Glossary and Acronyms

Definitions of words in purple follow Moffett (2000). Moffett's paper is the best effort to provide comprehensive definitions of basic terms in canopy biology, so I have followed Moffett wherever possible. See also Nadkarni et al. (2001).

Much of the lichen terminology is adopted from the illustrated glossary in McCune & Geiser (1997) and is indicated by brown words.

A-C -- D-G -- H-K -- L-N -- O-R -- S-V -- W-Z


alectorioid lichen: Pendulous hairlike lichens, typically yellowish, greenish, or brownish; also known as "forage lichens." See examples.

bryophyte: A member of the plant order Bryophyta, including the mosses, liverworts, and hornworts. See examples.

canopy: The aboveground plant organs within a community. This term is applied to a collection of plants rather than individual plants (see "crown").

crown: aboveground parts of a tree or shrub, sometimes more particularly applied to the topmost leaves and limbs.

community: The collection of organisms included in a sampling unit (plot, quadrat, stand, etc.). This is the community in the concrete sense. Some ecologists apply it in an abstract sense as a recurrent association of organisms.

crustose: A crust-like growth form that is closely attached to the substrate, like paint, generally adhering by all of the lower surface and lacking a lower cortex and rhizines.

cyanolichen: A lichen containing cyanobacteria. The cyanobacteria may be the primary photosynthetic partner, or sequestered in special structures as a secondary photosynthetic partner. See examples.


emergent: An individual tree growing higher than all (or virtually all, if in a clump) others in its vicinity within a forest, so that its crown rises markedly above the adjacent overstory.

epiphyte: A plant, fungus, or microbe sustained entirely by nutrients and water received nonparasitically from within the canopy in which it resides.

epiphyte mat: A carpet-like aggregation of canopy plants along with associated suspended soils and debris. Also called a "moss mat" when mosses dominate.

FEMAT: Forest Ecosystem Management Assessment Team. This was the group responsible for producing the first Northwest Forest Plan in 1993. See reference.

FHM: Forest Health Monitoring. An interagency program concerned with monitoring regional forest health in all forested areas in the United States. Currently the program is administered under the Forest Inventory and Analysis program (FIA) of the U. S. Forest Service. See McCune (2000) and the website for a summary of the use of epiphytic lichens in this program.

foliose: A lichen growth form with dorsiventral lobes (having upper and lower surfaces), usually loosely to tightly appressed to the substrate, 2-dimensional or weakly 3-D.

forage lichens: Pendulous hairlike lichens, typically yellowish, greenish, or brownish; commonly consumed by mammals, such as deer (hence "forage"); also known as "alectorioid lichens." See examples.

fruticose: A 3-dimensional growth form of a lichen, not differentiated into upper and lower surfaces, and including pendulous and stringy, upright, or bushy forms.

gap: A space in a canopy created by the partial or whole death of a plant.

green algal lichen: A lichen having green algae as its photosynthetic partner.

green-tree retention: A forest cutting method that leaves a sizable fraction of the living overstory trees. Typically 10-40% of the overstory canopy is not cut.


hardwood gap: A gap in the canopy of a primarily coniferous forest that is filled with hardwood trees or shrubs.

Heritage Program: The Natural Heritage Program in the United States is initially a collaborative effort of The Nature Conservancy and individual states to preserve the natural heritage of the country. Many states have fully adopted the programs. The program focuses on elements (ecosystems or individual species) needing protection.

host (or host plant): Any plant on or in which another species resides. ("Phorophyte" is an often seen but awkward and unnecessary word for the host of an epiphyte.)

interception loss: The part of the precipitation falling on vegetation that does not reach the ground, including water evaporated from or absorbed within the canopy.


lichen: An obligate mutualistic association between a fungus and a photosynthetic partner (either green algae, cyanobacteria, or both).

liverwort: A bryophyte belonging to the class Hepaticae. These are primitive photosynthetic plants. Liverworts have one of two forms: thalloid liverworts are strap-shaped while leafy liverworts have a "stem-and-leaf" form similar to mosses.

matrix lichen: A macrolichen species with a green-algal photosynthetic partner and not a forage lichen. This catch-all category is sometimes referred to as "other" macrolichens. Most matrix lichens are widespread in PNW forests and occur frequently in both young and old forests.

moss: A bryophyte belonging to the class Musci. These are primitive photosynthetic plants. Mosses have a "stem-and-leaf" form when viewed closely. See examples.

moss mat: An epiphyte mat dominated by mosses.

mutualism: An association or interaction between different species of organisms where both partners benefit from the association.


old-growth associate: A species that is most frequent in old-growth forests.

old-growth forests: Forests that have persisted for centuries without stand-replacing disturbances. These typically have old trees, uneven-aged, multi-layered overstories, and abundant coarse woody debris. This term is defined more precisely in many different ways depending on the purpose; there is no universally agreed-upon definition.

overstory: The stratum of trees that have outgrown the other vegetation in a forest to have their uppermost crown foliage largely or fully in direct sunlight, usually as a relatively continuous layer (excluding gaps).

parasite: A plant, fungus, or microbe that actively extracts nutrients or water from live host plant tissues, typically by means of intrusive organs or by living internally. (Of course animals may be parasitized or parasites too.)

pin lichens: Lichens whose reproductive structures resemble a minute pin and pinhead, usually less than 4 mm tall. Most pin lichens grow on bark and wood in sheltered, humid microsites, such as on the lower side of leaning tree trunks.

remnant tree: A trees surviving a disturbance that removes most of the trees in a stand. The term can be applied either to natural disturbances (usually fire) or human-caused disturbances (cutting).

riparian: The strip of habitat along streams or lakes, and presumably influenced by those bodies of water. Various more precise definitions have been used, but not agreed upon.

ROD: Record of Decision. The formal document that in 1994 adopted the Northwest Forest Plan. See reference.


S&M species: Survey-and-manage species. Species in the Pacific Northwest of the United States that are to be surveyed for and/or managed under the Northwest Forest Plan, as specified in the Record of Decision.

snag: A standing dead tree trunk and any attached branches.

trunk: A single, erect, columnar, often woody plant axis of substantial height.

understory: The stratum of trees that (barring gaps) lies in the shade immediately below the overstory. Also loosely applied to all woody strata below the overstory.


wolf tree: A tree with large living lower branches, resulting from growing in the open (without close competitors) or growing adjacent to canopy gaps or permanent openings in the forest.