Terrestrial & Palustrine Plant Communities of Pennsylvania 2nd Ed.
Concepts
Terrestrial and Palustrine Plant Communities of Pennsylvania 2nd Edition builds on Fike (1999) in that the plant community concept is based on characteristic vegetation and physiognomy; hydrology, ecological processes, and distribution are also presented.
The following presents the PNHP concept of a plant community, describes how communities were named, and identifies data sources used.
Community Concept
Plant communities are groups of plants sharing a common environment that interact with each other, animal populations, and the physical environment. Terrestrial and Palustrine Plant Communities of Pennsylvania 2nd Edition shares the definition of community concept with NatureServe, which bases communities on characteristic vegetation and growth as they currently exist on the landscape. Ecological conditions, such as landform, soils and other ecological and geographical factors are not directly considered classification criteria, but are used to guide the structure of the classification (Faber-Langendoen et al. 2012). While this classification only includes natural or semi-natural vegetation types and does not include managed vegetation types (e.g. roadsides, agricultural fields, forest plantations), it is acknowledged that all plant community types have experienced some degree of direct human influence.
Community Descriptions
Community descriptions include a list of characteristic species that may or may not be dominant, but are either commonly associated with or serve to distinguish that type from other closely related types. An individual example of a community type is not likely to contain all of the species listed in the description, and the description includes only a fraction of the species that may be present in a community. Environmental descriptions may include information on soils, geology, hydrology, chemistry, hydrology, and disturbance. In many cases we do not yet have sufficient information to describe the environmental processes associated with different community types.
Data
The majority of the plant community types described in this edition is supported by quantitative data collected in several PNHP studies and determined through statistical analysis. Specifically, floodplain, vernal pool, and wet-thicket (shrub wetland) communities were assessed and described (Podniesinski and Wagner 2002, Zimmerman and Podniesinski 2008, Leppo et al. 2009, Furedi 2011a, 2011b). The plant communities of all National Park lands in Pennsylvania were classified, described, and mapped by PNHP using standard quantitative mapping and classification protocols (Perles et al. 2004, 2007, 2008). These data are available through PNHP and the partner agencies that manage the lands studied.
Community Name
Community type names are merely labels, and are not meant to describe community types in and of themselves. Types cannot be understood from the names alone; the entire description must be read. Where possible, the name of an individual community includes one or more of the dominant species and possibly defining ecological factors, such as physiographic setting or landscape position. Where species names are separated by a dash ("-") both species are commonly both present. Where the community type does not have clear dominants or ecological descriptors, general descriptors are used.
Organization
Plant community types can be organized in a number of ways. Initially, we have provided the user with the ability to organize the classification two ways - by Physiognomic Category (e.g. forest, woodland, shrubland), and by Ecological Group, which organizes the plant communities by biogeography and ecosystem factors. An additional tool to organize community types is the Wetland Community Key, which has a slightly different structure than the Physiognomic Category and Ecological Group and based on categories easily identifiable in the field.
Physiognomic Categories
In the physiognomic classification, the community types are first divided into two major systems, palustrine (wetlands) and terrestrial (non-wetlands). These systems are then divided into physiognomic categories (e.g. forest, woodland, shrubland). For terrestrial types, a dichotomous key from Fike (1999) is provided for the introduction to assist the user in determining which system and physiognomic category best describe a given site. One additional division is made within some physiognomic categories. In categories dominated by woody plants (forests, woodlands, and shrublands), the division is based on the dominant species leaf type (conifer, broadleaf, or combined conifer-broadleaf). This hierarchical arrangement allows the user to classify a site at a coarser scale if that is more appropriate, or if a specific community type cannot be determined.
Ecological Group
Ecological Groups were created for wetlands types and are made up of communities occurring together on the landscape, often dictated by physical ecological processes. Ecological Groups are similar to the first editions Community Complexes, which listed community types commonly associated with the physiographic setting, such as River bed - bank - floodplain complex.- Instead of only including representative types as Community Complexes, the Ecological Groups include all communities found within the system, even commonly occurring, broader types that may be present in many environmental settings. Thus, there is a great deal of overlap in Ecological Groups. Ecological Groups were based on definitions of ecological systems adapted from the U.S. Fish and Wildlife Service wetland classification (Cowardin et al. 1979) and NatureServes Ecological Systems. Wetland types fall within one or more of the River Floodplain, Peatland Wetland, Great Lakes Region Wetland, Basin Wetland, Tidal Wetland, Coastal Plain Wetland, and Seepage Wetland categories.
As updates to the terrestrial community classification occur, PNHP will be identifying Ecological Groups for uplands as well as wetland types.
