Heavy metals can be essential micronutrients in trace concentrations but are often toxic at high concentrations. Physiologically stressful concentrations of heavy metals occur in natural, geological outcrops or result from human activities, such as mining and pollution. Although metal toxicity restricts the growth of sensitive species, some plants are more tolerant. The evolution of metal-tolerant populations has been demonstrated in several species growing on sites of anthropogenic metal contamination in the southeastern USA. The most common natural, metalliferous soils globally are serpentine soils derived from ultramafic rocks, which contain elevated nickel, cobalt, and chromium. The southeastern USA has few ultramafic exposures, but those at Soldiers Delight in Maryland and Buck Creek in North Carolina have been studied in some detail and are summarized here, including presentation of previously unpublished data. On both anthropogenic and natural sites, plants may tolerate edaphic metals by either exclusion or accumulation and sequestration. Plants known as hyperaccumulators take up and store metals at exceptionally high concentrations in their leaves. Hyperaccumulation is rare, with only about 580 species able to hyperaccumulate in the world. Only two examples of heavy-metal hyperaccumulation are known from the southeast: cobalt in Nyssa spp. and manganese in Phytolacca americana; however, these are unusual cases because the plants are widespread on nonmetalliferous soils and only occasionally occur on metal-contaminated soils where they can hyperaccumulate. In these situations, there is probably no selective advantage of hyperaccumulation, but it may occur as a side effect of other physiological processes.

High-elevation species in some Southern Appalachian communities have been shown to be dependent on frequent cloud immersion. However, little is known about the influence of clouds on rare and endemic species native to high-elevation rock outcrops. These outcrops are characterized by shallow soil and high insolation, exposing species to frequent water stress, which might be partially ameliorated by cloud immersion. We compared leaf gas-exchange characteristics of two rock outcrop specialists (Hydatica petiolaris and Sibbaldiopsis tridentata) and two forest-edge herb generalists (Potentilla simplex and Solidago flexicaulis) growing at a high-elevation outcrop in the Craggy Mountains in North Carolina. At least 1 hr of cloud immersion occurred on 67% of days, mostly in the morning hours, whereas most (54%) daylight hours were cloudy. Temperature was lower and humidity higher on cloudy days. Light response curves did not reveal differences among species. Diurnal gas-exchange curves revealed that leaf-to-air vapor-pressure deficits were lower on cloudy days, and on those days, outcrop specialists had higher stomatal conductance and internal CO₂ concentration, but there was no effect on net photosynthetic rates, suggesting little stomatal limitation to photosynthesis on clear days. Water-use efficiency varied among species but was not consistently higher for outcrop specialists. More research is needed to further elucidate the influence of clouds and cloud immersion on rock outcrop communities.

Canebrakes formerly occupied hundreds of thousands of hectares across the southeastern USA, but habitat conversion and fire suppression have reduced their size and extent. Currently, canebrakes are among the rarest vegetative communities in the southeastern USA. Research has focused on Arundinaria gigantea (river cane), with very little focus on Arundinaria tecta (switch cane). The fire history, area, associated flora, and species frequency of 13 canebrakes, dominated by switch cane, were examined at three Department of the Army locations and one game land in the Sandhills physiographic region. We determined canebrake area by identifying its unique vegetative signature in aerial photography at three time steps: earliest aerial photography, the beginning of the recorded burn history, and current aerial photography. We compared fire-return intervals to changes in canebrake area. We created a checklist and tallied 330 taxa of vascular plants (plus Sphagnum sp.) from the 13 canebrakes in our study and calculated species frequency. Estimated area of the 13 observed canebrakes has increased from 25.6 ha historically to 592.8 ha. Mean fire-return interval is within a range of 1–2.3 yr. As fire-return intervals decrease, canebrake area increases, but that increase starts to decline after 2 yr. The highest number of taxa recorded for individual canebrakes were found on Fort Jackson, South Carolina, at Buffalo Creek (236 species) and Fort Bragg, North Carolina, at Black Creek (201 species). Species frequency demonstrates that canebrakes are capable of supporting a mix of herbaceous, shrubby, and arboreal species, which includes rare taxa.

Seed dormancy is a common evolutionary adaptation in temperate plant taxa. Dormancy mechanisms can prevent seeds from germinating at inopportune times, such as a cold period. We report the influence of pregermination stratification treatments on in vitro seed germination and seedling development in Platanthera chapmanii, a rare temperate terrestrial orchid native to the southeastern USA. Seeds were subjected to 0, 8, or 12 wk of cold-moist stratification at 5°C; mean seed viability was 89%. At 9 mo after plating, seeds exposed to 8 and 12 wk of stratification resulted in higher germination (Stage 1; 32% and 35%, respectively) in comparison to 25% germination in nonstratified seeds. Once a protocorm developed a leaf primordium (i.e., reached Stage 2), development to Stage 3 (root development) was independent of the pregermination treatments. Exposure to artificial lights for 3, 4, and 5 mo resulted in 32%, 44%, and 63% of the Stage 2 seedlings, respectively, developing into Stage 3 photosynthetic root-bearing seedlings. Our results indicate that in vitro seed germination in this temperate terrestrial orchid can be improved by using cold stratification. Furthermore, leaf- and root-bearing seedlings can be obtained through the methods reported herein.

A new population of federally endangered Schwalbea americana (American chaffseed) was initiated at the state of South Carolina Department of Natural Resources Woods Bay Heritage Preserve, near Turbeville, South Carolina, in 2013–14. Based on improved survival over time, growth to maturity, evidence of reproduction, and size structure similar to that of a nearby natural population, we suggest that the new population has met the initial criteria for success. Persistence and growth of the population will depend on appropriate management in the form of prescribed fire or fire surrogates and, if necessary, continued demographic enhancement in the form of additional plantings.

Longleaf pine (Pinus palustris) regeneration is dependent on above-average masting (i.e., cone crop) years that occur over 5- to 7-yr cycles. Not understood, however, is how annual cone mast influences radial growth for longleaf pine. Here, we collected tree-ring data from one site in South Carolina and two sites in North Carolina to examine: (a) the relationship between longleaf pine mast and radial growth; (b) how timber thinning at one site affected this relationship; and (c) how previous October to current April Palmer drought severity index (PDSI) affects mast. We used dendroecological techniques to assemble three radial growth chronologies and compared annual radial growth to annual mast. We found the strongest negative correlation when mast was lagged 1 year from radial growth (i.e., mast of Year X with radial growth of Year X − 1), but current-year mast and growth were not significantly correlated. Mast/radial growth relationships were only detectible when radial growth indices less than 0.95, suggesting that trees reallocated resources from radial growth to mast production. Thinning improved annual mast yield, yet neutralized the negative relationship between mast and radial growth. Mast correlated with PDSI in the unthinned site, but not in the thinned site, suggesting that stand dynamics in the thinned site may have overridden climate/mast relationships. These findings reveal the utility of detecting endogenous factors in radial growth for longleaf pine and the benefits of reducing stand density for improving mast.

Southern Appalachian mountain wetlands, especially mountain bogs and swamp forest-bog complexes, are among the most imperiled ecosystems in the southern USA. The Sandy Bottom Wetland Preserve encompasses approximately 10 ha of wetlands along the floodplain of the French Broad River, including swamp forest-bog complex habitat, and is home to several threatened animal species. A total of 366 specimens of vascular plants were collected during 2013–2015 to develop a vouchered flora of the preserve. These specimens documented 221 species in 166 genera and 81 families, 11% of which are not native to the Appalachian Mountain region. We found no plant species that are tracked by the North Carolina State Plant Conservation Program. Plant community types are described and listed for each associated species.