Vascular Plant Survey of the Boston Harbor Islands National Park Area

Elliman, Ted

Results of vascular plant surveys on 32 Boston Harbor Islands by Ted Elliman. In a two-year project funded by the Island Alliance to study the vegetation of the Boston Harbor Islands National Park Area, 32 islands were surveyed and inventoried for vascular plant species. Field surveys began on 9 June 2001 and ended on 30 September 2002. Approximately 508 species in 99 plant families were identified on these 32 islands. Of the 508 vascular plant species identified on the Harbor Islands, 232 species (or 46%) are exotic plants. On many islands, non-native plants account for 50% or more of the total flora. The islands with the largest number of plant species are: World's End (300); Peddock's (224); and Thompson (207). These results are correlated with the size and habitat diversity of these large islands. Grape Island (172) also has high species numbers, attributable to its relatively undisturbed habitat conditions. Duration and type of human uses (industrial, institutional, residential, agricultural) are influential factors determining the present condition of the flora on each of the Islands. Six rare plant species listed as endangered (E), threatened (T), special concern (SC), or watch list (WL) by the Massachusetts Natural Heritage and Endangered Species Program) were documented on the islands in this survey. These rare species are: seaside angelica (Angelica lucida-WL, three populations), Carolina crane's-bill (Geranium carolinianum var. confertiflorum-WL, one population), seabeach dock (Rumex pallidus- T, three populations), bristly foxtail grass (Setaria geniculata-SC, two populations), showy goldenrod (Solidago speciosa-WL, one population), and coastal basswood (Tilia neglecta-WL, seven populations). Three previously documented rare plant species were not found. In the second year of the survey, 18 Harbor Islands were studied for their vegetation communities. The survey focus was upland habitats. Most of the Harbor Island plant communities have a high proportion of non-native vegetation. Communities identified include native and non-native forests and woodlands, maritime shrub communities, old fields, beach strand community, maritime cliff communities, and dune systems. The Islands' freshwater wetlands were inventoried as well. Most of these palustrine communities are dominated by invasive plants. Several communities are classified as rare community types by the Massachusetts Natural Heritage and Endangered Species Program. These plant communites include: red cedar woodlands, maritime cliff communities, and maritime shrub communities.

Vascular Plant Survey of the Boston Harbor Islands National Park Area

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