This five-year study (2007–2011) investigated the impacts of canopy thinning, deer fencing, acorn production, and deer density on tree seedling recruitment in contrasting Quercus-Carya forests to explore the fate of mast and non-mast seedlings in different understory environments. It was conducted at the Mashomack Preserve on Shelter Island near the eastern end of Long Island, NY where tree regeneration in mature forests is very sparse due to extremely high deer (Odocoilus virginianus) populations. Forest thinning increased seedling density (mainly Q. alba L., C. glabra (Mill.) Sweet, Acer rubrum L. and Ostrya virginiana (Mill.) K. Koch) in both fenced and unfenced plots for the duration of the study. Fenced plots had higher total seedling density and taller white Q. alba seedlings than the unfenced plots. Four Quercus plus one Carya species had at least one mast year between 2007 and 2010 and generally during different years with variable impacts on seedling establishment. Acorn/nut production for all species was lowest in the fall of 2011 following nearly two years of drought. Quercus alba seedling density increased dramatically following a 2007 mast year, but had no further increase after a 2010 mast year. Deer density estimates ranged from 82–129 per km² in 2007 to 2010, but dropped to 29 per km² in 2011 associated with very low mast production. There was 100% removal of 260 exposed Q. velutina Lam acorns placed in both deer fenced and unfenced areas throughout the preserve, suggesting an important role of small mammals or birds. The results of this study suggest that mast year, canopy thinning and deer fencing, either individually or in concert, played a positive but variable role by increasing Quercus and Carya seedling establishment and sustainability.

A critical aspect of early-stage invasive species management is determining the niche and assessing the impact of a new species. A multi-scale strategy to predict potential habitat and impacts at the ecosystem, community and species level presents a robust, efficient, and cost effective tool for invasive species management. Regional scale maximum entropy modeling and local scale field studies were used to characterize species-environment and species-species interactions of Oplismenus undulatifolius, a recent invader in Mid-Atlantic forest understories. Oplismenus undulatifolius was first discovered in the U.S. near Baltimore, Maryland in 1996 and is currently found in 13 counties in Maryland and Virginia. At the landscape scale the USDA estimates that 30 percent of the U.S. is suitable for the establishment of O. undulatifolius. Regional scale modeling indicated that 22% of the area modeled was suitable for O. undulatifolius, with 1% highly suitable. Local scale field studies indicated that O. undulatifolius thrives at low light levels (2–11 mols m⁻² day⁻¹) across a wide range of litter depths (0–6 cm) and that light and litter depth are involved in dominance of O. undulatifolius over Microstegium vimineum. Interactions with Fagus grandifolia result in decreased O. undulatifolius cover and dominance, and areas of high O. undulatifolius cover typically have low species richness. Oplismenus undulatifolius has the ability to invade a far greater portion of the forest than M. vimineum, and more research on the community and ecosystem-level effects of this new invasive forest understory species is needed.

I analyzed changes in the native flora of Worcester County, Massachusetts, between the mid-1900s and the early 2000s in relation to changes in land use and climate. I also identified genera and families in which declines and apparent losses were particularly high. Current floristic data came from a recent survey of the county and historical data were obtained largely from herbarium collections, especially a county-wide survey from the 1930s to the 1950s. Climate data came from records collected in Worcester beginning in 1950, and land use data came originally from aerial photographs taken in 1951, 1971, 1985, 1999 and 2005. Average daily temperatures increased by 0.15 °C per decade between 1950 and 2011. The most prominent land use changes during this period were an increase in disturbed land and a decrease in fields and pastures. Extent of forests declined slightly, though forest maturity increased. Northern species decreased relative to southern species, presumably reflecting climatic changes. Losses of northern species were most evident in the southernmost towns in their ranges and were more pronounced than gains of southern species. This difference in behavior of northern and southern species presumably reflects the fact that range extensions depend on dispersal mechanisms, which can be slow, whereas range retractions reflect unsuitability of conditions, which occurs more quickly. Species of disturbed sites increased and species of fields declined, consistent with patterns of habitat change. Several families and genera had high rates of species loss or decline, and some of these, including the Orchidaceae, Ophioglossaceae, Orobanchaceae and Violaceae, have shown high rates of loss or decline elsewhere in the Northeast. Some of these changes may be tied to succession or to active eradication efforts. Two declining families (Orchidaceae, Ophioglossaceae) have juvenile stages dependent on fungi. Changes in climate, patterns of land use and other factors are likely to continue and perhaps accelerate, leading to further changes in the flora and posing challenges for conservation of biodiversity.

Degradation of wetlands on agricultural lands contributes to the loss of local or regional vegetation diversity. The U.S. Department of Agriculture's Wetlands Reserve Program (WRP) funds the restoration of degraded wetlands on private ‘working lands’, but these WRP projects have not been studied in the Southeast United States. Wetland hydrogeomorphic type influences hydrodynamics and thus the vegetation of restored sites, but species composition may also be affected by prior land-condition and restoration methods. We examined the variation in restored wetland vegetation of 61 WRP sites (representing 52 projects) across the Southeast region. Field surveys identified the common plant species at each site, and species composition was analyzed in relation to hydrogeomorphic type and specific restoration methods that were linked to pre-restoration habitat status. At least 380 plant species were recorded across all sites. Site floristic composition generally reflected variation in wetness conditions and vegetation structure. Wetlands restored by ‘non-intensive’ methods overlapped in species composition irrespective of hydrogeomorphic type, as a consequence of successional dynamics related to natural hydrologic variation. More distinctive species composition occurred in wetlands restored by ‘intensive’ methods designed to compensate for intense agricultural land-use before restoration. In the Southeast U.S., WRP wetlands are supporting a variety of plant assemblages influenced by hydrogeomorphic settings, site land-use history, and differing restoration approaches.

Plum Island, New York, has one of the highest concentrations of rare plants in the state and supports a high diversity of native plant species. The island's varied topography and diverse ecological communities have contributed to the diverse flora; for much of the past 100 years, approximately 90% of the island has remained undeveloped. The vascular flora consists of 414 species within 270 genera and 92 families. Largest families include Asteraceae (61 spp.), Poaceae (60 spp.), and Cyperaceae (26 spp.) and largest genera include Carex (9 spp.), Cyperus (8 spp.), and Juncus (7 spp.). Twenty three species are listed as endangered, threatened, or rare in New York. Of these 23 species, 17 are extant, having been observed in the field during this study and six are considered extirpated. Plum Island provides a significant refugium for biodiversity and should be preserved and protected.

Balancing land management and restoration goals for ecosystems and for individual species can create challenges. Here we describe the responses of two federally endangered plants to experimental restoration of fire-suppressed xeric longleaf pine/wiregrass (sandhill) habitat on the Lake Wales Ridge in south-central Florida. We compared responses to prescribed fire with (saw & burn treatment) and without (burn-only treatment) prior felling of the oak subcanopy to an untreated control. We conducted a 7-year study of the demography of two endemic plants, scrub buckwheat (Eriogonum longifolium var. gnaphalifolium) and scrub plum (Prunus geniculata). Scrub buckwheat responded positively to the burn treatments, with high survival, positive growth, and increased flowering in both treatments. Likewise, scrub plum had high survival in all treatments, although severely burned, fire-consumed plants were more likely to die. Fire benefits scrub plum by increasing flowering 2–3 years after fire. These results for these two endemic species are consistent with vegetation studies in long-unburned Lake Wales Ridge sandhills in suggesting that chainsaw felling of the subcanopy can be an effective pre-burn treatment and, when followed by fire, can be useful in “speeding up” restoration. The ultimate goal of sandhill restoration, the return of a frequent low-intensity fire regime, will benefit scrub buckwheat and scrub plum. In this case, management for ecosystem goals benefits two of its rare component species.

Globally rare serpentine barren ecosystems support unique communities, but in the Mid-Atlantic region of the United States, these systems are threatened by forest encroachment in the absence of disturbance. Serpentine barrens are commonly high-stress environments with low water and nutrient availability, as well as high heavy metal content. Forest encroachment into barrens is often preceded by prolific growth of the vine, Smilax rotundifolia L. To better understand how S. rotundifolia is able to colonize these inhospitable environments, the water relations of this species were examined along a gradient from serpentine barren to encroaching forest. These data were compared to the water relations of dominant C₄ grasses in the barrens. Diurnal measurements of stomatal conductance and leaf water potential were made in June, July, and August 2012 at three study sites in southeastern Pennsylvania. Predawn water potential was often highest for S. rotundifolia growing in serpentine barrens, indicating higher soil moisture availability in these areas relative to the encroaching forest. However, no evidence of water stress in diurnal measurements of stomatal conductance or water potential was detected for S. rotundifolia along the barren to forest gradient. Similarly, neither of the C₄ grasses exhibited signs of water stress, and both grasses maintained high stomatal conductance in the afternoon, relative to S. rotundifolia. The C₄ grasses are likely to have a competitive advantage over S. rotundifolia, in terms of their ability to maximize carbon gain over the course of a day and growing season, but these species are liable to suffer if they become overtopped by S. rotundifolia. Smilax rotundifolia was not limited by water availability during the 2012 growing season, calling into question the common assertion that serpentine barrens impose plant moisture stress. Given its height advantage, S. rotundifolia is likely to effectively compete with serpentine barren vegetation in the absence of disturbance or active management.

The inflated bladderwort (Utricularia inflata, Lentibulariaceae) is a submersed freshwater macrophyte that has recently expanded its range in the northeastern United States. To evaluate the potential and actual spread of this plant, we experimentally tested the ability of small (1.0 and 5.0 cm) stem fragments without apical meristems to survive and grow, and of 10 cm apices to grow at different pH levels. We also sampled vegetation in seven lakes to document the quantitative importance of U. inflata, and qualitatively surveyed 29 additional sites for its presence.

All fragments of both lengths survived, and produced new branches at similar rates (t-test: P  =  0.62). Contrary to expectation, relative growth rates were 15% greater at pH 5 than pH 7 (P < 0.001), indicating that low pH per se does not limit this plant. Utricularia inflata has become an important component of the vegetation at greater depth in two of the seven lakes, and now occurs in 15 water bodies in three New York counties (Franklin, Hamilton, and Herkimer) - more than doubling the known locations for this invasive species. Current patterns of distribution strongly suggest that dispersal of U. inflata has occurred by downstream flow along chains of lakes, but also by boat traffic and/or waterfowl to account for its spread to new river drainages.

A summary of the recent introduction of Aldrovanda vesiculosa to eastern United States is presented, with discussion on the status of the species in New Jersey, New York, and Virginia. Several introduced populations include millions of individuals and have been self-sustaining for more than a decade. Aldrovanda is a globally endangered species and may soon be extinct in its natural Old World habitats.