PARENT SESSION
MA3 Assessing Effects from Multiple Stressors on Ecosystems.
9:00 AM to 12:30 PM, Monday, 07 May 2001
Session Chair: Theo Brock
Room 3

(026) The distribution of plant and nematode species in relation to environmental factors (including multi substance toxic stress).

van Wijnen, Harm¹, Vonk, Marijke¹, de Zwart, Dick¹, van de Meent, Dik¹, Schouten, Ton¹, Posthuma, Leo¹, ¹

ABSTRACT- The Species Sensitivity Distribution (SSD) concept can be used to quantify overall toxic pressure of toxic compounds at contaminated sites for specific taxa or as overall value. This is done using the multi-substance Potentially Affected Fraction (ms-PAF), as explained in a related contribution on the SSD-research line. In this contribution, we shortly introduce the dimensionless ms-PAF, and use calculated ms-PAF values to analyze the distribution of plant and nematode species in the Netherlands. Large data-sets on the occurrence of these species groups in the field have been compiled in association with measurements of the soil factors that may influence their distribution (pH, organic carbon content, clay content, soil water content, nitrogen content, ms-PAF). The data allow for an empirical analysis of the relative contributions of the soil factors to the distribution of species, i.e. a quantitative multi-variate analysis. By developing multi-variate models, the statistical association between the occurrence of species and the environmental factors was described. These analyses showed that ms-PAF is a meaningful parameter that explains part of the variation that has been observed in the field. It confirms that the SSD-based quantification of toxic pressure can be extrapolated to the field: ms-PAF is not simply a dimensionless number, it rather estimates true toxic pressure related to shifts in species dominance in the field. Further confirmation studies are executed by analyzing community-based experimental data, which are presented on a poster (Confirmation of the SSD concept by experimental data and field distribution patterns of species in The Netherlands).

Key words: multi-substance Potentially Affected Fraction (ms-PAF), multivariate analysis, environmental factors, GIS-analysis