INTERACTIVE EFFECTS OF ELEVATION AND BURIAL WITH WRACK ON PLANT COMMUNITY STRUCTURE IN SOME RHODE-ISLAND SALT MARSHES

1 The effects of disturbances and elevation on marsh plant communities were examined using experimental disturbances along an elevation grad ient in marshes with different disturbance histories. In addition, dif ferences in species composition among five marshes were determined at elevations at which the greatest concentration of burial by wrack occu rred. 2 Experimental wrack burial generally caused significant mortali ty of the high-marsh competitive dominants, Juncus gerardi and Spartin a patens, and strongly increased the abundance of the fugitive perenni al, Distichlis spicata. 3 The effects of experimental wrack burial int eracted strongly with abiotic factors associated with elevation to inf luence the distributions of both competitive dominants and annual fugi tive plants. 4 Frequent wrack burial in a marsh appears to lead to a p ersistent assemblage of plants dominated by competitively subordinate fugitives. This assemblage of fugitives tends to occur at intermediate elevations within the marsh, where wrack gets stranded for long perio ds of time and where the resistance of Juncus gerardi to wrack burial is lowest. 5 We suggest that wrack-burial disturbances interact strong ly with marsh elevation to influence the zonation of plants in New Eng land salt marshes, and discuss some implications of our results.