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We developed lists of plant species identified during July and August, 1995 in wetlands at Cottonwood Lake, Hawk's Nest, Sweet Grass, and Pilgrim's Rest (Table 1). Sample wetlands from each complex were selected based on their similarity in size and hydroperiod to wetlands at Cottonwood Lake; wetlands thus selected spanned the hydrologic continuum from ground-water recharge to ground-water discharge within each wetland complex evaluated. For each wetland sampled, we established five transects radiating from the wetland's center into the upland along randomly selected compass bearings. Along each transect, we randomly located a 0.25 m² plot within each wetland vegetation zone described by Stewart and Kantrud (1971), excluding the low-prairie zone. After we identified and recorded species within plots, we searched the remainder of each wetland for additional species and, if they occurred, added them to our species list for each wetland. Even though only native, wetland species were subsequently used in our calculations of floristic quality, all plants occurring within wetlands were identified to species for estimation of species richness and percent natives. From the species lists for each wetland, we assessed the quality of their native plant communities by calculating and FQI using two sets of independently derived C values. We also calculated species richness and percent natives for each wetland.

Panel-Assigned C values

We calculated and FQI for each wetland sampled using C values provided by the Northern Great Plains Floristic Quality Assessment Panel (2001). FQI was calculated as

Where N was the total number of native species present in a wetland. As is common practice, introduced species were not used in the calculations of either or FQI (Swink and Wilhelm 1994). We then calculated a mean and FQI for each of the four wetland complexes and established 95% confidence limits (Snedecor and Cochran 1980) for our estimates.

Species Richness

Even though only native plant species were included in our calculations of and FQI, we calculated species richness for each wetland both including and excluding non-native species. We then calculated average species richness estimates and the percentage of native species for each wetland complex and established 95% confidence limits around our estimates.

Data-Generated C Values

We also estimated and FQI for each wetland using data-generated C values. Gleason and Euliss (unpublished data) sampled the plant communities of 204 wetlands during the summer of 1997 as part of a larger effort to evaluate restored wetlands in the prairie pothole region of the United States (see http://www.npwrc.usgs.gov/wetland). The data-generated C values used in our study were derived from data from these 204 wetlands. The 204 wetlands Gleason and Euliss sampled included natural wetlands within native prairie (n = 46), natural wetlands within planted grass (n = 43), restored wetlands greater than five years old (n = 46), restored wetlands one to five years old (n = 31), and drained wetlands (n = 38). These sampled wetlands covered a range of disturbances from relatively undisturbed native prairie wetlands to greatly disturbed drained wetlands. All wetlands, except the native prairie wetlands, were situated on U.S. Department of Agriculture Conservation Reserve Program land or similar planted grasslands; the native prairie wetlands were located within natural grasslands. To sample plant communities of the 204 wetlands, Gleason and Euliss used methods modified from Kantrud and Newton (1996). They sampled wetland vegetation along four equally spaced transects radiating from each wetland's center. In each vegetative assemblage bisected by a transect, they centered a 1-m² plot in the middle of the assemblage and identified and recorded each plant species occurring within the plot. While walking between plots, they noted other plant species not occurring in the plots and added them to the species list. For the effort described here, we merged the species lists from all 204 wetlands to obtain a single list of plant species occurring in the sampled wetlands (Table 2).

We assigned C values to each native species occurring in the 204 wetlands using the following criteria. If a plant species only occurred in the native prairie wetlands sampled, it was considered to be very conservative and was assigned a C value of 10. If a species occurred in the native prairie wetlands and also in the planted grass wetlands, it was assigned a C value of 8 or 9 depending on whether it occurred more often in the native prairie or the planted grass wetlands. If a species occurred only in the planted grass wetlands, it was assigned a C value of 7. We assigned a C value of 6 to those species that occurred in native prairie, planted grass, and only the oldest restored wetlands sampled. Species that occurred in recently restored wetlands and drained wetlands were considered to be the least conservative and were assigned C values ranging from 0 to 5 depending upon which wetland type they occurred in most frequently (Table 3).