Growth response of Brachystegia longifolia to copper mining pollution-induced heavy metal stress

Elevated concentration of heavy metals has been reported in Brachystegia longifolia trees attributed to pollution emanating from a copper mine in Mufulira, Zambia. This study investigates the growth response of B. longifolia to copper mining pollution induced growth stress. Wood discs were extracted at breast height from eight sampling sites established along a transect up- and downwind of the mine, representing polluted and unpolluted areas. The annual ring width was measured using a LINTAB supported by TSAP-Win software. Significant decreases were observed in B. longifolia radial growth on polluted sites compared to control sites. The tree growth reduction was attributed to Cu and Fe phytotoxicities through a multivariate analysis and the reduced growth manifested in a decreased ring width in response to heavy metal stress on polluted sites. This study demonstrates that B. longifolia trees are vulnerable to copper mining pollution and that the mining activities affect the wood quality negatively.