CHEPLICK, GREGORY P.* AND HARRY DEMETRI. Department of Biology, College of Staten Island, City University of New York, Staten Island, NY 10314. - Population ecology of the annual grass Triplasis purpurea along the south shore of Staten Island, New York.
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
Key words: annual dunegrass, coastal ecosystem, Poaceae, population ecology, Triplasis purpurea