Salt Tolerances and The Distribution of Fugitive Salt Marsh Plants

Abstract

Fugitive species often live under harsh physical conditions, yet their ability to cope with environmental extremes has received little attention. We studied the association of fugitive plants and stressful physical conditions using salt marsh plants that live in hypersaline bare patches. In New England salt marshes, primary space is dominated by dense monospecific stands of perennial turfs, but disturbances frequently leave bare space that rapidly becomes hypersaline. Elevated salinities of bare patches result form direct exposure of soil to solar radiation and evaporative water loss. A number of fugitive plants that are rare in undisturbed salt marsh vegetation are commonly associated with bare patches before being displaced during secondary succession. Greenhouse studies show that plants that dominate undisturbed vegetation are stunted by high substrate salinities, whereas the photosynthesis and growth of patch—dependent fugitives are relatively independent of typical salinity variation. Moreover, in the field, watering more than doubled the survivorship and growth of seedlings in patches and more strongly affected dominants than patch—dependent fugitives. Our results show that physical conditions in salt marsh bare patches can limit plant colonization, and suggest that high salt tolerances may permit fugitive plants to utilize bare patches as refugia from competitors. Since fugitive plants are commonly restricted to physically stressful habitats, the ability to withstand harsh physical conditions is likely often an important aspect of their biology.