Classification of tree species based on their accumulation and exclusion of heavy metals, and the influence of heavy metals on species abundance on Copperbelt tailings dams in Zambia

Abstract

Classification of tree species into excluders or accumulators is vital for ecological restoration of mine tailings dams via phytostabilization. The study dealt with classification of indigenous tree species found on tailings dams and also how heavy metal concentration influence the abundance and distribution of tree species on tailings Storage facilities in the Copperbelt Province, Zambia. Among the studied species a number of them were classified into excluders and accumulators of the 12 metals. For example, Rhus longipes, Syzigium guineense, Senegalia polyacantha, Ficus craterostoma, Bauhinia thonningii, Albizia adianthifolia, Combretum molle, Peltophorum africanum and Ficus sycomorus, Albizia antunesiana, Albizia versicolor, Azanza garckeana, Bauhinia petersiana, Brysorcapus orientalis, Combretum molle, Combretum microphyllum, Dichrostachys cinerea, Dodonaea viscosa, Ficus capensis, Lannea discolor, Phyllanthus guineensis, Senna singueana, Terminalia mollis, Terminalia stenostachya, Combretum apiculatum and Vachelia sieberiana were classified as Cu excluders while Dombeya rotundifolia, Albizia amara and Parinari curatellifolia, Combretum zeyheri, Annona senegalensis and Ozoroa insignis were classified as Cu accumulators. All the species were classified as Mn accumulators while Albizia adianthifolia, Albizia antunesiana, Combretum apiculatum and Ficus capensis were classified as Zn excluders and the other 28 species classified as Zn accumulators. The dominance of species in terms of importance values varied from (a species with the lowest IVI value) to (Species with the highest IVI value). Species with high IVI values dominated the tailings dams than those with low IVI values. Rhus longipes, Syzygium guineense, Senegalia polyacantha, Ficus craterostoma, Bauhinia thonningii, Albizia adianthifolia and Combretum molle were identified as the most dominant species on Copperbelt tailings dams. Low species richness (composition) and abundance was observed in high metal concentration. Most species showed high affinity to heavy metals in low concentration while a few species (Rhus longipes, Albizia versicolor, Albizia amara Dombeya rotundifolia, Albizia antunesiana, Phyllanthus guineensis and Dichrostachys cinerea) showed high affinity to metals in high concentration. Furthermore, the study identified Ni, Cu, S, Cr, Al, Co, Mn, B, Mo and Cd as metals influencing species richness and abundance on the Copperbelt tailings dams.