Using phytostabilisation to conserve threatened endemic species in southeastern Democratic Republic of the Congo

Outcrops in the southeastern Democratic Republic of the Congo (DRC) are recognized as some of the largest copper–cobalt orebodies in the world. They support a unique vegetation with nearly 600 metallophytes that include rare and endemic species. Mineral exploitation has increased considerably in the region since the 1900s, affecting both environmental and public health. Phytostabilisation of polluted areas represents an opportunity to decrease the bioavailability of heavy metals in the highly polluted soils that result from ore extraction. Such a technique has been successfully implemented near Lubumbashi with the grass Microchloa altera. However, long-term maintenance requires a good understanding of interspecific relationships, such as competition and facilitation. This study tested the establishment success of four herbaceous species from the Katangan Copperbelt by assessing the potential role of Microchloa altera as a nurse species. Two annual and two perennial species were sown in an experiment designed to study the influence of soil amendment and vegetation cover on seedling emergence, growth, and survival. These variables were monitored during the vegetation growing season as well as resprouting success for perennials. Microchloa altera showed a distinct effect on the emergence and survival of annual and perennial species and negatively affected the growth of individuals belonging to both groups of species.