5th UF Water Institute Symposium Abstract

Submitter's Name Beth Middleton
Session Name Restoration and Connectivity
Author(s) Beth Middleton,  Wetland & Aquatic Research Center (Presenting Author)
  Hydrologic remediation revives stressed tree species in tidal swamps
  Freshwater supply is becoming a key conservation issue for coastal freshwater wetlands, because freshwater is becoming more limited due to increased anthropogenic water usage and climate-induced drought. Examples from Texas, Louisiana and Australia demonstrating the responses of tree species to high salinity, drought, and in some cases freshwater remediation will be described in this presentation. Excessive water extraction and drought in 2011−12 in Big Thicket National Preserve (BTNP, TX) increased salinity levels to above 6 ppt in tidal swamps, causing death of freshwater species. These observations were the basis for a new project to track groundwater salinity levels in tidal freshwater swamps across the Gulf of Mexico (USGS and UF). Earlier research assessing the hydrologic remediation effort following the Deepwater Horizon Incident demonstrated that freshwater could ameliorate salinity and biogeochemical stresses to trees in Jean Lafitte National Historical Park and Preserve (JLNHP&P; LA). Tree production increased in JLNHP&P after four months of hydrological remediation in 2010 versus other years (2007−12). Similarly, tree health increased dramatically after two months of hydrologic remediation in a study by another research group of drought/salinity stressed Eucalyptus forests along the Murray River (Australia). In JLNHP&P after freshwater remediation, elevation increased from 2011–14, and this phenomenon constituted a temporary directional change in elevation decline (regime shift) as tested using pairwise regression of elevation over time (2007−10 versus 2011−14). By 2015, the elevation in these swamps began to decline suggesting that remediation benefits may not be permanent. These studies suggest that hydrologic remediation could be a useful engineering tool to conditions for tree growth in impaired freshwater tidal forests. Even short−term releases of freshwater can benefit the health of freshwater tree species in tidal coastal forests. These water management tools may be used to offset future conservation problems due to climate change and/or water extraction.