Alliance & Association Nomenclature & Descriptions

Nomenclature
Alliances are named for constant dominants or codominants in the uppermost canopy layer. When a group concept contains two layers of vegetation (e.g. Tall temperate grassland with sparse broad-leaved evergreen shrubs), the alliance is named after species in the dominant stratum, while the association name includes species from the dominant and upper-most strata.

Associations are named with species from the alliance name, and have additional species that represent dominants or indicators from any layer of the vegetation. When an association has several layers, an attempt is made to include species that are dominants or indicators from at least the two most dominant layers. Indicator species are those species, other than dominants, which have been chosen to distinguish an association or alliance from others like it, or to indicate specific environmental conditions that have a controlling influence on vegetation in the community. However, the indicator species are seldom limited to controlling influence on vegetation in the community. Descriptive terms such as wetland, mesic, serpentine, etc., are used sparingly, when species composition for a type is not known well enough to provide full representation using species alone.

Parentheses around one or more species in a name indicate that the species may or may not occur within the alliance or association, and may or may not be present in combination with the other species within the parentheses. For instance, the Quercus alba – (Quercus rubra, Carya spp.) Forest Alliance includes forests dominated by a mixture of Quercus alba (approximately 25-75 percent and always present) and either or both Quercus rubra and Carya spp. (approximately 25-75 percent in combination; see I.B.2.N.a.27).

Descriptions
The various components of text in the alliance and association descriptions have been provided by NatureServe through central databases that house the International Classification of Ecological Communities. Some alliances or associations may not have all field completed. Below is an explanation of the field descriptors:

Global alliance code and global scientific name:
The alliance code represents its position in the hierarchy as a series of Roman numerals, letters, and Arabic numerals, with a terminal sequential number. The global scientific name is the name of the alliance or association using scientific botanical nomenclature. Some associations repeat the species of the alliance name and are labeled "Provisional." These associations are placeholders for the one or many association(s) that remain to be developed in the alliance. They often represent a large, heterogeneous group of stands that are likely to be divided into separate associations following analysis of additional information. It should be noted that "Provisionals" are attributed based on geographic gaps, not necessarily classification gaps. That is, the listing of a state in the distribution field for a "Provisional" association only means that we suspect that the alliance in which the "Provisional" is placed occurs within that state, and that none of the associations so far developed has been attributed to that state. When an alliance is known to occur within a state and a "Provisional" association exists under that alliance, the absence of a state in the distribution field does not imply that all of the associations for that state have been fully entitated.

Translated name:
This is the same as the alliance/association scientific name but with common names instead of scientific names for the species.

GRANK:
The global rank. Values are G1, G2, G3, G4, G5, GH, GX, G?, as defined earlier in this report (SEE ALSO Appendix I).

SRANK:
The state rank. Values are either S1, S2, S3, S4, S5, SH, SX, S?, as defined in Appendix I.

Concept (alliance/association description):
Description of the conceptual borders of the alliance/association in terms of vegetation composition and structure, expected geographic distribution, and expected environmental factors (such as characteristic landscape position, rock type, soil texture, hydrology, etc.).

Comments:
This field contains miscellaneous additional comments, such as information about the range and variability of the type, local information which has not been globally reviewed, sources of information, problems to be resolved, etc.

Range (Distribution):
This gives the states (United States and Mexico), provinces (Canada), and other countries in which the alliance is known or suspected to occur. A state, province, or country shown without a "?" indicates that the alliance is documented to occur there, or is very likely to occur there. A "?" indicates that the distribution is uncertain or speculative -- the uncertainty often related to taxonomic questions about the circumscription of the alliance, but sometimes simply the result of lack of information. For most alliances, this listing is intended to be (and should be) comprehensive. For some alliances, particularly those that are peripheral to our region from north, west, or south (tropical), the listing may only represent partial information, generally biased towards political units in close proximity to our area of concern. Note that a state, province, or country may be listed for an alliance and not for any association in that alliance; this generally indicates that other associations remain to be described in the alliance.

Other States/Provinces:
A listing of the two-digit abbreviations of states in which the alliance or association occurs. For Associations, the state abbreviation is sometimes followed by a state rank (S1, S2, S3, S4, S5, S?, SH, SX) as it appears in the NatureServe databases.

TNC Ecoregions:
TNC Ecoregions are listed, along with an indication of the confidence with which the association is attributed to the ecoregion. TNC Ecoregions are modified from Bailey (1981, 1994) and are defined as a geographically distinct assemblage of vegetation types that share a large majority of their species, ecological dynamics, and similar environmental conditions, and whose ecological interactions are critical for their long-term persistence. Confidence levels are appended to each ecoregion listed and are defined as follows: "C" - Certain, the association is confidently assumed or known to occur in the ecoregion; >95% certain; "P" - Probable, the association is predicted to occur in the ecoregion based on the presence of suitable habitat or environmental conditions, or based on historical record and/or presence in an adjacent area; at least 80% certain; "?" - Possible, the association possibly or potentially occurs in the ecoregion, the likelihood of occurrence is between 80% and 10%. Distribution and confidence levels for USFS subsections (Keys et al. 1995) have been developed for alliances and associations and are available, but are not printed in this document.

Physiographic Province, Section and Subsection:
Distribution and confidence levels for USFS subsections (Keys et al. 1995) have been developed for alliances and associations. These are assigned a hierarchical code that references the Province and Section. The codes are listed for the full range of the alliance/association. A full listing of the codes for the U.S. can be found in Keys et al. (1995). The subsection code is followed by a colon and up to three digits of confidence levels (e.g. 232Ac:CCC). The first three digits of the code refer to the physiographic province; the next capital letter refers to the section; the next lower case letter refers to the subsection. After the colon are values for confidence in the province, section, and subsection in that order. A value of C=confident or certain that it occurs in the province, section, or subsection; P=predicted or probably that it occurs in the province, section, or subsection based on fact patterns (e.g. suitable habitat and present in adjacent section); ?=possible occurrence in the province, section, or subsection.

Federal Lands:
This field lists federal land units (such as National Park Service units, individual National Forests, etc.) within which the association occurs. This field is incompletely populated. The intent is to develop a comprehensive listing of the occurrence of vegetation types on the lands of important federal land-managing agencies, especially (in the Southeast) the U.S. Forest Service, Department of Defense, National Park Service, U.S. Fish and Wildlife Service, and Corps of Engineers. Because the field is in the process of being populated, the absence of a federal land management unit should not be considered to indicate that the type is absent on that unit, but the listing of a federal land management unit is generally a reliable indication of the type’s likely occurrence there. The information is currently most complete for U.S. Forest Service units, and for selected other units on which effort has been concentrated.

Synonymy:
Synonymy is given for some other vegetation or natural community classifications. For alliances, synonymy is provided to the Society of American Foresters (SAF) classification of forest cover types (Eyre 1980). Synonymy to state Heritage Program classifications is given, but this synonymy is not fully populated. Synonymy is also given to names used in the scientific literature, especially when that literature has been used as a primary source for development of the taxonomic unit and its description.

References:
This field is more fully populated for alliances than for associations. It provides a listing, by no means complete at this time, of literature which deals with the alliance or association. References listed are those that have contributed directly to the concept of the alliance or development of the association.

Responsible authors:
Initials of responsible authors are listed in parentheses following the name.

Confidence:
This code describes the degree of confidence associated with the classification of the element. This is based on the quality and type of data used in its development, as well as the extent to which the entire (or potential) range of the element was considered. Values are 1=strong; 2=moderate; 3=weak. This latter category may be used for a new type for which supporting data is limited.

Identifier:
For alliances, this is a sequential counter assigned by the database in which the data are maintained (e.g. A.1062). For associations, this is a ten-digit alphanumeric code that identifies the association (e.g. CEGL003950).

Classification of Vegetation Communities of Maryland: First Iteration

A Subset of the International Classification of Ecological
Communities: Terrestrial Vegetation of the United States
March 2004