Distribution ofJuncus roemerianus in North Carolina tidal marshes: The importance of physical and biotic variables

Abstract

The physical habitat of Juncus roemerianus was examined at nine sites along a salinity gradient in the Cape Fear River Estuary, North Carolina. Soil salinity, drainage, redox potential, pH, etevati(m, percent sand, percent organic matter, and above-ground plant biomass and height were measured at each site, and from these data, the habitat of Juncus roemerianus was determined. Atl parameters varied over the salinity gradient, with soils at upriver sites having a high sand fraction, low organic fraction, and highest redox potentials. Downriver. well-established marshes had tow sand fractions, high organic fractions, and lowest redox potentials. Canonical Discriminant Analysis indicated that each site was statistically different from other sites due to salinity, elevation, and percent organic matter.Mean standing live bion~ss was 688 g m .z. and, despite differences in physical and chemical factors among sites, biomass of Juncus roemerianus did not vary. Juncus roemerianus was found to grow equally well within a broad range of physical and chemical habitats but did not occupy the total expanse of its potential habitat at any one site.Extensive overlap in physical habitat occurred between Juncus-dominated communities and adjacent communities dominated by other species, especially in the more established marshes. However, Canonical Discriminant Analysis statistically separated short and tall form Spartina alterniflora, Distichlis spicata, Scirpus robustus, and Juncus roemerianus mJcrohabitats based on elevation and redox potential. Thus, we found zonation in tidal marshes of the Cape Fear River Estuary was based on abiotie factors, but we recognize the importance of plant species interactions and marsh position within the landscape.

Stability ofJuncus roemerianus patches in a salt marsh

“…Thus, this species is highly resistant to replacement, a phenomenon noted in other marshes undergoing transition from forested conditions (Hackney et al 1996, Woerher andHackney 1997). Changes in the subsiding marsh seem largely independent of wrack deposition at this site, in contrast to our predictions.…”

“…Patterns of 3". roemerianus cannot be explained entirely by physical habitat differences (Woerner and Hackney 1997). Moreover, little is known regarding stability and persistence of the species.…”

Quantifying the Contribution of Sediment Compaction to late Holocene Salt-Marsh Sea-Level Reconstructions, North Carolina, USA

“…1B-E) with a narrow (~5 m), seaward fringe of Spartina alterniflora, interspersed with occasional patches of Distichlis spicata, Borrichia frutescens and Spartina patens (e.g. Eleuterius, 1976;Adams, 1963;Brinson, 1991;Woerner and Hackney, 1997).…”

Dynamics of zonal halophyte communities in salt marshes in the world

“…Flooding establishes a strong nonresource stress gradient across salt marshes, with soil anoxia and waterlogging decreasing from the seaward edge to the terrestrial border (Mendelssohn et al 1981;Woerner and Hackney 1997;Zedler et al 1999;Cui et al 2011). …”

“…Early work on zonation focused on the apparent correlation of vegetative patterns with variations in the physical environment (Lee 1990;Woerner and Hackney 1997). Most studies on zonation have been done in middle to high latitudes of the northern hemisphere, in euhaline or periodically hypersaline marshes with regular tides (Costa et al 2003).…”