COS 89-6 - Recovery of coastal wetland vegetation after Hurricane Katrina

Thursday, August 6, 2009: 9:50 AM
Santa Ana, Albuquerque Convention Center
Beth A. Middleton, National Wetlands Research Center, USGS, Lafayette, LA

This study asked whether post-hurricane environments could affect the recovery of vegetation in Gulf coastal wetlands.  In coastal marshes, seedlings and seedbanks were studied in relation to water depth and salinity at various distances from the shoreline using field observations and seed bank assays.  In baldcypress swamps, the volumes of structural damage were assessed by species, along with seedling recruitment in canopy openings.  Results/Conclusions Temporary changes occurred in the vegetation of coastal marshes and swamps of the northern Gulf Coast following Hurricane Katrina in 2005.  In mixed baldcypress swamps, Hurricane Katrina shifted the vegetation towards dominant species.  The storm did not damage dominant as much as subdominant species (0-1% vs. 0-100%), and opened the canopy (canopy coverage: 78.9 to 92.1%).  In these openings, tree seedling recruitment was mostly of dominant species.  The recovery of coastal marsh vegetation was flexible in that seed germination from the seed bank and seedling recruitment depended on water depth and salinity level. Seedling recruitment differed with distance from the shoreline of the marshes, so that recruitment was dependent on post-hurricane environments of flooding and salinity. Of the coastal marsh types, salinity reduced the recruitment of freshwater marshes the most.  Therefore, increased hurricane activity could potentially shift the outcome of vegetation recovery in both coastal marshes and forests.

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