To determine its potential to colonize disturbed habitats mostly devoid of other vegetation, four seedling populations of Triplasis purpurea, a North American native, summer annual grass, were surveyed on coastal beaches along the south shore of Staten Island, New York in early summer. For two populations, survivorship, growth, and reproduction were monitored at different distances from shore to determine the ability of this species to maintain viable populations. At three sites, T. purpurea occurred in >75% of all quadrats used for sampling and densities reached a maximum of 1,195 seedlings per square meter at one highly disturbed site. From 40-90 m from shore, density generally increased. Plants showed the greatest growth and reproduction at distances close to shore (30-40 m); some of this effect was due to density in one population, but when density effects were removed statistically, there still remained a decline in growth and reproduction with increasing distance from shore. Survivorship showed a Type III pattern, with low mortality throughout the summer growing season. Experimental evidence suggests that improved vigour nearest to shore may be due to continual sand deposition. By colonizing newly-deposited and continually shifting sands, T. purpurea can contribute to the earliest stages of dune formation and ecological succession along disturbed coastal beaches in eastern North America.

Key words: annual dunegrass, coastal ecosystem, Poaceae, population ecology, Triplasis purpurea