Exploratory site survey of Ni availability and accumulation in Odontarrhena serpyllifolia across the Bragança massif (Portugal)

Abstract Ultramafic soils from the Bragança massif (NE Portugal) harbour the Ni hyperaccumulator species Odontarrhena serpyllifolia . The present work investigated the phytomining suitability of this massif and its plant species and examined how different soil properties might hinder or facilitate plant biomass production and Ni accumulation. Plants and soils from four different sites in this massif were collected and analysed. Soils present high Ni concentrations, and all plants exhibited significant Ni accumulation in shoots, however, soil characteristics and plant yields show some variability between sites. Results showed that the highest plant yields were associated with soil pH, greater nutrient availability, particularly P and Na, more favourable Ca: Mg balances, and lower concentrations of soil elements including Mg, Fe, Co and Mn that may contribute to plant stress. Future long-term field trials and testing of soil amendments are key to addressing the full phytomining potential of the Bragança massif and may provide insights applicable to other Mediterranean ultramafic systems hosting Ni hyperaccumulator species.