title: How to assess species richness along single environmental gradients? Implications of potential versus realized species distributions.
abstract: Quantifying relationships between species richness and single environmental factors is challenging as species richness typically depends on multiple environmental factors. Recently, various methods have been proposed to tackle this challenge. Using a dataset comprising field observations of grassland vegetation and measured pH values, we compared three methods for deriving species richness response curves. One of the methods estimates species richness close to the maximum species richness observed at the sites, whereas the other two provide estimates of the potential species richness along the environmental gradient. Our response curves suggest that potential species richness of grasslands is slightly more sensitive to acidification than realized plant species richness. However, differences in corresponding environmental quality standards (EQS) for acidification were small compared to intrinsic spatial differences in natural soil pH, indicating that natural background values are more important to consider in the derivation of EQS for pH than methodological differences between the three approaches.
authors.affiliation: Department of Environmental Science, Institute for Water and Wetland Research, Radboud University Nijmegen, P.O. Box 9010, 6500 GL, Nijmegen, The Netherlands. Electronic address: tgoethem@science.ru.nl.
authors.forename: Thomas M W J
authors.initials: TM
authors.lastname: van Goethem
authors.affiliation: Department of Environmental Science, Institute for Water and Wetland Research, Radboud University Nijmegen, P.O. Box 9010, 6500 GL, Nijmegen, The Netherlands.
authors.forename: Mark A J
authors.initials: MA
authors.lastname: Huijbregts
authors.affiliation: Alterra, Wageningen University and Research Centre, P.O Box 47, 6700 AA, Wageningen, The Netherlands.
authors.forename: G W Wieger
authors.initials: GW
authors.lastname: Wamelink
authors.affiliation: Department of Environmental Science, Institute for Water and Wetland Research, Radboud University Nijmegen, P.O. Box 9010, 6500 GL, Nijmegen, The Netherlands.
authors.forename: Aafke M
authors.initials: AM
authors.lastname: Schipper
mesh_terms: D044822:Biodiversity; D004777:Environment; D004784:Environmental Monitoring / Q000379:methods*; D010944:Plants / Q000145:classification*; D012987:Soil
chemical_list: D012987:Soil
keywords: Environmental quality standards (EQS); Species sensitivity distributions (SSDs); Stressor–response relationships; Survey data; pH