Volume 63 – Issue 3 (Sep 1998)

Species composition and vegetation-environment relationships are described for Linville Gorge Wilderness, a rugged landscape straddling the Blue Ridge escarpment of the southern Appalachian Mountains. A hierarchical classification is presented for 28 community types, which span eight broad vegetation classes. Vegetation classes associated with infertile conditions are most widespread. THERMIC OAK-PINE FORESTS dominate ridgelines and upper-slopes. ACIDIC COVE AND SLOPE FORESTS are prominent on sheltered, mid- and lower-slopes. MONTANE OAK FORESTS and RICH COVE AND SLOPE FORESTS are present, but are limited in distribution. The atypical concentrations of the latter class on high-elevation ridgelines results from underlying nutrient-rich bedrock. Vegetation composition is most strongly associated with soil nutrients, soil texture, and topographic position. The combination of rugged topography, infertile soils, relatively low annual rainfall levels, and lack of anthropogenic disturbance is responsible for the unusual combination of southern Appalachian vegetation communities that characterize Linville Gorge Wilderness.

The Southern Blue Ridge Province of the Appalachian Mountains is defined by its geographic distribution, geology, soils, and vegetation. This province is bounded by the Piedmont Province to the east and the Valley and Ridge Province to the west and extends from northern Alabama and Georgia into southern Virginia. The underlying ancient rocks consist mostly of sandstones, shales, and related rocks that were metamorphosed and later overthrust onto rocks of the Valley and Ridge. Blue Ridge topography is but a remnant of a much more extensive mountain range. Present-day topography and climate are probably relicts of the Tertiary and Pleistocene. Because of the climate and bedrock, a dominant feature of the region is dynamic chemical weathering that has produced acidic soils and saprolite on dominantly steep slopes supporting acid-loving vegetation. The vegetation also has long history of development with many extant genera showing relationships to Pleistocene and earlier floras. The flora contains varied species including many genera that may be found in Tertiary fossils, such as Sassafras; tropically derived elements such as the filmy ferns, Trichomanes spp. and Hymenophyllum spp.; elements that are disjunct with other parts of the world, such as members of the magnolia family of southeast Asia; relicts of the glacial periods such as Trichophorum cespitosum; and narrow endemics such as Rhododendron vaseyi.

Spray cliff plant communities of the southeastern Blue Ridge, are best developed on steep gorge walls of the escarpment, and consist of an assemblage of plant species unique to the southern Appalachian Mountains. A quantitative study of both the vascular and nonvascular spray cliff vegetation was conducted in the Chattooga Basin, the western-most escarpment gorge. Nine plant associations were delineated using numerical classification techniques, revealing groups comprised of both habitat specialists (i.e., rock outcrop, wetland, and spray cliff restricted species) and generalists. The distributions of these nine associations are in part related to differences in exposure to direct potential solar radiation and local flooding regimes. Furthermore, these spray cliff communities show other features commonly associated with island systems in pattern (e.g., species richness-area relations) and floristic composition (e.g., high numbers of endemic and highly mobile, spore producing taxa). The exceptional vascular and nonvascular species richness, relative abundance of endemic, disjunct, and rare listed taxa documented on the Chattooga Basin spray cliffs illustrates both the high conservation value of this community type and the significant contribution of bryophytes to spray cliff community composition.

Review of historic records indicated a very low frequency of lightning ignited fires in the Chattooga River Watershed, Georgia, South Carolina, and North Carolina. Rates of reported natural ignition range from about five per decade for Satolah quadrangle, to less than one per decade for wetter, high elevation areas of the watershed in North Carolina. Records document an intensification of logging and severe fires within the watershed as a result of settlement, with a period of repeated severe disturbance from 1890 to 1940. Georgia land lottery records indicate the presettlement vegetation was dominated by xeric, fire-tolerant trees such as Quercus spp., Pinus spp., and Castanea dentata (87% total) while mesic species such as Liriodendron tulipifera were rare. Transects, 10 x 100 m, determined gap disturbance in old growth ranged from 0.8% to 2.9% per year. Increment cores indicated xeric, fire tolerant trees, including Quercus spp. and Pinus spp., were far more prevalent in age classes greater than 60 years, while mesic species such as Acer rubrum, were more common among stems less than 60 years old. The field sampling and historic records suggest Native American burning maintained fire-tolerant vegetation prior to settlement. Since the early 20th century, U.S. Forest Service management has greatly reduced the impacts of fire and more mesic canopy species are becoming increasingly dominant throughout the Chattooga River Watershed.

Montane cedar-hardwood woodlands are unusual eastern red cedar- (Juniperus virginiana var. virginiana) dominated plant communities occurring on steep south-facing rock outcrops in the Piedmont and southern Appalachian Blue Ridge Provinces. Permanent 0.1 ha plots were established in woodland and adjacent communities in North Carolina to characterize quantitatively the vegetation, dynamics, and environment of the woodland community type. Vascular plant species were inventoried using a nested quadrat sampling method. Three hundred eighteen vascular plant taxa (75 families) were identified in permanent plots. Juniperus virginiana var. virginiana dominated the woodland canopy, and Carya glabra var. glabra, C. alba, and Quercus prinus were common associates. The species rich herbaceous layer was dominated by Carex spp., Dichanthelium spp., Andropogon spp., Schizachyrium scoparium ssp. scoparium, Sorghastrum nutans, and Solidago spp. Basophilic species such as Dodecatheon meadia ssp. meadia, Amelanchier sanguinea, Lonicera flava, and Sedum glaucophyllum were also common. Cedar-hardwood woodlands appear to be relatively stable plant communities, with vegetative composition seeming to respond to a suite of environmental factors such as aspect, exposure, soil depth, and parent material. Patterns of compositional similarity were explored among stands using cluster analysis to segregate stands most typifying the cedar hardwood woodlands and to identify those species and site conditions most effective in characterizing the community type. Gradient analytical techniques were used to explore environmental relationships and to better understand the relative position of cedar-hardwood woodlands along regional compositional and environmental gradients. The woodlands were placed in an extreme position along regional gradients, in association with low fertility sites of the Blue Ridge Escarpment.

The effect of forest fragmentation on cove-forest herbs was studied in the Southern Blue Ridge Province. Patches of mesic forests were sampled with 4 ha study plots. The coverage and density of herb species were greater in large patches (>200 ha) than in small patches (<10 ha). Several ant-dispersed species, such as Disporum maculatum and Uvularia grandiflora, were more likely to be absent from small patches than from large patches. Wind-dispersed species, such as ferns and composites, were not affected by patch size and isolation. Small patches had reduced amounts of organic matter in the soil, suggesting that small patches have experienced more disturbance than large patches. Otherwise, there were no other differences in soil characteristics between patch sizes. Mechanisms hypothesized to have affected these populations include (a) disruption of population dynamics due to habitat fragmentation, (b) habitat degradation, and (c) anthropogenic disturbance via land use. Disturbances may have affected herb populations directly by increasing mortality rates and by degrading habitat. These habitat changes were confounded by the small size and isolation of small forest patches.

Yellow pines (Pinus rigida, P. virginiana, P. echinata, and P. pungens) and oaks (Quercus spp.) dominate xeric slopes and ridges in western Great Smoky Mountains National Park (GSMNP). In the late nineteenth and early twentieth centuries, these sites burned frequently. Since about 1940, the Park Service has suppressed fire, prompting concerns over possible changes in forest composition and structure. This study documents changes in xeric forests using non-permanent plots sampled in 1936-37, permanent plots established in 1977-79, and a subset of those permanent plots resampled in 1995. Some permanent plots burned just prior to sampling in the 1970s, while others have not burned since before 1940.

Between the 1930s and 1970s, canopy density, basal area, and canopy richness increased dramatically on fire-suppressed sites. While high-intensity fires reduced canopy density and basal area to low levels, low-intensity fires did not significantly reduce canopy density or basal area relative to fire-suppressed sites. Between the 1970s and 1995, canopy density on fire-suppressed and low-intensity fire sites remained relatively stable, while that on sites of high-intensity fires increased rapidly. During this period, abundant regeneration of yellow pines occurred on some burned sites. On fire-suppressed sites, densities of Acer rubrum, Nyssa sylvatica, Pinus strobus and Tsuga canadensis have increased. Changes in the canopies of xeric forests since the onset of fire suppression may alter response to future fire events and complicate the restoration of historical composition and structure in these communities.

We present a flexible protocol for recording vegetation composition and structure that is appropriate for diverse applications, is scale transgressive, yields data compatible with those from commonly used methods, and is applicable across a broad range of terrestrial vegetation. The protocol is intended to be flexible in the intensity of use and commitment of time, and sufficiently open in architecture as to be adaptable to unanticipated applications.

The standard observation unit is a 10 ✕ 10 m (0.01 ha) quadrat or “module.” Where the extent of homogeneous vegetation is sufficient, multiple modules are combined to form a larger, more representative sample-unit. All vascular species are recorded by cover class and in intensively sampled modules as present or absent in sets of nested quadrats. For each module, tree stems are tallied by diameter class; species with exceptionally high or low stem density can be sub- or supersampled to allow efficient collection of data and assessment of population structure. The most common plot configuration consists of 10 modules arranged in a 2 ✕ 5 array with four modules sampled intensively; this size is often necessary to capture the complexity of a forest community. For rapid reconnaissance or inventory purposes, fewer modules are typically employed, and less information is collected.

Fossil pollen and charcoal in peat deposits and pond sediments from three sites in the southern Appalachians yielded evidence for a direct relationship between prehistoric Native American use of fire and increases in the importance of oak-chestnut forest between about 3,000 and 1,000 years ago. At Cliff Palace Pond on the Cumberland Plateau of southeastern Kentucky, Tuskegee Pond, in the Ridge and Valley of East Tennessee, and Horse Cove Bog in the Blue Ridge Mountains of western North Carolina, increases in fire frequency corresponded with the change in Native American activities from hunting and gathering in the Late Archaic cultural period toward more sedentary lifestyles and cultivation of native plants in the Woodland cultural period. Forests of oak and chestnut became dominant on upper slopes, with fire-adapted pines establishing on ridge tops and disturbance-adapted hardwoods invading abandoned Indian old fields. We speculate that prehistoric Native American use of fire would have been an intermediate-scale disturbance regime that would have heightened ecotonal contrast across plant community boundaries and would also have increased biological diversity across the landscape.

The southern Appalachians have long intrigued us because they offer a fascinating, beautiful and limitless venue for scientific inquiry. Thus the idea of presenting an up-to-date series of papers on vegetation of the Blue Ridge Province emerged naturally when we began thinking of a symposium theme that would complement the location of the 1997 meeting of the Association of Southeastern Biologists.