Michel Ngongo Luhembwe

Bio: Michel Ngongo Luhembwe is an academic researcher from University of Lubumbashi. The author has contributed to research in topics: Compost & Soil water. The author has an hindex of 8, co-authored 15 publications receiving 296 citations.

Copper endemism in the Congolese flora: a database of copper affinity and conservational value of cuprophytes

Abstract: Background and aims - The occurrence of natural plant communities on Cuenriched substrates over significant areas of the earth's surface is exceptional. In Katanga (D.R.Congo), natural outcrops of copper-rich rocks are colonised by highly original plant communities. A number of plant species have been proposed as possibly endemic to those sites. Here we revise the taxonomic, phytogeographic and conservational status of these plants. Methods - Almost all the herbarium materials of supposed Cuendemics available in BR and BRLU have been revised and all relevant taxonomic revisions have been consulted. Literature and herbarium data have been supplemented by original observations in the field. Conservational status was established using IUCN criteria based on current and projected variation of population size and number. Key results - Thirty-two taxa are identified as strict endemics of Curich soil in Katanga, i.e. absolute metallophytes. Twenty-four of these are known from one to five localities only. Twenty-three other taxa are identified as broad endemics, i.e. with > 75% of occurrence on Curich soil. Fifty-seven other names formerly used for supposed endemics are rejected either for nomenclatural or phytogeographic reasons. A number of species formerly regarded as endemics have been discovered off copperenriched substrates due to progress in the botanical exploration of Katanga. The taxonomic value of a number of proposed endemics is still uncertain and requires further research. For a number of taxa, local geographic distribution still remains insufficiently known. The low proportion of endemics (c. 5%) in the flora of Curich soil in Katanga possibly indicates a recent origin of much of this flora. Arguments in favour of neoendemism and relictual endemism, respectively, are discussed briefly. Ten percent of strict endemics are extinct and 65% are critically endangered, due to actual or projected habitat destruction by copper mining. Endemics restricted to primary habitats may be the most difficult to conserve. Several species, mostly annuals, are able to thrive on secondary metalliferous habitats created by the mining industry and may thus be at lower risk. Conclusions - This review emphasizes the high conservation value of the flora of Curich soil in Katanga and should help prioritise future conservation efforts. © 2010 National Botanic Garden of Belgium and Royal Botanical Society of Belgium.

Phytostabilisation of Copper-Contaminated Soil in Katanga: An Experiment with Three Native Grasses and Two Amendments

Abstract: This study evaluates the feasibility of using the grass species Rendlia altera, Monocymbium ceresiiforme, Cynodon dactylon, and amendments (compost and lime) for the phytostabilisation of soils contaminated by Cu in the province of Katanga (Democratic Republic of Congo). Species were grown on control and Cu-contaminated plots (artificially contaminated with 2,500 mg kg-1 Cu) unamended (NA), amended with 4.5 kg compost m-2 or 0.2 kg lime m-2. R. altera was also grown on contaminated plots amended with 22.5 kg compost m-2 or 1 kg lime m-2. Plant survival, growth, and reproduction were monitored for two years. Cu-concentration in leaves of R. altera and M. ceresiiforme were analysed. pH and extractable Cu (0.01 M CaCl2) in soil were analysed in April 2007 and 2008. Results showed that R. altera seems to be the best candidate because of its highest survival on NA, followed by M. ceresiiforme, while liming was necessary to ensure survival of C. dactylon. Lime increased plant reproduction and reduced Cu accumulation in leaves compared to compost. However, higher survival and number of spikes of R. altera obtained in experiment 2 with 22.5 kg compost m-2 suggest that lime x compost interactions should be investigated in further studies. © Taylor & Francis Group, LLC.

Soil influence on Cu and Co uptake and plant size in the cuprophytes Crepidorhopalon perennis and C. tenuis (Scrophulariaceae) in SC Africa

Abstract: Cuprophytes are plants that mostly occur on Cu-rich soil in SC Africa. Crepidorhopalon perennis is endemic of a single site. C. tenuis has a broader niche, from normal to Cu-rich soil. Both have been considered as Cu-Co accumulators. We examined soil factors controlling heavy metal accumulation and plant fitness in natural populations. Plant mass and element concentrations in plants and soil were determined in 153 samples from five populations of C. tenuis on copper soil (CTC), two on normal soil (CTN) and the single population of C. perennis (CP). Soil in Cu-sites had higher concentrations of Ca, Mg, P, Mn, Zn, Cu, Co. Plants from Cu-sites were larger and had higher Cu and Co content, and lower Mg, Mn and Ca. Cu in shoots was influenced positively by Cu and Mn and negatively by Ca in the soil. Co in shoots was influenced positively by Co and negatively by Mn and Fe in the soil. Shoot mass was influenced positively by Cu and Mn (CT) or by Cu and Co (both species pooled) in the soil. The results suggest that C. tenuis and C. perennis are genuinely cuprophilous species. Large variation in metal accumulation in shoots can be accounted for by synergistic and antagonistic interactions among several heavy metals, yielding specific accumulation patterns in different populations.

May Rare Metallophytes Benefit from Disturbed Soils Following Mining Activity? The Case of the Crepidorhopalon tenuis in Katanga (D. R. Congo)

Abstract: Cuprophytes are plants that mostly occur on Cu-rich soil. In South Central Africa, these species are threatened by intensive mining exploitation destroying their habitats. Crepidorhopalon tenuis (Scrophulariaceae) is a tiny annual cuprophyte endemic to the Zambesian center of endemism and is particularly abundant in the Lubumbashi area. We investigate here the ecological niche of C. tenuis through the analyses of its abundance and distribution in relation to soil factors, plant community composition, and anthropogenic perturbations. Soil and vegetation data were collected in seven sites (five metalliferous and two nonmetalliferous). The current study shows that C. tenuis has its ecological optimum on copper-rich soil and can be referred to as an elective pseudometallophyte. This species is rare in primary steppic savanna on natural metalliferous soil. Its frequency and abundance peak in pioneer communities on bare soil. In particular, the species showed a surprising ecological plasticity as it was able to benefit from anthropogenic disturbance and to colonize the large areas of bare, contaminated soil left over by mining activities. Our results strongly suggest that C. tenuis was a very rare species in natural metalliferous communities, restricted to patchy areas of open soil in steppic savanna. Recent anthropogenic habitats may have conservation value for some rare metallophytes with colonizing traits and low competitive ability. © 2009 Society for Ecological Restoration International.

Three years of phytostabilisation experiment of bare acidic soil extremely contaminated by copper smelting using plant biodiversity of metal-rich soils in tropical Africa (Katanga, DR Congo)

Abstract: Copper smelting has created large surfaces of bare soil contaminated by trace metals (TMs: e.g. total Cu: 42,500mgkg -1 in bare soil vs. 220mgkg -1 in remote forest) in the Lubumbashi suburbs of the 'Cite Gecamines/Penga Penga' (Katanga, D.R. Congo). Human exposure to trace metals at the site has become a primary environmental concern. This study evaluated different strategies (spontaneous and assisted phytostabilisation) to promote plant establishment on bare soil at the contamination site for soil reclamation/remediation. First, soil chemical properties were assessed in three vegetation units (bare soil, metallophytic grassland patches, and termite mounds). Results showed lower nutrients, organic matter content, and pH in bare soil; however increased metal concentrations were not detected. Limestone (0, 2.5, 5, and 10tha -1 ) and compost (0, 45, and 225tha -1 ) were applied in a factorial design. Plant establishment was monitored for three years; and leaf TM concentration was assessed during the third year. Soil amendments improved bare soil conditions (higher pH and nutrients and lower TMs), and facilitated spontaneous plant establishment, with compost exhibiting the largest positive effects. Colonisers were primarily annual species; either true metallophytes or weedy taxa, which were sporadically present at the study site. However, only the perennial Microchloa altera survived during the 6-month dry season. Following three years of phytostabilisation experiment with M. altera by planting, substantial growth and high survival was observed in M. altera. A combination of soil amendments (lime and compost) was most effective to improve plant fecundity, and reduce metal uptake by leaves. Our results show promise for reclamation of bare soil contaminated by the mining industry in tropical climate.

Ecology and evolution of plant diversity in the endangered campo rupestre: a neglected conservation priority

Abstract: Botanists, ecologists and evolutionary biologists are familiar with the astonishing species richness and endemism of the fynbos of the Cape Floristic Region and the ancient and unique flora of the kwongkan of south-western Australia. These regions represent old climatically-buffered infertile landscapes (OCBILs) that are the basis of a general hypothesis to explain their richness and endemism. However, few ecologists are familiar with the campo rupestre of central and eastern Brazil, an extremely old mountaintop ecosystem that is both a museum of ancient lineages and a cradle of continuing diversification of endemic lineages. Diversification of some lineages of campo rupestre pre-dates diversification of lowland cerrado, suggesting it may be the most ancient open vegetation in eastern South America. This vegetation comprises more than 5000 plant species, nearly 15 % of Brazil’s plant diversity, in an area corresponding to 0.78 % of its surface. Reviewing empirical data, we scrutinise five predictions of the OCBIL theory, and show that campo rupestre is fully comparable to and remarkably convergent with both fynbos and kwongkan, and fulfills the criteria for a classic OCBIL. The increasing threats to campo rupestre are compromising ecosystem services and we argue for the implementation of more effective conservation and restoration strategies.

Resilience and restoration of tropical and subtropical grasslands, savannas, and grassy woodlands.

Abstract: Despite growing recognition of the conservation values of grassy biomes, our understanding of how to maintain and restore biodiverse tropical grasslands (including savannas and open-canopy grassy woodlands) remains limited. To incorporate grasslands into large-scale restoration efforts, we synthesised existing ecological knowledge of tropical grassland resilience and approaches to plant community restoration. Tropical grassland plant communities are resilient to, and often dependent on, the endogenous disturbances with which they evolved - frequent fires and native megafaunal herbivory. In stark contrast, tropical grasslands are extremely vulnerable to human-caused exogenous disturbances, particularly those that alter soils and destroy belowground biomass (e.g. tillage agriculture, surface mining); tropical grassland restoration after severe soil disturbances is expensive and rarely achieves management targets. Where grasslands have been degraded by altered disturbance regimes (e.g. fire exclusion), exotic plant invasions, or afforestation, restoration efforts can recreate vegetation structure (i.e. historical tree density and herbaceous ground cover), but species-diverse plant communities, including endemic species, are slow to recover. Complicating plant-community restoration efforts, many tropical grassland species, particularly those that invest in underground storage organs, are difficult to propagate and re-establish. To guide restoration decisions, we draw on the old-growth grassland concept, the novel ecosystem concept, and theory regarding tree cover along resource gradients in savannas to propose a conceptual framework that classifies tropical grasslands into three broad ecosystem states. These states are: (1) old-growth grasslands (i.e. ancient, biodiverse grassy ecosystems), where management should focus on the maintenance of disturbance regimes; (2) hybrid grasslands, where restoration should emphasise a return towards the old-growth state; and (3) novel ecosystems, where the magnitude of environmental change (i.e. a shift to an alternative ecosystem state) or the socioecological context preclude a return to historical conditions.

Copper and cobalt accumulation in plants: a critical assessment of the current state of knowledge

Abstract: This review synthesizes contemporary understanding of copper-cobalt (Cu-Co) tolerance and accumulation in plants. Accumulation of foliar Cu and Co to > 300 μg g-1 is exceptionally rare globally, and known principally from the Copperbelt of Central Africa. Cobalt accumulation is also observed in a limited number of nickel (Ni) hyperaccumulator plants occurring on ultramafic soils around the world. None of the putative Cu or Co hyperaccumulator plants appears to comply with the fundamental principle of hyperaccumulation, as foliar Cu-Co accumulation is strongly dose-dependent. Abnormally high plant tissue Cu concentrations occur only when plants are exposed to high soil Cu with a low root to shoot translocation factor. Most Cu-tolerant plants are Excluders sensu Baker and therefore setting nominal threshold values for Cu hyperaccumulation is not informative. Abnormal accumulation of Co occurs under similar circumstances in the Copperbelt of Central Africa as well as sporadically in Ni hyperaccumulator plants on ultramafic soils; however, Co-tolerant plants behave physiologically as Indicators sensu Baker. Practical application of Cu-Co accumulator plants in phytomining is limited due to their dose-dependent accumulation characteristics, although for Co field trials may be warranted on highly Co-contaminated mineral wastes because of its relatively high metal value.

Biodiversity hotspots and Ocbil theory

Abstract: Background Ocbil theory aims to develop hypotheses explaining the evolution and ecology of, and best conservation practices for, biota on very old, climatically buffered, infertile landscapes (Ocbils).