Sumter National Forest Final Report - NatureServe

When detailed information is available, two primary ranking factors are used in assessing the appropriate conservation status rank fora community element: (1) the total number of occurrences and (2) the total area (acreage) of the element. Secondary ranking factorssuch as the geographic range over which the element occurs, the threats to the occurrences, and the viability of the extant occurrencesalso affect the rank.Although community ranking is best done when information on all the factors listed above is available, it is often necessary toestablish preliminary ranks when this information is lacking or incomplete. This is particularly true for communities that have notbeen well described. In practice, four main factors have been useful in arriving at a preliminary assessment of a community’srangewide (global) rank:1. The geographic range over which the type occurs.2. The long term decline of the type across this range.3. The degree of site specificity exhibited by the type.4. The rarity across the range based on state ranks assigned by state Natural Heritage Programs.Most of the ranks currently applied to USNVC types are based on such preliminary assessments of rarity.Imperiled community types (and species), those ranked G1 through G3, are often regarded as the principal targets for conservationaction, although NatureServe is dedicated to the conservation of all native community types. Special attention is generally given totaxa of high endangerment, as opportunities for their conservation may be limited in space and time. However, some highly rankedcommunity types may be essentially secure because of their occurrence in areas that are remote from human alteration, that alreadyhave high degrees of protection, or that are unsuitable as human habitat. Others are essentially secure because of their intrinsicresistance to alteration or degradation. The conservation status of highly ranked communities should be assessed and steps should betaken to ensure their adequate protection.More common and less imperiled community types, those ranked G4 and G5, are also conservation priorities. In most parts of theworld, these more common community types have generally been highly altered and degraded by human action, and have often alsobeen fragmented and their functioning impaired. For the conservation of many rare and common species, these relatively securecommunities are of critical importance. In North America, a large tract of a common vegetation type in pristine condition that occursin an essentially intact landscape with relatively intact ecological processes is of high priority for conservation. Though the type itselfis common, large, high quality examples are rare and the opportunity to conserve such an example may be very limited. Generally,the conservation of lower ranked community types should be focused on examples in especially good condition, of large extent, withhigh landscape integrity/connectivity, and with ancillary conservation benefits. Because a primary purpose of the USNVC is to helpset conservation priorities for natural community types, the recognition and naming of units reflects their relative naturalness. Theregenerally exists a strong correlation between naturalness and conservation priority.The dynamic nature of vegetation presents some additional complications in the evaluation of the naturalness and conservationpriority of community units. Early- and mid-seral vegetation may be readily classifiable as distinct in composition and physiognomyfrom later seral vegetation, but may be transient on the landscape. Transience makes this vegetation difficult to “track” or monitorover time and the conservation of seral sequences will generally be dependent on the conservation of large landscapes that contain amosaic of seral stages.Also, disturbances cannot be clearly and cleanly classified as “natural” or “anthropogenic”. Some anthropogenic disturbances aresimilar enough to natural disturbances that the resulting successional communities cannot be clearly distinguished, while others maycreate unique and unprecedented communities that do not occur in the natural landscape.We therefore have developed categories and a resulting ranking system for communities that go beyond those used for speciesconservation. The various ranks used for communities presented in this document are listed and briefly described in Table 2. Forfurther information on ranking see Master (1991).TABLE 2: Global Rank DefinitionsGXGHG1ELIMINATED throughout its range, with no restoration potential due to extinction of dominant or characteristic species.PRESUMED ELIMINATED (HISTORIC) throughout its range, with no or virtually no likelihood that it will be rediscovered,but with the potential for restoration (e.g., Castanea dentata Forest).CRITICALLY IMPERILEDVegetation of Sumter National Forest April 30 2004Copyright © 2004 NatureServexi