Local knowledge and use of wild edible plants in eastern part of Nyungwe National Park in Rwanda: Prospects for forest biodiversity conservation

This research explored the local knowledge and use of wild edible plants in Nyungwe National Park (NNP) and its vicinity. Data were collected through semi-structured interviews with local elders on the use and knowledge of wild edible plants. Further, wild edible plants reported from the survey were investigated across transects and quadrats in NNP. Taxonomy of collected plants to species level, the identification of used and eaten parts, and the frequency of consumption were studied. A total of 35 species grouped into 21 families dominated by the families of Brassicaceae, Amaranthaceae, Cucurbitaceae, Rosaceae, Solanaceae, and Cyperaceae were the most known and used by local people. Three species namely Begonia meyeri-johannis, Carapa grandiflora and Rubus kulinganus were absolutely found inside the park, while other 13 species were absolutely collected in the vicinities of NNP. The remaining 18 species were found in both inside the park and in its vicinities. Leaves and young stems of wild edible plants are the most consumed by local people, especially during the periods of food scarcity. The research shows that local people have a good knowledge of wild edible plants and recommends sustainable measures for making the diversity of wild edible plants well known, used and conserved. Key words: Biodiversity, Conservation, Food insecurity, Sustainable use, Wild edible plant

Arundo donax L., a candidate for phytomanaging water and soils contaminated by trace elements and producing plant-based feedstock. A review

Plants and associated microorganisms are used to remediate anthropogenic metal(loid) contamination of water, soils and sediments. This review focuses on the potential of Arundo donax L. (Giant reed) for alleviating risks due to soils, water, and sediments contaminated by trace elements (TE), with emphasis on its advantages and limits over macrophytes and perennial grasses used for bioenergy and plant-based feedstock. Arundo donax is relevant to phytomanage TE-contaminated matrices, notably in its native area, as it possesses characteristics of large biomass production even under nutrient and abiotic stresses, fast growth rate, TE tolerance and accumulation mainly in belowground plant parts. Cultivating A. donax on contaminated lands and in constructed wetlands can contribute to increase land availability and limit the food vs. plant-based feedstock controversy. To gain more tools for decision-taking and sustainable management, further researches on A. donax should focus on: interactions between roots, TE exposure, and rhizosphere and endophytic microorganisms; biomass response to (a)biotic factors; sustainable agricultural practices on marginal and contaminated land; integration into local, efficient, energy and biomass conversion chains with concern to biomass quality and production; Life-Cycle Assessment including contaminant behavior, as well as environmental, agricultural and socio-economic benefits and drawbacks

Mapping spatio-temporal variations in water hyacinth (Eichhornia crassipes) coverage on Rwandan water bodies using multispectral imageries

The spatial and temporal knowledge on spread of invasive aquatic plants helps to determine their extent, abundance, and propagation rates in invaded water systems. Water hyacinth Eichhornia crassipes (Liliales: Pontederiaceae) appeared in Rwandan water bodies in 1957, and it was legislated and accepted as a problematic invasive species in Rwanda in 1999. Water hyacinth has led to a reduction in water quantity and threatened the livelihood of local communities that live off fishing. To comprehend the status of the water hyacinth invasion and assist management strategies, it is important to have detailed and consistent information on its spatio-temporal spread, magnitude, and rate of change dynamics in water systems. This was investigated using time series Landsat satellite images for the years 1989, 2002, and 2017. Image classifications using the nonparametric classifier random forest as well as change detection analysis were carried out to process the satellite data. The results revealed a fluctuation in the extent of water hyacinth over the time series of 1989, 2002, and 2017 with estimated percentage cover of 17.7%, 22.4%, and 20.8%, respectively. An annual increase of 1.9% in water hyacinth invasion was observed from 1989 to 2002; while, a decline of 1.7% per annum was observed from 2002 to 2017. The decline observed in 2017 could be due to manual control undertaken by the government since 2002. This study confirms the potential of using remotely sensed imagery as a valuable method for determining the change in the extent and distribution of invasive alien weeds over time

Mapping distribution of water hyacinth (Eichhornia crassipes) in Rwanda using multispectral remote sensing imagery

Water hyacinth, Eichhornia crassipes (C. Mart) Solms (Pontederiaceae), is an invasive aquatic macrophyte with major negative economic and ecological impacts in Rwanda and other East African countries since its establishment in the region in the 1960s. Reliable estimates of water hyacinth distribution are required to determine the severity of the problem and identify waterbodies requiring management. Remote sensing techniques, based on the Landsat 8 sensor, offer promising alternatives to accurately detect, map and monitor the extent of the water hyacinth invasion in Rwandan waterbodies. The aim of the current study was to investigate the utility of multispectral remote sensed imagery using Random Forest and Support Vector Machine algorithms to detect and map water hyacinth in Rwandan waterbodies. Random Forest had a high overall accuracy of 85%, compared with Support Vector Machine (65%). These algorithms confirmed different levels of water hyacinth infestations in three main Rwandan rivers. Many of the wetlands along these riparian systems and most of the lakes, particularly those from the Eastern Province of the country were found to be invaded by water hyacinth. These findings would, therefore, assist government partners and policy makers to put in place sustainable methods, such as biological control, along with integrated pest management, to control the of water hyacinth invasion in Rwanda

Trace element transfer from soil to leaves of macrophytes along the Jalle d’Eysines River, France and their potential use as contamination biomonitors

International audienc

Root biomass production in populations of six rooted macrophytes in response to Cu exposure: Intra-specific variability versus constitutive-like tolerance

Intra-specific variability of root biomass production (RP) of six rooted macrophytes, i.e. Juncus effusus, Phragmites australis, Schoenoplectus lacustris, Typha latifolia, Phalaris arundinacea, and Iris pseudacorus grown from clones, in response to Cu exposure was investigated. Root biomass production varied widely for all these macrophytes in control conditions (0.08 μM) according to the sampling site. Root biomass production of T. latifolia and I. pseudacorus in the 2.5–25 μM Cu range depended on the sampling location but not on the Cu dose in the growth medium. For P. australis, J. effusus, S. lacustris, and P. arundinacea, an intra-specific variability of RP depending on both the sampling location and the Cu-dose was evidenced. This intra-specific variability of RP depending on the sampling location and of Cu-tolerance for these last four species suggests that Cu constitutive tolerance for all rooted macrophytes is not a species-wide trait but it exhibits variability for some species