Floristic Quality Assessment


Leslie Smit DeBoer, Paul E. Rothrock*, Robert T. Reber, Scott A. Namestnik

Since the concept of creating and restoring wetlands as mitigation for impacted wetlands is still relatively new, the most effective method of assessing vegetation quality in mitigation wetlands has yet to be determined. United States Army Corps of Engineers permit requirements for wetland mitigations include periodic vegetation sampling, and Floristic Quality Assessment (FQA) has been recommended as a method of monitoring wetland quality. The goal of this study was to validate the use of FQA as a tool in monitoring wetland mitigations by comparing FQA performance against a priori Best Professional Judgement (BPJ) and traditional diversity indices. We also compared the variation in results from three regional FQA databases as well as the effect of quadrat size. A total of 21 wetland mitigation sites located throughout the Lower Peninsula of Michigan were included in this study. The sites exhibited a wide range of quality according to both a priori Best Professional Judgement (BPJ) and FQA data analysis. Based on the Michigan FQA database, BPJ exhibited strong correlation with standard FQA metrics, mean C (r = 0.83) and Floristic Quality Index (FQI; r = 0.70). The correlation was marginally lower when metrics were based upon the Indiana FQA database and smaller (0.25 m2) quadrats. In contrast, mean wetness and total species had low correlations (r = 0.45 and r = 0.19) with BPJ. Shannon’s Diversity Index, Simpson’s Diversity Index, and species evenness were poorly correlated with FQI (r < 0.45) and  very poorly with mean C (r < 0.20). FQA results from our 21 sites were very similar to those reported for ten other mitigation sites in northern Indiana. FQA results from all mitigation sites were lower than those seen in several natural wetlands. We conclude that wetland mitigations may not fully replace the vegetative functions of natural wetlands in the short term, but in terms of monitoring, FQA may be one tool used for assessing mitigation wetland quality.

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