We performed a comparative study of the vascular flora of a serpentine outcrop, Pine Hill, and that of a granite outcrop, Settlement Quarry, from Little Deer Isle and Deer Isle, respectively, Hancock County, Maine. We established four transects along a gradient from exposed to forested areas within each outcrop. Plants were recorded for presence and percent cover from circular plots along each transect. Soil and tissue samples were collected to examine soil-tissue elemental relations. One hundred thirty-two taxa were recorded from serpentine and 89 from granite. Fifty-seven taxa were shared by both sites. Species richness (α diversity) and diversity indices (Shannon-Weaver and Simpson) suggested significant differences between sites and within sites. Principle Component Analysis suggested substrates differed significantly between sites and between exposures within sites. Tissue analyses suggested intraspecific variation with respect to tissue elemental concentrations, especially in Achillea millefolium, Oenothera biennis, Prunus virginiana, Selaginella rupestris, Spiraea alba var. latifolia, and Vaccinium angustifolium. Serpentine populations of many taxa showed low tissue Ca∶Mg ratios (< 1) and high Ni concentrations. Two-way ANOVA showed significant substrate × species effects for several elements, including those that typically characterize serpentine substrates (Ca, Mg, Cr, Ni), suggesting significant genetic variation within species with respect to substrate. Finally, we compared our species list for Pine Hill with a plant survey done at Pine Hill and five additional serpentine sites of Maine in 1977 and provide a list of 285 vascular plant taxa from 62 families for serpentine in Maine.

The Allegheny River Islands Wilderness (ARIW) consists of seven islands located along 90 km of the Allegheny National Wild and Scenic River in northwestern Pennsylvania. I surveyed riparian plant communities in the ARIW to provide an inventory of the species composition and distribution of the alien flora and to identify species of potential management concern. Forty alien plant species (17.8% of the total surveyed flora) were tallied from 42 survey sites across the seven islands of the ARIW. The largely herbaceous floodplain scour community supported the greatest number of alien plant species (35 species; 18.9% of the community flora), followed by the Acer saccharinum–Platanus occidentalis floodplain forest community (23 species; 16.8% of the community flora) and the P. occidentalis–Carya cordiformis–Ulmus rubra floodplain forest community (14 species; 12.4% of the community flora). Ten alien plant species (24.4% of the alien flora) occurred across all three community types. The alien flora of the ARIW included a range of species with varied ecological impact potential, distribution across plant communities, and difficulty of control. Potential control strategies for alien plant species in the ARIW must address the influence of an altered hydrologic regimen as well as control protocols for specific species on the islands and surrounding river corridor.

The vascular flora of Timber Island, the largest undeveloped island in Lake Winnipesaukee, New Hampshire, was surveyed, and a vegetation analysis conducted. The island was found to have 187 vascular plant species, none of which are listed as rare or endangered for the state. The combination of tree species found throughout Timber Island indicates a forest type characteristic of the Central New Hampshire region. In the vegetation analysis, abundance and frequency data were recorded from 106 study plots and analyzed using a two-way indicator species analysis program (TWINSPAN). Six cover types (CT) were defined: Pinus strobus–Gaylussacia baccata CT, Fagus grandifolia–Ostrya virginiana CT, Pinus resinosa–Gaylussacia baccata–Vaccinium angustifolium CT, Tsuga canadensis CT, Acer rubrum–Dulichium arundinaceum CT, and Ruderal CT. Two additional cover types were recognized through qualitative field observation alone: Shoreline CT, and Vernal Woodland Pool CT. While not included in the floristic analysis, twenty-four bryophyte species were documented on the island, 15 of which are new records for Belknap County. A modified Line Intercept Analysis, employed to quantify ground cover, showed that herbaceous plant and bryophyte cover was sparse (7% each), with duff and leaf litter covering 74%, exposed rock outcrop 8%, vernal pools 3%, and 1% disturbed or bare soil. Soil analysis revealed a weak correlation with cover type. Two indices of similarity, Sørensen's Index and the Simple Matching Index, were utilized to compare the vascular plant flora of Timber Island to three other island floras in Lake Winnipesaukee: Rattlesnake Island, Bear Island, and Three Mile Island. Sørensen's Index showed a 50.0% similarity with Bear Island, 51.1% with Rattlesnake Island, and 52.7% with Three Mile Island. The Simple Matching Index showed higher levels of similarity: Bear Island, 51.66%; Rattlesnake Island 59.51%; and Three Mile Island 65.59%.