Abstract: To compare the phytoremediation potential of Casuarina equisetifolia cultivated in an artificially contaminated soil with copper (Cu), cadmium (Cd), lead (Pb) and manganese (Mn), we evaluated the tolerance of heavy metals (HMs) and accumulation capacity of one-year-old cutting seedlings of five clones (S₁₃, S₄₄, S₄₈, S₆₀ and S₈₀) ofC. equisetifolia. There were four HMs levels (CK, low (T1), medium (T2) and high (T3)) in this experiment. The plant growth, HMs accumulation and distribution characteristics were measured. The results showed that all clones could survive on the polluted substrate and maintain the normal growth. The five clones showed different tolerance levels to the HMs treatments. Compared to CK, HMs treatments significantly promoted the growth of S₁₃ and S₄₄. The growth of S₄₈, S₆₀ and S₈₀ showed no significant difference in the HMs treatments compared to CK. The HMs concentrations in tissues were increased with increasing HMs concentrations in soil. Furthermore, the HMs concentrations in tissues showed variation depending on metal speciation. For example, the concentrations of Mn in tissues were in the order of twig > stem > root. Moreover, the translocation factor (TF) values of Mn were greater than 1 in all clones and HMs treatments. The amounts of Mn in aboveground part of C. equisetifolia account for 86%, suggesting that C. equisetifolia had the higher Mn transfer capability. The concentrations of Cu, Cd and Pb in the roots were higher than in the stems and twigs. The amounts of HMs in the aboveground part were more than 50% of the total accumulation. Under the T3 treatment with the highest HMs concentration, there was no significant difference in comprehensive bioconcentration index (CBCI) of heavy metals among the five clones, indicating that they had similar accumulation capacity to heavy metals. According to the biomass and CBCI, clones S₁₃ and S₄₄ had a greater potential in phytoremediation. Taken together, C. equisetifolia had high tolerance, good accumulation and translocation capabilities for Cu, Cd and Mn. Therefore, C. equisetifolia could be a promising species for phytoremediation application on HMs pollution soil, especially for Mn pollution.

Key words: climate change, Gansu, food, direction.