Schneider, E. L. and S. Carlquist (Santa Barbara Botanic Garden, 1212 Mission Canyon Road, Santa Barbara, CA 93105). Origin and nature of vessels in monocotyledons. 7. Philydraceae and Haemodoraceae. J. Torrey Bot. Soc. 132: 377–383. 2005.—SEM studies of macerated stems and roots showed that long scalariform perforation plates are present in roots and probably also stems of Philydrum (Philydraceae). In Haemodoraceae, clearly recognizable vessel elements are present in roots; perforation plates range from scalariform to simple. In stems of Haemodoraceae, however, less clearly recognizable vessel elements are present: the presence of threadlike pit membrane remnants is one criterion that argues for vessel presence. Such tracheary elements can be considered transitional between tracheids and vessel elements. End walls of transitional tracheary elements may have narrower bars between perforations, less prominent borders, and pit membrane remnants rather than nonporose pit membranes. However, only one or two of these three character expressions may be present, suggesting that clear definitions of vessel elements and tracheids may not be possible. Haemodoraceae show a marked difference, or disjunction, in morphology between vessel elements in roots and the vessel elements transitional to tracheids of stems. The physiological and evolutionary correlations of this morphological disjunction may be related to seasonality of water availability.

Gowe, A. K. and J. S. Brewer (Department of Biology, University of Mississippi, University, Mississippi, 38677), The evolution of fire-dependent flowering in goldenasters (Pityopsis spp.), J. Torrey Bot. Soc. 132: 384– 400. 2005.—Although prescribed fire is thought to benefit fire-adapted species, unequivocal evidence for the existence of fire-adapted species is lacking in many systems. We present the results of a comparative ecological study of fire-dependent flowering in the genus Pityopsis (Asteraceae). We constructed a phylogeny of the genus based on published morphological data and then mapped fire-dependent flowering on the resulting topology. We examined relationships between floral induction, tree and groundcover canopy coverage, and presettlement fire frequency within each species' preferred habitat. Results of our investigations supported the following hypotheses: 1) Fire-dependent flowering occurred in one infrageneric taxonomic group (sect. Graminifoliae) but not in the other (sect. Pityopsis); 2) Fire-dependent flowering occurred in habitats or microsites that contained a dense groundcover canopy during years without fire, and 3) Fire-dependent flowering was more likely to occur in areas of relatively high fire and lightning frequency in the United States. The phylogenetic analysis suggested that the two sections of Pityopsis did not form separate monophyletic groups. Furthermore, the character used to distinguish sections in previous taxonomic treatments (i.e. basal rosette present at the time of flowering) may, in fact, be equivalent to fire-dependent flowering. We hypothesize that fire-dependent flowering is a form of adaptive phenotypic plasticity that was retained in the Graminifoliae section and permitted exploitation of a fluctuating competitive environment within a variety of different fire-prone savannas in the southeastern United States.

Andrew M. Hedberg, Victoria A. Borowicz, and Joseph E. Armstrong. (Behavior, Ecology, Evolution, and Systematics Section, Campus Box 4120—Biological Sciences, Illinois State University, Normal, IL 61790-4120). Interactions between a hemiparasitic plant, Pedicularis canadensis L. (Orobanchaceae), and members of a tallgrass prairie community. J. Torrey Bot. Soc. 132: 401–410. 2005.—Pedicularis canadensis (lousewort) is a hemiparasitic plant of open woodland and prairie habitats. The interactions between this hemiparasitic plant and selected members of a tallgrass prairie community were investigated via a greenhouse experiment and field observations in a restored prairie. The greenhouse experiment examined interactions between P. canadensis and hosts from each of three families prominent in prairie communities: big bluestem (Andropogon gerardii, Poaceae), tall goldenrod (Solidago canadensis, Asteraceae), and showy tick trefoil (Desmodium canadense, Fabaceae). Individual hemiparasites were grown with one host, with two hosts of a single species, or with two hosts of different species, in all combinations. P. canadensis reduced tall goldenrod shoot mass, marginally affected big bluestem shoot mass, and had no effect on root mass of these two host species or on shoot and root mass of showy tick trefoil. The presence of the hemiparasite did not alter competitive relationships between host species and its effect was similar to that of a competitor. Spearman rank correlations were calculated between P. canadensis cover and species richness and abundances, including bare ground, for Six-Mile Creek Prairie, a restored tallgrass prairie in McLean County, Illinois. Species richness was positively correlated with increasing P. canadensis cover. These results suggest P. canadensis can influence prairie community composition.

Mulhouse, J. M. (University of Georgia, Savannah River Ecology Laboratory, Drawer E, Aiken, SC 29802), D. De Steven (USDA Forest Service, Southern Research Station, Center for Bottomland Hardwoods Research, P.O. Box 227, Stoneville, MS 38776), R. F. Lide (Northwest Florida Water Management District, 81 Water Management Dr., Havana, FL, 32333), and R. R. Sharitz (University of Georgia, Savannah River Ecology Laboratory, Drawer E, Aiken, SC 29802). Effects of dominant species on vegetation change in Carolina bay wetlands following a multi-year drought. J. Torrey Bot. Soc. 132: 411–420. 2005.—Wetland vegetation is strongly dependent upon climate-influenced hydrologic conditions, and plant composition responds in generally consistent ways to droughts. However, the extent of species composition change during drought may be influenced by the pre-existing structure of wetland vegetation. We characterized the vegetation of ten herbaceous Carolina bay wetlands on the South Carolina Upper Coastal Plain during a period of average rainfall and again near the end of a four-year drought. We hypothesized that, as a group, bays dominated by less robust plant species (characteristic of open-water pond and depression meadow vegetation types) would show greater compositional change than bays dominated by dense, robust-form clonal graminoids (characteristic of grass and sedge marsh vegetation types). Aquatic species decreased during the drought in all wetlands, regardless of vegetation group. Compared to grass/sedge marshes, pond/meadow wetlands acquired more species, particularly non-wetland species, during the drought. Pond/meadow wetlands also had greater increases in the abundances of species that require unflooded conditions to establish. Prior to the drought, all wetlands were ponded almost continuously, but during drought the pond/meadow wetlands had shorter and more variable hydroperiods than the grass/sedge marshes. Thus, vegetation change may be partly confounded with hydrologic conditions that provide greater opportunities for species recruitment in pond/meadow bays. The results suggest that Carolina bay vegetation dynamics may differ as a function of dominant vegetation and climate-driven variation in wetland hydrologic condition.

Bowers, J. E. (U.S. Geological Survey, 1675 West Anklam Road, Tucson, AZ 85745). Effects of drought on shrub survival and longevity in the northern Sonoran Desert. J. Torrey Bot. Soc. 132: 421–431. 2005.—Permanent vegetation plots in the northern Sonoran Desert, USA, provided an opportunity to assess the effects of recent drought on desert shrubs and to examine survival in relation to rainfall variability during the past 76 years. Survival and maximum longevity of six species were determined for eight intercensus periods between 1928 and 2004. Average annual survival was Ambrosia deltoidea, 0.9167 ± 0.0415; Encelia farinosa, 0.7952 ± 0.0926; Janusia gracilis, 0.9334 ± 0.0247; Krameria grayi, 0.9702 ± 0.0270; Larrea tridentata, 0.9861 ± 0.0174; and Lycium berlandieri, 0.9910 ± 0.0077. The longest-lived species were Larrea, Lycium, and Krameria, with average maximum life spans of 330, 211, and 184 years. Janusia, Ambrosia, and Encelia were much shorter lived, with average maximum longevity of 53, 40, and 16 years. Winter rain equalled or exceeded 90% of the long-term average accumulation except during 1948 to 1959 (65% of average) and from 2001 to 2003 (49% of average). Summer rain did not drop below 90% of the average accumulation in any period. The 1950s drought caused modest declines in survival of Ambrosia, Encelia, Janusia, Krameria, and Lycium. The effects of the recent drought were much more pronounced, resulting in sharp declines in survival and maximum longevity of Ambrosia, Encelia, Krameria, and Larrea, and modest declines for Lycium. Despite heightened mortality during the recent severe drought, 72% of the deaths observed between 1928 and 2004 occurred during periods of average or better-than-average rain, providing support for the idea that demography of shrubs in arid regions is influenced by continuous as well as episodic processes.

Chiang, J-M., M. A. Arthur, and B. A. Blankenship (Department of Forestry, University of Kentucky, Lexington, KY 40546-0073). The effect of prescribed fire on gap fraction in an oak forest understory on the Cumberland Plateau. J. Torrey Bot. Soc. 132: 432–441. 2005.—Excessive shade in the understory has been widely cited as the most important factor causing poor oak regeneration in eastern deciduous forests. We examined the effect of single and multiple fires on forest stand structure and the consequent impacts on the gap fraction measured in the understory. Differences in midstory stem density (stems 2–15 cm diameter at breast height; DBH) before and after prescribed burning were highly correlated with fire frequency (R² = 0.86, P < 0.01). On average, each additional burn reduced midstory stem density by ∼550 stems per hectare. Hemispherical photography showed an increase of 3.8 % in understory gap fraction in the first growing season after burning. This increase in gap fraction, which was likely caused by the thinning of the midstory by prescribed burning, was quickly reduced in the next year. Decreases in gap fraction after the first year post-fire, which indicated progressive canopy closure, cannot be explained by the relatively stable midstory stem density in subsequent years after fire. Rather, the decreases in gap fraction after fire coincided with a rapid increase in stem density in the shrub stratum (> 50 cm in height and < 2 cm DBH) of more than two thousand stems/ha/year. The rapid flush of stump sprouts in the shrub stratum was the primary cause of the decrease in the understory gap fraction. Land managers whose goal is to improve oak regeneration by increasing the understory light environment through the use of prescribed burning will need to control the flush of stump sprouts to maintain the effectiveness of burning in increasing light availability. Multiple fires of the intensity used in this study failed to permanently reduce sprouts.

Nagel, T. A. and A. H. Taylor (Department of Geography, The Pennsylvania State University, 302 Walker Building, University Park, PA 16802). Fire and persistence of montane chaparral in mixed conifer forest landscapes in the northern Sierra Nevada, Lake Tahoe Basin, California J. Torrey Bot. Soc. 132: 442–457. 2005.— Tree cover in the mixed conifer zone in the Sierra Nevada is often interrupted by large shrub fields, or stands of montane chaparral. Chaparral stands are thought to be associated with either poor site conditions, or locations that have experienced severe fire. Fires have been excluded from mixed conifer forests for nearly a century because of a management policy of suppressing fire. This study quantifies the intervals between fires, and the response of chaparral shrubs and trees to fire and fire exclusion in six montane chaparral stands. Quercus vaccinifolia and Arctostaphylos patula were the dominant shrubs on all sites and the last fires burned in the six sites between 1861 and 1882. The mean point fire return interval before fire suppression was 28 yr (range 16– 40 yr), and fire frequency in chaparral was lower than in nearby forest. The age structure of shrubs and trees in the stands indicate that shrubs and trees regenerated immediately post-fire. Shrub and tree regeneration, however, were not confined to a brief post fire period, regeneration continued for at least another five decades. On our sites, exclusion of fire due to fire suppression has caused the average area of a chaparral stand to shrink by 62.4%. Chaparral has been replaced by forest and this vegetation change has reduced the heterogeneity of the mixed conifer forest landscapes in the Sierra Nevada.

Small, M. J., C. J. Small (Department of Botany, Connecticut College, New London, Connecticut 06320), and G. D. Dreyer (Goodwin-Niering Center for Conservation Biology and Environmental Studies, Connecticut College, New London, Connecticut 06320). Changes in a hemlock-dominated forest following woolly adelgid infestation in southern New England. J. Torrey Bot. 132: 458–470. 2005.—The hemlock wooly adelgid (HWA; Adelges tsugae), a small aphid-like insect introduced from Japan, has caused widespread hemlock (Tsuga canadensis) mortality throughout the mid-Atlantic and southern New England region over the last twenty years. We examined long-term (1952–2002) changes in hemlock-dominated stands before and after the appearance of the HWA in 1987 in the Connecticut College Arboretum, southeastern Connecticut. With HWA infestation, basal area of T. canadensis declined dramatically, dropping 70% from 1982 to 2002. Forest communities responded to the elimination of the dominant species by quickly filling various sized gaps. Black oaks (Quercus velutina, Q. coccinea, Q. rubra) increased from 28% of canopy basal area in 1982 to 41% in 2002. Sapling density increased markedly following HWA infestation, from 80 stems/ha in 1982 to nearly 5600 in 2002, with greatest increase in Sassafras albidum (0 to 1900 stems/ha) and Acer rubrum (4 to 1100 stems/ha). Ledge and ravine communities, formerly dominated by T. canadensis, became more compositionally distinct, with greater importance of black oaks on more xeric ledge sites and mixed canopy dominance in mesic ravine sites. Major trends associated with the decline of T. canadensis included a shift in canopy dominance to oak and mixed hardwoods, considerable understory development, including greater herb richness and abundance and increased density of clonal saplings, and expansion of several invasive shrubs and woody vines.

Goslee, S. C. (Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708), W. A. Niering (Department of Botany, Connecticut College, New London, CT 06320), D. L. Urban and N. L. Christensen (Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708). Influence of environment, history and vegetative interactions on stand dynamics in a Connecticut forest. J. Torrey Bot. Soc. 132: 471–482. 2005.—We examined the changing influence of environmental factors and land use history on the composition of the canopy tree, shrub, herb and tree seedling strata of a Connecticut forest over 45 years. The many herb and shrub species initially found in post-agricultural areas of this site declined or disappeared as the forest canopy closed. Tsuga canadensis ([L.] Carriere) increased in importance in the forest canopy until the introduction of the hemlock woolly adelgid (Adelges tsugae Annand). Shade-intolerant understory species are now increasing in abundance as the death of large T. canadensis opens gaps in the canopy. Mantel path analysis, a multivariate technique that allows examination of indirect and direct relationships among variables, was used to quantify the complex network of relationships among environment, land use history and plant community composition. Overall environmental variability was uncorrelated with vegetation, except within the shrub stratum. Slope and drainage were the most important individual environmental factors measured. Land use history was strongly correlated with all four strata, and the strength of this relationship decreased over time. The composition of the tree seedling stratum was highly variable through time; other strata showed more self-similarity between sample dates. Land use history appears to impact the vegetation so strongly as to conceal any effects of environmental variation on this site.

Runkle, James R. (Department of Biological Sciences, Wright State University, Dayton, OH 45435). Twenty-four years of change in an old Tsuga canadensis woods affected by beech bark disease. J. Torrey Bot. Soc. 132: 483–491. 2005.—Long-term studies are necessary to determine how various environmental and anthropogenic factors influence the rates of forest change. To study such changes a 2.02 ha permanent plot in the stand of Tsuga canadensis established about 1800 and located north of Lincoln Pond in the Edmund Niles Huyck Preserve, Rensselaerville, NY, was established in 1978 and resurveyed in 1986, 1994, and 2002. The species, stem diameter, injury type and location (nearest 0.1 m) for all living and dead stems ≥ 1 m tall were recorded. Overall, the stand decreased in density and increased in basal area, with similar proportional changes in each time interval. Tsuga canadensis, by far the most important species, increased its relative density and basal area, as did Quercus rubra. Fagus grandifolia decreased in both. Overall mortality rates decreased from 2.4 % to 2.1% to 1.7 %/yr during the three time intervals, primarily because of the decrease in density of small stems. Mortality rates of individual size classes and species were similar for all three time intervals. Minimum mortality rates occurred for stems newly reaching the canopy (11–30 cm dbh). Quercus rubra and Tsuga had low mortality rates and Fagus and Fraxinus americana high mortality for all time intervals. Previously described long-term trends (beginning with data from 1940) continued. The number of stems < 10 cm dbh decreased while the number of stems ≥ 25 cm dbh and total basal area increased. Deer browsing may be implicated in the decrease of small stems, which seems too continuous for climatic fluctuations to be responsible. The impact of beech bark disease is still apparent. Although the rate of Fagus decline has diminished in recent years, Fagus mortality is still higher than other species, especially for large stems. Snag densities, formation rates and deterioration rates remained nearly constant for stems ≥ 11 cm dbh, supplying that resource consistently for organisms requiring it.

Cook, J. (College of Natural Resources, University of Wisconsin Stevens Point, Stevens Point, WI 54481). Vegetation changes in a central Wisconsin floodplain from pre-settlement to mid-21^st century. J. Torrey Bot. Soc. 132:492–504. 2005.—The vegetation changes of a central Wisconsin floodplain from the mid-1800's to 2000 were documented, and the probable changes to 2050 projected. This was accomplished by use of survey witness trees in 1851, an extensive survey in 2000, and projection to ∼2050 using probable gap replacement frequencies and forest development theory. Between 1851 and 2000 extensive changes in relative abundance of tree species occurred. Silver maple (Acer saccharinum L.) exhibited the largest increase, and river birch (Betula nigra L.) and eastern white pine (Pinus strobus L.) the greatest decline; bur oak (Quercus macropcara Michx.) and yellow birch (Betula alleghaniensis Britton (B. lutea Michx. f.) were noted by the surveyor but not found in 2000. Conversely, two species [hornbeam (Carpinus caroliniana Walt.) and paper birch (Betula papyrifera L.)], that are present now were not found among the witness trees in 1851. The amount of open habitat remained approximately constant, but the degree of canopy closure in forests increased dramatically from 1851–2000. The probable causes of these changes were land clearing and harvesting during European settlement, supplemented by the hydrologic changes they induced. Collected data suggest that the current disturbance regime of scattered, small-scale canopy gaps will continue until the mid-21^st century. If true, it is likely that another major shift in relative abundance of arboreal species will occur and there will be an increase in open habitat. Green ash (Fraxinus pennsylvanica Marsh.) and red maple (Acer rubrum L.) will probably be the dominant tree species by mid-21^st century due to their ability to regenerate widely, replace other species and to tolerate growing season flooding. In the absence of widespread, severe disturbance (e.g., clearcutting), it does not appear that the arboreal composition of the landscape will return to either 1851 or late 20^th century conditions.

Burns, K. C. (Bamfield Marine Science Centre, 1 Pachina Drive, Bamfield, British Columbia, Canada, V0R 1B0). Effects of bi-colored displays on avian fruit color preferences in a color polymorphic plant. J. Torrey Bot. Soc. 132: 505–509. 2005.—Rubus spectabilis is a bird-dispersed shrub that produces both red and orange fruits. Although it has been the subject of several previous studies, the factors responsible for the maintenance of the polymorphism have not been identified. I hypothesized that the fruit color polymorphism in R. spectabilis is maintained by enhanced conspicuousness of bi-colored displays, created when the two color forms occur close together. To test this hypothesis, I constructed experimental displays of different relative abundances of red and orange fruits and presented them to free-ranging birds in British Columbia, Canada. Trials were conducted in different habitats and at different times during the fruiting season to test whether avian fruit color preferences were spatially or temporally variable. Results showed that birds did not prefer bi-colored displays and that removal rates of different colored fruits were similar in space and time. Therefore, processes other than enhanced conspicuousness of bi-colored displays must account for the maintenance of the fruit color polymorphism.

Rink, G. (Northern Arizona University, Department of Biological Sciences, PO Box 5640, Flagstaff, AZ 86001) J. Torrey Bot. Soc. 132: 510–532. 2005—A total of 243 new species records, 60 new generic records, and 11 new family records were documented for Canyon de Chelly National Monument, bringing the known flora of the Monument to 771 species. This work is part of an inventory carried out throughout the National Park Service as part of the Natural Resource Challenge, a legislative and administrative mandate. Four species are on or proposed for the Navajo Nation Endangered Species List. Additions to the flora include Carex specuicola, a Listed Threatened species, and Zigadenus vaginatus, both on the Navajo Endangered Species List. Astragalus chuskanus, Cirsium chellyense, Lupinus caudatus subsp. cutleri, and a white-flowered form of Mertensia oblongifolia are endemic to the Monument and surrounding area.