Rhizosphere characteristics, heavy metal accumulation and growth performance of two willow (Salix × rubens) clones

Abstract

High-biomass tree species holds promise for a clean up of metal contaminated soils. Root and fungal activities modify soil characteristics that are important factors for the phytoextraction process (metal availability and toxicity). In a rhizobox experiment, two clones of Salix × rubens derived from contaminated and non-contaminated sites were tested for growth performance and metal (Cd, Pb and Zn) accumulation on a polluted Calcaric Cambisol. The largest metal concentrations in leaves were 66.7 mg Cd/kg, 12.8 mg Pb/kg and 1090 mg Zn/kg. The results indicate that metal tolerance and accumulation of S. × rubens may be a constitutive rather than an adaptive property. Soil pH did not differ among rhizobox compartments. However, acid neutralization capacity was decreased in rhizosphere. DOC in rhizosphere was increased by 37% and seemed to enhance labile fraction of Pb and Zn, whereas Cd was not affected. The replenishment of labile metals from less labile soil fractions was efficient enough to almost compensate the plant uptake. S. × rubens can effectively induce chemical changes in the rhizosphere is very promising for a clean up of metal-polluted soils.