May 2003 Animal and Range Sciences Miscellaneous Report

The Index of Plant Community Integrity:

An Assessment Method for Wetland Plant Communities of the Prairie Pothole Region

Edward S. DeKeyser, Don Kirby, Michael J. Ell, and Lynn A. Foss

Introduction

Field Sampling Method

Data Analysis Using the IPCI Method

Summarization

Literature Cited

Field Data Forms

An Index of Plant Community Integrity (IPCI) has been developed by the Animal and Range Sciences Department of North Dakota State University and the North Dakota Department of Health (NDDH) to assess temporary, seasonal and semi-permanent wetland plant communities within the Prairie Pothole Region (PPR). The IPCI assessment method was developed by quantitatively measuring wetland plant community characteristics and comparing the results to a range of anthropogenic disturbance and disturbance intensity (DeKeyser 2000, DeKeyser et al. 2003). The purpose of an IPCI is to have a classification system that will categorize wetlands (Very poor to Very good) by vegetative composition in response to disturbance type and degree. Differences in community structure, such as species richness of native perennials, number of genera of native perennials, and number of introduced and annual species are used to categorize wetlands through a multimetric approach (Karr 1981, Karr and Chu 1999) as part of an IPCI.

The plant communities of a wetland are important measurable variables that can give an indication of the overall condition of a wetland. The use of the IPCI system for the evaluation of wetland plant communities can be beneficial by itself or in combination with the Hydrogeomorphic (HGM) Model. The IPCI approach is a tool for identifying and/or assessing wetland plant communities that may have potential for restoration or conservation. The IPCI can be a useful tool for refuge and private managers to track the progress of management efforts such as restored or reclaimed wetlands. Under current laws, many wetlands will need to be assessed for mitigation purposes. Also, researchers may want to use the IPCI technique as a source of consistency between separate studies, as well as developing a historical database that can be used by several researchers now and in years to come. 

The IPCI method for the assessment of wetland plant communities has been developed for temporary, seasonal, and semi-permanent wetlands because these wetlands are the most abundant types in the PPR, making up over 99% of the nearly 1.9 million wetlands found in North Dakota (U.S. Fish and Wildlife Service, unpublished data). Also, because of their size and nature these wetlands are more susceptible to anthropogenic disturbance. Identification of wetland classes should be accomplished using the classification system of Stewart and Kantrud (1971, 1972). Initial classification and location identification can be accomplished by using National Wetland Inventory (NWI) maps which are based on the national classification developed by Cowardin et al. (1992). Final determination of wetland class needs to be accomplished on site.

return to top

The quadrat method is used for gathering vegetative data. The method entails evenly distributing eight 1 m² quadrats in the middle of the low prairie zone to avoid overlapping of species from other zones (Figure 1). Seven 1 m² quadrats are evenly distributed in the wet meadow zone, and five 1 m² quadrats are evenly distributed in the shallow marsh zone and/or deep marsh zones. The technique used to record 1 m² quadrats is similar to that used by Kantrud and Newton (1996). Each species found within a quadrat is recorded as a primary species and is assigned a Daubenmire cover class based on the basal cover of that particular species in the quadrat (Table 1). All plant species not located within a quadrat but located between the placement of quadrats are recorded as secondary species. Additional variables recorded that may be useful as part of a hydrogeomorphic assessment include: litter thickness, water depth, percent open water, percent bare bottom, and percent standing dead. Field data forms are included in Appendix A. Plant species acronyms should be used in the recording process and follow the format of the Northern Great Plains Floristic Quality Assessment Panel (2001).

The distribution of quadrats in the exterior zone(s) can be estimated by pacing off the circumference of the zone and dividing by eight, seven, or five. For example, if the total number of paces in the low prairie zone is 800, then quadrats would be spaced 800/8=100 paces apart. If a seasonal or semi-permanent wetland has an area of open water, then an estimation of the percentage of open water area compared to emergent vegetation is made. The number of quadrats is distributed in each of the emergent and open water areas according to the estimation. For example, if the open water area in the deep marsh is estimated to be 60%, then three quadrats are placed in the open water area and two quadrats are placed in the emergent area. It is important to record as many of the plant species found within the wetland plant community as possible. It is not necessary to visit excessively deep water areas however, as only a few species might be overlooked and would not change the IPCI outcome.

Figure 1. Example of quadrat layout for a semi-permanent wetland.

return to top

The data for the IPCI analysis should be obtained from the primary and secondary plant species lists for all vegetative zones of individual wetland. Metric development and the final IPCI for PPR was accomplished by DeKeyser (2000) and described more recently in DeKeyser et al. (2003). A total of nine metrics were developed (Table 2). These metrics were chosen because of the notable quantitative change over an anthropogenic disturbance gradient.

Table 1. Daubenmire cover classes.

The first metric, Species Richness of Native Perennial Species is the total number of native perennial species observed. The Number of Genera of Native Perennials metric is the total number of all the genera of the species observed. The metric, Assemblages of Native Grass and Grass-like Species, is the total number of species that are included in the families Poaceae, Cyperaceae, and Juncaceae (Grasses, Sedges, and Rushes). The Number of Native Perennial Species in the Wet Meadow Zone metric is a total number of native perennial species found only in the wet meadow zone.

The metric, Percentage of the Annual, Biennial, and Introduced Species of the Entire Species List, was developed because of the resulting vegetation found on cultivated wetlands within the PPR. Cultivated wetlands often are completely tilled, as well as having some type of herbicide treatment. A wetland found in circumstances such as this may have a total of 25 species, and 20 species are annual, biennial and introduced species (20/25*100 = 80% are annual, biennial and introduced). In contrast, a wetland found on native prairie may have 75 species, but may also have 20 annual, biennial and introduced species (20/75*100 = 27% are annual, biennial, and introduced).

The metrics involving the Coefficients of Conservatism (C-values) and the Floristic Quality Index (FQI) are obtained from "Coefficients of Conservatism for the Vascular Flora of the Dakotas and Adjacent Grasslands" (The Northern Great Plains Floristic Quality Assessment Panel 2001). This publication can be obtained through the National Technical Information Service, 5285 Port Royal Road, Springfield, Virginia 22161 (1-800-553-6847 or 703-487-4650). The publication can also be found on the World Wide Web at http://www.npwrc.usgs.gov/resource/2001/fqa/fqa.htm .

The values obtained for each metric from the vegetative data must be placed in one of three value ranges. These value ranges are found in Table 3 for temporary wetlands, Table 4 for seasonal wetlands, and Table 5 for semi-permanent wetlands. Each of the three value ranges has a rating of a 1, 3, or 5. A metric rating of 5 would indicate a wetland area that might occur in high quality native prairie. A rating of 3 for a metric would be anticipated in a wetland area that has had moderate human impacts. A rating of 1 for a metric would be anticipated in a wetland area that has been highly impacted by human disturbance. Once the appropriate value range has been identified for the summarized metrics, each metric is then assigned a 5, 3, or 1. Once each metric has been assigned a 5, 3, or 1, then all the assigned numbers are summed. The resulting number would be considered the IPCI. An example of the assignment of 5, 3, or 1 and the final summation, can be found in Table 6. The observed metric values in Table 6 should be matched to the appropriate value range in Table 5 to develop a full understanding of the procedure. Suggested quality classes for the final IPCI for a wetland can be found in Table 7.

return to top

A precaution should be noted before performing an IPCI. A person with a strong background in systematic botany would easily be able to perform an IPCI assessment of the vegetative composition of temporary, seasonal, and semi-permanent wetlands. This individual would then apply the quadrat method by evenly spacing eight quadrats through the low prairie zone, seven quadrats through the wet meadow zone, and five quadrats through the shallow marsh and/or deep marsh zones. A secondary species list should also be recorded for those species found between quadrats. A reliable IPCI for plants can then be obtained by using the primary and secondary species recorded. Other information that might be needed may be recorded as well.

The IPCI outlined in this report will work on temporary, seasonal and semi-permanent wetlands located along the Northwestern Glaciated Plains ecoregion (Bryce et al. 1998) in central North Dakota during years of average to above average precipitation. The IPCI constructed was not performed during consecutive years of abnormally low precipitation; therefore, caution should be used in the application of the IPCI during periods of drought. Wetland vegetation is dynamic in nature, and it is unknown if the metric value ranges developed will be appropriate during years of drought. Use of the IPCI reported here is not recommended for dissimilar physiographic regions, although it is believed that the IPCI will work within ecoregions in the PPR (e.g. Northern Glaciated Plains).

The timing of the sampling period should be at or near the peak of the growing season. Many species may not be identifiable early in the growing season, and sampling during this period may affect the outcome of the metrics. The best periods for sampling wetlands in North Dakota is July to early August.

Bryce, Sandra. James M. Omernik, David E. Pater, Michael Ulmer, Jerome Schaar, Jerry Freeouf, Rex Johnson, Pat Kuck, and Sandra H. Azevedo. 1998. Ecoregions of North Dakota and South Dakota. [Two sided color poster with map, descriptive text, summary tables, and photographs.] Reston, Virginia: U.S. Geological Survey (scale 1:1,500,000). ISBN 0-607-89384-2. It is available from the U.S. Geological Survey Distribution Center. Denver, Colorado.

Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deepwater habitats of the United States. U.S. Fish and Wildlife Service Biological Services Program FWS/OBS-79/31.

DeKeyser, E.S. 2000. A vegetative classification of seasonal and temporary wetlands across a disturbance gradient using a multimetric approach. Ph.D. Dissertation. North Dakota State University, Fargo. 127pp.

DeKeyser, E.S., D.R. Kirby, and M.J. Ell. 2003. An index of plant community integrity: Development of the methodology for assessing prairie wetland plant communities. Ecological Indicators, (in press).

Kantrud, H.A. and W.E. Newton. 1996. A test of vegetation-related indicators of wetland quality in the Prairie Pothole Region. Journal of Aquatic Ecosystems Health 5:177-191.

Karr, J.R., 1981. Assessment of biotic integrity using fish communities. Fisheries 6(6), 21-27.

Karr, J.R., Chu, E.W., 1999. Restoring life in running waters: Better biological monitoring. Island Press. Washington, DC. 206pp.

Stewart, R.E., and H.A. Kantrud. 1971. Classification of natural ponds and lakes in the glaciated prairie region. U.S. Fish and Wildlife Service, Resource Publication 92. 57 pp.

Stewart, R.E., and H.A. Kantrud. 1972. Vegetation of Prairie Potholes, North Dakota, in relation to quality of water and other environmental factors. U.S. Geological Survey, Professional paper 585-D. 36 pp.

The Northern Great Plains Floristic Quality Assessment Panel. 2001. Coefficients of conservatism for the vascular flora of the Dakotas and adjacent grasslands. U.S. Geological Survey, Biological Resources Division. Information and Technology Report USGS/BRD/ITR – 2001-0001. 32 pp.

U.S. Fish and Wildlife Service. Habitat and Population Evaluation Team (HAPET) Office. Bismarck, N.D.

Zone: LP / WM / SM / DM / OW

% Bare Bottom_______________

% Bare Bottom_______________

% Bare Bottom_______________

% Bare Bottom_______________