Response of field-grown native plant species to a combined amendment for phytomanaging metal(loid)-mine tailings

Abstract Background and aims Phytostabilization of semiarid mine tailings involves establishing vegetation to reduce metal(loid) fluxes. Beyond biomass production and metal(loid) uptake, assessing ecophysiological traits is critical for selecting suitable species. This study examined six semiarid species (four shrubs, two conifers) in an 18 months field-scale tailing phytomanagement project using an organic amendment combining biochar and municipal organic waste. Methods Plant responses were evaluated in amended and unamended plots by measuring biomass (above- and belowground), foliar metal(loid) concentrations (As, Cd, Cu, Mn, Pb, Zn), nutrient content (N, P, K), and isotopic signatures (δ 13 C, δ 15 N, δ 18 O). Results Amended plots showed improved soil fertility, including a threefold increase in total N and tenfold increase in organic carbon. Up to five species in amended plots exhibited higher biomass. Foliar metal(loid) concentrations varied by species and element. While P deficiency was alleviated, foliar N concentrations did not increase despite higher soil N. Enhanced P uptake was linked to higher δ 13 C values, suggesting improved water-use efficiency. Among C3 species, isotopic indicators revealed contrasting water-use strategies. The conifers ( Pinus halepensis and Tetraclinis articulata ) showed conservative traits, with lower stomatal conductance and higher WUE. Tetraclinis articulata in amended plots exhibited tighter water regulation, reflected by reduced foliar Ca and elevated δ 18 O. In contrast, shrubs ( Dorycnium pentaphyllum , Maytenus senegalensis , Rhamnus lycioides ) displayed more spendthrift strategies, characterized by higher transpiration and foliar N content. Conclusions The contrasting water and nutrient acquisition strategies suggests that not all species respond equally to amendments, emphasizing the need for species-specific approaches in successful phytostabilization.