This study determines spatial patterns of plant species richness and diversity in three calcareous fens and quantifies individual species response and range/tolerance to hydrological, peat physical, and porewater nutrient gradients using nonlinear quantile regression. Species richness and diversity were highly variable across the sites, with no single species occupying more than 25% of the area surveyed. Variable hydrological regime was related to distance from the principal source area of water to the fens. Surface peat organic matter and calcium carbonate content ranged from 11 to 91% and 2 to 83%, respectively. Dissolved inorganic nitrogen (DIN) and potassium concentrations from the shallow porewater ranged from 0 to 4 mg l−1, whereas available phosphorus was < 100 µg l−1. Species exhibited various response shapes to the environmental gradients, which produced segregated realized ranges. The duration of initial saturation of the peat from the start of the growing season and the peat organic matter content produced the greatest number of complete species responses and ranges. Aggregation of species across growth types based on environmental responses mirrored visually described communities, demonstrating the applicability of the method of analysis. The generation of species response curves for a suite of readily measured environmental variables can be a useful tool for assessing conceptual models of ecosystem functioning and wetland restoration/creation success. Copyright © 2011 John Wiley & Sons, Ltd.