Nickel accumulation in plants from the Shebenik Mountain massif, Albania

Hyperaccumulators are unusual plants that accumulate specific metals or metalloids in their living tissues to concentrations that may be hundreds or thousands of times greater than those normal for most plants. Hyperaccumulator plants are of practical importance as they can be used in soil remediation technologies. The Shebenik Mountain massif, located on the eastern border of Albania, hosts a wide diversity of rare and endemic plant species, including nickel hyperaccumulators. The aim of this study was to evaluate the taxa present on the Shebenik Mt. in relation to soil conditions and to test their potential for phytomining in a replicated field trial. Previous morphological and karyological analyses of material from field collections across ultramafic outcrops of the Shebenik resulted in the identification of the following nickel hyperaccumulator taxa: Odontarrhena chalcidica (Janka) Španiel & al., Odontarrhena smolikana subsp. glabra (Nyár.) Španiel & al., Odontarrhena rigida (Nyár.) L. Cecchi & Selvi, and Bornmuellera baldaccii (Degen) Heywood. In addition, a species of the genus Noccaea, formerly referred to Noccaea ochroleuca (Boiss. & Heldr.) F.K. Mey, but likely belonging to a still undescribed taxon, was also collected. An in situ replicated trial was undertaken to evaluate the potential for phytomining of three nickel (Ni) hyperaccumulators collected in the Shebenik Mt. Measurement of aboveground biomass, analysis of nickel in the biomass, and analyses of plant-available nickel in the soil allowed calculation of bioaccumulation and phytoextraction yield. This provides a realistic evaluation of the efficacy of the plant taxa in hyperaccumulating nickel and their potential use for phytoextraction/phytomining technologies.