RECOVERY OF FRESH-WATER MARSH VEGETATION AFTER A SALTWATER INTRUSION EVENT

Greenhouse mesocosms of freshwater marsh vegetation were exposed to a simulated saltwater intrusion event followed by a recovery period duri ng which water levels and interstitial water salinity were adjusted ov er a range of conditions. Virtually all above-ground vegetation, inclu ding the three dominant species, Sagittaria lancifolia L., Leersia or oryzoides (L.) Swartz, and Panicum hemitomon Schultes, was killed by t he initial saltwater intrusion event. P. hemitomon did not recover, bu t S. lancifolia and L. oryzoides, as well as many of the other species initially present, exhibited some ability to recover depending on pos t-saltwater intrusion conditions. Increasingly harsh recovery conditio ns (for freshwater marsh vegetation), including more reduced soil cond itions, higher interstitial salinities, and higher interstitial sulfid e concentrations were associated with decreased live above-ground biom ass and species richness. The effect of elevated salinity on vegetativ e recovery became more pronounced under flooded conditions. This exper iment illustrates that the response of a freshwater marsh community to the longterm disturbance effect of a transient saltwater intrusion ev ent will be strongly influenced by post-intrusion salinity and water l evels.