Evans, L. S. (Laboratory of Plant Morphogenesis, Biological Sciences Research Laboratories, Manhattan College, Bronx, NY 10471), Y. Okawa (Laboratory of Plant Morphogenesis, Biological Sciences Research Laboratories, Manhattan College, Bronx, NY 10471) and D. G. Searcy (Department of Biology, University of Massachusetts, Amherst, MA 01003). Anatomy and morphology of red mangrove (Rhizophora mangle) plants in relation to internal airflow. J. Torrey Bot. Soc. 132: 537–550. 2005.—Mangroves cover large areas of shoreline in the tropics and subtropics where they are important components in the productivity and integrity of their ecosystems. Many mangrove plants are rooted (most are stilt roots-adventitious roots derived from stems) directly through standing sea water into anoxic substrate. Under these conditions, shoots must provide O₂ to roots. The purpose of this research was (1) to understand the tissues involved with the predominant airflow pattern in red mangroves (Rhizophora mangle) from leaves to roots (2) to understand the anatomical characteristics of air conducting tissues, and (3) to quantify these structures and tissues. Cork warts (density = 0.17 mm⁻²) on abaxial leaf surfaces are responsible for air uptake. Cork warts deliver air to an aerenchyma tissue near adaxial leaf surfaces. This aerenchyma layer is about 60 μm thick over the entire leaf so that the volume of aerenchyma in a typical leaf is about 0.23 cm³. The aerenchyma in each leaf is linked to the aerenchyma in each petiole (mean cross-sectional area, 0.0024 cm²). Petiole aerenchyma then joins the aerenchyma in the innermost portion of stems (aerenchyma constitutes about 2 to 4% of total stem area). Air descends the stem aerenchyma and then passes to the inner aerenchyma of stilt roots (inner aerenchyma constitutes about 18% of the cross-sectional area of roots). Our results indicate that air descends into the smallest roots growing in anoxic substrates where it may provide O₂ to the most rapidly growing portions of the roots. From these growing areas, air ascends the outer aerenchyma of roots (outer aerenchyma constitutes over 70% of such roots) where it may be released through lenticels. Surface densities of lenticels ranged from 0.68 mm⁻² in air roots (adventitious roots that have not reached substrate) to 1.07 mm⁻² in mud roots (the lower portions of stilt roots in anoxic substrate). Densities of lenticels on mud roots were greater than densities on air roots (P = 0.0001). We believe this report to be the first documentation of the path of airflow within tissues of red mangrove plants including the quantitative anatomical characteristics of these tissues. Taken together these results provide a quantitative assessment of the tissues involved in airflow in R. mangle plants.

Walker, J. L. and A. M. Silletti (USDA Forest Service, Southern Research Station, 233 Lehotsky Hall, Clemson University, Clemson, SC 29634). A three-year demographic study of Harper's Beauty (Harperocallis flava McDaniel), an endangered Florida endemic. J. Torrey Bot. Soc. 132: 551–560. 2005.—Harperocallis flava is a federally listed endangered plant narrowly endemic to the Florida panhandle. A lack of knowledge about Harperocallis population dynamics currently hinders conservation planning. Our objectives included describing ramet size, reproductive status, and mortality and recruitment rates in natural populations of H. flava. In 1998, we established permanent plots and marked individual ramets at six sites representing two habitat types in Apalachicola National Forest. At each site, we established ≥ 3 plots of varying size (0.12–1.8 m²) to include ∼300 ramets / site. In the first year we tagged, recorded reproductive status of, and measured individual ramets (# of leaves, longest leaf length). In 1999 and 2000, new ramets were tagged and all tagged ramets were re-measured. Analysis of variance methods were used to detect site, year, and habitat effects on response variables. Total number of ramets sampled varied between sites and declined from year to year. The proportion of ramets bearing reproductive structures was low (0.01 to 0.10) and varied with site and year. Logistic regression indicated that larger ramets were more likely to produce reproductive structures, and that smaller ramets suffered higher mortality. There were significant habitat and year effects on mortality; recruitment differed between years. The relatively short duration of this study precluded examination of potentially important fire effects. A rhizomatous habit and unexpected levels of crayfish-induced mortality suggest that knowledge of population structure and processes at larger scales is needed to develop effective monitoring and management strategies for H. flava.

Sanders, S. and J. B. McGraw (Department of Biology, West Virginia University, Morgantown, WV 26505). Population differentiation of a threatened plant: variation in response to local environment and implications for restoration. J. Torrey Bot. Soc. 132: 561–572. 2005.—Intraspecific genetic variation in plants is frequently associated with adaptation to local environments. Detection of ecotypic differentiation can promote an understanding of a species' distribution and be an important consideration in restoration efforts. We performed a classical reciprocal transplant study using four natural populations of Hydrastis canadensis to test for localized adaptation. Hydrastis canadensis exhibited plasticity in response to site quality variation, and at the site level there was no evidence of local genetic adaptation or differential performance of plants derived from distinct source populations. However, the four H. canadensis sources responded differentially to microsites within the transplant site. A second study examined the importance of including multiple sources when introducing new populations for restoration purposes by comparing H. canadensis performance in populations that were mixtures of three natural sources versus populations that were monocultures of each natural source. We found that populations established with plant material from single sources performed better than those established with multiple sources. Collectively, our findings indicate that restoration efforts should involve multiple sources dispersed over multiple sites as a bet-hedging strategy to increase the likelihood of suitable source-site compatibility. However, within a given restoration site, these sources should be spatially separated, such that numerous populations are introduced, each comprised of only a single source.

Leicht, S. A., J. A. Silander Jr., and K. Greenwood (University of Connecticut, Department of Ecology and Evolutionary Biology, 75 North Eagleville Rd. U-3043, Storrs, CT 06269). Assessing the competitive ability of Japanese stilt grass, Microstegium vimineum (Trin.) A. Camus. J. Torrey Bot. Soc. 132: 573–580. 2005— Microstegium vimineum (Japanese stilt grass) is an invasive grass in the eastern half of the United States which can form dense monocultures in forest understories, displacing native species. Although the loss of native species has been observed in the field, the actual competitive ability of this grass has not been examined. Microstegium vimineum was grown under controlled environment, greenhouse conditions in competition with Lolium perenne ssp. multiflorum (annual rye grass) and Muhlenbergia mexicana (Mexican muhly) in varying density ratios in full and low light treatments. Microstegium vimineum had a greater aboveground biomass, relative growth rate, and reproductive output than both competitors in both light treatments. The high competitive ability of Microstegium vimineum, especially in low light conditions, reflects its highly aggressive nature in forested or other landscapes of eastern North America.

Raimúndez-Urrutia, E. (Departamento de Biología de Organismos, División de Ciencias Biológicas, Universidad Simón Bolívar, Caracas, Venezuela) and C. Varela (Postgrado en Ciencias Biológicas, Universidad Simón Bolívar, Caracas, Venezuela). Predispersal reproductive ecology of Gronovia scandens L. (Loasaceae), a plant from disturbed habitats. J. Torrey Bot. Soc. 132: 581–589. 2005.—Gronovia scandens is a short-lived climbing herb that lives in disturbed sites and has become a weed in crop lands as a result of its rapid vegetative expansion and population growth, although it can also develop in late succesional stages. Study of its predispersal reproductive ecology showed that this plant is a self-compatible outcrossing annual with delayed autogamy; i.e., it exhibits a mixed mating system in which outcrossing has a temporal advantage over selfing. The outcrossing advantage is revealed by the high biomass allocation to male structures and pollinator attractants in the flower and the high pollen/ovule ratio. The delayed autogamy is mainly due to the fact that the anthers adhere to the stigma at the end of anthesis allowing seed production when outcrossing fails. The hymenopterans that were captured and identified as pollinators made non-specialized foraging movements and loaded scarce pollen on their bodies, although the body areas with pollen made contact with the stigma. Nevertheless, the presence of a single ovule per flower, delayed autogamy and a relatively low fruit cost related with the flower cost, favor a high efficiency in fruit (seed) production.

Huisinga, K. D., D. C. Laughlin, P. Z. Fulé, J. D. Springer, and C. M. McGlone (Ecological Restoration Institute and School of Forestry, Northern Arizona University, Box 15017, Flagstaff, AZ 86011). Effects of an intense prescribed fire on understory vegetation in a mixed conifer forest. J. Torrey Bot. Soc. 132: 590–601. 2005.—Intense prescribed fire has been suggested as a possible method for forest restoration in mixed conifer forests. In 1993, a prescribed fire in a dense, never-harvested forest on the North Rim of Grand Canyon National Park escaped prescription and burned with greater intensity and severity than expected. We sampled this burned area and an adjacent unburned area to assess fire effects on understory species composition, diversity, and plant cover. The unburned area was sampled in 1998 and the burned area in 1999; 25% of the plots were resampled in 2001 to ensure that differences between sites were consistent and persistent, and not due to inter-annual climatic differences. Species composition differed significantly between unburned and burned sites; eight species were identified as indicators of the unburned site and thirteen as indicators of the burned site. Plant cover was nearly twice as great in the burned site than in the unburned site in the first years of measurement and was 4.6 times greater in the burned site in 2001. Average and total species richness was greater in the burned site, explained mostly by higher numbers of native annual and biennial forbs. Overstory canopy cover and duff depth were significantly lower in the burned site, and there were significant inverse relationships between these variables and plant species richness and plant cover. Greater than 95% of the species in the post-fire community were native and exotic plant cover never exceeded 1%, in contrast with other northern Arizona forests that were dominated by exotic species following high-severity fires. This difference is attributed to the minimal anthropogenic disturbance history (no logging, minimal grazing) of forests in the national park, and suggests that park managers may have more options than non-park managers to use intense fire as a tool for forest conservation and restoration.

Hart, J. L. and D. Shankman (Department of Geography, University of Alabama, Box 870322, Tuscaloosa, AL 35487). Disjunct eastern hemlock (Tsuga canadensis) stands at its southern range boundary. J. Torrey Bot. Soc. 132: 602–612. 2005.—Eastern hemlock (Tsuga canadensis) occurs throughout much of the Appalachian Mountains, extending from southern Quebec and Ontario southward to Georgia and along the Appalachian Plateau to Alabama. Eastern hemlock is one of the most dominant trees in Appalachian forests. Near its southern boundary in central Alabama, eastern hemlock occurs in small, isolated populations restricted to cool, moist slopes with north to east aspects and low and middle slope positions. Ten stands of eastern hemlock, believed to be the southernmost populations, were studied in order to determine reproductive viability and habitat characteristics. In each of the stands, eastern hemlock dominates the canopy and is present in a wide range of size and age classes. Eastern hemlock is most abundant in seedling size classes and the number of individuals generally decreases with increasing size. Population size, age, and vertical structure indicate that eastern hemlock stands at the species' southernmost boundary contain viable populations that are regenerating, even if highly localized. During the late Pleistocene and early Holocene, eastern hemlock likely had a broader distribution in the southern Appalachian Mountains. The remnants of this larger distribution are now restricted to steep slopes where a combination of sandstone outcrops, seepage, and springs maintain adequate microclimatic conditions needed for regeneration of the species.

Orrock, J. L. (Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011) and E. I. Damschen (Department of Zoology, North Carolina State University, Raleigh, NC 27695). Fungi-mediated mortality of seeds of two oldfield plant species. J. Torrey Bot. Soc. 132: 613–617. 2005.—Fungi are a significant source of seed mortality. Although the seeds of pokeweed, Phytolacca americana, are known to contain antifungal compounds, it is unknown if these compounds confer the presumed benefit of increased persistence of P. americana seeds in soil compared to seeds of potential competitors. We buried seeds of P. americana with seeds of a sympatric species, Chamaecrista fasciculata, that is not known to exhibit antifungal properties. Half of the buried seeds were treated with a fungicide. After three months, seeds were exhumed. Treatment of buried seeds with fungicide significantly increased the number of intact C. fasciculata seeds recovered (82% recovered with fungicide addition, 39% recovered from controls). Recovery of intact P. americana seeds was 100% for both control and fungicide treatments. Results from a complementary experiment using non-buried seeds in a growth chamber experiment confirmed that P. americana was much less susceptible to fungal attack compared to C. fasciculata. Our work demonstrates that the antifungal properties of P. americana significantly improved survival of P. americana seeds in the seedbank. Moreover, this increased survival may promote P. americana persistence in communities where species without antifungal properties, such as C. fasciculata, also exist.

McEwan, R. W. (Department of Environmental and Plant Biology, Ohio University, Athens, OH 45701), R. D. Paratley (Department of Forestry, University of Kentucky, Lexington, KY 40546), R. N. Muller (Santa Barbara Botanical Garden, Santa Barbara, CA 93105), and C. L. Riccardi (U.S. Forest Service, Pacific Northwest Research Station, Seattle, WA 98103). The vascular flora of Big Everidge Hollow, an old-growth mixed mesophytic forest. J. Torrey Bot. Soc. 132: 618–627. 2005.—Because the goal of natural areas management is often the preservation of biodiversity, documenting botanical species richness is critically important. We conducted a series of botanical surveys in Big Everidge Hollow, a 52 ha watershed containing old-growth forest, on the Cumberland Plateau of eastern Kentucky. We contrasted our findings with a floristic survey that included parts of our study area, conducted approximately 20 years prior. Our research, from 1999 through 2001, yielded 263 species from 176 genera and 82 families, including 19 species that were new records from the site. These new species may have been overlooked in the previous study because of their scarcity or highly cryptic taxonomy, or they may have established in the years between studies. Of the 263 species recorded in our surveys, only one is considered non-native. This remarkable absence of exotic species indicates the high levels of “ecological integrity” inherent the study site and suggests an increasingly vital role for old-growth forests as reference ecosystems.

Stalter, R. (Department of Biological Sciences, St. John's University, Jamaica, NY 11439) and E. E. Lamont (Honorary Research Associate, Institute of Systematic Botany, The New York Botanical Garden, Bronx, NY 10458). The historical and extant flora of Great Gull Island, New York. J. Torrey Bot. Soc. 132: 628–634. 2005.—Great Gull Island, Suffolk County, New York was surveyed for vascular plants in 2002. The island's past and present flora consists of 207 species, 148 genera, and 55 families; the largest families are the Asteraceae (35 spp.) and the Poaceae (34 spp.). Fifty seven percent (119 spp.) of the flora is not native. The greatest change in the flora since the 1970s has been the addition of 16 species of composites and 12 species of grasses. The island's long history of human impact is reviewed, especially the impacts upon the flora resulting from management of the island as a wildlife preserve for nesting birds. Significant changes in the island's flora and vegetation have occurred during the past two decades.

Lamont, E. E. (Local Flora Committee, Torrey Botanical Society, The New York Botanical Garden, Bronx, NY 10458) and S. M. Young (New York Natural Heritage Program, 625 Broadway, Albany, NY 12233). Juncus diffusissimus, an addition to the flora of New York, with notes on its recent spread in the United States. J. Torrey Bot. Soc. 132: 635-643. 2005.—The first New York State record for Juncus diffusissimus Buckley (Juncaceae) is reported from Suffolk County, Long Island. An historical account of the species' original range and post-1900 migration in the United States is presented. The nativity status of J. diffusissimus and several other species that have spontaneously migrated into new territories in eastern United States during the past 100 years is discussed.