Rock-type control of Ni, Cr, and Co phytoavailability in ultramafic soils

Abstract

Background and aimsUltramafic soils constitute an extreme environment for plants because of specific physico-chemical properties and the presence of Ni, Cr, and Co. We hypothesized that type of ultramafic parent rock depending on their origin affects the composition of soils and plants. Therefore, phytoavailability of metals would be higher in soil derived from serpentinized peridotite compared to serpentinite because of differences in susceptibility of minerals to weathering.ResultsBased on DTPA-CaCl2 extractions, we noted that soil derived from the serpentinized peridotite is characterized by a higher phytoavailability of Ni compared to soil derived from the serpentinite. On the contrary, plant species growing on soil derived from the serpentinite contain higher concentrations of metals.ConclusionsOur study suggests that the metal uptake by plants is controlled by the mineral composition of parent rocks, which results from both their original magmatic composition and later metamorphic processes. Chemical extractions show that the phytoavailability of Ni and Co is higher in soil derived from the serpentinized peridotite than the serpentinite. Surprisingly, plants growing on the soil derived from the serpentinite contain higher levels of metals compared to these from the serpentinized peridotite derived soil. This contrasting behavior is due to higher abundances of Ca and Mg, not only Ni and Co, in soil derived from the serpentinized peridotite as compared to those in the soil derived from the serpentinite. Calcium and Mg are favored by plants and preferably fill the available sites, resulting in low Ni and Co intake despite their higher abundances.