal of tree cover sufficient to create a site for an even-aged crop of regeneration.
Division: It is the combination of 3 to 4 ranges. (See range in sense 2). Divisional Forest Officer (DFO) controls the division.
DNA or deoxyribonucleic acid: One of two types of Nucleic Acid (the other is RNA); a complex organic compound found in all living Cells and many Viruses. It is the chemical substance of Genes. Its structure, with two strands wound around each other in a double helix to resemble a twisted ladder, was first described (1953) by Francis Crick and James D. Watson. Each strand is a long chain (polymer) of repeating Nucleotides: adenine (A), guanine (G), cytosine (C), and thymine (T). The two strands contain complementary information: A forms hydrogen bonds only with T, C only with G. When DNA is copied in the cell, the strands separate and each serves as a template for assembling a new complementary strand; this is the key to stable Heredity. DNA in cells is organized into dense protein-DNA complexes called Chromosomes. In Eukaryotes these are in the nucleus, and DNA also occurs in mitochondria and Chloroplasts (if any). Prokaryotes have a single circular chromosome in the cytoplasm. Some prokaryotes and a few eukaryotes have DNA outside the chromosomes in Plasmids. (See also Genetic Engineering and Mutation). (Pic)
d.o.b.: Abbreviation for “diameter outside bark.”
Dodo: Extinct flightless bird (Raphus cucullatus) of Mauritius, first seen by Portuguese sailors about 1507. Humans and the animals they introduced had exterminated the dodo by 1681. It weighed about 50 lbs (23 kg) and had blue-gray plumage, a big head, a 9-in. (23-cm) blackish bill with a reddish hooked tip, small useless wings, stout yellow legs, and a tuft of curly feathers high on its rear end. The Reunion solitaire (R. solitarius), also driven to extinction, may have been a white version of the dodo. Partial museum specimens and skeletons are all that remain of the dodo. (Pic)
Dog: Any member of the Canine genus Canis, particularly the domestic species, Canis familiaris. Domestic dogs seem to have descended from the wolf or a wolf-like ancestor. Dogs were apparently the first animals to be domesticated, and domestication seems to have begun in various parts of the world at roughly the same time. Selective breeding by humans has resulted in myriad domestic breeds that vary widely in size (from the tiny Chihuahua to the huge Mastiff), physical form (e.g., the short-legged Dachshund and the flat-faced Bulldog), coat texture and length (e.g., the sleek Doberman Pinscher and the long-haired Afghan Hound), and behavioral patterns (e.g., sporting dogs, toy dogs, and working dogs). The American Kennel Club now recognizes almost 150 breeds; other clubs, such as the United Kennel Club, recognize many more. (Pic)(Max)
Dogfish: Any of several species of small Sharks. The spiny dogfish (Squalus acanthias, family Squalidae) has a sharp spine in front of each of its two dorsal fins. It is abundant along northern Atlantic and Pacific coasts. It is gray with white spots, about 2–4 ft (60–120 cm) long, and often found in schools. It preys on fishes and invertebrates and often steals bait and damages fishing nets. It yields liver oil or is ground for fertilizer. Other well-known species are the spotted dogfishes (family Scyliorhinidae), which are sold as food, and the smoothhound or smooth dogfish (Mustelus canis, family Triakidae), one of the most common sharks on the U.S. Atlantic coast.
Dolomite: Type of limestone, the carbonate fraction of which is dominated by the mineral dolomite, calcium magnesium carbonate CaMg(CO3)2. The carbonate mineral dolomite occurs in marbles, talc schists, and other magnesium-rich metamorphic rocks. It occurs in hydrothermal veins, in cavities in carbonate rocks, and less often in various sedimentary rocks as cement. It is most common as a rock-forming mineral in carbonate rocks.
Dolphin: One of a large group of small, gregarious, streamlined whales or one of two species of oceanic sport and food fishes. Mammalian dolphins are small Toothed Whales, usually with a well-defined, beaklike snout. (They are sometimes called Porpoises, but that name is properly reserved for a blunt-snouted whale family.) The common dolphin (Delphinus delphis) and the Bottlenose Dolphin, both of the family Delphinidae, are found widely in warm temperate seas, though some inhabit tropical rivers. Most of the 32 delphinid species are marine; gray, blackish or brown above and pale below; and about 3–13 ft (1–4 m) long. River dolphins (family Platanistidae; five species) live mainly in fresh water in South America and Asia. One of the two fish species, Coryphaena hippuras (family Coryphaenidae), also called mahimahi and dorado, is a popular fish of tropical and temperate waters worldwide. The pompano dolphin (C. equiselis) is similar. (Pic)
Domestic cat or house cat: Domesticated Carnivore (Felis catus) that retains many characteristics of the larger wild Cats but differs in coat and size. Breeds are either shorthaired (e.g., Siamese) or longhaired (e.g., persian). Domestic cats are usually white, black, yellow, or gray and sometimes have markings of a different colour. A pattern of dark stripes or swirls on a lighter background is called tabby. Males may reach lengths of 28 in. (71 cm), and females are usually about 20 in. (51 cm) long. Weights generally vary from 6 to 10 lb (2.5 to 4.5 kg), though non-pedigreed cats may weigh up to 28 lb (13 kg). The most closely related wild species are the North African wildcats (including Felix lybica). Valued for their mouse and rat hunting, which protected farmers’ grain supplies, cats were being domesticated in ancient Egypt by 1500 BC. The Cat Fanciers’ Association now recognizes about 37 breeds.
Dominance: In genetics, the greater influence by one of a pair of Genes (alleles) that affect the same inherited trait. If an individual pea plant that has one allele for tallness and one for shortness is the same height as an individual that has two alleles for tallness, the tallness allele is said to be completely dominant. If such an individual is shorter than an individual that has two tallness alleles but still taller than one that has two shortness alleles, the tallness allele is said to be partially or incompletely dominant and the shortness allele is said to be recessive (See Recessiveness).
Dominance potential: The relative ability of a tree or plant species to dominate a forest ecosystem, given an opportunity equal to that of its associates.
Dominant trees: Trees with crowns extending above the general level of the crown cover and receiving full light from above and partly from the side; larger than the average trees in the stand, with crowns well developed, possibly somewhat crowded on the sides. (See crown class)
Donkey or burro: Descendant of the African wild ass that has been used as a beast of burden since 4000 BC. The average donkey stands about 40 in. (100 cm) high at the shoulder, but breeds range from 24 to 66 in. (61–168 cm). Coats range from white to gray or black, usually with a dark stripe from mane to tail and a crosswise stripe on the shoulders. The mane is short and upright, and the tail has long hairs only at the end. The very long ears are dark at the base and tip. Donkeys are surefooted and can carry heavy loads over rough terrain. (See also Mule).
Door: Movable barrier installed in the entry of a room or building to restrict access or provide visual privacy. Early doors were hides or textiles. With monumental architecture came pivoting doors of rigid, permanent materials; important chambers often had stone or bronze doors. Pompeiian doors looked much like modern wooden doors; they were constructed of stiles (vertical planks) and rails (horizontal planks) fastened together to support panels and occasionally equipped with locks and hinges. The typical Western medieval door was of vertical planks backed with horizontal or diagonal bracing. In the 20th century, a single, hollow core panel door became most common. Other types include the revolving door, folding door, sliding door (inspired by the Japanese Shoji), rolling door, and Dutch door (divided horizontally so that the lower or upper part can be opened separately).
D-plus (D +) rule. A rule of thumb in thinning; estimate desired spacing by adding a given number to the d. b. h. of the crop tree: a “D + 4” rule would mean that a 16in d.b.h. tree would need 16 + 4 or 20 ft of growing space.
Dormancy: A biological process in which a plant ceases most growth activities and simply maintains existing tissue. Caused by periods of moisture and/or temperature stress.
Dorsal: Of or belonging to the upper surface; top.
Dormant: Dormant refers to plants that are living but are not growing. This is typical of seeds, plants that live in temperate regions of the earth, lose their leaves during the winter, and stop growing. In the spring, these plants break dormancy and begin to grow. Seeds break dormancy by soaking up moisture and beginning to send out shoots and roots.
Dorsoventral: From top to bottom; from the upper surface to the lower surface.
Dorsum: The upper surface; top.
Dose: A measured concentration of a toxicant for a known duration of time (concentration per unit time).
Double: Descriptive of flowers that have more petals than normal.
Doubly serrate: Serrate, with small teeth on the margins of the larger ones.
Douglas fir: Any of about six species of coniferous evergreen timber trees (see Conifer) that make up the genus Pseudotsuga, in the Pine family, native to western North America and eastern Asia. Long, flat, spirally arranged yellow- or blue-green needles grow directly from the branch. The North American tree commonly called Douglas fir is P. menziesii (sometimes P. douglasii). Douglas firs may grow to 250 ft (75 m) tall and 8 ft (2.4 m) in diameter. One of the best timber trees in North America, it is also a popular ornamental and Christmas tree and is used for reforestation along the Pacific Coast.
Dove: Any of certain birds of the pigeon family (Columbidae). The names pigeon and dove are often used interchangeably. Though “dove” usually refers to the smaller, long-tailed members of the pigeon family, there are exceptions: the common street pigeon, generally typical for birds designated as pigeons, is frequently called the rock dove. The common names of these birds do not necessarily reflect their accurate biological relationships to one another. (Pic)
Downed tree: Any tree that is lying on the ground, whether uprooted, stem-broken, or deliberately cut.
Dragonfly: Any member of the insect suborder Anisoptera (order Odonata), characterized by four large, membranous, many-veined wings, that, when at rest, are held horizontally rather than vertically (See Damselfly). Dragonflies are agile and have bulging eyes that often occupy most of the head and a wingspan of about 6 in. (16 cm). The dragonfly is one of the fastest-flying and most predaceous insects; in 30minutes it can eat its own weight in food. Dragonflies differ from most other insects by having the male copulatory organs at the front part of the abdomen rather than at the back end. Male and female often fly in tandem during sperm transfer. (Pic)
Drag scarification: Towing one or more rows of anchor chains, shark fin barrels, tractor pads, alone or in various combinations, to break up and possibly spread slash and to loosen the forest floor and topsoil or expose mineral soil.
Draining: Removal of water from soil artificially by measures for hastening removal, (e.g., by ditching).
Drainage: 1. Hydrology/engineering: The process of removal of water from soil, particularly by surface runoff and subsurface percolation and artificially by measures for hastening removal, e.g., by ditching. 2. Pedology: The frequency and duration of the periods when the soil is free of saturation or partial saturation. A measurable characteristic (including rapidity and extent), but generally assessed from profile morphology, e.g., graying and color, and landform. Commonly described in terms of subjective drainage classes, extending from very poorly drained to excessively drained.
Drip line: On the ground, the line that marks the outer edge to which a tree’s (or other plant’s) branches spread. The drip line usually signals a change in microclimate, where the area under the tree, which sees less precipitation, sunlight, and wind and may also be subject to competition from the tree’s roots (see root zone), meets an area that isn’t sheltered by the tree.
Drip stone: Protective groove: a protective groove cut in a sill or other overhang of a wall or building to cause water to drip freely
Drip torch: Firefighters use these torches, that drip a flaming liquid mixture of diesel fuel and gasoline, to ignite fires in burnout operations.
Drosophila: Any member of about 1,000 species in the Dipteran genus Drosophila, commonly known as Fruit Flies but also called vinegar flies. Some species, particularly D. melanogaster, are used extensively in laboratories for experiments on genetics and evolution because they are easy to raise and have a short life cycle (less than two weeks at room temperature). More data have been collected concerning the genetics of Drosophila than for any other animal. In the wild, its larvae live in rotting or damaged fruits or in fungi or fleshy flowers.
Drought: Lack or insufficiency of rain for an extended period that severely disturbs the Hydrologic Cycle in an area. Droughts involve water shortages, crop damage, streamflow reduction, and depletion of groundwater and soil moisture. They occur when evaporation and transpiration exceed precipitation for a considerable period. Drought is the most serious hazard to agriculture in nearly every part of the world. Efforts have been made to control it by seeding clouds to induce rainfall, but these experiments have had only limited success.
Drum Chopping: A site preparation technique in which logging debris is leveled by a bulldozer pulling a large drum filled with water. Chopped areas are often burned to further reduce debris and control sprouting before seedlings is planted.
Drupe: Fruit in which the outer layer is a thin skin, the middle layer is thick and usually fleshy (though sometimes tough, as in the almond, or fibrous, as in the coconut), and the inner layer (the pit) is hard and stony. Within the pit is usually one seed. In aggregate fruits such as the raspberry and blackberry (which are not true berries), many small drupes are clumped together. Other representative drupes are the cherry, peach, mango, olive, and walnut.
Dry packing: In tree injection, a method of banding that uses a tight waterproof bandage packed with a chemical, either dry or in paste form.
Dry rot: 1. A decay of the “brown rot” type, caused by specialized fungi capable of conducting moisture from an available source and extending their attack to wood previously too dry to decay. Found chiefly in buildings. The term is open to the misinterpretation that wood will rot when dry, which is not true. 2. Symptom of fungal disease in plants (see Fungus), characterized by firm spongy to leathery or hard decay of the stem (branch), trunk, root, rhizome, corm, bulb, or fruit. The fungus consumes the cellulose of wood, leaving a soft skeleton that is readily reduced to powder.
Duck: Any of various relatively small, short-necked, large-billed waterfowl (several genera in subfamily Anatinae, family Anatidae). The legs of true ducks (Anatinae) are placed rearward (as are those of swans), resulting in a waddling gait. Most true ducks differ from swans and true geese in that male ducks molt twice annually, females lay large clutches of smooth-shelled eggs, and both sexes have overlapping scales on the skin of the leg and exhibit some differences between sexes in plumage and in call. All true ducks except shelducks and sea ducks mature in the first year and pair only for the season. They are generally divided into three groups: perching ducks, dabbling ducks, and diving ducks. The whistling duck species, also called tree ducks, are not true ducks but are more closely related to geese and swans.
Duff: Forest litter and other organic debris in various stages of decomposition on top of the mineral soil; typical of coniferous forests in cool climates, where rate of decomposition is slow and where litter accumulation exceeds decay.
Dung beetle: Any member of one subfamily (Scarabaeinae) of Scarab beetles, which shapes manure into a ball (sometimes as large as an apple) with its scooperlike head and paddle-shaped antennae. They vary from 0.2 to more than 1 in. (5–30 mm) long. In early summer it buries itself and the ball and feeds on it. Later in the season the female deposits eggs in dung balls, on which the larvae will later feed. They are usually round with short wing covers (elytra) that expose the end of the abdomen. They can eat more than their own weight in 24 hours and are considered helpful because they hasten the conversion of manure to substances usable by other organisms.
Dust: To sprinkle a powdery substance over something
Dwarfism: Growth retardation resulting in abnormally short adult stature. It is caused by a variety of hereditary and metabolic disorders. Pituitary dwarfism is caused by insufficient Growth hormone. Hereditary dwarfisms include achondroplasia, with normal trunk size but short limbs and a large head; hypochondroplasia, similar except for normal head size; and diastrophic dwarfism, with progressive, crippling skeletal deformities. Intelligence is normal in these forms of dwarfism. Some kinds include mental retardation. Dwarfism may also result from inadequate nutrition in early life.
Dwarf varieties: Varieties bred to grow smaller than their parent plants. Dwarf plants may lose the ability of the parents to set fruit (Bailey’s dwarf highbush cranberry, Viburnum trilobum ‘Bailey’s Compact’). They may not resemble miniatures of their parents (dwarf Alberta spruce, Picea glauca var. albertiana ‘Conica’).
Dysgenic: Detrimental to the genetic quality of a population and future generations. (cf. eugenic).
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Naeem Javid Muhammad Hassani