Florisztikai Minőségfelmérési Index

Floristic Quality Assessment Index – FQAI


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Purpose of the method: To provide an objective standard (Floristic quality assessment index) for describing the quality of plant communities. Used to make relative comparisons in environmental and natural resources management.

The method is based on field data - may include GIS component.

Method description:

The principle concept of FQAI is “the quality of a natural community can be objectively evaluated by examining the degree of ecological conservation (or fidelity) of the plants species in that community” (Andreas et al. 2004). The FQAI is developed by assigning a numeric score from 0 to 10 (the C of C) to each plant species growing in a specified region, as follows:

C of C Description (source: Andreas et al. 2004)

0 Plants with a wide range of ecological tolerances. Often these are opportunistic invaders of natural areas (e.g., Phragmites australis, Phalaris arundinacea) or native taxa that are typically part of a ruderal community (e.g., Polygonum pensylvanicum, Ambrosia artemisifolia).

1-2 Widespread taxa that are not typical or (or only marginally typical of) a particular community like Solidago canadensis or Impatiens capensis.

3-5 Plants with an intermediate range of ecological tolerances that typify a stable phase of some native community, but persist under some disturbance (Asclepias incarnata, Ulmus rubra, Spartina pectinata)

6-8 Plants with a narrow range of ecological tolerances that typify a stable or near “climax” community (e.g., Goodyera pubescens, Veronicastrum virginicum, Cephalanthus occidentalis)

9-10 Plants with a narrow range of ecological tolerances that exhibit relatively high degrees of fidelity to a narrow range of habitat requirements (e.g., Potamogeton robbinsii, Cypripedium candidum)
After the C or C’s are assigned, calculate the floristic quality assessment index (FQAI). A common formula is:

I = Sum of [ CCi divided by the square root of N (native)] where:

I = the FQAI score
CCi = the coefficient of conservatism of plant species “i”
N (native) = the total number of native species occurring in the community being evaluated.

Refer to Andreas et al. (2004) pages 6-8 for discussion on variations to this equation.

Coefficient of Conservatism (C of C):
a numeric value that expresses a taxon’s autecological value with respect to all other taxa in a region’s flora. The higher the value, the more conservative is the taxon, that is, it is more restricted to very specific environmental conditions. Presence of many conservative species reflects relatively unaltered conditions.

Floristic Quality Index:
an index derived from floristic inventory data and calculated by the following formula from Swink and Wilhelm (1979)

Applicable Habitat Types:

Terrestrial: Herbaceous (e.g., prairie, grassland), Shrubland  Riparian Forest: Non-woody, Woody

Nontidal Wetland: Non-vegetated, Vegetated   Tidal Wetland : Vegetated 

Other Habitats: Peatland

Regions Developed for: Initially for Chicago Illinois, but subsequently has been modified for use in a few additional states.

Applicable Regions :

  • Alaska (AK)
  • Atlantic (Puerto Rico, Virgin Islands)
  • Intermountain (AZ, CO, MT, NM, OK, TX, UT, WY)
  • Midwest (AR, IA, IL, IN, KS, MI, MN, MO, ND, NE, OH, SD, WI)
  • National Capital (DC, DE, MD, VA)
  • Northeast (CT, MA, ME, NH, NJ, NY, PA, RI, VT, WV)
  • Pacific (Hawaii, Guam, American Samoa)
  • Pacific West (CA, ID, NV, OR, WA)
  • Southeast (AL, FL, GA, KY, LA, MS, NC, SC, TN)

Application of Method to New Areas: Additional calibration or references needed (e.g., development of new HGM models, IBI metrics/indices).

Expertise: Not stated, but advanced skill in identifying plants, especially rare species, seems necessary.


Andreas, B.K., J.J. Mack, and J.S. McCormac. 2004. Floristic quality assessment index (FQAI) for vascular plants and mosses for the state of Ohio. Division of Surface Water, Ohio Environmental Protection Agency, Columbus, OH.

Bernthal, T.W. 2003. Development of a floristic quality assessment methodology for Wisconsin. Wisconsin Department of Natural Resources, Madison, WI.

Herman, K.D., L.A. Masters., M.R. Penskar, A.A. Reznicek, G.S. Wilhelm, W.W. Brodovich, and K.P. Gardiner. 2001. Floristic quality assessment with wetland categories and examples of computer applications for the State of Michigan, Revised, Second Edition. Michigan Department of Natural Resources, Gladstone, MI.

Ladd, D. The Missouri floristic quality assessment system. Nature Conservancy. The Nature Conservancy, St. Louis, Missouri.

Ladd, D. The Missouri floristic quality assessment system. Nature Conservancy. The Nature Conservancy, St. Louis, Missouri.

Miller, S.J. and D.H. Wardrop. 2006. Adapting the floristic quality assessment index to indicate anthropogenic disturbance in central Pennsylvania wetlands. Ecological Indicators 6(2): 313-326.

Mushet, D.N., N.H. Euliss, Jr., and T.L. Shaffer. 2002. Floristic quality assessment of one natural and three restored wetland complexes in North Dakota, USA. Wetlands 22: 126-138.

Northern Great Plains Floristic Quality Assessment Panel. 2001. Floristic quality assessment for plant communities of North Dakota, South Dakota (excluding the Black Hills), and adjacent grasslands. Northern Prairie Wildlife Research Center Home Page. Retrieved June 17, 2004 from http://www.npwrc.usgs.gov/resource/2001/fqa/fqa.htm (Version 26JAN2001)

Taft, J.B., G.S. Wilhelm, D.M. Ladd, and L.A. Master. 1997. Floristic quality assessment in Illinois: A method for assessing vegetation integrity. Erigenia 15: 3-95.

Wilhelm, G.D. and L.A. Masters. 1995. Floristic quality assessment in the Chicago region and application computer programs. Morton Arboretum, Lisle, Illinois.