Sumter National Forest Final Report - NatureServe

The use of a joint physiognomic-floristic classification influences the alliance concept developed in the national classification. Thealliance is constrained both by the floristic patterns of the associations it contains and by the physiognomic-ecologic patterns of theformation that it represents. From a top-down perspective, this facilitates identification of alliances. Information from a wide varietyof sources that describes the dominant species of different formations (e.g., wet meadows, saturated peatlands, or temperate broadleavedevergreen forests) can be used to develop some initial floristic groupings. From a bottom-up perspective, however, this maylead to alliances that differ physiognomically, but otherwise share many species in common. Associations that share a number ofdominant or diagnostic species may be placed under different alliances that are in separate formations.Guidelines for alliance nomenclature are as follows. Dominant and diagnostic species are identified from the dominant and/or topstrata of the vegetation. Species placed in parentheses are less consistently found in all associations of the alliance, and the nameswithin parentheses generally are listed alphabetically. Vascular plant species nomenclature follows the nationally standardized list,Kartesz (1999), with very few exceptions. Nomenclature for nonvascular plants follows Anderson (1990), Anderson et al. (1990),Egan (1987, 1989, 1990), Esslinger and Egan (1995), and Stotler and Crandall-Stotler (1977). Alliance names include the formationclass in which they are listed, e.g., Pinus ponderosa Forest Alliance. For wetland alliances, the hydrologic regime that the alliance isfound in is always provided for clarity, e.g., Acer saccharinum Temporarily Flooded Forest Alliance. Therefore, all alliances that haveno hydrological modifier are upland alliances. Environmental or geographic descriptors are used sparingly, to more clearly separatealliances with the same nominal species or to provide clarity when differential species are not yet known (e.g., Quercus stellataFlatwoods Forest Alliance; Acer grandidentatum Montane Forest Alliance; Taxodium ascendens Tropical Woodland Alliance).THE ASSOCIATION CONCEPTThe association (or plant association) is the finest level of the classification system. For the terrestrial system, plant association is defined as“a plant community of definite floristic composition, presenting a uniform physiognomy, and growing in uniform habitat conditions”(Flahault and Schroter 1910). This basic concept has been used by most schools of vegetation classification (Whittaker 1962, Braun-Blanquet 1965, Westhoff and van der Maarel 1978). In this traditional sense, the plant association concept applies to existing vegetationregardless of successional status. The terms "association", "plant association", “community”, and “community association” are usedinterchangeably.The plant association is differentiated from the alliance level by additional plant species, found in any stratum, which indicate finer scaleenvironmental patterns and disturbance regimes. This level is derived from analyzing complete floristic composition of the vegetation unitwhen plot data are available. In the absence of a complete data set, approximation of this level is reached by using available information onthe dominant species or environmental modifiers, and their hypothesized indicator species. NatureServe will primarily use the plantassociation as the level at which community inventory and conservation action are aimed.While this definition of a plant association is still generally accepted as an international standard, a few clarifications of the use of thedefinition for the USNVC may be helpful:• “Habitat” refers to the combination of environmental conditions and ecological processes influencing the community.• Uniformity of physiognomy and habitat conditions may include patterned heterogeneity (e.g., hummock/hollow).• As a rule, community elements occur repeatedly over the natural landscape.• The scale of the community element varies. Among other factors, the variation is determined by the size and apparent homogeneity ofthe occurrences across the landscape, the amount of data that has been collected and the interpretation of these data by the field experts.• The community element may be composed of a complex of plant associations that constitutes a functioning ecological unit if the plantassociations always occur together (e.g., prairie mound and intermound, wooded ridge and swale complex).Associations are named with one or more species from the alliance name, and have additional species that represent dominants orindicators from any layer of the vegetation. Associations are named with one or more component plant species, separated bypunctuation to indicate strata, followed by a descriptor of the physiognomic class. Strata are separated by the 'forward slash' /, whilespecies within strata are separated by hyphens. Nominal species which are substantially inconstant, that is, often absent in a givenoccurrence (stand) of the type, are placed in parentheses. Within a stratum, parenthetic species are always placed followingnonparenthetic (more constant) species. If more than one species in a stratum is parenthetic, the species are separated by commas andalphabetized. For instance, the Pinus palustris - Pinus (echinata, taeda) Woodland can include stands dominated by a mixture ofPinus palustris and either or both Pinus echinata and Pinus taeda. An environmental or geographic descriptor such as wetland,mesic, serpentine, etc., are used sparingly, when species composition for a type is not known well enough to provide fullrepresentation using only species in a name. When an environmental/geographic descriptor is used, it is inserted between the floristicnominals and the class descriptor.EXAMPLES:Quercus palustris - Quercus bicolor - Quercus macrocarpa - Acer rubrum Sand Flatwoods ForestQuercus falcata - Quercus alba - Carya spp. Interior Plateau ForestVegetation of Sumter National Forest April 30 2004Copyright © 2004 NatureServeix