Volume 68 — Issue 1 (March 2003)

Little Manatee River State Park is located in southwestern Hillsborough County, Florida. It covers 979.6 ha and includes eleven natural plant communities plus ruderal and developed areas. Communities range from xeric habitats such as scrub and scrubby flatwoods to hydric habitats such as floodplain forest and blackwater stream. The objective of this study was to develop a comprehensive listing of the taxa occurring in the park and make site-specific observations of the floristic communities. A survey of the park’s vascular flora was conducted between April 1998 and May 2000. The survey resulted in the documentation of 523 taxa, 329 genera, and 116 families. Three hundred and seventy-one new additions were made to the existing documented taxa within the park. Four hundred and thirty-six (83.4%) of the taxa are native. Twenty-nine (5.5%) are endemic to Florida. Eighty-eight (16.8%) are exotic. Twelve of the collections are county records. Occurrence of the recently described species Rhynchospora megaplumosa is documented. The plant communities are briefly described with emphasis on the floristic composition of each. Results of the floristic survey are compiled in an annotated list.

Are oak-dominated forests immune to invasive exotic plants? Herbarium and land classification data were used to evaluate the extent of spread of nine invasive exotic plants and to relate their distributions to remotely-sensed land use types in West Virginia. Collector-defined habitats indicated that the most common habitat was roadsides, but seven of the nine species were found in forests. Regression analyses indicated that the most significant variables were urban land use and population per km², but these were only significant for three of the species. Detrended correspondence analysis showed a forest to urban gradient and that one of the species, Rosa multiflora, was significantly correlated to heavily forested counties while Ailanthus altissima was significantly correlated with more urbanized counties. Although forests clearly are not immune to invasion, the lack of spatial and temporal patterns among the species support the need for intensive plot-level monitoring before predictions of spread can be made.

Invasive non-native species are important because of the potential negative ecological and economic effects that they have. Because of the number and variety of invasive species, it is important to prioritize them in terms of their presence in and their potential impacts on natural ecosystems. At least 167 non-native, invasive plant species occur on the United States Department of Energy Oak Ridge National Environmental Research Park, Oak Ridge, Tennessee. Our objective was to assess the distribution, abundance, impact, and potential for control of 18 of the most abundant invasive species on the Research Park. In 2000, we conducted field surveys of 16 Research Park management areas to acquire qualitative and quantitative data on the distribution and abundance of these taxa. Survey results were used to rank the relative importance of these species using a quantitative ranking system developed by the United States Geological Survey. Microstegium vimineum, Japanese honeysuckle (Lonicera japonica), and Chinese privet (Ligustrum sinense) were ranked first, second, and third-most problematic, respectively. Other non-native, invasive species, in decreasing rank order, included kudzu (Pueraria lobata), multiflora rose (Rosa multiflora), and Chinese lespedeza (Lespedeza cuneata). Results can be used to prioritize management and research activities related to these invasive taxa on the Research Park.

Noteworthy Collections: North Carolina, Southern Range Limits of Carex ozarkana P. Rothrock & Reznicek (Cyperaceae), Arkansas, Louisiana, Texas, Alabama, and Mississippi

We investigated the composition and spatial distribution of tree species and their environmental and edaphic correlates within the Snyder-Middleswarth Natural Area old-growth forest located in the narrow and steep ravine of Swift Run in central Pennsylvania. Eighty nested quadrats sampled along 5 topographic transects (16 quadrats each) encountered eastern hemlock (Tsuga canadensis), yellow birch (Betula alleghaniensis), black birch (Betula lenta), chestnut oak (Quercus montana), red maple (Acer rubrum), striped maple (A. pensylvanicum), and eastern white pine (Pinus strobus). The occurrences of these species differed by topography. Increasing soil phosphorus and potassium, and elevation correlated significantly with shift from hemlock and yellow birch-dominated bottomlands to ridge tops dominated by chestnut oak and red maple. Increasing soil acidity was significantly correlated with the shift from yellow birch dominated quadrats to those primarily occupied by hemlock. Size distributions suggest that hemlock and yellow birch populations are stable, while those of black birch indicate episodic recruitment that may follow tree falls and other perturbations. Size distributions for chestnut oak imply impacts from white-tail deer browsing.

The southeastern United States endemic plant species Trepocarpus aethusae (Apiaceae) behaves as a winter annual, with seeds germinating in autumn and bolting, flowering, and seed production occurring the following growing season. Vernalization was not required for flowering, and plants flowered under both short and long days. Like seeds of two other winter annuals in the Apiaceae, Chaerophyllum tainturieri and Ptilimnium nuttallii, those of T. aethusae have underdeveloped, physiologically dormant embryos, and thus they have morphophysiological dormancy. Physiological dormancy was broken by warm stratification, and after it was broken embryo growth and germination occurred in 68-73% of the seeds in light and in 52-65% of those in darkness at 15/6, 20/10, and 25/15℃. Unlike seeds of C. tainturieri and P. nuttallii, which can re-enter physiological dormancy in autumn and undergo annual dormancy/nondormancy cycles, only 1-12% of T. aethusae seeds re-entered physiological dormancy. However, T. aethusae forms a long-lived persistent soil seed bank; it mostly is attributed to a delay in loss of physiological dormancy and not to dormancy cycling. A comparison of dormancy-breaking and germination requirements does not reveal any reason why C. tainturieri is more weedy than the other two species of Apiaceae. However, seeds of C. tainturieri mature in late May-early June, those of P. nuttallii in mid to late June, and those of T. aethusae in mid to late August and early September. Thus, C. tainturieri can grow in fields and on roadsides and complete its life cycle before these habitats are disturbed by human activities, but the other two species could not complete their life cycle under these conditions.

One-year-old, greenhouse-grown seedlings of Lindera melissifolia (pondberry) were transplanted to permanent plots in Butler County, Missouri in 1990. In 1993, in situ seeding was done on the same tract and near naturally-occurring pondberry populations in Ripley County, Missouri. Plant heights of transplants have fluctuated but averaged slightly shorter in 2000 than in 1993 due to frequent die-backs and resprouting. Direct seeding yielded increasing cumulative germination for the first three years with a leveling off thereafter. Seven years after planting, fifty-two percent of seeds had germinated but survival was only 5%. Mean height of one-year-old seedlings was 8.44 cm.

Facultative biennials are plants that have the potential to flower in their second or a later year of life (typically 3, 4, or 5), whereas obligate biennials always flower in their second year of life (Kelly 1985, Klinkhamer et al. 1987a, Klinkhamer and de Jong 1988). This difference is explained in many facultative biennials by the fact that their rosettes (Juveniles) must reach a certain minimum size, depending on the species, population, and individual, before they can be vernalized and bolt (produce a flower stalk) (Werner 1975, Baskin and Baskin 1979a, van der Meijden and van der Waals-Kooi 1979, Gross and Werner 1983, Klemow and Raynal 1985, Lacey 1986, Wesselingh and Klinkhamer 1996, Reekie et al. 1997), whereas those of obligate biennials do not have this requirement-i.e., even seedlings or small juveniles can be vernalized (Baskin and Baskin 1984). Thus, many so-called biennials do not, in fact, flower in their second year because they do not reach the critical size for vernalization during their first growing season. In both facultative and obligate biennials, the entire plant dies after it reproduces once; the plants are monocarpic (semelparous).

Eleutherococcus trifoliatus and Ehretia acuminata are reported as new to the flora of Florida, and significant new county records are listed for seven additional species. All are non-native species and some have invasive potential.