Seed Dispersal Dynamics in a Restored Salt Marsh: Implications for Restoration Success

 

       P. L. Hicks, Ecology and Evolution Program, Rutgers, The State University of New Jersey

phicks@aesop.rutgers.edu, 732-932-4320

 

                   J. M. Hartman, Dept. of Landscape Architecture, Rutgers, The State University of New Jersey

 

Restoration of wetland habitats, including salt marshes, still suffers from a high failure rate.  This is due, in part, to gaps in our ecological understanding and a lack of rigorous testing of restoration practices.  Salt marshes are characterized by low floral diversity and distinct zones of vegetation occurring within specific tidal ranges.  During a typical salt-marsh restoration, the tidal hydrology is restored and then the site is either left to be colonized or only one or two dominant salt-marsh species are planted.  It is assumed that seeds of other marsh species will be carried into the site by tidal forces (secondary dispersal).  Neither the reliance on natural colonization for restoration activities nor the dynamics of secondary dispersal in a salt-marsh system have been well studied.  Furthermore, in highly urbanized and fragmented estuarine systems such as the Hackensack Meadowlands, the ability to incorporate these dynamics into restoration projects is even more uncertain.  A majority of the wetlands within the Hackensack Meadowlands are degraded salt-marsh communities dominated by Phragmites australis.  Therefore, the native plant populations that are potential seed sources for restoration projects are greatly diminished and far removed.  To elucidate the influence of natural colonization and secondary dispersal on restoration success in the Hackensack Meadowlands, we quantitatively examined plant community development, seed input and secondary dispersal within a four-year-old restored salt marsh.  We analyzed monitoring data collected over three years to identify successional changes in the vegetation community.  To characterize the seed input, we placed seed traps within the low marsh, high marsh and upland transition zones.  The monitoring data indicate that over the first three years the low and high marsh zones were dominated by annual species that, while common, are not dominants of salt marshes.  The seed input was primarily comprised of annual forbs, including Pluchea odorata and Atriplex patula, some graminoids, such as Cyperus strigosus, but not the typical dominant salt-marsh grasses.  Preliminary results indicate that although secondary dispersal is occurring, incoming seed rain is not reflective of a typical salt-marsh community.