Soil-plants relations diversity in extreme ecosystems and implications for restoration: the case of the cupriferous vegetation, in Katanga, D.R. Congo

Katangan copper and cobalt hills in the D. R. Congo are isolated ecosystems on highly toxics substrates (>10.000 ppm Cu, with strongly marked gradients). As a result, those outcrops host singular vegetal communities – with a diversity of specialized metallophytes species – related to soil metals content. Recent resumption of mining activities in the area threatens those ecosystems. To allow the restoration of those communities a fine understanding of the relationship maintained with the edaphic factors is required, as well as a characterization of the intra and inter sites variation.
Three outcrops have been studied on the basis of a systematic grid, following the a priori trace elements gradient. In 1m² quadrats, a composite soil sample (0-15 cm depth) was taken and the cover (%) of each species of vascular plants was recorded. Soils were analyzed for pH, C, N, and bioavailables Cu, Co, Zn, Mn, Fe, K, Mg, Ca and P.
The cluster analysis and Canonical Correspondence Analysis show that different sites present different soil conditions and vegetation. Concentrations in Cu are an important explicative factor of the flora’s variation but gradients in others edaphic parameters (pH, Mg, Mn, K, Ca) appear to be essential. However, parameters explaining the diversity of communities vary from one site to another indicating a great diversity of those ecosystems and the need to develop restoration strategies relevant for each site.