Annual plants are important colonizers of the bare sandy areas that typify the pioneer zone of many coastal beaches. The spatial distribution of the potential seed rain in autumn, transient seed bank in early spring, and seedling recruitment in late spring were examined for the summer annuals in a 40 × 45 m section of beach on Staten Island, NY. The relationship of the dominant perennial, Ammophila breviligulata, to recruitment was also explored. Estimated seed rain was very high, showing species-specific distribution patterns along the shore-to-land gradient for Triplasis purpurea, Cenchrus tribuloides, and Heterotheca subaxillaris, the most abundant native annuals. Seed rain and spring recruitment for T. purpurea and C. tribuloides were greatest in regions of the beach where A. breviligulata was less abundant. Recruitment of T. purpurea and C. tribuloides, but not H. subaxillaris, was negatively associated with living A. breviligulata. Summed over all annuals, recruitment was 73.6 ± 5.2 seedlings m⁻² in the absence of litter and 45.8 ± 4.3 seedlings m⁻² where A. breviligulata litter occurred. Thus, the distribution and abundance of A. breviligulata was inversely related to the seed rain and recruitment of annuals. The weedy annual Mollugo verticillata was most abundant in the transient seed bank (669 ± 205 seeds m⁻²), but T. purpurea was also common (211 ± 32 seeds m⁻²) mean total density of all species was 1,082 seeds m⁻². For the three natives, only a small proportion (ca. 1–30%) of the seed rain was detected in the transient seed bank. Depletion of seeds over the transition from seed bank to seedling recruitment was 77% for C. tribuloides, over 90% for T. purpurea and H. subaxillaris, and 99% for M. verticillata. Thus, only a very small fraction of the potential seed rain in autumn resulted in successful seedling recruitment the following spring. Despite the massive loss of seeds across seasons, patches of annual species maintain viable populations from year to year and provide vegetation cover on the coastal beach.

Soil seed banks are especially important for forest regeneration in stands with few understory species and individuals. The understory of hemlock (Tsuga canadensis)-dominated stands in New England primarily consists of hemlock seedlings and saplings, but all size classes of hemlock are attacked by the hemlock woolly adelgid (Adelges tsugae). Prior to the initiation of a large-scale manipulative experiment designed to examine the impact of the adelgid on hemlock forest ecology, we documented the seed bank composition of eight large (0.81 ha) experimental hemlock-dominated and young hardwood-dominated plots. The seed bank samples from the hemlock-dominated plots contained significantly fewer species (rarefied species richness = 24; 95% confidence interval = 20–28) than those from the hardwood-dominated plots (species richness = 30). Seed banks from all plots were dominated by Betula lenta, Rubus spp., and Carex pensylvanica. Among plots, there was little compositional relationship between the forest overstory and its understory on the one hand, and its seed bank on the other hand. Because seeds of hemlock and birch persist for only a few years in the seed bank, and because hemlock seedlings are readily attacked and killed by the adelgid, damaged hemlock stands are more likely to be replaced by stands of black birch and other hardwoods than by hemlock.

Lysimachia asperulifolia Poir., rough–leaf loosestrife, is a federally endangered species that is restricted to longleaf pine savanna – pocosin ecotones in North and South Carolina. Potential causes of the limited fruit and seed production typical of this species and possible effects of prescribed fire on these causes were examined. It was determined that insects rarely visit flowers and that the visitors, Augochlorella spp. and Lasioglossum spp., are not effective pollinators. However, results of artificial pollinations do not support the hypothesis that pollinator limitation alone restricts seed production. Levels of fertility and S allele diversity may vary across natural populations and, combined with ineffective pollination, enforce restricted fruit and seed production. Pollen fertility, amount of flowering, and number of fruits produced in natural populations did not increase following prescribed fire. Restricted seed germination further limits recruitment of genetic variation into populations. Pollinations and propagule dispersal among populations are precluded by habitat fragmentation. Alternative courses of action designed to increase fruit and seed production and seedling recruitment are recommended to those developing loosestrife conservation plans.

The combination of protandrous flowers and acropetal inflorescence development in bee-pollinated species is thought to maximize cross-pollination because bees visit vertical inflorescences from the bottom up. However, incomplete protandry may allow bees to carry out geitonogamous pollinations. We examined the overlap in male and female phases in the rare orchid Spiranthes diluvialis, a plant with the above combination of characteristics. We found that unvisited male phase flowers proceed to a hermaphroditic phase, not a female phase, because each flower's single pollinarium remains viable and may be removed by pollinators throughout anthesis. Pollinator visitation rates, as estimated by pollinaria removal rates, varied among five populations in Utah and Colorado, USA. More hermaphroditic phase flowers accrued on inflorescences in populations with low visitation rates than in those with higher visitation rates. We conclude that the cross-pollination mechanism of S. diluvialis requires some minimum threshold of bee visits in order to work optimally. When bees are plentiful, male and female functions remain temporally separated and cross-pollination is maximized. In contrast, the potential for geitonogamy in this self-compatible species is much higher in populations with low visitation rates. We suggest that pollinator abundance may affect the mating system of other protandrous, acropetal, bee-pollinated plants if protandry depends upon the timely removal of long-lived pollen.

Soil nutrients and disturbance are two of the main abiotic factors that influence plant dominance (canopy cover), density, and fecundity in early successional old field plant communities. The manner in which the dominant species in old field successional systems respond to the interaction of nutrients and disturbance is poorly known. We examined the dominance, density of flowering tillers, and reproductive output of Tridens flavus, a perennial, warm-season bunchgrass that is important in old field succession, to varying soil nutrient and disturbance regimes. We tested the hypothesis that the interaction between nutrients and disturbance would influence the performance (cover, density, fecundity) of T. flavus. To test this hypothesis, we subjected 25 m² experimental plots to various combinations of fertilizer and mowing treatments for eight years after initially plowing the field. The performance of T. flavus was measured by estimating percent cover for 8 years (1996–2003) and both density of flowering tillers and reproductive output (panicle length and number of branches per panicle) for three years (2001–2003). The pattern of canopy cover of T. flavus over the first eight years of succession varied over time depending on mowing regime. Dominance was significantly higher in plots that were fertilized only in years one and five than in annually fertilized and unfertilized control plots. The length of panicles and density of flowering tillers were both significantly greater in annually mowed plots than in unmowed plots. In the absence of mowing in particular, T. flavus became overtopped by woody species and declined in this old field community. Therefore, disturbances such as mowing and fertilization may be important in maintaining grasses such as Tridens flavus in old fields.

Psittacanthus is the only genus in the family Loranthaceae that is considered a significant pest of woodlands and farmlands in Mexico and Central America, but relatively little attention has been given to the reproductive biology and pollination of natural populations. We present quantitative information on the floral morphology, breeding system, flowering phenology, nectar production, floral visitors, and pollinators of the mistletoe Psittacanthus calyculatus in Tlaxcala, México. Its flowering phenology extends from April to October, with a major peak in July. Flowers last 5 days and produce abundant nectar (2.34 ± 0.175 µl per flower) with a constant sugar concentration (ca. 22%) throughout flower life span. Hand self-pollinations showed that this species is partially self-compatible (44% fruit set), whereas emasculated flowers produced no seeds. Hand out-crossed flowers produced a similar number of fruits (96%) compared to unmanipulated control flowers visited by birds and insects (84%), showing no evidence for pollen limitation. Four hummingbird species were frequent visitors of mistletoe flowers, but they varied in visit duration and number of probes per flower. Artificial pollination of flowers with stuffed hummingbirds of the four species suggested that Hylocharis leucotis was the most effective pollinator.

The box huckleberry (Gaylussacia brachycera) is a slow-growing, dwarf evergreen groundcover that is native to eight states in the Eastern United States. It is a rare plant with conservation status of rare to critically imperiled. Genetic relationships among 24 accessions of G. brachycera were determined using 66 polymorphic AFLP markers from 8 primer pairs. Accessions collected in western Virginia were the most distantly related to the other accessions, while accessions from Kentucky were the most variable. The information gained from this study will be useful to guide decisions regarding conservation, preservation, breeding, and re-introduction of this species.

Distance sampling methods are widely applied to witness tree data from General Land Office (GLO) survey records to determine historic vegetation. Most researchers apply modifications of the point-centered quarter or random pairs distance methods to witness tree distances as if these data were collected according to the procedures required for the methods. Application of five methods (three modifications of the point-centered quarter method (Q₁, Q₂, and Q₁ Q₂) and random pairs with 180° or 203° exclusion angles) to GLO records from the 345,000 ha Shawnee National Forest Purchase Area in southern Illinois, resulted in tree density ranging from 117.8–177.5 trees ha⁻¹. We present a new procedure, the adjustable exclusion angle method, which empirically estimates the exclusion angle of the random pairs method based on the proportion of trees in quadrants opposite versus adjacent to the quadrant of the first witness tree. For our data, the distributions of witness trees in quadrants was best described as if surveyors used a random pairs method with an exclusion angle of 203° in their selection of witness trees. This method resulted in the highest estimates of tree density. There were significant differences (P < 0.0001) in the square root of the mean area among the five distance methods used. A surveyor bias for selecting trees near the center of the area between the ordinal directions was discovered.

Over decades, and especially on public lands subject to multiple uses, land use activities can affect forest composition or structure. We asked if current ground layer vegetation composition or stand structure (canopy openness, tree density, plus depth of the soil A layer) in 32 mixed pine-hardwood forest stands at Fort Benning, GA, reflects military use or fire frequency over the last 20 years. The 32 stands, half on sandy and half on clayey soil, were assigned to two military use categories (heavier, open to tracked vehicles, or lighter, with dismounted infantry training) and three fire frequency (# fires/20 yr) categories [low (0–2 fires), medium (3–4 fires), and high (5–6 fires)]. Ordination reflected abundance of grass and legume species, the proportion of pine in the canopy, canopy openness, and tree density and age; it revealed a relatively stronger influence of military land use and canopy composition, and weaker influence of fire frequency (over the past 20 years), on ground layer vegetation differences among the stands. Soil A-horizon depth, abundance of disturbance features, and tree density differed between lighter and heavier military use categories, but not among fire frequency categories. Our results suggest that mechanized military training has led to a loss of topsoil and convergence on abundant pines, grasses, and legumes, while a range of fire frequencies has led to an array of ground layer composition in stands with lighter military use. Under all land use scenarios examined, 70% pine canopy may be favorable for abundant grasses and legumes in ground layer vegetation.

Greentree reservoir management was initiated during a period when riparian forests of the Mississippi Alluvial Valley were disappearing rapidly. Greentree reservoirs (GTRs) were intended to provide a refuge for overwintering migratory waterfowl within a landscape of decreasing habitat availability. However, GTRs frequently are flooded as much as 2.5 months longer than unimpounded bottomland forests (UBF), and previous work has shown that such unnatural hydroperiods can have substantial negative effects on such ecosystem attributes as tree assemblage composition and invertebrate production. We conducted the present study to quantify (1) frequency of canopy gaps and (2) tree species composition in GTRs, as compared with UBFs. In general, GTRs were quite similar to UBF stands, in terms of canopy density, proportion of trees in the canopy versus mid-story, degree of stress exhibited by individual trees, gap frequency, and species diversity. However, multivariate comparisons of GTRs versus unimpounded areas indicated differences in species composition. Indicator Species Analyses and examination of the dominant species showed clear differences between GTRs and UBFs, with GTR tree species being, on average, better adapted to flooded conditions, based on wetland indicator status. Greentree reservoir canopies generally were dominated by a Taxodium distichum – Acer rubrum – Quercus lyrata mix, whereas unimpounded forest canopies were characterized as Liquidambar styraciflua – mixed Quercus stands. The midstories of the groups were more similar to one another, with dominance by Acer– Carpinus caroliniana – Planera aquatica in GTRs and Liquidambar – Carpinus – Acer in unimpounded stands. The GTRs included in this study had been managed for 40 to 48 years, providing a long history of flooding which served to select for highly adapted species assemblages.

Forty-three scaled chrysophytes (Synurophyceae: 26 Mallomonas spp., nine Synura spp.; Chrysophyceae: three Chrysosphaerella and Spiniferomonas spp., and two Paraphysomonas spp.) in 41 water samples from Columbia, Franklin, Hamilton, Herkimer, Otsego and St. Lawrence Counties, New York, were identified using TEM. Fourteen taxa are new records from New York, including one new report for the U.S. Temperature, pH, and conductivity ranges of the prevalent species are discussed. Non-siliceous scales of two colorless free-living flagellates, Gyromitus disomatus, an organism of uncertain taxonomic affinity, and the organic scaled chrysophyte-like Pseudodendromonas vlkii, were also observed.

Mosses were collected during field work in the Black Rock Forest, Cornwall, NY between 1990 and 2000. No previous reports of mosses in the Forest exist. Sixty three species were identified. Fontinalis hypnoides Hartm., Leucobryum albidum (Brid.) Lindb., Orthotrichum anomalum Hedw., Plagiothecium laetum Schimp., Polystichum pallidisetum Funck, Steerecleus serrulatus (Hedw.) Robins., Sphagnum riparium Ångstr., and Sphagnum subtile (Russ.) Warnst. have not been previously reported for Orange County, New York.