USDA Forest Service

Northeastern Research Station


Northeastern Research Station
11 Campus Blvd.
Suite 200
Newtown Square, PA 19073

(610) 557-4017
(610) 557-4132 TTY/TDD

United States Department of Agriculture Forest Service.

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Research & Development

Themes: Glossary

abiotic: not involving or produced by organisms; abiotic agents or stressors - forces or factors that aren't biological, such as weather or soil parent material; stressors are stress-causing forces or factors.

age-class distributions: an age-class is a distinct aggregation of trees originating from a single natural event or regeneration activity, or a grouping of trees, e.g., a 10-year age class, as used in inventory or management. An age-class distribution is the location and/or proportionate representation of different age classes in a forest.

anthropogenic: of, relating to, or influenced by the impact of humans on nature.

aquatic ecosystems: abiotic and biotic components of bodies of water and associated terrestrial areas, including streams, lakes, ponds, springs, estuaries, and oceans.

atmospheric deposition: the transfer of materials from the atmosphere by dry and wet deposition to the surface of the earth. Acidic deposition involves the transfer of acidic or acidifying materials.

atmospheric pollution: solid, liquid, or gaseous materials that occur in the troposphere in quantities in excess of normal amounts--they may result from both human and natural processes.

biocontrol:the control of insect pests and diseases through the use of a living organism (e.g., viruses, parasitic wasps, and mice and all feed on or use the life stages of the gypsy moth as host).

biological diversity: the variety and abundance of life forms, processes, functions, and structures, including the relative complexity of species, communities, gene pools, and ecosystems at spatial scales that range from local through regional to global.

biogeochemical cycling: the flow of energy, water, and elements between the atmosphere, biomass, soil, and geologic material. Nutrient cycles focus on chemical elements essential for life (e.g., carbon, nitrogen, or calcium).

bioindicator: changes in organisms that can be reliably used to indicate a change in the environment. These changes may be physiological, chemical, or behavioral.

biomass: the total quantity, at a given time, of living organisms of one or more species per unit area.

biorational: the control of insect pests and diseases through the use of a biological agent other than a living organism -- for example proteins (e.g., Bt toxins) that are toxic to insects are used as biorational control agents.

carbon budget: the balance of exchanges of carbon between carbon reservoirs (e.g., forest biomass, forest soil) -- carbon budgets indicate whether a reservoir is emitting or storing carbon dioxide.

exotic organisms: non-indigenous plants, animals, and microbes found beyond their natural ranges.

experimental forest: an area administered by the United States Forest Service, sometimes with cooperators, "to provide for the research necessary for the management of the land."

FIBER: "Forest Increment Based on Ecological Rationale" is a stand projection growth model for the major commercial tree species in New England -- a range of even-aged and uneven-aged silviculture treatments and harvesting schedules can be applied to forest stands growing ecological land classifications of sugar maple-ash, beech-red maple, oak-white pine, spruce-fir, hemlock-spruce, and cedar-black spruce.

gap dynamics: a regeneration process whereby small-scale, localized disturbance gaps form in the canopy, as one or a few trees die, and release resources of light, nutrients, water, etc. for colonization of the gap by seedlings or saplings of the same or replacement species.

genetic engineering: the manipulation of nucleic acid sequences -- the manipulation of a gene(s) in an organism to achieve a desired change in phenotype -- the transfer of a gene from one organism (e.g., the human insulin gene) into another (e.g., E. coli) for the purpose of producing the protein coded for by that gene (human insulin).

genotype: the genetic constitution of an individual or group.

geomorphology: the study of the land and submarine relief features of the earth's surface and their genetic interpretation.

genetic marker: a dominant gene or trait that can be used to identify a gene or phenotypic trait(s) associated with it.

geographic information systems: systems known as Geographic Information Systems vary widely in capability, but they all essentially contain functions for the capture, storage, retrieval, transformation, manipulation, analysis and display of spatial data--a spatial database management system.

GypsES: a GIS-based decision support system for gypsy moth management, under development by the Northeastern Research Station and cooperators.

hardwood log grading: a method of classifying merchantable woods-run logs in log classes (grades) that reflect yield and potential value.

hydrological cycle: the continuous circulation of water from the atmosphere to earth and oceans and back again, powered by solar energy.

in vitro selection: the choice and propagation of desirable trees or other plants using plant cultures and biotechnology.

molecular marker: a gene or DNA sequence that can be used to identify an organism, species, or strain or phenotypic trait(s) associated with it.

natural disturbance regimes: the temporal and spatial relationships of a disturbance on a site; includes the frequency of occurrence, the return interval (time to the next occurrence), and the rotation interval (time to disturb an entire area).

NED: a set of computer-based decision-support tools for natural resource management for multiple objectives, under development by the Northeastern Research Station and cooperators.

nutrient budget: the measure of the input and outflow of elements through the various components of an ecosystem.

pathogen: a specific causative agent of disease.

remote sensing: the acquisition of information about an object without physical contact. The result can be either photographs or digital imagery, and can contain a wide range of spectral, spatial, and temporal scales. Image analysis, whether manual or computer-assisted, is an important technique for deriving information from remotely-sensed imagery for input into a GIS.

riparian: relating to or situated on the bank of a river or stream.

silvics: the study of the life history and general characteristics of forest trees and stands with particular reference to locality factors, as a basis for the practice of silviculture.


smolt: a young salmon that is about two years old and at the stage of development when it assumes the silvery color of the adult.

spatial scale: the size of area at which different ecological processes occur -- for example, photosynthesis occurs at a cellular scale, measured in microns, while tornadoes occur at a landscape scale, measured in tens to thousands of square miles.

stand: a contiguous group of trees sufficiently uniform in age class distribution, composition, and structure, and growing on a site of sufficiently uniform quality, to be a distinguishable unit.

sustainability: a measure of the extent to which our activities meet "the needs of the present without compromising the ability of future generations to meet their own needs."

technology transfer: the transfer of ideas, information, methods, procedures, techniques, tools, or technology from the developers to potential users. Methods of technology transfer include scientific publications in peer-reviewed journals, articles in management-oriented publications, computer programs, training sessions, tours, workshops and others.

understory: generally, trees and woody species growing under the largest trees in a forest or forest stand; sometimes the plant community on the forest floor, including tree seedlings.

urban forestry: the management of vegetation, particularly trees and forests, to improve the urban environment and the quality of life of people who live, work, and spend their leisure time in urban and urbanizing landscapes.

vegetative strata: a distinct layer of vegetation within a forest community.

vernal pool: a temporary pool of water formed during a spring thaw.

USDA Forest Service - Northeastern Research Station
