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A Vegetation Index of Biotic Integrity (VIBI) and Tiered Aquatic Life Uses (TALUs) for Ohio Wetlands

Contact: John J. Mack

 A Vegetation Index of Biotic Integrity (VIBI) for wetlands was previously developed using vascular plants as the indicator taxa group from sites sampled in Ohio between 1996-2000 representing different wetland types and ecological regions. This paper represents the second major evaluation of the VIBI since it was originally proposed (Macket al.2000, Mack 2001b) and the fourth iteration (Fennessy et al. 1998a and 1998b, Mack et al. 2000, Mack 2001b) in overall development of vegetation-based wetland assessment tools for the State of Ohio. Subsequent testing and refinement is an important step in the development of a robust
IBI. The VIBI is actually three IBIs for use with emergent, forest, or shrub dominated wetlands (VIBI-E, -F, -SH). Data collected in 2001 and 2002 from additional wetland types and ecoregions was used to test the VIBI (Mack et al. 2000, Mack 2001b). The VIBI
continued to correlate significantly with the original disturbance gradient as well as an alternative disturbance gradient derived from land use percentages within a 1km radius of the wetlands. Analysis of individual metrics resulted in refinement and replacement of some metrics. The most serious metric problems occurred with the VIBI-Forest. New data from disturbed forests colonized by shade intolerant, native and adventive herbaceous and shrub species, exposed a previously unseen forest metric sensitivity to this disturbance-induced increase in diversity. This sensitivity resulted in over-performance of some metrics and inflated VIBI-F scores for these disturbed forests vis-a-vis intact forests. Metrics were refined or selected to only include forest (shade, facultative shade) and hydrophyte species. The VIBI was evaluated for significant differences due to ecological region, landscape position (HGM class), and dominant plant community. Significant ecoregional differences were observed for
the first time. Wetlands, other than slope wetlands and bogs, located in the unglaciated Allegheny Plateau had, on average, significantly higher VIBI scores than similar types of wetlands in all other Ohio ecological regions. Hydrogeomorphic class and dominant plant community were also significant variables. Significant differences in some combinations of ecoregion, HGM class, and plant community were also observed. Tiered Aquatic Life Uses (TALUs) for wetlands are proposed with differing biological expectations based on landscape positions, plant communities, and ecoregions in Ohio. This represents the first time wetland
TALUs applicable to all wetlands in a state have been published.
Link: http://www.epa.state.oh.us/portals/35/wetlands/PART4_VIBI_OH_WTLDs.pdf