Climate change has altered the phenological timing of plants across the globe. These changes are especially concerning for plants with small distributions and in unique ecological sites. Here, we examined changes in phenology with respect to temperature and year over a 125-yr span for 12 herbaceous species native to the lowlands of the New Jersey Pine Barrens using herbarium specimens and citizen science observations. Among early summer flowering species, flowering occurred on average 1.42 days/°C earlier in the spring of the corresponding year. Early summer flowering species flowered at an average rate of 0.071 days/yr earlier over the 125-yr study period, whereas no significant change was detected in flowering times of late summer species. Exploration of a set of sister taxa with differing range sizes resulted in no detectable shifts in phenology, which may be explained by evolutionary relatedness or flowering in late summer. The variation in responses to species in the New Jersey Pine Barrens may alter the balance of this ecosystem in the future, as some species respond to changing temperatures, whereas others do not. These results add to a growing body of work suggesting that variations in temperature due to climate change are affecting plant phenology.

Occurrences of Phacelia dubia in the Piedmont of South Carolina have been taxonomically enigmatic. Prior work had shown that there was partial reproductive isolation when plants from South Carolina were hybridized with any of the other varieties but evidence of morphological differentiation was lacking. In this study, a new morphological analysis showed South Carolina plants differed significantly in corolla lobe size, sepal size, and leaf dissection in comparisons with neighboring varieties, P. dubia var. dubia and P. dubia var. georgiana. A preponderance of evidence showing differentiation from all other varieties supports recognition of a new variety, P. dubia var. rionensis. Field work and an updated analysis of herbarium records showed the new variety is found in nine contiguous counties in the central and northern Piedmont of South Carolina and two counties in the inner Coastal Plain. We posit a hypothesized biogeographic pathway based on migration of a P. dubia ancestor from the Great Plains or Mexico to the Nashville Basin cedar glades, then to South Carolina piedmont granite outcrops, followed by a migration south to Georgia and Alabama piedmont granite outcrops and a separate migration north to rocky woodlands in North Carolina.

Snow is an important temperature insulator for overwintering plants, and as the depth and duration of snowpack decreases with warmer weather and the frequency of extreme climate events increases, belowground tissues may be exposed to colder temperatures. Determining the cold tolerance of overwintering plant tissues for native species could help predict species persistence following winter climate change, yet most plant cold tolerance studies are about agricultural crop species, woody plants, or aboveground tissues. Also, plants can acclimate and deacclimate to winter so measuring cold tolerance across seasons provides a more accurate assessment of a species susceptibility to winter climate change. Here, we measure root cold tolerance of two native perennial grassland forbs (Solidago rigida and Silphium integrifolium) in a restored prairie across time to examine cold acclimation and deacclimation to seasonal temperature changes. Average root cold tolerance varied between the two species. Over time, the roots of S. rigida predictably gained cold tolerance as fall progressed and lost cold tolerance in spring. However, roots of S. integrifolium had variable cold tolerance across both seasons. The differences in cold tolerance development between grassland forb species may be a contributing factor explaining species persistence under continued winter climate change. Further research on the cold tolerance of native plant species and belowground tissues is needed to predict the response of temperate plant species and communities to winter climate change.

Both abiotic and biotic factors can influence distributions of invasive plant species, and it is important to understand how such factors contribute to invasion success in order to develop successful management strategies. Microstegium vimineum, known as stiltgrass, is an invasive annual grass in U.S. eastern deciduous forests that can outcompete native understory species, decrease diversity, and prevent the regeneration of native trees. Microstegium is also known to form associations with arbuscular mycorrhizal fungi (AMF), but research has yet to demonstrate whether this association has a role in Microstegium invasion and dominance over native vegetation. We conducted a field survey in invaded and uninvaded habitats across six sites near Louisville, KY, USA, to explore the relative importance of biotic versus abiotic factors in predicting Microstegium abundance and size. Canopy openness was the strongest predictor of Microstegium abundance, followed by soil moisture. Soil nitrogen was the strongest predictor of Microstegium tiller height. Surprisingly, AMF extraradical hyphal abundance and root colonization were not significant predictors of Microstegium abundance or size. In terms of abiotic factors, our results confirm previous studies that have demonstrated that Microstegium grows best in areas with high light and high soil moisture; however, our analysis provides further insight by assessing the relative importance of each of these factors for Microstegium invasion.

Asplenium platyneuron growing at two locations (outer sunlit location and inner shaded location) in a low brick and masonry wall in upper Manhattan (New York City) was studied to assess the effects of the two different microenvironments on the ecophysiology of the two fern populations. The intensity of illumination at the inner location was ca. 40% of the intensity at the outer location, where the photosynthetic active radiation (PAR) at mid-day was ca. 1,484 µmol m^–2 s^–1. Generally, root space temperatures tracked air temperature, varying from 26 to 31 °C for the outer location, and 25 to 28.7 °C for the inner location. Based on prior published literature with other fern species, we hypothesized that samples of A. platyneuron growing on the outer surface exposed to maximum illumination would exhibit higher maximum photosynthesis rates, higher respiration in the light, and smaller leaves compared to the less illuminated samples growing on the inner surface. The results supported our hypothesized relationships. Mean leaf length (cm) was longer for leaves of plants at the shaded inner location (30 ± 1.1) compared to those of plants at the more illuminated outer location (9 ± 1.2). The maximum photosynthetic rate (A_max) for the outside sample of ferns (6.3 ± 0.25) was statistically significantly different from the A_max for the inside sample (4.3 ± 0.72) as hypothesized. The mean respiration in the light was significantly larger for the ferns growing outside (-0.52 ± 0.03) compared to those inside (-0.36 ± 0.04). Additionally, light response (A–Q) curves and relevant other physiological evidence are presented for ferns at the two sampling sites.