The bark from many species in the Thymelaeaceae (Daphne, Mezereum, fiber-bark, or rope-bark family) can be peeled from stems in long strips and used for cordage, clothing, decorations, and paper. Although observations in the field indicate that the bark from members of this family is unusually resistant to breakage, the physical strength of bark from members of the Thymelaeaceae has not been measured and compared with that of bark of species from other families. We therefore characterized the ultimate tensile strength of bark of 19 species: 13 within the Thymelaeaceae and one from each of six other families. The four species of the genus Dirca L. were of particular interest to us because, unlike most other members of the Thymelaeaceae, they are indigenous to North America, where practical uses of bark from two of the species have been documented. The bark of the four species of Dirca did not differ in ultimate tensile strength and averaged 82 MPa. Ultimate tensile strength of the bark of Dirca mexicana Nesom and Mayfield, which was selected to represent the genus in subsequent analyses, was not different from the ultimate tensile strength of bark of 9 of 15 other species; eight of those nine species were members of other genera in the family Thymelaeaceae. Of the six species with lower ultimate tensile strength than that of D. mexicana, only one, Peddiea africana Hook, was in the Thymelaeaceae. This pilot study of bark tensile strength suggests that unusually break-resistant bark may be a common but not universal trait within the Thymelaeaceae. The comparatively high ultimate tensile strengths of bark of Dirca spp. are consistent with reports of practical uses of bark from these species.

Iris verna L. var. smalliana Fernald ex M.E. Edwards (Family Iridaceae, hereafter referred to as Iris verna) is currently listed as endangered in Pennsylvania. The six extant populations in Pennsylvania are all located in one state forest and represent the northern end of the range for the species. There is little known about the basic biology of I. verna throughout its range, making preservation of threatened populations difficult. Iris verna was tested for self-compatibility and the ability to autonomously self-pollinate in 2016. Pollinator limitation studies were conducted on three of the Pennsylvania populations in 2015 and 2016 by comparing hand-pollinated and naturally pollinated flowers. Potential animal pollinators or seed dispersers were identified through in-person observation and video camera use. Iris verna was found to be self-compatible, with no significant reduction in seed production in selfed flowers, but the species does require a pollinator for pollen transfer. Seed production in I. verna was limited by pollinators during both years of the study and seed production in both control and hand-pollinated flowers was variable across years, suggesting resource availability also limits sexual reproduction. Ants were the only observed animals potentially coming in contact with reproductive organs while visiting flowers, and were also identified as seed dispersers. Our findings suggest that pollinators can be an important limiting factor to sexual reproduction in these endangered populations of I. verna in Pennsylvania.

Systematic field surveys were conducted in 2010–13 for the threatened, globally rare plant species, Helonias bullata L. (swamp pink: Liliaceae) in New Jersey, which contains 60% of known populations. A total of 90 sites were visited, including 56% of extant populations, focusing on the highest quality, largest, and most geographically representative populations in the state in order to comprehensively assess the species' status. A complete census and threat assessment was conducted for each population, using standardized methods adopted during previous surveys in 1997–2001, and population trends were determined by comparing results between data sets. The results found declines in 83% of Helonias populations in the past 10 yr, including severe declines (> 67%) in 53% of populations, and another 26% experiencing declines of 20% or more. Analyses of past and present data sets found the primary cause of declines appeared to be herbivory by white-tailed deer (Odocoileus virginianus), which had not been previously regarded as a significant threat to the species, followed by hydrological changes caused by human development and/or water consumption. Browse damage to Helonias was directly observed in 84% of populations, with an average of 40% of Helonias clusters exhibiting recent damage at each site. Concern for observer bias was also explicitly addressed in the methods and analyses providing further confidence in the results. Implications for the conservation and recovery of Helonias are discussed, as well as the benefits and limitations of the standardized methods used for long-term studies of this and other rare plant species in the future.

Kudzu (Pueraria montana (Lour.) Merr. var. lobata (Willd.)) has long been regarded as one of the most destructive invasive species in temperate forests. Despite this, little is known about the specific impacts of kudzu on native plant communities. In this study we compared plant communities of mixed pine-oak forest sites in Mississippi infested with kudzu to those in uninvaded sites,and asked if kudzu generally suppresses the plant community or has unequal effects on species differing in weediness, shade tolerance, or growth form. At each site we determined species richness; percentage of cover of understory species; density of large trees, saplings, and seedlings; and species composition of sample plots. Kudzu-invaded sites had lower species richness, less understory cover, and lower density of woody species than control sites. Species persisting in kudzu-invaded sites were a subset of species found in control sites, and persistence was unrelated to growth form, weediness, or shade tolerance. Both light limitation and nitrogen fixation by kudzu may be related to these results but further study will be required to evaluate their relative impact on kudzu-invaded communities.

Light heterogeneity commonly occurs in natural environments, and N deposition has increased sharply in recent decades, affecting both the growth and invasion of exotic plants. We used an exotic species, Coreopsis grandiflora, distributed in natural and urban areas throughout China, to study the combined effects of light exposure and N addition on leaf physiology, height, crown area, total biomass (TB), and phenotypic plasticity. We exposed C. grandiflora seedlings to one of three light (15, 65, and 100% of full irradiation) and one of three nitrogen treatments (0, 8, and 20 g N m^–2 yr^–1). The shade significantly increased leaf chlorophyll, N, and P concentrations, aboveground biomass allocation, and specific leaf area, allowing plants to capture more light, which did not result in a change in TB, indicating that C. grandiflora seedlings have shade tolerance. Nitrogen addition generally increased the TB, leaf biomass, crown area and leaf N concentration. In addition, N supply did not increase TB of C. grandiflora in the shade. For approximately half of the traits measured, the phenotypic plasticities of C. grandiflora responding to light differ greatly from those responding to N addition. Under light and N deposition treatments, photosynthetic N use efficiency had higher phenotypic plasticity than other leaf physiological traits, whereas the maximum quantum yield of photosystem II, leaf N, and P concentrations had lower phenotypic plasticity, suggesting that hierarchical plasticity occurs among the various leaf physiological traits. Light intensity increased the plasticity of C. grandiflora in response to N deposition. Thus, with high plasticity, invasiveness of C. grandiflora may increase under high N deposition and illumination conditions.

Hypericum fasciculatum and Stillingia aquatica are abundant codominant shrubs in South Florida depression ponds. Hypericum fasciculatum was studied from multiple perspectives: its competitive context, its adaptations to depression marsh seasonal extremes, and its reproductive biology. Hypericum fasciculatum showed slight intraspecific competition among mature individuals. Its seedling densities diminished with water depths. Interspecific competition with S. aquatica was not detected, probably due in part to markedly divergent root systems. Hypericum fasciculatum is more tolerant of competition from neighboring graminoids than is S. aquatica. The former has wide-spreading sinuous shallow main roots topped with short branch roots rising vertically into the overlying wet substrate. The leaves are dimorphic, with the mature foliage needlelike, having the stomates in abaxial slits. The inner bark is spongy, water-retentive, and substantially thicker than that of other measured local shrubs. Flowering is year-round with usually high fecundity, although flowers abort during drought stress. Seeds per fruit diminished in the wet vs. dry season and with insect-exclusion vs. open pollination. Flowering is protogynous, the buds opening before dawn with the stamens clumped at the base of the style. As the day progresses, the stamens become erect serially with the stigmatic pollen load increasing correspondingly, including with pollinators excluded. Evidence supports extensive self-pollination mixed with entomophily. Insect visitors are diverse.

Halecania robertcurtisii is described as new to science from dry sandstone cliffs and overhangs in Ohio, USA, in eastern North America. It has a smooth and continuous to rimose-areolate thallus, pseudolecanorine apothecia with reddish to rust colored disks, and lacks lichen substances. The species is similar to Halecania subsquamosa but lacks the diagnostic unidentified terpenoid present in that taxon.

Epiphytes are a unique group of plants that live nonparasitically on other plants (“hosts”) and constitute approximately one-fifth of Neotropical vascular plant diversity. However, the processes governing early epiphyte community assembly are poorly understood and have scarcely been experimentally tested. Here, we use an in situ experiment in the cloud forest of Santa Fé, Panama, to evaluate the extent to which host substrate texture regulates early epiphyte establishment. We experimentally varied the surface roughness of native wood substrates, applied bromeliad and orchid seeds to the substrates, and monitored emergence of epiphyte seedlings and their persistence for a year. Rougher substrates facilitated higher initial abundance of epiphyte seedlings; after two months, 81% of the 1,934 total germinated epiphytes occurred on the substrates with experimentally added roughness. Via photo analysis, we also show that epiphytes disproportionately established early on in the experimental grooves, wherein 71% more epiphytes per unit area occurred within 1.5 mm of the grooves than on nearby smooth surfaces. While epiphyte cohort survival rates differed between rough and smooth substrates in the first six months, more than 99% of all seedlings died after one year, regardless of experimental roughness treatment. Only 10 seedlings survived through the end of the experiment. Our results suggest that while substrate texture explains some variation in early epiphyte emergence, roughness alone is not sufficient to explain epiphyte persistence to adulthood. Moreover, our results highlight the importance of removal processes (e.g., wind, rain, animals) in structuring early epiphyte community assembly. Variation in substrate texture may contribute to differences in epiphyte diversity and community composition within- and among-host tree species, but more experiments are needed to disentangle removal processes from substrate-mediated host affinity.