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

Format of this Document

This publication presents a Maryland subset of the current International Classification of Ecological Communities. Data used have been extracted from NatureServe biological conservation databases and are current as of April 2003. The format in which the classification is presented, and the current completeness of information in various fields in the classification, requires some explanation.

General
The classification is presented in the order of the hierarchy. Only those hierarchy units currently documented or suspected to occur in Maryland with a high degree of confidence are presented. The hierarchy is presented in full in Grossman et al. 1998. The complete hierarchy offers a broad perspective on the physiographic/floristic structure on the classification. The hierarchical presentation of the alliances and associations generally places closely related vegetation types near one another. Thus, the Forest Class (vegetation dominated by closed canopies of trees) is followed by the Woodland Class (vegetation dominated by open canopies of trees). All mixed needle-leaved evergreen-cold-deciduous forests will be found together in the Mixed Evergreen-Deciduous Forest Subclass. Of course, such a linear ordering of types that does not and cannot capture all relationships, and sometimes communities that are closely related floristically are separated widely by the physiographic hierarchy. For instance, Mixed Needle-leaved Evergreen –Cold deciduous woodlands are group together in II.C, separate from the Mixed Needle-leaved Evergreen-Cold deciduous Forests. Some examples of close relationships that are particularly prone to cut across the hierarchy are:

Forests (I) and Woodlands (II). The structure of the hierarchy between the Forest Class and the Woodland Class is relatively parallel, and in many cases, forests and woodlands with similar composition may be found in both classes.

In the "woody classes," Forests (I), Woodlands (II), Shrublands (III), and Dwarf-shrublands (IV), there are often close relationships between "mixed evergreen - deciduous" (Subclass C) and both "evergreen" (Subclass A) and "deciduous" (Subclass B). This is especially true in most parts of the Southeast, where there is not a strong dominance of either deciduous or evergreen life strategies; species with both strategies often occur in variable mixtures, and two closely related associations may be best placed in different subclasses because of a difference in prevalent dominance of several evergreen and deciduous species.

Woodlands (II) and Shrublands (III) with particularly open woody structure are often closely related to herbaceous types (V), especially grasslands (V.A).

Sparsely Vegetated (VII), Nonvascular (VI), and Herbaceous (V) are often closely related.