Floristic Quality Index

Washtenaw County

An Explanation of the Floristic Quality Assessment Summary Report
See attachments below

Most natural areas within the city parks, and some other natural areas in Ann Arbor, have been inventoried by Natural Area Preservation (NAP). The report is arranged in descending order of their Floristic Quality Index (FQI) values, from highest to lowest quality sites.

  • Total Species is the total number of different plant species (native and non-native) identified within each site since NAP started its plant inventories in 1994.
  • Native Species is the number of species considered indigenous, or native, to Michigan.
  • E-T-SC is the number of species listed by the State of Michigan Department of Natural Resources as being endangered, threatened, or special concern in the state. Endangered and threatened plants have a protected legal status.
  • Ave Rating is the average “Coefficient of Conservatism” for all the plant species at the site.

A coefficient of conservatism is assigned to each native Michigan plant species as part of the Michigan Floristic Quality Assessment System developed by botanists and the Michigan Department of Natural Resources. The 0-10 scale generally describes how confident you can be that you are in a high-quality natural plant community – mimicking pre-European settlement conditions – when you encounter a particular species. It is tempting to think of the coefficient as the same as a measure of rarity. Although it is often true that rare plants also have a high coefficient, sometimes they don’t, and sometimes a plant with a high CoC is fairly common. It is important to remember that the coefficient is a measure of how faithful a plant is to a certain undisturbed ecosystem, not how rare it is. The Ave Rating is one of the numbers used to calculate the Floristic Quality Index (FQI) for a site. But the Ave Rating itself provides information about the botanical quality of a site because over 85% of Michigan’s total native flora has a coefficient of 4 or greater1. Non-native plant species are not assigned a Coefficient of Conservatism, and thus do not directly contribute to the Ave Rating, or to the Floristic Quality Index (FQI). But indirectly, non-native plant species effect these numerical values by displacing the native species that would otherwise grow there.
The Flor. Qual. Index for a site is calculated by multiplying the Ave Rating by the square root of the number of Native Species. So, a site with 100 native plant species (square root of 100 = 10) and an average rating of 4.0 has an FQI of 40 (10 x 4). When used in a consistent manner to compare similar sites, the FQI is a standard method to quantify the botanical, or floristic, quality of a site. A higher number may indicate a higher quality or more diverse site – at least in terms of its plant communities. Most undeveloped land in Michigan has an FQI of less than 20. In contrast, areas with an FQI of higher than 35 are generally considered to be floristically important enough to merit protection and ecological land management. In fact, the authors of the reference article cited at the end of this document suggest “that areas with known high floristic quality (FQI > 35) cannot be routinely restored to their original floristic quality and therefore are unmitigable.”1 Areas rated 50 or higher are rare and may harbor an appreciative amount of Michigan’s native biodiversity. The Floristic Quality Assessment System does not take into account how important the site is for other biological or social reasons such as wildlife, open space, passive recreation, scenic vistas, linkage corridors, etc…
Certainly Ann Arbor has some extremely biologically rich natural areas. Our restoration and stewardship efforts are being targeted primarily in those sites in an attempt to preserve their ecological integrity.

Updated Sept 28,2006

Other FQI information

DNR – Plants & Habitat at Risk – State of MichiganFloristic Quality Assessment (FQA) is a tool to assist environmental consultants, scientists, natural resource managers, land stewards, environmental decision-makers, and restorationists in assessing the floristic, and implicitly, natural significance of any given area throughout Michigan. It is intended to be a simple, consistent, and repeatable method for evaluating the relative significance of tracts of land in terms of their native floristic composition.

The Universal Floristic Quality Assessment (FQA) Calculator: an online tool for ecological assessment and monitoring, Methods in Ecology and Evolution, Nov 2015Floristic Quality Assessments (FQAs) are measurements of a natural area’s ecological integrity based on their plant species composition. Widely used by government agencies and conservation organizations to monitor and assess natural areas, FQA data bases have been developed for much of the United States and beyond.

Notes on the Third Edition of the Floristic Quality Assessment of Michigan, Bradford S. Slaughter, Michigan Natural Features Inventory, Michigan State University Extension; and Anton A. Reznicek, Michael R. Penskar, and Beverly S. Walters, Herbarium, University of Michigan, Sept 2015In addition to its traditional, widespread use in identifying wetlands and in assessing success of wetland mitigation activities (Herman et al. 2001) (Figure 6), there is continued interest in and adoption of the tool for evaluations of ecological integrity.

Effects of White-tailed Deer (Odocoileus virginianus Zimm.) Herbivory in Restored Forest and Savanna Plant Communities, American Midland Naturalist, April 2012Despite the widespread interest in plant community restoration, few studies have assessed white-tailed deer (Odocoileus virginianus Zimm.) herbivory on herbaceous species and even fewer studies have focused on deer herbivory in restored plant communities. During 2007–2009, we investigated the effect of deer density and associated deer browse on two restored forest and three restored savanna plant communities in Lake County, Illinois. We used 300 small (1.4 m diameter × 1.6 m height) exclosed plots and 1-m2 unexclosed plots to compare the effects of deer herbivory on forbs. We quantified and compared percent non-herbaceous ground cover, species diversity, species evenness, and floristic quality between exclosed plots and unexclosed plots, as well as among preserves within each plant community type. Species diversity and floristic quality of forbs may be maximized at a deer density between 6–22 deer km2 in restored forest communities in northeastern Illinois. Floristic quality was higher in exclosed plots compared to unexclosed plots at all savanna sites. In both plant communities, species evenness may have increased with higher deer density due to an increase in non-preferred plants and non-native species invading locations where preferred native forbs were chronically consumed. Our results highlight the importance of assessing the species diversity, evenness, and floristic quality of target plant communities to determine the impact of deer herbivory at varying deer densities.

Successional trends in Floristic Quality, Journal of Applied Ecology, Greg Spyreas, Scott J. Meiners, Jeffrey W. Matthews, and Brenda Molano-Flores, 2012 Simple, conservation-relevant, plant community measures are sought by resource managers. In this context, the use of Floristic Quality Assessment (FQA) has increased exponentially over the past 30 years. FQA measures a habitat’s Floristic Quality and conservation value by summarizing the relative anthropogenic disturbance tolerances of its plant species (i.e. their Conservatism). However, despite their widespread use in research, restoration and conservation work, the behaviour of FQA values in communities during succession is not understood.

Regeneration of Woodland Vegetation after Deer Browsing in Sharon Woods Metro Park, Franklin County, Ohio, Ohio Journal of Science, April 2006Overbrowsing by deer can decrease plant abundance and change plant species composition,
especially in isolated forest fragments. Sharon Woods Metro Park, Franklin County, OH is a 308 ha suburban woodland preserve that had a deer population of 347 individuals in 1992 (112 deer/km2), which was subsequently reduced to the currently maintained level of ~40 individuals (14 deer/km2). Deer exclosures (~0.4 ha) established in 1990 in three habitats were used to compare vegetation that recovered under complete protection with that which had sustained continued browsing. Tree seedlings, herbaceous and shrub species richness, diversity, and floristic quality were quantified in browsed and fenced treatments as indicators of plant diversity. Percent ground cover was assayed as a measure of plant biomass. Total percent ground cover was significantly lower in browsed treatments in two of the three habitats. Species richness and floristic quality of forest floor species were consistently, though not significantly, lowered in browsed treatments where the more disturbance-tolerant native species increased in frequency and abundance. Reduced deer browsing has allowed some plant species to regenerate but not others. For example, pawpaw, American beech, and jewelweed are disturbance tolerant and/or unpalatable species that may inhibit regeneration of more
sensitive species under browsing pressure. A further reduction in deer density to ~4 deer/km2 and continued vegetation monitoring are recommended next steps for vegetation management at Sharon Woods.

DEVELOPMENT OF A FLORISTIC QUALITY ASSESSMENT METHODOLOGY FOR WISCONSIN, Final Report to USEPA – Region V, June 2003Floristic Quality Assessment can be valuable for restoration evaluation. It can be applied to mitigation projects that occur as a result of regulatory decisions or for evaluating
“voluntary” restoration and management activities undertaken by agencies and non-profitconservation groups.

Floristic quality assessment, Minnesota Pollution Control AgencyThe floristic quality assessment (FQA) is a vegetation-based ecological assessment approach that can be used for wetland quality monitoring and assessment. FQA is based on the Coefficient of Conservatism (C), which is a numerical rating (0 –10) of an individual plant species’ fidelity to specific habitats and tolerance of disturbance. Plant species that have narrow habitat requirements and/or little tolerance to disturbance have high C-values and vice versa. FQA metrics derived from on-site vegetation data and the C-values have been found to be effective indicators of wetland quality–similar to Indices of Biological Integrity (IBIs).

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