Effects of Biomass Removal and Elevation on Species Richness in a New England Salt Marsh

Abstract

An experimental study of the effects of biomass removal and elevation on species richness was conducted in a New England salt marsh. We compared recovery of salt marsh vegetation at low, medium, and high elevations within the marsh (corresponding to high, medium, and low tidal flood stress, respectively). During the second growing season of the study, biomass removal affected species richness in a complex manner. By the end the second growing season of the study, biomass-removal plots had greater species richness than controls at high elevations (4.6 vs 2.4), while at low elevations, biomass-removal plots had lower species richness than controls (0.9 vs 1.8). At middle elevations, species richness in removal plots was not significantly different from that in controls. By the end of the third growing season of the study, species richness in removal plots was nearly equal to that of control plots at all elevations. The decline in species richness between the second and third growing seasons of the study in removal plots at high elevations was due to the fact that clonal perennials persisted and assumed dominance in removal plots. while annual species were extirpated. Our results suggest that abiotic stress (i.e., high salinity, low redox) limited local species richness at low elevations in the marsh and that positive interactions (i.e. the presence of vegetation) ameliorated this abiotic stress. Competitive interference of seedling establishment limited local species richness at high elevations.