15 - 17 - TR EL ERDC/ Ecosystem Management and Restoration Research Program Floristic Quality Index of Restored Wetlands in Coastal Louisiana Glenn M. Suir and Charles E. Sasser August 2017 Laboratory Environmental Environmental Approved for public release; distribution is unlimited. The U.S. Army Engineer Research and Development Center (ERDC) solves the nation’s toughest engineering and environmental challenges. ERDC develops innovative solutions in civil and military engineering, geospatial sciences, water resources, and environmental sciences for the Army, the Department of Defense, civilian agencies, and our nation’s public good. Find out more at www.erdc.usace.army.mil. To search for other technical reports published by ERDC, visit the ERDC online library at http://acwc.sdp.sirsi.net/client/default. Ecosystem Management and Restoration ERDC/EL TR-17-15 Research Program August 2017 Floristic Quality Index of Restored Wetlands in Coastal Louisiana Glenn M. Suir Environmental Laboratory U.S. Army Engineer Research and Development Center Wetlands and Environmental Technologies Research Facility Louisiana State University – Military Sciences Building Baton Rouge, LA 70803 Charles E. Sasser Louisiana State University School of the Coast and Environment Department of Oceanography and Coastal Sciences Energy Coast and Environment Building Baton Rouge, LA 70803 Final report Approved for public release; distribution is unlimited. Prepared for U.S. Army Corps of Engineers Washington, DC 20314-1000 Under Project 454745, Use of Remote Sensing Technologies and Field Data Collection to Quantify the Effects of Dedicated Dredging and Use of Dredged Sediments for Ecosystem Restoration. ERDC/EL TR-17-15 ii Abstract Restoration efforts in the United States have created or benefitted large expanses of wetlands. Typical goals of wetland restoration efforts are to conserve, create, or enhance wetland form and to achieve wetland function that approaches natural conditions. Measures of wetland condition have been used to monitor and assess project performance, resilience, and adaptive management needs. An emerging tool for performing bioassessments in wetland systems is the Floristic Quality Index (FQI). This study assessed the use of a modified FQI (FQImod) to evaluate site development, plant community establishment, and wetland condition. Three restoration sites in coastal Louisiana were used to evaluate the utility of an FQImod for assessing the performance and resilience of restored wetlands by comparison to reference wetlands. Results demonstrate that the FQImod data successfully reflected large disturbance events — namely hurricanes and salinity spikes. The data also identified vegetation differences due to elevation, age, and hydrology. The modified FQI provided useful measures of restoration type (e.g., planted versus not planted, marsh creation versus nourishment), chronosequence (condition and stability over time), and trajectory (i.e., intersecting trend lines when restored marsh FQI approaches reference marsh condition). The FQImod provides a rapid and effective system for assessing wetland condition and performance. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR. ERDC/EL TR-17-15 iii Contents Abstract .......................................................................................................................................................... ii Contents ........................................................................................................................................................ iii Figures and Tables ........................................................................................................................................ iv Preface ............................................................................................................................................................. v Unit Conversion Factors .............................................................................................................................. vi 1 Introduction ............................................................................................................................................ 1 1.1 Background .................................................................................................................... 1 1.2 Approach ........................................................................................................................ 3 1.3 Objective ........................................................................................................................ 5 2 Methods .................................................................................................................................................. 6 2.1 Study sites ...................................................................................................................... 6 2.2 Assessment units .......................................................................................................... 7 2.3 Vegetation survey data .................................................................................................. 9 2.4 Floristic quality index ..................................................................................................... 9 3 Results and discussion ......................................................................................................................12 3.1 Community descriptions.............................................................................................. 12 3.1.1 Sabine vegetation ..................................................................................................... 12 3.1.2 Atchafalaya vegetation ............................................................................................. 14 3.1.3 Little Lake vegetation ............................................................................................... 16 3.2 Coefficients of conservatism ...................................................................................... 21 3.3 Floristic quality ............................................................................................................. 22 3.3.1 Sabine FQI ................................................................................................................. 22 3.3.2 Atchafalaya FQI ......................................................................................................... 24 3.3.3 Little Lake FQI ........................................................................................................... 26 3.3.4 FQI summary ............................................................................................................. 27 4 Conclusion ............................................................................................................................................ 31 References ................................................................................................................................................... 33 Report Documentation Page ERDC/EL TR-17-15 iv Figures and Tables Figures Figure 1. Location map of study areas (Sabine, Little Lake, and Atchafalaya), assessment units (Project, Project Reference, and Subwatershed Reference), and data collection sites. ............. 8 Figure 2. Percent cover and CC values for species within the Sabine assessment units. ................. 18 Figure 3. Percent cover and CC values for species within the Atchafalaya assessment units. .............................................................................................................................................................. 19 Figure 4. Percent cover and CC values for species within the Little Lake assessment units. ........... 20 Figure 5. Average CC for all survey stations within study site assessment units. ............................... 22 Figure 6. Floristic Quality Index (FQImod) scores for all survey stations within the Sabine assessment units by year. Vertical lines and inset chart provide tropical storm (TS) activity (wind speed miles per hour) and salinity data, respectively. ................................................................. 24 Figure 7. Floristic Quality Index (FQImod) scores for all survey stations within the Atchafalaya assessment units by year. Vertical lines and inset chart provide tropical storm (TS) activity (wind speed miles per hour) and salinity data, respectively. ................................................................. 25 Figure 8. Floristic Quality Index (FQImod) scores for all survey stations within the Little Lake assessment units by year. Vertical lines and inset chart provide tropical storm (TS) activity (wind speed miles per hour) and salinity data, respectively. ................................................................. 27 Tables Table 1. General description and criteria for assignment of Coefficient of Conservatism (CC) scores to different plant species (based on Andreas et al. 2004, Cohen et al. 2004, Cretini et al. 2012, and Swink and Wilhelm