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The response of Ammophila breviligulata and Spartina patens (Poaceae) to grazing by feral horses on a dynamic mid‐Atlantic barrier island
Author(s) -
Seliskar Denise M.
Publication year - 2003
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.3732/ajb.90.7.1038
Subject(s) - biology , grazing , spartina , inflorescence , overgrazing , botany , poaceae , population , agronomy , ecology , marsh , wetland , demography , sociology
Ammophila breviligulata , American beachgrass, and Spartina patens , salt meadow hay, have been grazed by feral horses on the dunes of Assateague Island for hundreds of years; however, because of a significant increase in the horse population since the 1960s, overgrazing and dune erosion have become problems. Grazing was assessed on foredunes of four different morphologies along a 21‐km stretch of the Maryland portion of the island using 17 exclosure plot pairs. In addition to decreased cover and biomass of the two species, plant structure was significantly affected by grazing. Leaf length and width, stem diameter, and stem density of A. breviligulata and stem diameter of S. patens were reduced in the grazed plots. Especially sensitive to grazing were reproductive characteristics. Percentage of plants in flower, height of flowering stems, and inflorescence length were all significantly reduced by grazing (nongrazed individuals measured). Species composition was not affected by horse accessibility.