Changes in plant communities along soil pollution gradients: responses of leaf antioxidant enzyme activities and phytochelatin contents.

This work describes an ecological and ecotoxicological study of polluted wasteland plant communities in a former coke-factory located in Homécourt (France). Ecological analyses were performed along two transects to investigate changes in plant community structure through species richness (S), biological diversity (H') and evenness (J). Five species (Arrhenatherum elatius, Bromus tectorum, Euphorbia cyparissias, Hypericum perforatum and Tanacetum vulgare) were then selected to assess cellular responses through antioxidant enzyme activities and phytochelatins (PCs) contents. The results showed that species richness and biological diversity correlated negatively to Cd and Hg concentrations in soil suggesting that soil concentration of non-essential heavy metals was the primary factor governing vegetation structure in the industrial wasteland. Moreover, for all studied species, abundances were partly related to metal levels in the soils, but also to plant antioxidant systems, suggesting their role in plant establishment success in polluted areas. Data for PC contents led to less conclusive results.