Impact of saltwater spray and sand deposition on the coastal annual Triplasis purpurea (Poaceae)

Pioneer coastal plants occur in areas where sand movement and airborne salt are common. The objectives of this study were to (I) quantify natural leve ls of salt and sand deposition in relation to distance from the shoreline o f Staten Island, New York, and (2) experimentally determine the impact of s altwater sprays and partial sand burial on growth and reproduction of the n ative dunegrass Triplasis purpurea. This summer annual matures most seeds i n cleistogamous spikelets on leaf sheath-enclosed axillary panicles along c ulm internodes. Levels of salt deposition onto T. purpurea shoots over 6 d were determined with a conductivity meter to be 175 mu g/cm(2) at 39 m from shore in 1997, but declined rapidly with increasing distances to 90 m. San d deposition over 1 mo in the summer averaged 30 mm at 72-90 m from shore. In a greenhouse factorial experiment, seedlings were unburied, buried to 50 % height, or buried to 75% height and simultaneously subjected to no sprays , two sprays/wk, or six sprays/wk of seawater over the summer. Sand deposit ion increased plant size and seed production, but seawater sprays were most ly detrimental, reducing plant size, seed production, and seed mass. Howeve r, T. purpurea tolerated moderate levels of salt deposition. The stimulatio n of growth and reproduction in partially buried plants is adaptive on the sandy soils. Prolific seed production and tolerance to moderate levels of a irborne salt allow this annual to maintain high population densities close to short.