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PLT Glossary

The Glossary defines terms that are highlighted in bold in the Background or Doing the Activity sections of Explore Your Environment: K-8 Activity Guide. In some cases, these terms have a slightly different or more refined definition in a science or environmental context than in everyday use.

262 terms

A
ABIOTIC

a nonliving factor or element in an environment; e.g., light, water, heat, rock, and gases.

ACID RAIN

precipitation with a pH less than 5.6 (the pH of normal tap water) that forms in the atmosphere when certain pollutants mix with water vapor. The major sources of acid rain pollutants are sulfur dioxide and nitrogen oxide emissions from fossil fuel-burning power plants and motor vehicles.

ACTIVE MANAGEMENT

Attaining desired forest objectives to enable future conditions using silvicultural operations and forest management practices.

ADAPTATION

1) a trait that allows for survival or increased reproduction. For example, a plant with unusually long roots, enabling it to absorb water over a wide area, may be more likely to survive during periods of drought. 2) the process of adjusting to the environment over time through developing traits that promote survival or reproduction.

AIR QUALITY

a gauge of the concentration of one or more pollutants in the atmosphere that could potentially be harmful to humans, other animals, vegetation, or materials.

ANGIOSPERM

a vascular plant (one containing xylem and phloem) that produces fruit surrounding its seed.

ANNUAL

a plant that completes its life cycle from seedling to mature seed-bearing plant to death during a single growing season.

AQUATIC HABITAT

An area in the environment where water is the principal medium and species are adapted to aquatic conditions.

ATMOSPHERE

the blanket of gases surrounding Earth, made up of distinct layers that differ in temperature, density, and composition. The layers include the troposphere (lowest level), stratosphere, mesosphere, and thermosphere (highest level).

B
BACTERIA

single-celled microorganisms that lack chlorophyll. Many bacteria break down organic matter in the air, water, and soil. Some bacteria are capable of causing diseases in humans, other animals, and plants.

BARK

the tough exterior covering of a woody root or stem.

BIENNIAL

a plant that lives for two growing seasons, producing vegetative structure during the first season and flowers and seeds during the second.

BIODEGRADABLE

the property of a substance that permits it to be broken down by microorganisms into simple, stable compounds such as carbon dioxide, water, and minerals.

BIODIVERSITY

the variety of life on Earth, reflected in the variety of ecosystems and species, their processes and interactions, and the genetic diversity within and among species.

BIOFUEL

a fuel, such as ethanol or biodiesel, that is derived from plant or algae material or from animal waste.

BIOLOGICAL DIVERSITY

See BIODIVERSITY.

BIOMASS

1) the total mass or volume of organisms in a given area. 2) plant or animal material used as a fuel or as raw material for industrial processes. Woody biomass is made of the limbs and tops of trees and woody plants that are the by-products of forest management.

BIOME

a complex of communities characterized by a distinctive type of vegetation and maintained under the climatic conditions of the region. The biomes of North America include the tundra, desert, eastern deciduous forest, prairie, northern boreal forest, and western coniferous forests.

BIOPHILIA

derived from the Latin terms bio + philia for "love of life" to mean the pleasure humans experience from connections to nature, natural materials, and natural processes.

BIOPHILIC DESIGN

a building design approach that seeks to increase connections to nature through natural materials, natural light, vegetation, and the placement of spaces.

BIOSPHERE

the part of the Earth's crust, water, and atmosphere where living organisms can exist.

BIOTA

the animal and plant life of a region or period.

BIOTIC

an environmental factor related to or produced by living organisms.

BOARD FOOT (BF)

a unit of wood equivalent to a piece of wood 12 inches (30 cm) square and 1 inch (2.5 cm) thick.

BOREAL FOREST

the forest growing in the climate or region that stretches across northern North America, Europe, and Asia and is characterized by long, cold winters and short summers. The boreal forest is dominated by coniferous trees, as deciduous trees struggle to grow during the short growing season in northern climates.

BROADLEAFED

describes a plant with wide-bladed leaves, such as an oak or maple. This term is generally used to describe flowering trees (angiosperms) rather than conifers (gymnosperms).

BUD

a small swelling on a plant that grows into a leaf or flower. Leaf buds grow into leaves and flower buds grow into flowers.

C
CAMBIUM

a thin layer of living, dividing cells just under the bark of trees. This layer gives rise to the tree's secondary growth.

CAMOUFLAGE

color, tones, patterns, shapes or behavior that enable an organism to blend in with its surroundings. Some organisms, for example, have a skin or coat color that enables them to hide from predators.

CANOPY

the forest layer formed by the leaves and branches of trees or shrubs. There may be several canopy layers.

CARBOHYDRATES

sugars, starches, and celluloses that are produced by green plants and are important nutritional sources of energy for many animals.

CARBON CYCLE

the circulation and recycling of carbon atoms, especially through the processes of photosynthesis, respiration, and decomposition.

CARBON SINK

a carbon pool or reservoir (such as the ocean or vegetation) that stores more carbon than it releases, thus lowering the concentration of CO2 in the atmosphere.

CARNIVORE

an animal that consumes other animals.

CARRYING CAPACITY

the maximum number of individuals of a given species that can survive in a particular ecosystem on a long-term basis.

CELL

the smallest living unit of an organism.

CELLULOSE

a complex carbohydrate that constitutes the chief part of the cell walls of higher plants and yields fiber for many products.

CHLOROPHYLL

a group of pigments that produce the green hue of plants, essential to photosynthesis.

CHLOROPLASTS

the structures within plant cells that contain chlorophyll and enable photosynthesis to occur.

CIRCULAR ECONOMY

a systemic approach to eliminating waste and the continual use of resources through the use of compostable materials or through the reuse, remanufacturing, or recycling of products.

CLAY

a fine soil particle less than 0.002 mm in size. Some clay particles are so small that they cannot be seen in ordinary microscopes.

CLIMATE

the kind of weather a place has over a period of years, based on conditions of heat and cold, moisture and dryness, clearness and cloudiness, wind and calm.

CLIMATE CHANGE

a change in global or regional climate patterns. In particular, the term refers to a change apparent from the mid-20th century onward and attributed largely to the increased levels of atmospheric CO2 from the burning of fossil fuels.

COMBUSTION

an oxidative chemical process that results in the creation of heat and light.

COMMUNITY

all organisms in a particular habitat that are bound together by food chains and other interrelationships.

COMPOST

a mixture of decaying organic matter, as from leaves and manure, used to improve soil structure and provide nutrients.

COMPOSTABLE

capable of being broken down into natural substances that can be added to soil to improve soil fertility.

COMPOUND LEAF

a leaf that is subdivided into many leaflets.

CONDENSATION

the physical change of state in which a gas or vapor is transformed into a liquid, as in the formation of water droplets when water vapor cools.

CONE

a structure composed of many spirally-arranged scales in which pollen ovules are produced.

CONIFER

a plant that bears its seeds in cones. Usually refers to needleleaf trees, although some needleleaf trees, such as the yew, do not bear cones. The term "coniferous" means belonging to or pertaining to conifers.

CONSERVATION

1) the use of natural resources in a way that assures their continuing availability to future generations. 2) the intelligent use of natural resources for long-term benefits.

CONSUMER

1) an organism that obtains energy by feeding on other organisms and their remains. Usually, consumers are classified as primary consumers (herbivores), secondary consumers (carnivores), and microconsumers (decomposers). 2) any person using goods for his or her own needs.

CROWN

the top branches of a tree.

CROWN SPREAD

the width of a tree's crown measured from its outermost branches.

D
DECIDUOUS

describes a plant that periodically (typically in autumn) loses all its leaves. Most North American broadleaf trees are deciduous. A few conifers, such as the larch and cypress, are also deciduous. 

DECOMPOSER

a plant or organism that feeds on dead material and causes its mechanical or chemical breakdown.

DEFOLIATION

the loss of leaves from plants.

DEFORESTATION

the permanent replacement of forests by non-forest uses.

DENDROCHRONOLOGY

the science of dating events and variations in the environment in former periods by comparative study of growth rings in trees and aged wood.

DENDROLOGY

a branch of botany devoted to the study of trees.

DIAMETER AT BREAST HEIGHT (DBH)

the diameter of a tree's trunk as measured at breast height. Standard DBH is measured at 4.5 feet (135 cm) above the ground.

DIVERSITY

variety or complexity. See BIOLOGICAL DIVERSITY.

E
ECOLOGICAL DIVERSITY

the variety of forests, deserts, grasslands, oceans, streams, lakes, and other biological communities interacting with one another and with their nonliving environment.

ECOLOGICAL SUCCESSION

See SUCCESSION.

ECOLOGY

the scientific study of the relations of living things to one another and to their environment. A scientist who studies these relationships is called an ecologist.

ECOSYSTEM

1) the interacting system of a biological community and its nonliving environment. 2) the place where these interactions occur.

ECOSYSTEM MANAGEMENT

use of ecosystem concepts to predict effects of management actions on the ecosystem and to guide management planning and actions.

ECOSYSTEM SERVICES

the benefits people obtain from healthy ecosystems, including providing food, fresh water, fuel, fiber, and other goods; regulating climate, water, and pollination; and aesthetic and cultural benefits.

ENDANGERED SPECIES

a species that is in imminent danger of extinction.

ENERGY EFFICIENCY

reducing energy consumption by using less energy to perform the same task.

ENERGY FLOW

the one-way passage or transfer of energy through an ecosystem according to the laws of thermodynamics.

ENERGY STORAGE

the conversion of electrical energy into a different form from which it can be converted back to electrical energy at a later time. Electric power grids may use pumped water, compressed air, batteries, or thermal energy to store energy.

ENVIRONMENT

the sum of all external conditions and influences that affect the development and, ultimately, the survival of an organism or group of organisms.

ENVIRONMENTAL JUSTICE

the fair treatment and meaningful involvement of all people regardless of race, color, national origin, or income with respect to the development, implementation, and enforcement of environmental laws, regulations, and policies.

EROSION

the wearing away of the land surface by wind or water. Erosion occurs naturally from weather, runoff, or wave action, but it may be intensified by some human practices.

ETHANOL

a grain alcohol produced by fermentation or the anaerobic (occurring in the absence of oxygen) digestion of plant materials with a high sugar content. Ethanol is also an unconventional or alternative fuel source for automobile engines.

EVAPORATION

a physical change of state in which a liquid is transformed into a vapor or gas.

EVAPOTRANSPIRATION

The process by which water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces and by transpiration from plants.

EVEN-AGED STAND

a forest area in which all the trees are the same age due to simultaneous planting or harvesting or having originated following a major disturbance event, such as a wildfire.

EVERGREEN

a plant that retains its leaves year-round. In temperate zones, these are most often conifers.

EXTINCTION

the complete elimination of a species from the Earth.

F
FIBER

a thread-like body or filament many times longer than its diameter. Paper pulps are composed of fibers, usually of vegetable origin, but sometimes animal, mineral, or synthetic, for special types of papers.

FIELD

a terrestrial area devoid of trees, and generally characterized by grass or other herbaceous vegetation.

FOOD CHAIN

the transfer of food energy from organisms in one nutritional level to those in another.

FOOD WEB

the complex and interlocking series of food chains.

FOREST

a large area of land primarily covered with trees as well as the other organisms, soil, water, and air associated with them.

FOREST CERTIFICATION

a systematic and documented verification process to obtain and evaluate evidence objectively to determine whether a forest management organization’s work conforms to the requirements of a forest management standard. These requirements include measures to protect water quality, biodiversity, wildlife habitat, species at risk and forests with exceptional conservation value.

FOREST COVER

The dominant tree species or combination of tree species present. Forests can be classified according to their cover type.

FOREST FLOOR

the layer of decomposing material that covers the soil in a forest.

FOREST HEALTH

The perceived condition of a forest based on its age, structure, composition, function, vigor, presence of unusual levels of insects or disease, and resilience to disturbance.

FOREST MANAGEMENT

the practical application of scientific, economic, and social principles to the administration of a forest.

FOREST PRODUCT

Any item or material derived from forests for commercial use, such as lumber, paper, mushrooms or forage for livestock.

FORESTLAND

an area at least one acre in size and containing 10% or more tree cover.

FORESTRY

the principles and practices utilized in the management, use, and enjoyment of forests. Forestry includes a broad range of activities such as managing timber, fish, wildlife, range, watersheds, and recreation.

FOSSIL FUEL

coal, oil, and other energy sources that formed over millions of years from the remains of ancient plants and animals. Fossil fuel use is a major factor in greenhouse gas emissions, which contribute to climate change.

FRAGMENTATION

the dividing of large, continuous ecosystems and habitats into smaller isolated parcels. Fragmentation can impact forests, prairies, and aquatic habitats.

FUNGI

A kingdom of organisms that lack chlorophyll and cellulose in their cell walls, and which include mushrooms and molds. Fungi are important decomposers of organic wastes.

G
GENETIC DIVERSITY

variability in the genetic or hereditary makeup among individuals within a single species.

GEOTHERMAL ENERGY

heat transferred from the earth's interior to underground concentrations of steam or hot water trapped in fractured or porous rock.

GLACIER

a flowing body of ice, formed in a region where snowfall exceeds melting.

GLOBAL CLIMATE CHANGE

See CLIMATE CHANGE.

GLOBAL WARMING

the observed increase in the average temperature of the Earth's innermost atmosphere, which is believed to be a result of the greenhouse effect. See CLIMATE CHANGE.

GLOBALIZATION

The increasing interdependence of countries and economies brought by greater movement of goods and people around the world.

GRASSLAND

a vegetation community in which grasses are the dominant plants.

GREENHOUSE EFFECT

the trapping of heat by gases, such as carbon dioxide, methane, and nitrous oxides in the Earth's atmosphere.

GREENHOUSE GASES

gases in Earth's lower atmosphere (troposphere) that trap heat. Examples are carbon dioxide, methane, nitrous oxide, and water vapor.

GROSS NATIONAL PRODUCT (GNP)

total market value in current dollars of all goods and services produced by a country's economy for final use during a year.

GROUNDWATER

water that infiltrates into the soil and is stored in slowly flowing and slowly renewed underground reservoirs called aquifers.

GYMNOSPERM

a plant that produces "naked" seeds that are not enclosed in a fruit.

H
HABITAT

an area that provides an animal or plant with adequate food, water, shelter, and living space in a suitable arrangement.

HARDWOOD

1) a deciduous or broadleaf tree. 2) the wood from such trees.

HEARTWOOD

the older, harder, nonliving central portion of wood of some trees that is usually darker, denser, less permeable, and more durable than the surrounding sapwood. Many trees do not form a true heartwood.

HERB

any flowering plant or fern that has a soft, rather than woody, stem. Generally refers to aromatic plants.

HERBICIDE

a substance or preparation used for killing undesirable plants.

HERBIVORE

an organism that feeds on vegetation.

HORTICULTURE

the science of growing plants.

HUMUS

decomposed material in the soil that is a highly complex mixture of organic and inorganic substances.

HYDROCARBONS

organic compounds that occur in fossil fuels that contain only hydrogen and carbon.

HYDROELECTRICITY

electric energy produced by falling or flowing water. Also known as hydropower.

I
INCREMENT BORER

an instrument used to take core samples allowing one to determine the rate of a tree's radial growth and its age.

INDICATOR SPECIES

a species that is intended to reflect the state of or changes in an environment (to act as an "index" without more costly quantification) and that is used to assess the impacts of management actions on a particular area.

INNER BARK

See PHLOEM.

INVASIVE SPECIES

a plant, animal, or other organism that is typically nonnative (or alien) to a particular ecosystem and whose introduction causes, or is likely to cause, harm to the economy, the environment, or human health. Killer bees and water hyacinth are two examples of invasive species.

L
LANDFILL

a specially engineered site for disposing of solid waste on land, designed to confine the refuse to the smallest practical area and reduce it to the smallest practical volume.

LATERAL ROOT

a secondary root that branches horizontally from a plant's main root.

LEACHING

the removal of soluble substances from soil by percolating water.

LEAF

a thin, flat structure that grows out from a plant's stem and that is the main organ of photosynthesis and transpiration. The term for more than one leaf is leaves.

LIFE CYCLE

the phases, changes, or stages through which an organism passes during its lifetime.

LIVABILITY

the sum of factors that add up to a community’s quality of life.

LOAM

soil containing a mixture of clay, silt, sand, and humus. Loam contains a variety of particle sizes, which makes it ideal for most trees and other plants as it provides a balance of water retention and aeration.

M
MANAGEMENT INDICATOR SPECIES

See INDICATOR SPECIES.

MARSH

a wetland without trees, and which often has standing water.

MICROCLIMATE

a local set of atmospheric conditions that differ from those in the surrounding areas.

MICROHABITAT

a "small habitat" within a larger habitat in which environmental conditions differ from those in the surrounding area.

MINERAL

a naturally occurring inorganic crystalline material found in the Earth's crust.

MIXED FOREST

a forest that includes both coniferous and broadleaf trees.

MULTIPLE-USE MANAGEMENT

the management of forests for more than one purpose, often including the long-term yield of wood or other forest products and one or more other objectives, such as wildlife.

N
NATIVE SPECIES

a species that occurs naturally in an area or habitat.

NATURAL GAS

a naturally occurring fossil fuel energy source formed deep beneath Earth's surface and consisting primarily of the gas methane.

NATURAL RESOURCES

those raw materials supplied by the Earth and its processes. Natural resources include nutrients, minerals, water, plants, animals, etc.

NEEDLELEAF

describes a tree or shrub with narrow, needle-like leaves. See CONIFER.

NICHE

both the ecological role played by a species and the range of conditions necessary for its persistence. Also refers to specific places where an individual organism can live.

NON-NATIVE SPECIES

a species that has been introduced by human action, either intentionally or by accident, into areas outside its natural range. Other names for these species include alien, exotic, and introduced.

NONRENEWABLE RESOURCE

A naturally occurring raw material or form of energy that, once used, cannot be replaced in this geological age. Oil, gas, copper, and gold are examples of nonrenewable resources. The terms nonrenewable energy and nonrenewable also refer to this type of resource.

NUCLEAR ENERGY

Energy that comes from splitting atoms in a reactor to heat water into steam, turn a turbine, and generate electricity.

NURSE LOG

a decaying tree stump or fallen tree that provides nutrients and moisture for new plants and space for them to grow.

NUTRIENT

a substance required for growth and development. Plants, for example, need water and minerals in order to grow and reproduce.

O
OLD GROWTH FOREST

a forest that contains a disproportionate percentage of trees of the oldest age class for that forest type. What age category qualifies as "old growth" will depend on the forest type, region, and life history of the surrounding trees and landscape.

OMNIVORES

organisms that eat both animals and plants.

OPEN SPACE

land that is not developed. In urban settings, this term is sometimes used interchangeably with the term green space.

ORGANIC

referring to or derived from living organisms. In chemistry, any compound containing carbon.

ORGANISM

an individual living thing.

OUTCOMPETE

to more successfully use the resources shared by other. species, often resulting in displacement of those species.

P
PARTICULATE MATTER

a mixture of extremely small particles and liquid droplets, which may include chemicals, metals, and soil or dust particles.

PASSIVE MANAGEMENT

Managing a forest area by letting nature take its course.

PEAT

moist, semi-decayed organic matter.

PERCENTILE

a value on a scale of 100 that indicates the percent of a distribution that is equal to or below it.

PERENNIAL

a plant that lives for several years and when mature usually produces seeds each year.

PEST

an undesirable, harmful, or noxious organism.

PESTICIDE

an agent used to control undesirable organisms. This can be an insecticide for insect control, an herbicide for weed control, a fungicide for control of fungal plant diseases, or a rodenticide for killing rats and mice.

PETROLEUM

an oily flammable mixture of mostly hydrocarbons that is used to produce products such as gasoline and other fuels.

pH

a measure of the acidity or alkalinity of a material, liquid, or solid. A substance's pH is represented on a scale of 0 to 14: 7 represents a neutral state; 0, the most acidic; and 14, the most alkaline.

PHLOEM

the plant tissue that transports dissolved nutrients from the leaves to the other parts of the plant. Also called the inner bark.

PHOTOSYNTHESIS

the process by which green plants manufacture simple sugars in the presence of sunlight, carbon dioxide, and water. Chlorophyll is essential to the series of complex chemical reactions involved.

PIGMENT

a chemical substance that reflects or transmits only certain light rays and thus imparts color to an object. For example, a substance that absorbs all but red rays, which it reflects, will appear red.

PIONEER SPECIES

a hardy species that is among the first to colonize a barren environment or an environment that has undergone a major disturbance, such as a volcano or fire.

PLANTATION

a forest established by planting seeds or seedlings.

POLLINATION

the transfer of pollen from the male part of the plant (anther) to the female portion of the plant (stigma).

POLLUTANT

any introduced gas, liquid, or solid that makes a resource less useful or unfit for a specific purpose.

POLLUTION

harmful substances deposited in the air, water, or land, leading to a state of dirtiness, impurity, or unhealthiness.

PRECIPITATION

water from the atmosphere that falls to the ground as rain, snow, sleet, or hail.

PREDATOR

an animal that hunts or captures other animals for food.

PRESCRIBED BURNING

the planned application of fire to a forest, stand, prairie, or slash pile with the intent to confine the burning to a predetermined area.

PRIMARY ENERGY SOURCE

something that can be extracted or captured directly from the environment and used to power lights, cooking, heating, machines, etc. Petroleum, natural gas, coal, wind, and solar are examples of primary energy sources.

PRIMARY SUCCESSION

the establishment of vegetation and animal species on a site previously unoccupied by living organisms, such as on a cooled lava flow or on a sand dune.

PRODUCER

an organism that synthesizes organic compounds from inorganic substances via photosynthesis (by green plants) or chemosynthesis (by anaerobic bacteria).

PROTOPLASM

the complex of protein, other organic and inorganic substances, and water that constitutes the living nucleus, cytoplasm, plastids, and mitochondria of the cell.

PUBLIC LAND

land owned by the citizens and administered and managed by the local, state/provincial, or federal government agencies.

PULP

fibrous material prepared from wood, recovered paper, cotton, grasses, etc., by chemical or mechanical processes for use in making paper or cellulose products.

R
RANGELAND

an open region of land that produces grasses and other forms of vegetation on which organisms can feed. Two common types of rangeland are pasture (enclosed, managed grazing lands) and open range (unmanaged, open grazing lands).

RARE SPECIES

a species that populates a site or region infrequently or in very low numbers. However, rare species are not necessarily endangered.

RECYCLABLE

a resource or product that can be collected and reprocessed and made into new products.

RECYCLE

1) a multi-phased process which includes removal, separation, and or diversion of materials from the waste stream. 2) use of such materials as raw materials for the manufacture of new products; and use of the new product.

REFORESTATION

the renewal of forest cover by natural regeneration or the planting of seeds or seedlings.

REGENERATION

the renewal of vegetation by natural or artificial means.

RENEWABLE RESOURCE

a naturally occurring raw material or form of energy that has the capacity to replenish itself through ecological cycles and sound management practices. The sun, wind, falling water, and trees are examples of renewable resources. The terms renewable energy and renewable also refer to this type of resource.

RESPIRATION

a process that occurs in the cells of most living organisms in which nutrient organic molecules such as glucose combine with oxygen and produce carbon dioxide, water, and energy.

RIPARIAN ZONE

The area that surrounds wetlands, lakes, rivers, or streams, forming a transition zone between aquatic and upland habitats.

ROOT HAIRS

a filamentous outgrowth near the tip of a rootlet that functions in absorption of water and minerals.

ROOTLET

a small root.

ROTATION

the planned number of years between the formation of a crop and its final cutting at a specified stage of maturity.

RUNOFF

water from precipitation and melting ice that flows on the ground surface into nearby streams, lakes, wetlands, and reservoirs.

S
SAMARA

a dry, one-seeded, winged fruit, i.e. the fruit of a maple or elm tree.

SAND

a course, granular soil particle between 0.05 to 2.0 mm in size.

SAP

the fluid part of a vascular plant or, more specifically, the material transported via the xylem and the phloem of a tree.

SAPLING

a young tree normally more than 4½ feet (1.5 m) high and less than 4 inches (10 cm) in diameter, depending on the species.

SAPWOOD

the younger, softer, living or physiologically active outer portion of a tree's wood that lies between the cambium and the heartwood and is more permeable, less durable, and usually lighter in color than the heartwood. The tree's water and nutrient needs are transported within the sapwood.

SAVANNA

a grassland with scattered trees or clumps of trees. Savannas are common to tropical and subtropical regions.

SCAVENGER

an animal that eats the dead remains and wastes of other animals and plants.

SECONDARY ENERGY SOURCE

something that has been transformed from a primary energy source into a more useful form for powering lights, cooking, heating, machines, etc. Electricity, gasoline, and biofuels are examples of secondary energy sources.

SECONDARY SUCCESSION

the sequential development of communities in an area in which natural vegetation has been removed but the soil is not destroyed.

SEDIMENT

1) the solid precipitate or matter that settles to the bottom of a liquid. 2) the material deposited by water, wind, or glaciers.

SEED

a flowering plant's unit of reproduction, capable of developing into another such plant.

SEED TREE

a tree left behind when a stand is harvested or partially cleared to provide a source of seed for the species desired to be renewed.

SEEDLING

a young tree grown from a seed up to a small sapling.

SELECTION HARVEST

removal of individual or small clusters of trees to manage a forest stand for a mixture of age classes and products. Also known as selection system harvest.

SEROTINOUS

describing a pine cone or other seed case that requires heat from a fire to open and release the seed.

SHRUB

a woody plant less than 12 feet (4 m) tall, usually with more than one stem rising from the ground.

SILT

a medium-size particle of soil, between 0.005 and 0.02 mm in diameter. Silt is found in soil and as sediment, either mixed in suspension with water or deposited at the bottom of a stream, river, or lake.

SILVICULTURE

the art and science of managing and regenerating forests to influence their composition, structure, and growth.

SINGLE-TREE SELECTION

harvesting single trees in a forest stand.

SNAG

a standing dead tree from which most of the branches have fallen. Snags frequently provide homes for wildlife.

SOFTWOOD

a coniferous tree. The term softwood is commonly used but not strictly accurate; the wood of many conifers is harder than that of some nominally "hardwood" trees.

SOIL

The layer of earth in which plants grow, typically consisting of mineral particles, living and nonliving organic matter, water, air, and soil organisms.

SOLAR ENERGY

radiant light and heat from the sun that can be used to perform work.

SOLID WASTE

discarded solid materials, excluding recovered materials.

SPECIES

1) genetically similar organisms capable of breeding among themselves. 2) a naturally occurring taxonomic unit.

SPECIES DIVERSITY

the number of different species and their relative abundances in a given area.

STAND

a contiguous group of trees sufficiently uniform in species composition, arrangement of age classes, and condition to be considered a distinguishable unit.

STEWARDSHIP

the concept of responsible caretaking, based on the premise that humans are responsible to future generations for natural resources and environmental health.

STOMATA

microscopic openings in the surface of a leaf that allow gases to pass in and out.

SUCCESSION

the gradual replacement of one ecological community by another. It may also be called ecological succession.

SUCCESSIONAL STAGE

a distinguishable stage in the process of succession.

SUSTAINABLE

using natural and human resources in a way that does not compromise the needs of future generations.

SUSTAINABLE FORESTRY

To meet the needs of the present without compromising the ability of future generations to meet their own needs by practicing a land stewardship ethic that integrates reforestation and the managing, growing, nurturing, and harvesting of trees for useful products and ecosystem services such as the conservation of soil, air and water quality,
carbon, biological diversity, wildlife and aquatic habitats, recreation and aesthetics.

SUSTAINABLE YIELD

the highest rate at which a resource may be used without reducing its long-term availability or limiting its ability to renew itself.

SUSTAINABLY MANAGED FORESTS

forests managed meet the needs of the present without compromising the ability of future generations to meet their own needs by practicing a land stewardship ethic that integrates reforestation and the managing, growing, nurturing, and harvesting of trees for useful products and ecosystem services such as the conservation of soil, air and water quality, carbon, biological diversity, wildlife and aquatic habitats, recreation and aesthetics.

SWAMP

a wetland dominated by trees.

SYMBIOSIS

species interaction in which two kinds of organisms live together in close association, with members of one or both species benefiting from the association.

T
TAPROOT

1) a primary root that grows vertically downward and gives off small lateral roots. 2) one that has a deep central position in a line of growth or development.

TEMPERATE FOREST

a forest growing in a region or climate that has moderate year-round temperatures and distinct seasons and that is neither tropical nor polar. A temperate forest is characterized by both broadleaf evergreens and conifers.

THIN

to selectively remove some of the trees in a forest area, allowing more water, sunlight, and nutrients for the trees that remain.

THREATENED SPECIES

a species that is declining numbers and is at risk of becoming endangered. See ENDANGERED SPECIES.

TIMBER

a forest stand containing trees of commercial size and quality suitable for sawing into lumber.

TIMBER CRUISE

a survey of a forest or forest stand to evaluate timber volumes and species composition, to mark trees for harvesting, or to identify other values or hazards.

TIMBER HARVEST

Removal of trees from a forest to restore ecological health or to obtain income from the wood products.

TIMBERLAND

forests that are capable of growing 20 cubic feet (.6 m3) per acre per year of commercial wood.

TIMBERLINE

the upper limit of tree growth on mountains.

TISSUE

a group of cells, usually a particular kind, that function together and form a structural material in an organism.

TRADITIONAL ECOLOGICAL KNOWLEDGE

The knowledge base learned and shared by indigenous and local peoples over many hundreds of years through direct contact with the environment.

TRANSPIRATION

the process by which water evaporates from plant tissues.

TREE

a woody plant usually 12 or more feet (4 or more m) tall with a single main stem (trunk) and a more or less distinct crown of leaves.

TREE COVER

The degree to which trees dominate a given geography, often expressed as a percentage of the spatial extent (eg. “the tree cover in that urban space was nearly 40%”).

TROPICAL RAINFOREST

wet, evergreen forests circling the equator in South and Central America, Africa, Asia, and many of the Pacific Islands. Their environment is distinguished by a warm, humid climate, capable of supporting an immense variety of life.

U
UNDERSTORY

the layer formed by the crowns of smaller trees in a forest.

UNEVEN-AGED STAND

a forest area composed of intermingled trees that differ markedly in age.

URBAN FOREST

The collection of trees growing in a city or town, including woodlands, street trees, and trees in parks and gardens.

V
VEGETATION

the mass of plants that covers a given area. Flora, a term often wrongly used interchangeably with vegetation, is a list of the species of plants that compose the vegetation.

VEGETATIVE PROPOGATION

asexual means of reproducing plants through root shoots, bulbs, leaf cuttings, underground stems, etc.

W
WASTE STREAM

the flow of discarded or excess materials from source through disposal.

WATER CYCLE

the constant movement of Earth's water as it evaporates from Earth's surface, rises into the atmosphere, cools and condenses into rain or snow in clouds, and falls again to the surface.

WATERSHED

the land area that collects precipitation and runoff water and drains it into a common stream or river.

WETLAND

an area that is regularly wet or flooded, and where the water table stands at or above the land surface for at least part of the year, and which has a plant community comprised of species which require wet soil.

WILDERNESS AREA

an area established by the federal government to be managed and preserved in an essentially untouched condition. Wilderness areas are open to some recreational activities. Use of machinery, mining, logging, and many other commercial pursuits are often excluded from wilderness areas.

WILDFIRE

any fire other than a controlled or prescribed burn occurring on wild land.

WILDLAND–URBAN INTERFACE

the area or zone where homes and other human development meet or intermingle with undeveloped wildlands.

WILDLIFE

all organisms (except humans) that live naturally in an area, including mammals, birds, fish, insects, plants, and other lifeforms.

WIND ENERGY

power harnessed from the wind by the use of windmills or turbines.

WOODLAND

an area of land covered with trees.

WOODY BIOMASS

forest residues (such as fallen limbs and leaves) and sawdust and wood scraps from sawmills that can be converted into energy.

X
XYLEM

the complex woody tissue of higher plants that includes systems for transporting water, storing nutrients, and providing structural support.