Soil pollution is usually associated with biodiversity loss. However, soils enriched with zinc, lead and cadmium can support unique vegetation such as calamine grasslands, which are priority habitats for nature conservation programmes. This study investigates a declining calamine grassland in Northern France, which developed in the 1960s in the immediate vicinity of a former smelting plant. It was initially dominated by two locally rare and absolute metallophyte dicot species, Armeria maritima and metal-hyperaccumulating Arabidopsis halleri , in association with Agrostis capillaris . From then on, the grassland gradually declined and developed into a meadow, largely dominated by a tussock-forming grass: Arrhenatherum elatius . Possible explanations include landscaping, a decrease in soil metal concentrations or the replacement of pioneer species by later successional species. To better understand the causes of the decline and to discuss restoration strategies, we carried out an ecological study including: (1) compilation of available data to reconstruct the history of the site, (2) chemical analysis of soil element concentrations, (3) functional analysis of potential plant-plant interactions, and (4) a 7-year restoration experiment including vegetation monitoring. The results suggest that in the absence of significant anthropogenic disturbance, while soil metal concentrations remain elevated, grassland decline is best explained by plant successional dynamics. Accordingly, repeated disturbances, such as the removal of A. elatius tussocks by annual mowing of the vegetation with organic matter removal, not only stopped the expansion of A. elatius but also allowed a partial recovery of the calamine grassland.
Pauwels et al. (Tue,) studied this question.