Regional Wetland Plant Responses to Sulfur and Other Porewater Chemistry in Calcareous Rich Fens

Many wetland environmental gradients structure plant community composition, yet controls of plant community composition within rich fens, botanically diverse groundwater-fed wetlands, are still incompletely understood. Porewater chemistry and plant community composition were recorded for eight calcareous rich fens encompassing both calcium carbonate and calcium sulfate geological inputs in the Central New York State region. As expected, porewater sulfate and sulfide concentrations were, on average, higher for wetlands overlying calcium sulfate than for wetlands overlying calcium carbonate. However, within-wetland heterogeneity in porewater chemistry was high. Moss species density, moss cover, and total plant cover decreased with increased sulfide. Moss, dicot, and total cover also had a negative relationship with calcium. There were a number of species-level responses to calcium, sulfide, phosphorus, and ferrous iron. Plant height had a positive relationship with nitrogen. The strength and relative importance of some plant responses to sulfide and calcium in the current regional study differed from a previous sub-hectare scale study. The observed decrease in some metrics of site-level plant diversity with increased sulfide variability across fens highlighted the need to characterize species-environment relationships across spatial scales.