Kinds of Ecological Communities

Planted/Cultivated Areas Vegetation

• Dominated by vegetation which has been planted in its current location by humans and/or is treated with annual tillage, a modified conservation tillage or other intensive management or manipulation.
• The majority of these areas are planted and/or maintained for the production of food, fiber or seed.

Natural/Near-Natural Vegetation

• Plant communities that appear not to have been modified by human activities or to have only been marginally impacted by such activities.
• Where impacts are apparent, there exists a clear, naturally maintained analogue for the existing physiognomic and floristic patterns.

Semi-Natural/Altered Vegetation

• Plant communities where the species composition and/or the structure of the vegetation has been altered through anthropogenic disturbance such that no clear natural analogue is known.

Ruderal Communities

• Vegetation resulting from succession following anthropogenic disturbance of an area.
• They are generally characterized by unnatural combinations of species. (These are primarily native species though they often contain slight to substantial numbers and amounts of species alien to the region as well.)

Invasive Communities

• Dominated by invasive alien species.
• Though these communities are often casually considered as "planted/cultivated", they are spontaneous, self-perpetuating and not the (immediate) result of planting, cultivation or human maintenance.
• Land occupied by invasive communities is generally permanently altered (converted) unless restoration efforts are undertaken.

Modified/Managed Communities

• Vegetation resulting from the management or modification of natural/near-natural vegetation but producing a structural and floristic combination not clearly known to have a natural analogue.
• Modified vegetation may be easily restorable by either management, time or restoration of ecological processes.

Reference
Grossman, D.H., D. Faber-Langendoen, A.S. Weakley, M. Anderson et. al. 1998. International classification of ecological communities; terrestrial vegetation of the United States. Vol. 1, The national vegetation classification system: development, status and applications. The Nature Conservancy, Arlington VA.