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Restriction of the upper distribution of New England cobble beach plants by wave‐related disturbance
Author(s) -
Kennedy Coleman W.,
Bruno John F.
Publication year - 2000
Publication title -
journal of ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.452
H-Index - 181
eISSN - 1365-2745
pISSN - 0022-0477
DOI - 10.1046/j.1365-2745.2000.00496.x
Subject(s) - cobble , seedling , intertidal zone , spartina alterniflora , forb , biology , ecology , population , microsite , habitat , environmental science , agronomy , grassland , wetland , marsh , demography , sociology
Summary 1 The New England cobble beach plant community is an intertidal assemblage of halophytic forbs found exclusively behind fringing beds of the grass Spartina alterniflora . The purpose of this study was to determine the life stage and factors that limit the upper (landward) distribution of cobble beach plants in Narragansett Bay, Rhode Island, USA. 2 Seed traps and soil samples above the community border contained large numbers of seeds and buried seedlings of three cobble beach species, indicating that seed supply and germination do not limit vertical plant distribution. Experimentally added seeds of four species germinated above the community border, but seedlings did not emerge suggesting that seedling emergence is the proximate life stage limiting population and community distribution. 3 Measures of wave disturbance (cobble movement and change in cobble depth) indicated that substrate instability is substantially greater above than within the community, probably due to the lack of buffering by the S . alterniflora bed at higher tidal heights. 4 A second seed addition experiment demonstrated that seedlings of Suaeda linearis , a common cobble beach forb, are only able to emerge and grow into reproductive adults above the community border when the substrate there is artificially stabilized. Seedling transplants and glasshouse manipulations demonstrated that neither herbivores nor soil quality limited seedling emergence. 5 Overall, the vertical restriction of habitat modification by S . alterniflora appears to result in substrate instability at higher tidal elevations sufficient to prevent seedling emergence and limit the vertical distribution of cobble beach plants.