Named types of communities have
- structure (such as being forested or not forested),
- characteristic species that usually occur in that type of community,
- and dominant species that control or influence the growth of other species (for example, hemlock trees shade the ground so thoroughly that they limit what other species will be present).
Physical conditions influence the types of communities that can occur in particular areas:
- degree of wetness,
- abundance of nutrients,
- presence of salt,
- and many other physical factors control the species that occur and therefore the community type.
Red Maple Swamps and Level Bogs are types of Palustrine (wetland) natural communities where the presence of water controls the species present and, thus, the community type. Sandplain Grasslands occur in dry conditions on sandy soils.
Natural communities are not discrete units with neat boundaries; there is overlap among and between communities in their composition, structure, and physical characteristics. Large and mobile animals often include many community types in their habitats. Natural communities may be restricted or widespread in their distribution across the state.
We inventory and track the distribution and status of Priority Natural Communities and exemplary occurrences of more common types across the state. In June, 2016, the NHESP natural community datalayer on MassGIS was updated to include the mapped and described Priority and Exemplary Low-Priority Natural Communities in the NHESP database. The updated GIS layer uses the revised names and attributions from the 2020 Classification of Natural Communities of Massachusetts. Along with the revised Classification, NHESP produced new fact sheets, one per defined type of natural community, that include photos and distribution maps.