Biochar produced from diverse invasive species improves remediation of cadmium-contaminated soils

Biodiversity commonly contributes to ecosystem functioning and provides ecosystem services. Biochar application is frequently used to remediate soils contaminated with heavy metals. As many invasive plant species can quickly form huge amounts of biomass, they are potentially useful for producing biochar for remediating contaminated soils. However, it remains untested whether invasive species richness contributes to biochar-mediated soil remediation. We applied single biochar made from each of six invasive plant species and biochar mixtures (i.e., mixtures of biochar derived from 2, 3, and 6 invasive plant species) to soils contaminated with cadmium (Cd), with no biochar application as the control. We then grew native plant communities on these soils. Compared to the control, biochar application significantly decreased Cd bioavailability (− 34% averaged across the three richness treatments) in the soils, and this effect increased with increasing invasive species richness involved in the biochar mixtures (from − 22 to − 38%). Biochar application significantly increased both the concentration (+ 126%) and pool size (+ 59%) of Cd in roots of the native plant community, although it significantly decreased its biomass (− 25%). Thus, invasive species diversity can contribute to biochar-mediated remediation of soils contaminated with Cd. Our findings indicate a novel biodiversity-mediated ecosystem service, i.e., the use of multiple invasive plant species for the production of biochar. As harvesting of invasive species for biochar production may also contribute to their management, this might mitigate the two ecological problems at once.