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Dolomite prairies are rare natural plant communities, with a few high-quality examples in northeastern Illinois. In this study, three dolomite prairies located in southwestern Will County, Illinois, were surveyed to assess species composition and quality. Two of the dolomite prairies were located on the Des Plaines Wildlife Conservation Area (i.e., Blodgett Road Dolomite Prairie Natural Area and Grant Creek Nature Preserve) and the third in the Midewin National Tallgrass Prairie (i.e., Exxon Mobil Natural Area). Overall, a total of 438 taxa were recorded: 318 at Blodgett Road, 255 at Exxon Mobil, and 270 at Grant Creek, with 129 common to them all. Of these, 97 were mesic or wet prairie species, 26 were nonnative taxa, and six were native woody species. Three state endangered and two state threatened species were found associated with these dolomite prairies. The Blodgett Road site was dominated by the annual grass Sporobolus vaginiflorus, along with Andropogon gerardii, Sporobolus heterolepis, and Ambrosia artemisiifolia. The Exxon Mobil site was dominated by the exotic species Poa compressa and Daucus carota, and several native taxa including Sporobolus vaginiflorus, Allium cernuum, Andropogon gerardii, and Solidago altissima. The Grant Creek location was dominated by Sporobolus heterolepis, Rosa carolina, Sorghastrum nutans, and Solidago altissima. These three dolomite prairies can be considered good quality natural areas based on species richness and floristic quality. However, the presence and occasional dominance of nonnative species suggests the need for implementation and continuation of management practices that should maintain or improve their quality.
Species distribution modelling has revealed shifts in the spatial distribution of the range of eastern hemlock (Tsuga canadensis (L.) Carrière) in eastern North America. Models project a decline in eastern hemlock at the southern portion of its range, but not contraction of the southern boundary. In 2003, the vertical, horizontal, and diameter structure and diameter-age relationships of eastern hemlock were quantified in 10 stands thought to represent the species' 10 southernmost stands on the Cumberland Plateau in Alabama. In 2013, we resurveyed these stands to document changes in stand characteristics over the past decade. In addition, we explored additional reaches of stream corridors known to support eastern hemlock to document additional stands previously undescribed in the literature. Results from our resampling revealed that stands had similar stem frequencies over the 10-yr period, but, generally, the number of canopy stems and the number of seedlings declined. The decline in seedlings may have been a result of mortality or recruitment to larger size classes. The decline in canopy trees may have been caused by regional drought in 2007 or localized severe weather events. Our additional sampling yielded one stand not previously described. Although we cannot rule out additional disjunct stands in the area, we speculate that no eastern hemlock stands occur farther south than those documented here. Based on our results, we suggest that these stands are reproductively viable with episodic regeneration, and there has been no evidence of range contraction at the southern range limit over the past decade.
A study of the vascular plants of the Palm Hammock Nature Area, a designated natural area on the west side of the Eckerd College campus in Pinellas County, Florida, was carried out between January 2012 and January 2013. The site is situated entirely on dredged fill soil, rendering it an intriguing site on which to study natural succession. This floristic inventory provides baseline data on the species composition at the site for use in future studies of the Palm Hammock and other forested dredge and fill sites. A total of 157 vascular species were collected from the 4.6 ha site, including 155 angiosperms. Of these, 99 species are native to North America, and 58 species are not native. Of the nonnative species, 20 are considered invasive. The most frequently represented families included Asteraceae (18), Fabaceae (18), Poaceae (14), and Cyperaceae (11). The Palm Hammock Nature Area, which comprises small patches of cabbage palm/oak hammock, cabbage palm stands, and grasslands similar to coastal savannas, shares characteristic species and composition with both maritime and mesic hammocks.
The Panther Knob Preserve is important in the Central Appalachians because it is the region's largest high-elevation pitch pine (Pinus rigida) community, containing numerous rare and threatened plants and animals. Plant community structure and evidence of fire in 2008 were quantified to (a) document successional changes since 1985, and (b) test the hypothesis of pitch pine regeneration failure without recent fire. Diameter at breast height (dbh) of trees and percent cover of plants within 19 plots, each 20 × 20 m, were measured. Increment borings were used to estimate stand age, and evidence of fire, such as bark charring and soil charcoal, was recorded. Mineral soil from the top 10 cm was collected to evaluate the connection between soil characteristics and plant composition. Cluster analysis of percent cover values identified four plant community types. Diameter distributions, age structure, and the presence of only seven seedlings indicated little recent pine regeneration on the plateau. Comparisons with Fleming's (1985) observations showed that pines are taller but declined in percent cover, that ericaceous shrubs are denser, and that the threatened variable sedge, Carex polymorpha, has declined. Charred woody debris, fire scars, or soil charcoal occurred at 16 of 19 sites. Plant community structure, represented by nonmetric multidimensional scaling (NMS) ordination axes, was not correlated directly with the presence of fire evidence or soil mineral nutrients (principal components analysis [PCA] axes). A new conceptual model of pine dynamics on Panther Knob is introduced. Successional pathways with and without fire are discussed in the context of management.
Aldrovanda vesiculosa L., a free-floating aquatic carnivorous plant native to the Old World, has been documented from several ponds and connecting wetlands at U.S. Army Garrison, Fort A.P. Hill in Caroline County, Virginia. This species is believed to have been introduced from a nearby cultivated population, and has spread rapidly throughout many of Fort A.P. Hill's acidic wetlands, which is surprising given Aldrovanda's extreme rarity in its native Old World habitats. The unusual biological vigor of this species at Fort A.P. Hill warrants closer attention from the regional scientific community because very little is known about this species' behavior in North America, the effects on local trophic dynamics, and its short- and long-term interactions with native species. With limited information available, it is difficult to predict to what extent Aldrovanda will influence the natural ecosystem and how this species should be managed. One of Fort A.P. Hill's early objectives is to raise regional awareness of this species, and provide early documentation of Aldrovanda within central Virginia.