Herbarium collections and field data-based plant diversity maps for Burkina Faso

A map of plant species diversity in Burkina Faso is presented based on field observations and specimen data from the Ouagadougou University Herbarium (OUA) and the Herbarium Senckenbergianum (FR). A map of collecting intensity and field observations illustrates centres of botanical research activities in Burkina Faso. To overcome problems associated with biased sampling intensity, distributions of species have been modelled and extrapolated to maps of vascular plant diversity, life forms and diversity of four selected families (Poaceae, Cyperaceae, Dioscoreaceae and Rubiaceae). The area of most intensive collection and observation is around Gorom‐Gorom and Fada N’Gourma. Modelled diversity generally increases towards the south, as does the proportion of phanerophytes, lianas and hemicryptophytes, while the opposite trend is observed for therophytes. Poaceae diversity is highly correlated with total vascular plant diversity, making the family especially suitable as an indicator for overall plant diversity. Cyperaceae are rather evenly distributed throughout the country, Dioscoreaceae are restricted to the Sudanian Zone. Rubiaceae have their highest diversities in the very south. Our approach can be transferred to areas with a similar database, certainly to other areas within West Africa. Future research should focus on distribution data for rare species, enabling our approach to evaluate the West African system of protected areas.     

Comparison of aboveground vegetation and soil seed bank composition at sites of different grazing intensity around a savanna-woodland watering point in West Africa

Grazing removes a plant’s aboveground vegetative and reproductive tissues and can modify the soil seed bank, potentially impacting the restoration of preferred species. Knowledge about aboveground vegetation and species composition of soil seed bank and the processes that contribute to vegetation recovery on and surrounding watering points subjected to grazing is lacking. Successful restoration strategies hinge on addressing these knowledge gaps. We assessed the effects of livestock grazing on aboveground vegetation and soil seed bank characteristics along a river bank and surrounding areas subject to different grazing intensities and draw implications for restoration. Plots (50?×?50 m) were established along five transects representing differing levels of grazing intensity. Soil samples were taken from three layers within each plot to determine soil properties and species composition of soil seed bank using the seedling emergence method. Heavy grazing resulted in the disappearance of perennial grasses, a reduction in species diversity and a decrease in soil nutrients with increased soil depth. Overall, the similarity between the extant aboveground vegetation and flora within the soil seed bank was low. The soil seed bank was dominated by herbaceous species and two woody species, suggesting that many woody species are not accumulating in the soil. With increasing soil depth, the seed density and richness declined. Canonical correspondence analyses (CCAs) showed that emerged seedlings from the soil seed bank were significantly influenced by soil carbon, organic matter, total nitrogen, total potassium and soil cation exchange capacity. This finding suggests that current grazing practices have a negative impact on the vegetation surrounding watering points; hence there is a need for improved grazing management strategies and vegetation restoration in these areas. The soil seed bank alone cannot restore degraded river banks; active transfer of propagules from adjacent undisturbed forest areas is essential.     

Diversity and occurrence of herbaceous communities in West African savannas in relation to climate,land use and habitat

In the face of the current changes in land use and climate as well as habitat destruction, it is important to study herbaceous vegetation as an indicator of changes occurring in savanna ecosystems. We investigated the effects of climate, land use and habitat, both alone and in combination, on the diversity and occurrence of West African savanna herbaceous plant communities. Floristic data and environmental variables were sampled in Burkina Faso and subjected to ordination and indicator species analysis to explore the variation in nine vegetation types. Regression analyses showed that climate, land use, humidity gradient, soil fraction and vegetation structure discriminate herbaceous plant communities. Climate, habitat and their interaction had the greatest effect on the occurrence of these communities. Changes in species richness of the studied communities were mainly due to climate, land use and their interaction, which were more important for increasing rather than decreasing diversity. In all cases, climate conditions remained the most important environmental factor driving vegetation variation in West African savannas. Beside this, the effects of habitat degradation in interaction with land use and climatic conditions indicate land use to be a threat for the diversity of the herbaceous vegetation.     

Plant biodiversity patterns along a climatic gradient and across protected areas in West Africa

Knowledge of spatial patterns of biological diversity is fundamental for ecological and biogeographical analyses and for priority setting in nature conservation, particularly in West Africa where the existing high biodiversity is increasingly threatened by human activities. The maximum entropy approach was used to model the geographic distribution of 3,393 vascular plant species at a spatial resolution of 0.0833°. Species richness decreases along temperature and precipitation gradients with high species numbers in the south and lower numbers towards the north of the transect. All centres of plant species diversity are confined to humid areas in concordance with the high positive correlation between species richness and rainfall which appears to be the most important delimiter for the distribution ranges of many species in the area. The effectiveness of the existing protected areas at regional and national levels is investigated based on the proportion of species covered. Considering the whole study area, 95% of all species are covered by protected areas according to their distribution ranges. However, the proportion of species covered is considerably lower for some countries such as Benin and Togo. Our results could provide guidance for essential land use management interventions to decision‐makers and conservationists in the region.     

Impact of environmental conditions on fruit production patterns of shea tree (Vitellaria paradoxa C.F.Gaertn) in West Africa

A better knowledge of the impact of environmental conditions on shea tree’s fruit production is critical to improve the species management. Fruit production of 237 shea trees was monitored over five successive years (2014–2018) to understand how climatic variables, shea tree population and land use could affect fruit production patterns of the species in Burkina Faso. Data were collected in 12 shea tree populations distributed in three climatic zones with two contrast land use systems. The results showed that fruit production was negatively correlated with mean annual temperature, temperature seasonality, rainfall seasonality and solar radiation, while it was positive with annual rainfall. Therefore, fruiting modelling is needed to predict the impact of future climate change on reproductive ability of the species. In each climatic zone, fruit production was significantly different among shea tree populations (p < 0.05). Within populations, fruit production greatly varies among years with specific patterns of variation. Land use had significant effect on fruit production of shea tree (p < 0.05). Annually, shea trees produced about 12 times more in agroforestry parklands than in protected areas. Interannual variation in fruit production at individual tree level was higher in protected areas. The cultivation of shea tree is recommended to improve its fruit productivity.     

Phytoplankton assemblages and community structure in tropical temporary freshwater ponds in sub‐Saharan Africa1

Anthropogenic and climatic factors are important determinants of algal distribution in aquatic systems. This study aimed to identify temporary pond‐groups of phytoplankton assemblages and to establish the interactions between environmental variables and phytoplankton structure. Phytoplankton samples were collected and preserved with 5% formalin; water samples for chemical analysis were taken in August and September 2007, 2008, and 2009 in 86 ponds randomly selected in the Sahelian sector and the Sudanian sector (protected and unprotected areas) of Burkina Faso. Plankton species were examined using light microscopy and identified using standard methods. A Fuchs‐Rosenthal chamber was used for algal cell counting. NMDS ordination, indicator species analysis and canonical analysis were performed using Pc‐Ord and CANOCO. Kruskal–Wallis and Mann–Whitney U‐tests using the software Statistica were performed to compare parameters between pond‐groups. Three pond‐groups were identified: the Sahelian pond‐group, dominated by Lyngbya martensiana and Pseudanabaena constricta; the protected area pond‐group, dominated by Euglena caudata and Trachelomonas raciborskii; and the unprotected area pond‐group, dominated by Closterium venus and Euglena proxima. At P < 0.05, species composition and abundance in algal groups were mostly associated with nitrate, pH, dissolved oxygen, and conductivity. The Sahelian and the Sudanian sectors were different in pH, water transparency, and species richness. Univariate and multivariate analyses illustrate that variations in the physicochemical properties of water and algal structure followed climatic and anthropogenic gradients. The classification of ponds into algal associations demonstrated that algal assemblages may be used as reliable indicators of habitat conditions.     

Mycobacterium bovis in Burkina Faso: Epidemiologic and Genetic Links between Human and Cattle Isolates

Background

In sub-Saharan Africa, bovine tuberculosis (bTB) is a potential hazard for animals and humans health. The goal of this study was to improve our understanding of bTB epidemiology in Burkina Faso and especially Mycobacterium bovis transmission within and between the bovine and human populations.

Methodology/principal findings

Twenty six M. bovis strains were isolated from 101 cattle carcasses with suspected bTB lesions during routine meat inspections at the Bobo Dioulasso and Ouagadougou slaughterhouses. In addition, 7 M. bovis strains were isolated from 576 patients with pulmonary tuberculosis. Spoligotyping, RDAf1 deletion and MIRU-VNTR typing were used for strains genotyping. The isolation of M. bovis strains was confirmed by spoligotyping and 12 spoligotype signatures were detected. Together, the spoligotyping and MIRU-VNTR data allowed grouping the 33 M. bovis isolates in seven clusters including isolates exclusively from cattle (5) or humans (1) or from both (1). Moreover, these data (genetic analyses and phenetic tree) showed that the M. bovis isolates belonged to the African 1 (Af1) clonal complex (81.8%) and the putative African 5 (Af5) clonal complex (18.2%), in agreement with the results of RDAf1 deletion typing.

Conclusions/Significance

This is the first detailed molecular characterization of M. bovis strains from humans and cattle in Burkina Faso. The distribution of the two Af1 and putative Af5 clonal complexes is comparable to what has been reported in neighbouring countries. Furthermore, the strain genetic profiles suggest that M. bovis circulates across the borders and that the Burkina Faso strains originate from different countries, but have a country-specific evolution. The genetic characterization suggests that, currently, M. bovis transmission occurs mainly between cattle, occasionally between cattle and humans and potentially between humans. This study emphasizes the bTB risk in cattle but also in humans and the difficulty to set up proper disease control strategies in Burkina Faso.     

An untargeted liquid chromatography–mass spectrometry‐based workflow for the structural characterization of plant polyesters

Cell wall localized heterogeneous polyesters are widespread in land plants. The composition of these polyesters, such as cutin, suberin, or more plant‐specific forms such as the flax seed coat lignan macromolecule, can be determined after total hydrolysis of the ester linkages. The main bottleneck in the structural characterization of these macromolecules, however, resides in the determination of the higher order monomer sequences. Partial hydrolysates of the polyesters release a complex mixture of fragments of different lengths, each present in low abundance and therefore are challenging to structurally characterize. Here, a method is presented by which liquid chromatography–mass spectrometry (LC‐MS) profiles of such partial hydrolysates are searched for pairs of related fragments. LC‐MS peaks that show a mass difference corresponding to the addition of one or more macromolecule monomers were connected in a network. Starting from the lowest molecular weight peaks in the network, the annotation of the connections as the addition of one or more polyester monomers allows the prediction of consecutive and increasingly complex adjacent peaks. Multi‐stage MS (MSn) experiments further helped to reject, corroborate, and sometimes refine the structures predicted by the network. As a proof of concept, this procedure was applied to partial hydrolysates of the flax seed coat lignan macromolecule, and allowed to characterize 120 distinct oligo‐esters, consisting of up to six monomers, and containing monomers and linkages for which incorporation in the lignan macromolecule had not been described before. These results showed the capacity of the approach to advance the structural elucidation of complex plant polyesters.     

Impacts of land-use on West African savanna vegetation: a comparison between protected and communal area in Burkina Faso

Biodiversity matters in many aspects for human well-being by providing timber and non-timber products. The most important ecosystems providing these products in West Africa are savannas. In the context of land-use changes, there is an urgent need to understand the impact of land-use on savanna vegetation and biodiversity. This study assesses the impact of land-use on savannas by comparing protected and communal areas. Vegetation relevés were performed in the W National Park and its surrounding communal area in Burkina Faso. Vegetation types were established using ordination and clustering methods. We analyzed to find which environmental factors determine the occurrence of the vegetation types and whether land-use has a specific effect on diversity of vegetation types occurring in both areas. Furthermore, we tested the effect of land-use on vegetation structure and the occurrence of life forms and highly valued tree species. Our results reveal five vegetation types occurring in both areas. Elevation and soil characteristics played the most important role for the occurrence of the vegetation types. Land-use had an effect on vegetation structure, diversity, and the occurrence of life form and highly valued species. Our findings suggest that traditional human land-use does not automatically lead to loss of species and degradation of savanna habitats and that combination of communal and protected areas may be of great importance for the conservation of broad spectrum of biodiversity. Our study demonstrates the complexity of land-use impact on biodiversity patterns and provides insights on what kind of management activities may be most appropriate in both areas.