RARE PLANTS 



To date, 84 species of vascular plants in the coastal zone are considered rare 

 in Maine (table 20-2; Eastman 1978a and b) . Six of these are trees, 15 are 

 shrubs, 58 are herbaceous dicots, 17 are herbaceous monocots, and 6 are lower 

 vascular plants (ferns and club mosses). Six species are annuals, 3 are 

 biennials, and 75 are perennials. 



Of the 84 rare species, 28 are located near the southern edge of their ranges, 

 42 are located near the northern edge, and 14 are located near the center 

 portion of their range. Many of the northern species are relict populations 

 from the last glacial period ( 12,000 years ago ), and many of the southern 

 species are relict populations from the hypsithermal period (a warm period), 

 which ended about 2500 years ago. 



The habitats, or plant communities, where rare plants are found include: 

 mature forest; sphagnum bogs, fens, and Atlantic or northern white cedar 

 forested wetlands; wet meadows and alluvial thickets; estuarine emergent 

 wetlands and estuarine shorelines; outer coastal headlands and islands; ledges 

 and open ground; and non-sphagnous palustrine wetlands. Many of these plant 

 communities are unique or rare. Associations of three or more rare plants 

 occur in coastal plateau bogs, on outer headlands and islands, and in 

 freshwater and brackish tidal marshes. 



Locations where rare plants have been known to occur in coastal Maine are 

 plotted on atlas map 4. Most locations are based on herbarium specimens which 

 usually identify only the general location (i.e., a particular bog) and not 

 the exact place of growth (i.e., location within the bog). The Critical Areas 

 Program has additional data on the exact locations of species for which they 

 have prepared critical area reports or botanical fact sheets, and species for 

 which they are currently conducting inventories (see table 20-2). 



UNIQUE OR RESTRICTED PLANT COMMUNITIES 



There are several plant communities found along the Maine coast that have 

 restricted distributions in Maine or the United States, or that support 

 several rare plant species. These include coastal plateau bogs and shrub 

 slope peatlands, some outer headland and coastal island plant communities, 

 freshwater and brackish water intertidal emergent wetland communities, a 

 forested wetland community dominated by Atlantic white cedar, and several sand 

 beach and dune communities (sand beach and dune communities are discussed in 

 chapter 4, "The Marine System"). 



Plant communities are composed of groups of species whose range of ecological 

 requirements overlap. Individual species or groups of species are not 

 restricted to particular plant species associations, rather each species is 

 distributed along environmental gradients almost without regard to the 

 occurrence of others. The more important ecological gradients influencing 

 plant distribution in the coastal zone are atmospheric moisture (rainfall, 

 runoff, and fog), soil and air temperature, evapotranspiration rate, substrate 

 type (mineral vs. organic), nutrient availability, salinity (including salt 

 spray), tidal regime, drainage, and others. These factors may act 

 independently or interact to influence plant species distribution. 



20-15 



10-80 



