Plant communities are groups of plants sharing a common environment that
interact with each other, animal populations, and the physical environment. Certain
plant communities often occur together on the landscape due to shared
environmental requirements. This provides a way to organize biological
information, creating mappable units for land management and conservation
Communities are often defined by dominant plant species, which provide
useful habitat information for many animal species. This provides an efficient
starting point for biological surveys.
jurisdictional agency for plants in Pennsylvania, DCNR has developed a plant community classification for Pennsylvania through its
partnership with the Pennsylvania Natural Heritage Program (PNHP).
Plant Community Classification
role of the plant community classification is to define and standardize the
concept for each plant community type.
Plant community descriptions provide information about:
The common and
rare species found within them
Typical species composition
appearance and structure of vegetation
The physical environment with which
they are associated.
types provide a common framework for ecologists, foresters, environmental
planners, and others to use in a variety of ways, including vegetation mapping,
ecological restoration, environmental planning, and conservation.
DCNR’s land managers use PNHP’s Terrestrial and Palustrine Plant
Communities of Pennsylvania (2nd Edition) for describing forest and plant community types on state
forest lands and park lands.
currently has 127 documented plant communities, including 78 wetland and 49
terrestrial community types. These
community types can be organized or classified in several ways.
Classifying by Physical Appearance
One way is by “physiognomy,” which groups
types by the physical appearance of the plant community, such as forest, open
woodland, shrub land or herbaceous (dominated by grasses and non-woody
plants). Forest and woodland types can
also be further split by whether the dominant tree species are conifers (e.g.,
pines, hemlock or spruces) or broadleaf deciduous (e.g., maples, oaks, birches,
Classifying by Environmental Conditions
Another way to
classify communities is by “ecological groups,” which groups together plant
communities that tend to occur in similar environmental conditions.
For example, while there are 78 different
wetland plant community types in Pennsylvania, only five different types
regularly occur in vernal pools and a completely different set of
thirteen plant communities are associated with peatland wetlands (bogs and
communities vary in their distribution and extent across the commonwealth. Some plant communities are common and
widespread across different regions. For example, the Northern Hardwood Forest
community is the most common type across the northern tier of Pennsylvania,
while the Dry Oak -- Heath and Dry Oak -- Mixed Hardwood Forests are common
across much of the Ridge and Valley and Pocono Plateau Regions.
Other plant communities are relatively
uncommon and restricted to very specific habitats. The Serpentine Grassland is limited to a
handful of sites in the southeast corner of the state where serpentine bedrock is
at or near the surface. The unique
chemistry of serpentine bedrock (high in magnesium and heavy metals such as
nickel and chromium) result in a unique mix of serpentine-adapted species not
seen anyway else in Pennsylvania.
Plant Community Classification
plant community classification has been evolving over the past 35 years as the
PNHP continues to survey and collect
data across the commonwealth.
the wetland portion of the classification was updated and expanded, while the
terrestrial portion of the classification is under review and revision.
classification includes crosswalks to the National Vegetation
Classification, which allows you to see where the same or similar plant
communities occur in other states.