Vegetation and Elevational Gradients within a Bottomland Hardwood Forest of Southeastern Louisiana

Abstract

Abstract Twelve belt transects were used to sample woody vegetation in a 110-y-old regrowth forest on a natural levee ridge bordering Bayou Sauvage, Orleans Parish, Louisiana. Elevation was measured along each transect and species flood tolerances, based upon measured elevational ranges, were assessed. Codominant native hardwoods included Celtis laevigata, Quercus virginiana and Salix nigra; palmetto (Sabal minor) was the principal understory species. An invasive exotic species, Sapium sebiferum, was found throughout the study site (2485 adults >2 m tall per ha), and showed high flood tolerance. Among saplings (0.3–2 m tall), S. sebiferum abundance (3916 per ha) far exceeded that of all native species combined. The forest showed complex species zonation along an elevational gradient of 163.5 cm across a forest-marsh ecotone. Correspondence analysis delimited at least three plant communities, two dominated by single woody plant species and a third with 15 species. These communities were: (1) a Salix nigra ...