Volume 67 — Issue 4 (Dec 2002)

Vegetation at two dry sandstone barrens in Pope County, Illinois was sampled to provide baseline data on composition, structure, diversity, and species-abundance patterns for comparison with vegetational changes resulting from applications of prescribed fire. Permanent plots were established at both sites. Data were collected from canopy, subcanopy/shrub, and ground-cover strata. One site, Gibbons Creek Barrens, is the fire treatment site while the other, Forest Service Barrens, serves as a fire-free control site. The vegetation at these barrens remnants is similar in many regards facilitating their use as treatment and control units for experimental study of fire effects. Both sites are dominated strongly in the canopy by Quercus stellata Wangh. The subcanopy shrub/sapling stratum is dominated by Ulmus alata Michx.; however, several other taxa are common to occasional. Size-class distribution of over-story trees suggests a pattern of change characterized by stand closure as recruitment of Quercus stellata and Ulmus alata alters the open barrens structure. Patterns of subcanopy recruitment and tree size-class distribution support an interpretation of sites that are compositionally stable and structurally unstable in the over-story.

The same six ground-cover species are the most abundant species at both sites; however, rank abundance differs. At Gibbons Creek Barrens the dominant herbaceous species is the C₄ prairie grass Schizachyrium scoparium (Michx.) Nash. while at Forest Service Barrens the dominant species is the C₃ dry woodland grass Danthonia spicata (L.) Beauv. Ground-cover species are distributed in somewhat discrete patches with C₄ grasses occurring in open areas, C₃ grasses and sedges more generally distributed but predominating in more closed areas, and several open woodland species occurring in the barrens edges and where Q. stellata is in relatively low abundance. Ground-cover species diversity is correlated inversely with density of Quercus stellata. Stand areas exceeding about 25 trees per 0.05 ha particularly have lower diversity suggesting a benchmark for vegetation management designed for maintaining vegetational diversity. Both sites appear to be high-quality natural areas, support a rich assemblage of native species, and lack an adventive flora.

Two new subspecies of Alnus maritima, A. maritima subsp. oklahomensis from south-central Oklahoma and A. maritima subsp. georgiensis from northwestern Georgia, are described based on differences in growth habit, leaf and fruit morphology, and geographic isolation. The two new subspecies, along with subsp. maritima found in Maryland and Delaware on the Delmarva Peninsula, formalize the infraspecific classification of three widely disjunct populations of A. maritima, which have undergone considerable divergence since their isolation. Numerical analyses of 23 characters of mature trees from natural sites and 22 characters of seedlings grown in a uniform environment revealed many differences and allowed the determination of relative taxonomic distances between subspecies. Our examination of morphology, growth habit, distribution, and habitat of the three subspecies also rendered a plausible explanation for the peculiar disjunct occurrence of A. maritima.

Yalobusha County, located in the north-central portion of Mississippi, consists of 130,535 hectares. Vascular plants were collected and documented between August 1998 and April 2001. A total of 805 species is documented, representing 414 genera and 133 families. Poaceae is the largest family (11.3%), followed by Asteraceae (10.6%) and Cyperaceae (9.0%). One hundred eighteen species can be considered exotic. A new state record, the fern Deparia petersenii, is reported. Eight state-listed species, Scleria reticularis (S1), Carex stricta (S2), Celastrus scandens (S2/S3), Chelone glabra (S3), Matelea carolinensis (S3), Panax quinquefolium (S3), Staphylea trifolia (S3), and Muhlenbergia sylvatica (SU) are reported. Voucher specimens of each species are deposited at Delta State University (DSC).

Morphometric and genetic variation were assessed in populations of Eriocaulon koernickianum Van Heurck & Muller-Argoviensis, an uncommon species that is disjunct between the southern Appalachian and the Ozark and Ouachita Mountains, and adjacent regions. The eastern populations possessed smaller and fewer leaves and flowering scapes than the western populations. However, no discontinuities in floral morphology were apparent between populations from the two geographic regions. Furthermore, little genetic variation or divergence, as measured by isozymes, was observed within or among populations, suggesting that a genetic bottleneck occurred in the recent past in this predominantly-outcrossing species. The limited genetic variation suggests that simple vicariance and contemporary long distance seed dispersal are unlikely, and instead that fragmentation and recolonization (perhaps following the Pleistocene epoch) may explain the current biogeography.

Keys and descriptions are presented for the two genera and 33 taxa of the Violaceae of the southeastern United States. Hybanthus is represented by one species. Viola is represented by 25 species, two additional subspecies, and five varieties. In addition to taxonomic descriptions and habitat information, the range of each species within the southeast as well as adjacent states and beyond is provided. A cross referencing of nomenclature with pertinent floras is included.

Noteworthy Collections: Ohio, Delaware, and Maryland

The human population in the United States is predicted to grow through the 21st century. As this occurs, we will continue to fragment the natural environment with development, urbanization, and suburban sprawl. This fragmentation will divide species distributions and preclude gene transfer from one pocket of protected natural habitat to another. The fragmented habitats and separated populations will render these islands of biodiversity even more vulnerable to the impacts of diseases or the effects of climatic change. As scientists and educators, we can and must act today to help ameliorate this bleak view of the future.