Limited Evidence For Indicator Species of High Floristic Quality Wetlands In The US Southern Plains

Floristic Quality Assessment requires compiling a full list of vascular plant species for the wetland. Practitioners may lack the time and taxonomic skills for full-community vegetation surveys, especially when wetlands are large and complex. In this paper we broadly ask whether floristic quality indicator species may exist for wetlands, specifically evaluating indicator species potential for high floristic quality wetlands in the US southern plains region. Indicators were identified for a broader context (wetlands in Oklahoma prairie ecoregions) and narrower context (depressional wetlands in the northern Central Great Plains ecoregion of Oklahoma) based on indicator value, indicator validity, hydrophytic status, and ecological conservatism. No candidate indicators satisfied all criteria for high floristic quality. Indicator values improved with increasing spatial-environmental context, but many candidates occurred too frequently in non-high quality sites or too infrequently in high quality sites, relative to predicted rates. The best performing indicator (Eleocharis compressa) lacked validity in the broader context and showed high false-positive rates in the narrower context. Combining E. compressa with select other candidates (Amorpha fruticosa, Juncus torreyi, Leersia oryzoides, Schoenoplectus pungens) may compensate for weaknesses but the combinations may rarely be found across the region. Overall, these results do not support relying on indicator species to rapidly identify or verify high floristic quality wetlands in the US southern plains. We recommend similar studies in other regions and testing other quality levels (low, moderate) before broadly concluding that floristic quality indicator species do not exist for wetlands.

Plant diversity and conservation value of wetlands along a rural–urban gradient

Background: Wetlands are the most threatened ecosystem in South Africa despite the range of ecosystem goods and services they provide. A significant cause of wetland destruction and degradation is a lack of understanding, by planners, policymakers and developers, of their ecological and socio-economic importance.Objectives: This study assessed the floristic composition and diversity of wetlands in the former Tlokwe Municipal area along a rural–urban gradient.Methods: Fourteen wetland sites were surveyed along an urbanisation gradient. Vegetation surveys were done in quadrats along transects in each wetland recording the cover-abundance of each species. The data were analysed by using ordinations, similarity percentages, and the adjusted Floristic Quality Assessment Index.Results: Overall, the proportional species composition of urban and rural wetlands was mainly similar. Trends indicated that the alpha diversity increased with both habitat size and heterogeneity along a rural–urban gradient. In all wetlands, indigenous species were the most abundant, with the highest score in the largest urban wetland. The floristic quality varied widely along the gradient with none of the sites in pristine condition.Conclusion: The similarity in species composition and floristic quality of the wetlands, as well as the high levels of indigenous species richness, indicated that urban wetlands are worthy of conservation. However, the signs of disturbances and the presence of alien species means that restoration strategies need to be implemented to improve the quality of the wetlands.