Plant biodiversity offsets negative effects of metals and metalloids soil multi-contamination on ecosystem multifunctionality.

Despite increasing metals and metalloids (MM) human-driven soil contamination, how it simultaneously alters biodiversity and ecosystem functioning remains unknown. We used a wide gradient of a 170-year-old MM soil multi-contamination in Mediterranean scrublands to assess the effects of soil multi-contamination on multiple plant biodiversity facets, microbial communities and ecosystem multifunctionality (EMF). We found an overall positive effect of plant biodiversity on EMF mediated by microbial communities, and allowing offsetting the negative impacts of MM soil multi-contamination, especially on soil water holding capacity and nitrogen content. The diversity of distant plant lineages was the key facet promoting EMF by enhancing microbial communities, whereas the subordinate species richness altered EMF. By developing a holistic approach of these complex relationships between soil multi-contamination, plant biodiversity, microbial communities and ecosystem functioning, our results reveal the potential of plant biodiversity, and especially the diversity of evolutionary distant species, to offset the alteration of ecosystem functioning by MM soil multi-contamination. In this worldwide decade of ecosystems restoration, our study helps to identify relevant facets of plant biodiversity promoting contaminated ecosystem functioning, which is crucial to guide and optimize management efforts aiming to restore ecosystems and preserve human health.

Functional Trait-Based Screening of Zn-Pb Tolerant Wild Plant Species at an Abandoned Mine Site in Gard (France) for Rehabilitation of Mediterranean Metal-Contaminated Soils.

The selection of plant species at mine sites is mostly based on metal content in plant parts. Recent works have proposed referring to certain ecological aspects. However, plant traits for plant metal-tolerance still need to be accurately assessed in the field. An abandoned Zn-Pb mine site in Gard (France) offered the opportunity to test a set of ecological criteria. The diversity of micro-habitats was first recorded through floristic relevés and selected categorical and measured plant traits were compared for plant species selection. The floristic composition of the study site consisted in 61 plant species from 31 plant families. This approach enabled us to focus on seven wild plant species naturally growing at the mining site. Their ability to form root symbioses was then observed with a view to phytostabilization management. Four species were considered for phytoextraction: Noccaea caerulescens (J. et C. Presl) FK Meyer, Biscutella laevigata L., Armeria arenaria (Pers.) Schult. and Plantago lanceolata L. The metal content of their aerial and root parts was then determined and compared with that of soil samples collected at the same site. This general approach may lead to the development of a knowledge base for assessment of the ecological restoration trajectory of the site and can help in plant selection for remediation of other metal-rich soils in the Mediterranean area based not only on metal removal but on ecological restoration principles.