Floristic Quality Index and Forested Floristic Quality Index: Assessment Tools for Restoration Projects and Monitoring Sites in Coastal Louisiana

Authors

Kari F. Cretini, Cherokee Nation Technologies, Wetland and Aquatic Research Center
William B. Wood, Coastal Protection and Restoration Authority of Louisiana, Lafayette Field Office
Jenneke M. Visser, School of Geosciences, University of Louisiana at Lafayette
Ken W. Krauss, U.S. Geological Survey, Wetland and Aquatic Research Center
Leigh Anne Sharp, Coastal Protection and Restoration Authority of Louisiana, Lafayette Field Office
Gregory D. Steyer, U.S. Geological Survey, Southeast Region, Baton Rouge
Gary P. Shaffer, Department of Biological Sciences, Southeastern Louisiana University
Sarai C. Piazza, U.S. Geological Survey, Wetland and Aquatic Research Center

Document Type

Article

Date of this Version

2017

Citation

Wetland and Stream Rapid Assessments. https://doi.org/10.1016/B978-0-12-805091-0.00049-9

Comments

U.S. Government Work.

Abstract

In 2003, the Coastwide Reference Monitoring System (CRMS) program was established in coastal Louisiana marshes and swamps to assess the effectiveness of individual coastal restoration projects and the cumulative effects of multiple projects at regional and coastwide scales (Steyer et al., 2003). In order to make these assessments, analytical teams were assembled for each of the primary data types sampled under theCRMS program, including vegetation, hydrology, landscape, and soils. These teams consisted of scientists and support staff from the US Geological Survey and other federal agencies, the Coastal Protection and Restoration Authority of Louisiana, and university academics. Each team was responsible for developing or identifying parameters, indices, or tools that can be used to assess coastal wetlands at various scales. The CRMS Vegetation Analytical Team has developed a Floristic Quality Index (FQI) for coastal Louisiana to determine the quality of a wetland based on the composition and abundance of its herbaceous plant species (Cretini et al., 2012). The team has also developed a Forested Floristic Quality Index (FFQI) that uses basal area by species to assess the quality and quantity of the overstory at forested wetland sites in Louisiana (Wood et al., 2017). Together these indices can provide an estimate of wetland vegetation health in coastal Louisiana marshes and swamps. The FQI has been developed and used for several regions throughout the United States to provide an objective assessment of the vegetation quality or biological integrity of wetland plant communities. The FQI was first developed as a weighted average of the native plant species at a site (Swink and Wilhelm, 1979). It is based on a coefficient of conservatism (CC) score that is scaled from 0 to 10 and is applied to each plant species in a local flora. The score reflects a species’ tolerance to disturbance and specificity to a particular habitat type. Species adapted to disturbed areas are often not habitat specific and, as such, have a low CC score. In contrast, habitat-specific species are generally not tolerant to disturbances and, as such, have a high CC score. A group of experts on local plants agrees upon and assigns CC scores. The FFQI, which is similar to the FQI, was developed to evaluate ecosystem structural changes among forested wetland sites. The FFQI will be used to (1) evaluate forested wetland sites on a continuum from severely degraded to healthy, (2) assist in defining areas where forested wetland restoration is needed, and (3) determine the effectiveness of future restoration projects aiming to return degraded forested wetlands to healthy ecosystems. While the FQI is based on the percent cover of emergent herbaceous species, the FFQI uses this emergent herbaceous layer data in conjunction with the basal area at a species level and canopy cover. As such, the FFQI is a natural extension of the FQI and can be used in conjunction with the FQI of the understory herbaceous community in forested wetland systems, as there is typically an inverse relation between tree and herbaceous layer vegetation dominance in Louisiana’s coastally restricted forested wetlands that represents natural succession (Conner and Day, 1992a; Shaffer et al., 2009; Nyman, 2014). As environmentally driven temporal shifts occur in the ecosystem, the FFQI contains valuable information that depicts a trajectory in system function. Generally, coastal flooded forested wetlands have transitioned to shrub-scrub; fresh, floating, and intermediate marshes; and open water. Conversely, in a few select locations, such as the Atchafalaya River Delta, the natural deltaic cycle causes the reversal of this trend. In this emerging deltaic environment, the succession of fresh marsh is transitioning into young forested wetlands populated by low value pioneer and disturbance woody species, leading to the development of fledgling swamps (Johnson et al., 1985; Shaffer et al., 1992). These two contrasting successional trajectories occurring within the same coastal system and same monitoring network highlight the need for a multivariable and index approach to site and restoration assessment.