TESTING THE FLORISTIC QUALITY ASSESSMENT INDEX AS AN INDICATOR OF WETLAND CONDITION

Abstract

Biological indicators of ecosystem integrity are increasingly being sought for use in ecosystem assessment and goal-setting for restoration projects. We tested the effectiveness of a plant community-based bioassessment tool, the floristic quality assessment index (FQAI) in 20 depressional wetlands in Ohio, USA. A priori, the 20 depressional wetlands were classified by type and ranked to form a disturbance gradient according to the local landscape condition. Ranks were based on surrounding land cover characteristics, vegetated buffer characteristics, and the extent of human-induced hydrologic alteration at the wetland site. The index was negatively correlated with the disturbance rank of a wetland and with the distance to neighboring wetlands (P = 0.01). Index values were lower for wetlands surrounded by agricultural or urban land use, wetlands with less vegetation on the wetland perimeter, and wetlands with more hydrologic modification, and at sites with greater distances to other wetlands. The wetlands with lower FQAI values tended to be dominated by plants that are typical of heavily cultivated landscapes or urban regions. Thus, the index is interpreted as a measure of environmental factors that maintain and control plant communities. The index was not correlated with differences in wetland surface water chemistry (α = 0.05) but was positively correlated with soil total organic carbon (P = 0.01), phosphorus (P = 0.05), and calcium (P = 0.05). Repeated wetland sampling in the summer and autumn revealed that the floristic quality assessment index could be useful for the assessment and monitoring of wetland ecosystems and for tracking wetland restoration projects over time.