At least 50 angiosperm families have plants that produce both chasmogamous flowers and cleistogamous flowers. Various environmental and physiological factors, including the plant growth regulators gibberellins (GAs), have been reported to influence the flower types. Here, the relationship between GAs and flower production was studied for the first time in Viola, a genus famous for the large number of species with the mixed breeding system. Orthologs of genes for GA20 oxidase (VGA20ox) and GA3 oxidase (VGA3ox) were identified by reverse transcription polymerase chain reaction (RT-PCR) from a widespread North American species, Viola pubescens. Semi-quantitative RT-PCR indicated that both genes had increased expression in chasmogamous flowers as compared to cleistogamous flowers, supporting a role for GA in the differential production of flower type. However, the application of exogenous GA3 (the most common commercially available GA) to V. pubescens failed to induce a conversion of production of cleistogamous flowers to chasmogamous ones. Thus, increased levels of GAs in the floral buds appeared be related to flower type in the chasmogamous-cleistogamous mixed breeding system in V. pubescens, but exogenous application was not sufficient to induce an alteration in the type of flower produced.

Northern Wild Senna (Senna hebecarpa) is a native perennial wildflower that was once common in New England, but is now restricted to only seven extant populations in the region. The species thrives in moist alluvial soils along riverbanks and roadside ditches, and its decline has been attributed to forest succession, human development, and changes in hydrology. Given its increasing rarity, individual plants are becoming more isolated, which creates the potential for reduced pollination if the plant is self-incompatible or the potential for reduced fitness from inbreeding depression if it is self-compatible. Results from pollination experiments confirmed that the species is self-compatible, but requires a pollinator to effect pollination. Since the species is self-compatible and therefore capable of inbreeding, we examined the impact of selfing on fitness at both the level of parental fecundity and progeny success. Comparisons between fully selfed and crossed plants revealed that inbred plants had on average slightly lower fecundity, and that their progeny had on average slightly lower viability and fecundity. To better understand the impact of inbreeding on fitness we extended our analysis of individual measures of fitness to include cumulative effects. These results showed that when the small, marginally significant differences for individual fitness parameters were taken together over the course of successive life history stages the net result was that selfed plants produced significantly fewer viable progeny. This finding shows that S. hebecarpa is sensitive to a loss of fitness due to inbreeding depression, which has implications for its conservation.

Pyrrocoma racemosa var. racemosa, is a rare, endemic species found in six remnant Willamette Valley wetland prairie sites in western Oregon, USA. Due to its rarity and association with high-quality wetland habitat, P. r. var. racemosa is a focal species for reintroduction and genetic rescue. However, no genetic studies for this species have been undertaken. I conducted a pollen addition experiment between the two largest P. racemosa populations to determine the effects of selfing, intrapopulation crosses and interpopulation crosses on plant fitness. An ANOVA indicated that the percentage of filled achenes from intrapopulation crosses was significantly greater (≈ 30% more filled achenes) than both interpopulation crossing and selfing, which did not statistically differ from each other. Pollen viability, inferred through flourescein diacetate staining, did not differ statistically over the time span that it took to gather and perform the pollen addition treatments, suggesting that the diminished seed set from the interpopulation crosses was due to genetic incompatibility. Although the two P. r. var. racemosa populations are only about 6 km apart, the established seed transfer zones for other locally rare plants are considerably larger and if applied would not likely provide an effective genetic safeguard.

Our collective knowledge of the natural history traits of our native species is commonly lacking, and this deficit puts us at a disadvantage as we try to predict responses of species, communities, and ecosystems to current, widespread environmental changes wrought by human activities. Erythronium americanum Ker Gawler is a common spring ephemeral in the forests of the eastern United States and it plays an important role in biogeochemical cycling and food webs. Yet, there remain unresolved questions about its developmental patterns and therefore capacity to respond to environmental change. In this study, I collected 30 corms with no roots that had recently formed from droppers and 30 older corms in the spring, replanted them adjacent to Plexiglas for viewing, and monitored their development semi-annually for two years. Older corms produced a second set of roots during the summer. Young corms formed roots during the first summer of their existence. Both old and new corms only formed droppers in the spring following transplanting. Not all second year corms produced droppers. Corms that formed droppers did not persist when a new corm was formed at the end of the dropper. These results indicate that Erythronium americanum faces a delay in its response to environmental changes, and not all young corms respond significantly within two years even though most young corms can form droppers.

Forest floor litter communities include detritivorous, predacious, and parasitic arthropods that feed on, or forage within, the decaying organic material. Although this substrate is heterogeneous, little research has investigated the preferential feeding tendencies of these arthropods. The objective of this study, conducted in the lowland rain forest of French Guiana, was to examine some of the factors that may influence foraging behavior. Plots were covered with either leaf or floral litter from three species of Lecythidaceae (Brazil nut family), and traps were set within and above each plot. Traps baited with floral litter yielded significantly more arthropods than those baited with leaf litter. Floral and leaf tissues were subsequently analyzed for moisture, fiber, sugar and nutrient concentrations. These analyses indicate that, relative to leaf litter, floral litter provides a quantitatively richer nutrient source available at lower energy expenditure, suggesting that these arthropods (mostly insects) may be operating under optimal foraging strategy.

Habitat specificity of tree species has traditionally been determined by identifying synchronous abiotic characteristics and species presence on the landscape. On a local scale this identifies many species as specialists; however, on a regional scale, most tree species are classified as generalists because individual species are present across a wide-range of edaphic and topographic conditions. To improve our ecological understanding of habitat specificity in trees, we classified white oak (Quercus alba) based on two performance currencies: responsiveness to climate and maximum tree age. We sampled tree rings from both ridge and valley stands in the southern Appalachian Mountains to contrast the dendroclimatic response at these topographic positions. White oak had radial growth responses to Palmer Drought Severity Index, temperature, and precipitation that was not dependent upon topographic position (ridge vs. valley), suggesting that white oak is a generalist species. A dendroclimatic response that is not dependent upon topographic position should allow white oak to adapt readily to climatic shifts that span a range of environmental conditions. Tree age has served as a successful performance currency in relatively undisturbed forests; however, in the southern Appalachian Mountains where there is a long history of human disturbance, maximum tree age revealed more about regional logging history than about white oak habitat specificity. Understanding habitat specificity of plant species improves predictions of species' response to environmental change. Traditionally trees have been classified based on occurrence on the landscape; however, in heavily-impacted forests occurrence is a reflection of land-use history. Dendroclimatology offers a more accurate tool to assess a tree's habitat specificity and was successfully applied in several ridge and valley sites in the Appalachian Mountains to identify white oak as a generalist species.

Long-term changes in biomass and demography of a second-growth forest in central New York were quantified based upon re-measurement of 16 permanent plots (0.4 ha) originally established in 1935. We hypothesized that as the average age of the forest overstory reaches 125 years, biomass, structure, and composition would be approaching steady state. Aboveground live biomass (AGB) of the forest continued to increase steadily and significantly from 1985–2008, reaching 233 Mg ha⁻¹. Empirical observations closely matched predictions by the Forest Vegetation Simulator (FVS) from 1935–2008, and the FVS projected peak in AGB of 247 Mg ha⁻¹ at age 174 years. Aboveground net primary productivity averaged 772 g m⁻² yr⁻¹ and wood production was significantly higher on well-drained than more poorly-drained upland sites. Recent changes (1993–2008) in composition and structure continued long-term trends with increasing biomass of sugar maple, red maple, white ash, eastern hemlock and red oak, while beech and basswood declined, owing to effects of exotic pests. Until recently, beech was the only species exhibiting abundant regeneration in the forest, through vegetative sprouting. In the future, mortality from exotic insect pests is likely to alter trends in biomass, composition and structure of this forest and probably others in the region.

Hardwood-dominated riparian forest was surveyed in 83 quadrats on 3 floodplains, 11 lower terraces, and 8 upper terraces along 11 km of Zoar Valley Canyon, a minimally disturbed segment of 5^th–6^th order Cattaraugus Creek in western New York State, USA. Increment core-based stand ages from 8 to >300 years constituted the longest middle-order riparian sequence yet studied in the East. Comparisons of aerial images starting in 1929 with present-day increment cores indicated trees have reached breast height and persisted on recent lower terraces within at most 6–27 years after deposition, suggesting landform age and type associated primary succession rather than flood-regime driven secondary succession or maintenance of early seral stages. In 2009, the second largest flood since 1940 caused only modest damage even to floodplain stands, supporting this premise. Regressions of stand characteristics on age across the 300-year sequence revealed logarithmic increases in tree diameter and height, stand basal area, and shade tolerance as succession has progressed. Non-metric multidimensional scaling (NMDS) ordination of stand characteristics and species distributions further revealed coherent successional gradients, including affinity vs. divergence among species of varying life history traits; e.g., an association between late-seral Acer saccharum and Fagus grandifolia and their divergence from pioneering Populus deltoides and Salix nigra. It also revealed a convincing association of biotic variables with a directional and strongly discriminated ordination distribution of landform types of increasing maturity; i.e., geomorphic patterns. Successional trends eventually leveled off beyond ∼150–200 years' stand age, suggesting a dynamic equilibrium (perhaps now reflecting a gap-phase and no longer true primary succession) that bears structural, compositional, and aesthetic resemblance to scattered old-growth in the surrounding uplands. It has been questioned, especially in the East, whether riparian succession often proceeds so far, or if hydrologic processes more likely interrupt the progression. In Zoar Valley, where vegetational succession appears to have been generally protected from both natural (flood damage, inundation) and anthropogenic disruption (logging, flow regulation), multi-aged old-growth stages occur on upper terraces throughout the riparian zone.

Old field succession has been reviewed extensively in many community settings; however, secondary succession in maritime communities, especially forest and shrub communities is poorly understood. Maritime communities of the North American Atlantic coast are unique and often fragmented ecosystems that provide critical stopover sites for migratory birds. Historical losses coupled with rising developmental pressures have created the need for conservation and restoration to protect these globally rare communities. We examined secondary succession by analyzing the vegetation community composition and soil seed bank of an abandoned agricultural field initially and at seven years (2009) after initiation of state-agency site restoration that used a combination of active and passive restoration techniques. The restoration field was divided into three projected habitats: early maritime forest (16 ha), maritime shrub (12 ha), and coastal grassland (8 ha). A trend was observed with loss of species richness across habitat types. There was a high proportion of species turnover, yet there were no significant differences in the number of species belonging to functional groups for each habitat between the two sampling years (2003 and 2009). Zones where active restoration techniques were used were more indicative of restoration success compared to areas that relied on spontaneous succession. Long-term vegetation surveys are critical to assess the success of restoration operations, and to describe and predict successional trajectories. Accessible vegetation survey data may become increasingly important in the future as land managers place more emphasis on protecting and restoring these overdeveloped, unique coastal communities.

The shores of the Delaware River south of the Fall Line in Pennsylvania were once lined with coastal plain forests; however, this forest type is nearly gone from the state due to human activity. One remaining example is Delhaas Woods, a 239-acre coastal plain forest located in Bristol Township, Bucks County. Because of the rarity of this type of habitat in Pennsylvania, a study was developed to characterize the vegetation and community assemblages present at this locality. Site visits were conducted throughout the summer and fall of 2009 resulting in a vascular plant inventory of 373 species, including 297 (80%) native species and 41 (11%) species of concern tracked by the Pennsylvania Natural Heritage Program (PNHP). Oldenlandia uniflora, not previously known to occur in Pennsylvania, and Listera australis, a species new to Bucks County, were recorded. Vegetation transects were conducted using the point-quarter method for tree canopy analysis and the area-plot method for shrub and herbaceous layer analysis, and the resulting data were used to describe and delineate the community assemblages present in Delhaas Woods, two of which, Red Maple-Magnolia Palustrine Forest and Sweetgum-Oak Coastal Plain Forest, are state-ranked rare community types. Preliminary soil investigations were conducted. Locations of PNHP-listed plant species were mapped and management actions were suggested to preserve the integrity and diversity of this unique landscape and biodiversity hotspot.

Loss of small herbaria is an unfortunate global trend and initiation of new collections at small academic institutions is an increasingly rare occurrence. In 2006, a new herbarium was established at the State University of New York College at Plattsburgh. The PLAT herbarium has since grown to more than 7,000 specimens, many of them representative of the flora of northeastern New York (especially Clinton County). Previous to 2006, this region was without a recognized herbarium, the nearest in-state collections being more than 150 miles away. Although botanists have previously worked in the region, relatively few plant species were recorded for Clinton County by the New York Flora Atlas—a resource providing species distribution records based on specimens accessioned in herbarium collections. Given the dearth of available distribution data for Clinton County (including the eastern Adirondack Mountains and the western Lake Champlain valley), this project sought to provide records of previously unreported species by comparing NY Flora Atlas maps with current holdings. 203 species will now be added to the NY Flora Atlas for Clinton County, roughly half of those considered exotic. This exercise has amplified the importance of supporting and maintaining small regional herbaria as repositories of valuable biodiversity information. Likewise, this project also highlights the enduring value of training in floristics and taxonomy.