Biological elements can be divided into two main types: species-related elements and ecological communities. An ecological community is defined as a distinct assemblage of plant species with similar total species composition and vegetation structure that can often be associated with particular environmental conditions. Given the right conditions, it reoccurs predictably.
Ecological communities can be separated into three major types:
Rare ecological communities include, but are not limited to, communities on the Alberta Ecological Community Tracking and Watch List. These are community types that have been described as unusual, uncommon, of limited extent or encountered infrequently. They also include community types that have been described by vegetation experts as in decline or as threatened in some way. All are considered to be significant at the provincial scale. Some may be nationally or globally significant. A rare ecological community may or may not include individual plant species of conservation concern. It is the grouping, the community itself, which is the element of interest. Ecological communities are "not just containers for species but complex, dynamic systems in themselves" (Anderson et al. 1999).
These have been developed through a review process, and continue to be refined as new community types are proposed and as more information is gathered on types already on the list. The communities on the lists are first split into terrestrial or aquatic types, then further organized into physiognomic classes. The work to document the ecological communities of Alberta is ongoing and new types not yet documented are to be expected. Some will be rare types that should be added to the tracking list.
There are many different kinds of ecological communities, ranging from those that are natural, to those that are dominated by cultivated species. Only natural, near-natural and some modified/managed communities are considered of conservation concern from the ecological community perspective. For example, communities that have formed in roadside ditches or those that have been planted or substantively altered by cultivation may well provide habitat for species of conservation concern, and hence be significant for other reasons, but they would not be considered rare communities.
Together, matrix and large patch communities usually make up the main, representative vegetation of an area. Small patch communities, although small in area, "contain a disproportionately large percentage of the total flora, and also support a specific and restricted set of associated fauna (e.g. invertebrates or herpetofauna) dependent on specialized conditions" (Anderson et al. 1999). Rare ecological communities are often, but not always, small patch types. An occurence for a tracked community should meet the minimum patch size specification.
Ecological communities are named using dominant and diagnostic species. Species within the same stratum are separated by a hyphen (-), species in different strata separated by a slash (/).
Anderson, M., P. Comer, D. Grossman, C. Groves, K. Poiani, M. Reid, R. Schneider, B. Vickery, A. Weakley. 1999. Guidelines for representing ecological communities in ecoregional conservation plans. The Nature Conservancy, Arlington VA. 74 pp.