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

Abstract

In Katanga, Democratic Republic of Congo, unique metallophyte communities supporting numerous endemic species occurred on the highly mineralized copper cobalt (Cu-Co) hills throughout the province. These hills are economically valuable mineral reserves, mining activities represent therefore a threat to the long-term persistence of these communities. Ex-situ conservation program was set up by a mining company to rescue and conserve the diversity of Cu-Co communities until restoration activities are initiated. Two kind of Cu-Co communities, the steppe and the steppic savanna were translocated using topsoil spreading and whole-turf translocation. In this study we assessed the effectiveness of these two techniques in conserving Cu-Co communities and their potential use in future restoration programs. More than two years after the translocation, whole-turf translocation appeared to be the better technique for ex-situ conservation of endemic Cu-Co species.Not only did whole-turf successfully translocate numerous target species that were not present in the topsoil areas, but it also resulted in fewer ruderal and non-target species compared to topsoil spreading. Topsoil spreading recorded low seedling emergence from seed bank due to large proportions of dormant seeds or the absence of a seed bank, especially for the steppic savanna. Restoration of the steppe, is currently more successful than for steppic savanna where the lack of dominant and structuring species likely contributed to divergence in species composition compared to reference ecosystem. Our study stress the fact that tropical old-growth grasslands, which require probably several centuries to assemble, are difficult to restore or translocate.

Restoring Brazilian savanna ground layer vegetation by topsoil and hay transfer

“…While these two techniques (i.e. topsoil and hay transfer) have been tested in various grassland types in temperate climates, we found only a few studies from the tropical grassy biomes (Le Stradic et al for hay transfer and Ferreira et al , Le Stradic et al for topsoil translocation). In this context, the present study was designed to provide insights on the following basic questions regarding restoration of cerrado old‐growth grasslands ( sensu Veldman et al ): (1) can topsoil or hay transfer provide the recovery of the floristic composition and the proportion of life forms in reference ecosystems?…”

Biodiversity hotspots and Ocbil theory

“…The vulnerability of Ocbil communities to topsoil removal is now evident in the campo rupestre (Le Stradic et al 2014a, b), New Caledonia (Losfeld et al 2015) and in metal-rich grasslands in Congo (Le Stradic et al 2016), as well as in the SWAFR. In campo rupestre, natural regeneration struggles to return even after decades following soil removal .…”

No recovery of campo rupestre grasslands after gravel extraction: implications for conservation and restoration

“…Poaceae, Cyperaceae, Xyridaceae, Eriocaulaceae, or Velloziaceae) disperse unassistedly, and only a few species produce fleshy fruits that are dispersed mainly by birds (Guerra et al ). Consequently, postdisturbance plant communities are composed largely of nontarget and ruderal species, which establish by taking advantage of the soil modifications and high proportion of bare soil (Hobbs & Huenneke ; Shea & Chesson ; Hansen & Clevenger ; Le Stradic et al ). Therefore, a collateral effect of soil modification is the introduction of competition from non‐native and/or ruderal species, which may further limit establishment of native species.…”

“…The technique is commonly used to rehabilitate mines and quarries (Koch ; Rivera et al ), but it is more successful in temperate grasslands than in tropical grasslands (Le Stradic et al ). In our case, the poverty of the seed bank in reference campo rupestre areas implies that a technique such as bulk topsoil transfer would have limited efficacy in reestablishing campo rupestre herbaceous vegetation in degraded areas, as has been demonstrated for other old‐growth grasslands (Le Stradic et al ). In addition, topsoil transfer has the disadvantage that donor sites are destroyed and may not recover easily due to the lack of seeds.…”