Investigating the Vegetation–Soil Relationships on the Copper–Cobalt Rock Outcrops of Katanga (D. R. Congo), an Essential Step in a Biodiversity Conservation Plan

Abstract

Plant communities of soils naturally enriched in copper and cobalt in Katanga (D. R. Congo) are critically threatened in the short term due to mining activities. For biodiversity conservation and ecosystem restoration purposes, there is an urgent need to acquire more knowledge on those plant communities including their diversity and their relationships to environmental factors. The classification of 62 vegetation plots located in 6 metal-rich rocky hills in the Tenke Fungurume mining area resulted in 3 well-defined steppic and steppic savanna communities. Canonical analysis showed that the community comprising the largest proportion of strictly endemic metallophytes (i.e. species that only occur on metal-rich soils) developed in the soils with the most elevated concentrations of Cu and Co. However, contrasting species assemblages in the two other plant communities were explained by soil nutrients and percentage rocks in addition to heavy metal concentrations. The results of this study will assist with restoration efforts because they (1) provide a rigorous assessment of communities before a disturbance and (2) define essential edaphic conditions needed for the reestablishment of critical communities.

Comparison of translocation methods to conserve metallophyte communities in the Southeastern D.R. Congo

“…Steppe contains shallow soils, commonly around 40cm in depth (unpublished data), which limits root breakage and increases survival translocation. In addition, higher Cu and Co concentrations in steppe soils (Saad et al 2012;Séleck et al 2013) reduce colonization and competition by invasive species that are not adapted to harsh edaphic conditions (Bullock 1998). Population reinforcement should be planned to prevent the decline of some particular species which might be observed (i.e.…”

“…As these communities often occur on economically-valuable mineral deposits, many are threatened by quarrying and mining activities (Whiting et al 2004). As opportunities for in situ conservation of metallophyte communities are often limited, there has been increasing attention on ex-situ conservation methods including use in phytostabilisation ) and ecological restoration (Whiting et al 2004;Faucon et al 2012;Saad et al 2012). …”

“…Typically, the steppe is located in the upper part of the hill and is characterized by shallow soils with high metal concentrations (Cu-EDTA of 3 500-10 000 mg Cu.kg.soil -1 ) and a large number of endemic species. The steppic savanna occurs along the lower slopes on deeper sols with lower metal concentrations (1 000-3 500 mg Cu.kg.soil -1 ) (Saad et al 2012;Ilunga et al 2013;Séleck et al 2013). …”

Chemical soil factors influencing plant assemblages along copper-cobalt gradients: implications for conservation and restoration

“…Besides the conservation of representative areas of metalliferous ecosystems in untouched nature reserves, the most straightforward strategy to ensure the survival of metallophytes in mining concessions is to promote their use in ecological restoration and site rehabilitation at the point of mine closure (Faucon et al 2012a, b;Saad et al 2012;Whiting et al 2004). Such a conservation strategy can only be reached through a deep understanding of patterns and processes of the plant community's variability (Whiting et al 2004).…”

“…Natural Cu concentrations span a large range on Katangan copper hills (total Cu from~100 mg.kg -1 to values as high as 35 000 mg.kg −1 , Saad et al 2012) and largely exceed those of normal soils (total Cu <100 mg.kg −1 in normal soils, Duvigneaud 1958;Faucon et al 2011). Cobalt concentrations may also be as high as 1,000 mg.kg −1 .…”