Seed Dispersal and Seedling Emergence in a Created and a Natural Salt Marsh on the Gulf of Mexico Coast in Southwest Louisiana, U.S.A.

Authors

  • Tracy Elsey-Quirk,

    Corresponding author
    1. College of Marine and Earth Studies, University of Delaware, 700 Pilottown Road, Lewes, DE 19958, U.S.A.
      Address correspondence to T. Elsey-Quirk, email telsey@udel.edu
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  • Beth A. Middleton,

    1. USGS National Wetlands Research Center, 700 Cajundome Boulevard, Lafayette, LA 70506, U.S.A.
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  • C. Edward Proffitt

    1. Department of Biological Sciences, Florida Atlantic University, c/o Harbor Branch Oceanographic Institute, 5775 Old Dixie Highway, Fort Pierce, FL 34946, U.S.A.
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Address correspondence to T. Elsey-Quirk, email telsey@udel.edu

Abstract

Early regeneration dynamics related to seed dispersal and seedling emergence can contribute to differences in species composition among a created and a natural salt marsh. The objectives of this study were to determine (1) whether aquatic and aerial seed dispersal differed in low and high elevations within a created marsh and a natural marsh and (2) whether seedling emergence was influenced by marsh, the presence of openings in the vegetation, and seed availability along the northern Gulf of Mexico coast. Aerial seed traps captured a greater quantity of seeds than aquatic traps. Several factors influenced aquatic and aerial seed dispersal in a created and a natural salt marsh, including distance from the marsh edge, cover of existing vegetation, and water depth. The natural marsh had a high seed density of Spartina alterniflora and Distichlis spicata, the low-elevation created marsh had a high seed density of S. alterniflora, and the high-elevation created marsh had a high seed density of Aster subulatus and Iva frutescens. The presence of adult plants and water depth above the marsh surface influenced seed density. In the natural marsh, openings in vegetation increased seedling emergence for all species, whereas in the low-elevation created marsh, S. alterniflora had higher seedling density under a canopy of vegetation. According to the early regeneration dynamics, the future vegetation in areas of the low-elevation created marsh may become similar to that in the natural marsh. In the high-elevation created marsh, vegetation may be upland fringe habitat dominated by high-elevation marsh shrubs and annual herbaceous species.

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