Alaska Photos ~ Alaska Stock Photography ~ Alaska Pictures

Glossary of Alaska Natural History Terms:
References listed at the bottom

A   B   C   D   E   F   G   H   I   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z  

A

Active layer. A seasonally thawed surface layer of soil in arctic or alpine regions that lies above permanently frozen ground and is between a few centimeters and about 3 meters thick.

Afforestation. The establishment of forest by natural succession or by the planting of trees on land where they did not grow formerly. Afforestation. The establishment of forest by natural succession or by the planting of trees on land where they did not grow formerly.

Alcids. Any of the Alcidae family (Order Charadriiformes) of marine birds having a stout bill, short wings and tail, webbed feet, a large head and heavy body, and thick, compact plumage. Confined to the northern parts of the Northern Hemisphere, alcids include auks, guillemots, murres, and puffins. Any of the Alcidae family (Order Charadriiformes) of marine birds having a stout bill, short wings and tail, webbed feet, a large head and heavy body, and thick, compact plumage. Confined to the northern parts of the Northern Hemisphere, alcids include auks, guillemots, murres, and puffins.

Alevin. A young fish, particularly a young salmon that is still attached to the yolk sac. A young fish, particularly a young salmon that is still attached to the yolk sac.

Algae. The common name for the relatively simple type of unicellular or multicellular plant which is never differentiated into root, stem, and leaves, contains chlorophyll a as its photosynthetic pigment, has no true vascular system, and has no sterile layer of cells surrounding its reproductive organs. Found in most habitats on Earth, though the majority occur in freshwater or marine environments. The common name for the relatively simple type of unicellular or multicellular plant which is never differentiated into root, stem, and leaves, contains chlorophyll a as its photosynthetic pigment, has no true vascular system, and has no sterile layer of cells surrounding its reproductive organs. Found in most habitats on Earth, though the majority occur in freshwater or marine environments.

Alluvial. Of or relating to river and stream deposits. Of or relating to river and stream deposits.

Alluvial soil. Soil formed in material deposited by the action of running water, such as a floodplain or delta. soil. Soil formed in material deposited by the action of running water, such as a floodplain or delta.

Alpine tundra. A treeless region above the tree line of high mountains, characterized by cold winters and short, cool summers and having permafrost below a surface layer that may melt in summer. tundra. A treeless region above the tree line of high mountains, characterized by cold winters and short, cool summers and having permafrost below a surface layer that may melt in summer.

Amphidromous. Referring to the migratory behavior of fishes moving from fresh water to the sea and vice versa, not for breeding purposes but occurring regularly at some stage of the life cycle (such as feeding or overwintering).Amphidromous. Referring to the migratory behavior of fishes moving from fresh water to the sea and vice versa, not for breeding purposes but occurring regularly at some stage of the life cycle (such as feeding or overwintering).

Anadromous. Referring to the life cycle of fishes, such as salmon, in which adults travel upriver from the sea to breed, usually returning to the area where they were born. Referring to the life cycle of fishes, such as salmon, in which adults travel upriver from the sea to breed, usually returning to the area where they were born.

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B

Boreal forest. The circumpolar, sub arctic forest of high northern latitudes that is dominated by conifers. The boreal forest stretches across North America, Europe, and northern Asia (regions characterized by short summers and long, cold winters). It is found south of the tundra in the Northern Hemisphere and often contains peaty or swampy areas. Boreal forest. The circumpolar, sub arctic forest of high northern latitudes that is dominated by conifers. The boreal forest stretches across North America, Europe, and northern Asia (regions characterized by short summers and long, cold winters). It is found south of the tundra in the Northern Hemisphere and often contains peaty or swampy areas.

Brackish. Water that is saline but not as salty as seawater. Water that is saline but not as salty as seawater.

Braided channel. A stream consisting of a network of interlacing small channels separated by bars, which may be vegetated and stable or barren and unstable. channel. A stream consisting of a network of interlacing small channels separated by bars, which may be vegetated and stable or barren and unstable.
Brooks Mountain Range. Alaska's northern most mountain range at the northwest end of the Rocky Mountains and range in elevation from 4,000 to 9,000 feet. Atigun pass, the highest elevation along the Dalton Highway, cuts through the range at an elevation of 4,643 feet

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C

Chlorophyll a. Chlorophyll, the green photosynthetic pigment found chiefly in chloroplasts of plants, occurs in variants of a, b, c, and d. Chlorophyll a is a waxy, blue-black microcrystalline, C₅₅H₇₂MgN₄O₅, with a characteristic blue-green alcohol solution.

Cirque. A steep hollow, often containing a small body of water, found at the upper end of a mountain valley.

Corridor. A more or less continuous connection between land masses or habitats; a migration route that allows more or less uninhibited migration of most of the animals of one faunal region to another. In terms of conservation biology, a connection between habitat fragments in a fragmented landscape.

Crevasse. A breach in a levee along the bank of a river through which floodwater may flow and produce sheetlike deposits of gravel or sandy sediment; or, a large, open fissure forming in a glacier as it moves and is deformed.

Crown fires. Fires that spread from tree crown to tree crown, usually indicative of particularly hot fires in dry conditions.

Crustacean. Any of a large class (Crustacea) of mostly aquatic mandibulate arthropods that have a chitinous or calcareous and chitinous exoskeleton, a pair of often modified appendages on each segment, and two pairs of antennae; includes lobsters, shrimps, crabs, wood lice, water fleas, and barnacles.

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D

Deciduous. Plants having structures that are shed at regular intervals or at a given stage in development, such as trees that shed their leaves seasonally.

Delta. An alluvial deposit at the mouth of a river or tidal inlet. Deltas occur when a sediment-laden current enters an open body of water, at which point there is a reduction in the velocity of the current, resulting in rapid deposition of the sediment, as at the mouth of a river where the river discharges into the sea or a lake.

Delta plain. A nearly horizontal portion of delta that, during low tide or other regression of water, is largely exposed to the atmosphere.

Diurnal. Occurring or active only in daylight.

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E

Ecosystem. A community of organisms and their physical environment that interact as an ecological unit.

El Niño. (Also called El Niño-Southern Oscillation Event, or ENSO.) A warm water current which periodically flows southward along the coast of Ecuador, associated with the Southern Oscillation in the atmosphere, and which affects climate throughout the Pacific region. Approximately once every seven years in late December, prevailing trade winds weaken and the equatorial countercurrent strengthens. Warm surface waters, normally driven westward by the wind to form a deep layer off Indonesia, flow eastward to overlie the cold waters of the Peru Current. The Southern Oscillation is a fluctuation of the intertropical atmospheric circulation in which air moves between the southeastern Pacific subtropical high and the Indonesian equatorial low, driven by the temperature difference between the two areas.

Endemic. Belonging or native to a particular people or geographic region; a genetically unique life form.

Estuary. A semi-enclosed coastal body of water which has a free connection with the open sea and where fresh water derived from land drainage (usually mouths of rivers) is mixed with seawater; often subject to tidal action and cyclic fluctuations in salinity.

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F

Fauna. The animal life of a region or geological period.

Flora. Plant or bacterial life forms of a region or geological period.

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G

Geomorphology. The study of landforms on a planet's surface and of the processes that have fashioned them.

Geotropic. Referring to the involuntary response of a plant or one of its parts to gravity. Geotropism may be a positive or negative response: primary taproots show positive geotropism; vertical primary shoots show negative geotropism.

Greenhouse effect. Heating of the Earth's atmosphere that is loosely analogous to the glass of a greenhouse letting light in but not letting heat out. Radiation from the sun easily enters the atmosphere as light waves, heating the Earth's surface and causing it to emit infrared radiation. Gases such as water vapor, carbon dioxide, methane, and chlorofluorocarbons absorb infrared radiation, preventing its energy from leaving the Earth.

Gregarious. Tending to form into groups which possess a social organization, such as schools of fish, herds of mammals, flocks of birds.

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H

Habitat. The place, including physical and biotic conditions, where a plant or an animal usually occurs.

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I

Igneous rock. Rock formed by solidification of molten magma.

Indicator species. An organism whose presence or state of health is used to identify a specific type of biotic community or as a measure of ecological conditions or changes occurring in the environment.

Indigenous. A species that occurs naturally in an area; native.

Interglacial. A warm period between glacial epochs.

Intertidal. Relating to the littoral zone above the low-tide mark.

Invertebrate. An animal without a backbone, such as snails, worms, and insects.

Isotherm. A line on a map or chart of the Earth's surface connecting points having the same temperature at a given time or the same mean temperature for a given period.

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K

Karst. A limestone landscape that is char- acterized by sinks, underground streams, and caverns.

Krill. Planktonic crustaceans and larvae that constitute the primary food of baleen whales.

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L

Lagoon. A shallow waterbody that is near or connected to a larger body of water.

Larvae. The wingless and often wormlike hatchlings of insects; also, the early form of an animal (such as a frog or sea urchin) which at birth or hatching is fundamentally unlike its parent and must metamorphose before assuming adult characteristics.

Lichen. A composite organism consisting of a fungus and an alga or cyanobacterium living in symbiotic association. Lichens may be crust like, scaly or leafy, or shrubby in form and are classified on the basis of the fungal partner. Many lichens are extremely sensitive to atmospheric pollution and have been used as pollution indicators.

Littoral zone. The biogeographic zone in a body of fresh water where light penetration is sufficient for the growth of plants; the intertidal zone of the seashore.

Long-line fishing. A method of fishing which utilizes a piece of ground line (often kilometers in length) to which short (0.5 to 1.0 meter) ganglion lines are attached at intervals of 1 to 10 meters, with a baited hook at the end of each ganglion line.

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M

Macrofauna. Animals large enough to be seen with the naked eye.

Marsh. An ecosystem of more or less continuously waterlogged soil dominated by emersed herbaceous plants but without a surface accumulation of peat. A marsh differs from a swamp in that it is dominated by rushes, reeds, cattails, and sedges, with few if any woody plants, and differs from a bog in having soil rather than peat as its base.

Metamorphic rock. Preexisting rock that is restructured by high temperature and pressure.

Midden. A heap of refuse. Also, a pile of seeds or of various items that were gathered by a rodent, for example, by a squirrel or packrat.

Mollusk. An organism in the phylum Mollusca (for example, snails, clams, or squids), whose soft, unsegmented body parts are frequently enclosed in a shell.

Moraine. An accumulation of boulders, stones, or other debris carried and deposited by a glacier.

Morphology. The form and structure of organisms.

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N

Nonindigeneous. (Also called exotic, nonnative, introduced, and alien.) A plant or animal that is not native to the area in which it occurs; it was either purposely or accidentally introduced.

Nunatak. An exposed hill or mountain completely surrounded by glacial ice.

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O

Old-growth. Referring to an ecosystem or community, particularly a forest, which has not experienced intense or widespread disturbance for a long time relative to the lifespans of the dominant species and which has entered a late successional stage; usually associated with high diversity of species, specialization, and structural complexity.

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P

Paleoecology. The application of ecological concepts to fossil communities.

Passerine. Of or relating to the largest order (Passeriformes) of birds, which includes more than half of all living birds and consists primarily of perching songbirds, whose young are hatched in an immature and helpless condition.

Pelagic. Referring to or occurring in the open sea.

Perennial. A plant that normally lives for more than two seasons and which, often after an initial period, produces flowers annually.

Permafrost. A permanently frozen layer of soil at variable depth below the surface in frigid regions of a planet. It may be discontinuous, that is, it may be interspersed with areas that are free of permafrost.

Phytoplankton. One of two groups into which plankton are divided, the other being zooplankton. Phytoplankton comprise all the freely floating photosynthetic forms in the oceans.

Pingo. A low hill or mound forced up by hydrostatic pressure in an area underlain by permafrost and consisting of an outer layer of soil covering a core of solid ice. Pingos range from 2 to 50 meters in height.

Pinniped. Any of a suborder of aquatic carnivorous mammals with all four limbs modified into flippers; includes seals, sea lions, and walruses.

Pioneer. The first species or community to colonize or recolonize a barren or disturbed area, thereby commencing a new biological succession.

Placer mining. The removal of ore from placers, which are glacial or alluvial deposits of sand or gravel containing valuable minerals.

Plankton. One of three major ecological groups into which marine organisms are divided, the other two being the nekton and the benthos. Plankton are small aquatic organisms (animals and plants) that, generally having no locomotive organs, drift with the currents. The animals in this category include protozoans, small crustaceans, and the larval stages of larger organisms, while plant forms are mainly diatoms.

Pleistocene. The earlier epoch of the Quaternary period or the corresponding system of rocks; 1.6 million-10,000 years ago; the "Ice Age."

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Q

Quaternary. The period of geological time, a sub-era of the Cenozoic, which covers the last 1.6 million years; comprises the Pleistocene ("Ice Age") and the Holocene epochs to the present and is noted for numerous major ice sheet advances in the northern hemisphere.

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R

Riparian. Relating to, living, or located on the bank of a natural watercourse (such as a river) or sometimes of a lake or a tidewater.

Rookery. A breeding or nesting place for some gregarious mammals and birds.

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S

Savanna. (Also spelled savannah.) A grassland-woodland mosiac vegetation type found in tropical and subtropical regions with long dry periods and receiving more rainfall than desert areas but not enough to support complete forest cover. A savanna is characterized by scattered trees or scattered clumps of trees and drought-resistant grasses. Fire often plays an important role in maintaining the vegetation.

Sinkhole. A hollow place or depression in which water collects and goes underground, generally occurring in limestone regions and formed by solution or by collapse of a cavern roof.

Slough. A swamp, marsh, or muddy backwater.

Smolt. The stage in the life of salmon and similar fishes in which the subadult individuals acquire a silvery color and migrate down the river to begin their adult lives in the open sea.

Snag. A standing dead tree or stump that provides habitat for a broad range of wildlife, from beetle larvae (and the birds that feed upon them) to dens for raccoons. Or, a tree or branch embedded in a river or lake.

Spawn. The eggs of certain aquatic organisms; also, the act of producing such eggs or egg masses.

Subalpine. The zone just below tree line on temperate mountains, usually dominated by a coniferous forest ecologically similar to boreal forest. The elevation of this zone increases with a decrease in latitude.

Subspecies. A race of a species that is granted a taxonomic name; rules for designating subspecies are subjective, but subspecies are generally geographically distinct and form populations (not merely morphs) which differ to some degree from other geographic populations of the species.

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T

Tailings. The fine-grained waste materials from an ore-processing operation.

Tectonic movement. The formation of faults and folds on the crust of a planet.

Thermokarst. A landscape characterized by shallow pits and depressions caused by selective thawing of ground ice, or permafrost.

Topography. The natural and constructed relief of an area.

Tree line The upper limits of tree growth in mountains or at high latitudes.

Tundra. A level or rolling treeless plain in the arctic or sub arctic regions; the soil is black and mucky, the subsoil is permanently frozen, and the vegetation is dominated by mosses, lichens, herbs, and dwarf shrubs. A similar environment occurs in mountainous areas above the timberline.

Tussock. A compact tuft of grass or sedges, or an area of raised solid ground, which is held together by roots of low vegetation, found in a wetland or tundra.

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U

Ungulate. Any four-footed, hoofed, grazing mammal (such as a ruminant, swine, camel, hippopotamus, horse, tapir, rhinoceros, elephant, or hyrax) that is adapted for running but is not necessarily related to other ungulates.

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V

Vertebrate. An animal with a backbone; includes mammals, birds, reptiles, amphibians, and fishes.

Volant. Flying or capable of flying.

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W

Wetland. A general term applied to land areas which are seasonally or permanently waterlogged, including lakes, rivers, estuaries, and freshwater marshes; an area of low-lying land submerged or inundated periodically by fresh or saline water.

Woodland. A vegetation community that includes widely spaced large trees. The tree crowns are typically more spreading in form than those of forest trees and do not form a closed canopy. Grass, heath, or scrub may develop between the trees.

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X

Xeric. Dry; tolerating or adapted to dry conditions.

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Y

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Z

Zoeae. The free-swimming, planktonic larval forms of many decapod crustaceans (especially crabs) that have a relatively large cephalothorax, conspicuous eyes, and fringed antennae and mouthparts.

Zooplankton. See plankton.

The definitions above are taken from the following references:

The Concise Oxford Dictionary of Ecology, edited by M. Allaby, published by Oxford University Press, Oxford, England, 1994; The Dictionary of Ecology and Environmental Science, edited by H. W. Art, published by Henry Holt and Company, 1993; A Dictionary of Ecology, Evolution, and Systematics, edited by R. J. Lincoln, G. A. Boxshall, and P. F. Clark, published by Cambridge University Press, Cambridge, England, 1982; Glossary of Oceanography and the Related Geosciences with References, by Steven K. Baum, Texas Center for Climate Studies, Texas A&M University; Marine Biology: Function, Biodiversity, Ecology by Jeffrey Levinton, published by Oxford University Press, New York; and Webster's Third New International Dictionary, pub- lished by Merriam-Webster, Springfield, Massachusetts, 1961, 1993.The definitions below are taken from the following references: The Concise Oxford Dictionary of Ecology, edited by M. Allaby, published by Oxford University Press, Oxford, England, 1994; The Dictionary of Ecology and Environmental Science, edited by H. W. Art, published by Henry Holt and Company, 1993; A Dictionary of Ecology, Evolution, and Systematics, edited by R. J. Lincoln, G. A. Boxshall, and P. F. Clark, published by Cambridge University Press, Cambridge, England, 1982; Glossary of Oceanography and the Related Geosciences with References, by Steven K. Baum, Texas Center for Climate Studies, Texas A&M University; Marine Biology: Function, Biodiversity, Ecology by Jeffrey Levinton, published by Oxford University Press, New York; and Webster's Third New International Dictionary, pub- lished by Merriam-Webster, Springfield, Massachusetts, 1961, 1993.