Influence des activités anthropiques sur la diversité floristique des communautés végétales de la forêt marécageuse de Lokoli au Sud-Bénin

La forêt marécageuse de Lokoli est située à Zogbodomey au Sud-Bénin et ses Produits Forestiers Non Ligneux (PFNL) constituent des sources de revenus pour les populations riveraines. L’objectif de l'étude est dedéterminer l'influence de l'exploitation des PFNL sur les communautés végétales. Sur la base de relevés phytosociologiques et des enquêtes ethnobotaniques, une étude comparative a été faite sur la diversitéfloristique de sept communautés végétales identifiés et des PFNL prélevés. Les résultats ont montré que la richesse spécifique était comprise entre 50 espèces au niveau de la forêt primaire inondée à Alstonia congensiset Xylopia rubescens et 131 espèces au niveau de la prairie marécageuse à Rhynchospora corymbosa et Ludwigia abyssinica. La richesse spécifique était liée au degré d’hydromorphie des sols et à l’intensité de la pression anthropique sur les communautés végétales. D’après nos résultats, au lieu d’une évolution régulière, la diversité spécifique a connu une baisse du nombre d’espèce au niveau de 2 communautés végétales, la raphialeà Raphia hookeri et Anthocleista vogelii et la savane marécageuse à Ficus asperifolia et Paullinia pinnata. Une gestion plus rationnelle du prélèvement des PFNL par les exploitants doit permettre un développement durable de la forêt marécageuse de Lokoli.Mots clés: Produit forestier non ligneux, exploitation durable, richesse floristique, Zogbodomey, Sud-Bénin

Pentaclethra macrophylla Benth. dans la forêt communautaire de Payo (Est- Cameroun): inventaire, productivité et commercialisation

Cette etude a ete conduite a l'Est du Cameroun, dans la foret   communautaire de Payo. Elle a pour objet d'evaluer l'importance   ecologique, productive et socioeconomique de P. macrophylla. Le dispositif d'inventaire est constitue de quatre transects de 40 m x 2000 m2 (8 ha chacun) avec un taux de sondage de 2%. Toutes les tiges de diametre a hauteur de poitrine .10 cm ont ete marquees, georeferencees, comptees et leur diametre mesures a la hauteur 1,30 cm. Les observations et entretiens, ainsi que le suivi de la filiere de commercialisation ont ete realises a Payo puis dans la ville de Lomie. L'espece est abondante dans les forets secondaires jeunes avec une densite de 6 tiges/ha. Le diametre moyen et la surface terriere des tiges recencees sont respectivement  estimes a 56,91 ± 14 cm et 19,46 m2/ha. Lfindice de regeneration   naturelle est evalue a 4,8 et influence par lfintensite lumineuse qui   parvient dans le sous bois. La production de 35 arbres pour une saison de fructification est estimee a 5 157 graines soit en moyenne 147,34  graines/arbre. La production annuelle est estimee a 1 261 255 graines  equivalant a 11 571 combo (unite de mesure locale). La valeur marchande de ces graines est estimee a 5 785 572 Frs CFA (11836 $US).   Lfexploitation des graines de P. macrophylla represente ainsi de bonnes perspectives de revenus pour cette localite.Mots cles : Production, commercialisation, Pentaclethra macrophylla, foret communautaire

Vascular flora inventory and plant diversity of the Ruvubu National Park, Burundi

peer reviewe

Analyse de la distribution spatiale des Acanthaceae en Afrique Centrale et comparaison avec les théories phytogéographiques de Robyns, White et Ndjele.

Cette étude a pour but d\'analyser les modèles de distribution spatiale des Acanthaceae, récoltées en République Démocratique du Congo, au Rwanda et au Burundi et de comparer leur répartition spatiale avec les systèmes phytogéographiques qui couvrent cette zone. Elle porte sur 9181 échantillons regroupés en 48 genres et 310 espèces. Un système d\'information géographique a été utilisé pour réaliser des cartes de distribution de chaque espèce. La méthode multi variée de classification, appuyée par deux indices de structure spatiale (équitabilité et fragmentation) a permis de stratifier la zone d\'étude afin de permettre une comparaison visuelle avec les systèmes phytogéographiques définis par Robyns, White et Ndjele. On note une large distribution spatiale pour certaines espèces sur l\'ensemble du territoire, alors que d\'autres sont inféodées à certains territoires phytogéographiques bien déterminés. Les savanes situées au Sud de l\'équateur contiennent des sites plus riches en Acanthaceae que celles situées au Nord. Les centres d\'endémisme Guinéo-Congolais, Zambézien et Afromontagnard pourraient être les sources de migration des taxons. Les Acanthaceae suivent relativement bien le système phytogéographique de White et sont utilisables en tant que bioindicatrices afin de rapprocher la distribution spatiale des communautés végétales décrites par ce système.By means of 9181 samples representing 48 genus and 310 species, the spatial distribution models of the Acanthaceae family in Central Africa (Democratic Republic of Congo, Rwanda and Burundi) were analysed. Consequently, a comparison to existing phytogeographic systems for the study region was executed. Spatial distribution maps for each species were created using a geographic information system. Subdivision of the study area was realised using a multivariate classification analysis. Using two indices of spatial pattern (fragmentation, class size evenness), the classification result was compared to the phytogeographic zones defined by Robyns, White and Ndjele. While certain species showed a distribution throughout the study area, the presence of other species was found to be bound to one single phytogeographic territory in particular, or to a restricted number of them. The savannas situated in the southern part of the study area contained more Acanthaceae species than the zones situated north of the equator. The Guineo-Congolian, the Zambezian and the Afromontane centre of endemism are suggested to be the origins of taxon migration. Since it was observed that the spatial pattern of the Acanthaceae species corresponded up a certain extent to the phytogeographic system proposed by White, it can be concluded that the Acanthaceae could be used as bio-indicators to proxy the spatial distribution of plant communities as described by this system. Keywords: phytogeography, spatial analysis, Acanthaceae, Central Africa, district, sector.Sciences & Nature Vol. 5 (2) 2008: pp. 101-11

Détermination des zones potentielles de conservation de la biodiversité : un aperçu sur l’approche méthodologique basée sur la diversité spécifique et les espèces endémiques

peer reviewe

Radial Distribution of the Dust Comae of Comets 45P/Honda–Mrkos–Pajdusáková and 46P/Wirtanen

There was an unprecedented opportunity to study the inner dust coma environments, where the dust and gas are not entirely decoupled, of comets 45P/Honda–Mrkos–Pajdusáková (45P/HMP) from 2016 December 26 to 2017 March 15, and 46P/Wirtanen from 2018 November 10 to 2019 February 13, both in visible wavelengths. The radial profile slopes of these comets were measured in the R and HB-BC filters most representative of dust, and deviations from a radially expanding coma were identified as significant. The azimuthally averaged radial profile slope of comet 45P/HMP gradually changes from −1.81 ± 0.20 at 5.24 days preperihelion to −0.35 ± 0.16 at 74.41 days postperihelion. Contrastingly, the radial profile slope of 46P/Wirtanen stays fairly constant over the observed time period at −1.05 ± 0.05. Additionally, we find that the radial profile of 46P/Wirtanen is azimuthally dependent on the sky-plane-projected solar position angle, while that of 45P/HMP is not. These results suggest that comets 45P/HMP and 46P/Wirtanen have vastly different coma dust environments and that their dust expansion properties are distinct. As evident from these two comets, well-resolved inner comae are vital for detailed characterization of dust environments. © 2022. The Author(s). Published by the American Astronomical Society.We would like to thank everyone who participated in the data-gathering process. This includes all students from the Lunar and Planetary Laboratory course PTYS 495B/595B (Fall 2018). We would also like to thank the additional organizers of the 4*P Campaign: Matthew Knight (United States Naval Academy) and Tony Farnham (University of Maryland). We would like the thank the Steward Observatory technical staff for the amount of time they dedicated to this project. Finally, we would like to thank the SSO grant No. NNX16A670G (Walt Harris) and the NESSF grant No. 80NSSC18K1241 (Cassandra Lejoly; P.I.: Walt Harris) for allowing this work to be completed. We would also like to thank the Slovak Academy of Sciences grant No. VEGA 2/ 0023/18 (Oleksandra Ivanova) and the Slovak Research and Development Agency under the Contract no. APVV-19-0072 (Oleksandra Ivanova)

The Sloan Digital Sky Survey Reverberation Mapping project : key results

Funding: Y.S. acknowledges support from NSF grants AST-1715579 and AST-2009947. C.J.G. acknowledges support from NSF grants AST-2009949 and AST-2108667. J.I.L. is supported by the Eric and Wendy Schmidt AI in Science Postdoctoral Fellowship, a Schmidt Futures program. Y.H. was supported as an Eberly Research Fellow by the Eberly College of Science at the Pennsylvania State University. J.R.T. acknowledges support from NSF grants CAREER-1945546, AST-2009539, and AST-2108668. W.N.B. acknowledges support from NSF grant AST-2106990 and the Eberly Endowment at Penn State. L.C.H. was supported by the National Science Foundation of China (11721303, 11991052, 12011540375, 12233001) and the China Manned Space Project (CMS-CSST-2021-A04, CMS-CSST-2021-A06). C.T. acknowledges Tsinghua University for the support to her work.We present the final data from the Sloan Digital Sky Survey (SDSS) Reverberation Mapping (RM) project, a precursor to the SDSS-V Black Hole Mapper RM program. This data set includes 11 yr photometric and 7 yr spectroscopic light curves for 849 broad-line quasars over a redshift range of 0.1 < z < 4.5 and a luminosity range of Lbol = 1044−47.5 erg s−1, along with spectral and variability measurements. We report 23, 81, 125, and 110 RM lags (relative to optical continuum variability) for broad Hα, Hβ, Mg ii, and C iv using the SDSS-RM sample, spanning much of the luminosity and redshift ranges of the sample. Using 30 low-redshift RM active galactic nuclei with dynamical-modeling black hole masses, we derive a new estimate of the average virial factor of ⟨logf⟩ = 0.62±0.07 for the line dispersion measured from the rms spectrum. The intrinsic scatter of individual virial factors is 0.31 ± 0.07 dex, indicating a factor of 2 systematic uncertainty in RM black hole masses. Our lag measurements reveal significant R–L relations for Hβ and Mg ii at high redshift, consistent with the latest measurements based on heterogeneous samples. While we are unable to robustly constrain the slope of the R–L relation for C iv given the limited dynamic range in luminosity, we found substantially larger scatter in C iv lags at fixed L1350. Using the SDSS-RM lag sample, we derive improved single-epoch (SE) mass recipes for Hβ, Mg ii, and C iv, which are consistent with their respective RM masses as well as between the SE recipes from two different lines, over the luminosity range probed by our sample. The new Hβ and Mg ii recipes are approximately unbiased estimators at given RM masses, but there are systematic biases in the C iv recipe. The intrinsic scatter of SE masses around RM masses is ∼0.45 dex for Hβ and Mg ii, increasing to ∼0.58 dex for C iv.Peer reviewe

The Sloan Digital Sky Survey Reverberation Mapping Project: Key Results

We present the final data from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project, a precursor to the SDSS-V Black Hole Mapper Reverberation Mapping program. This data set includes 11-year photometric and 7-year spectroscopic light curves for 849 broad-line quasars over a redshift range of 0.1<z<4.5 and a luminosity range of Lbol=1E44-47.5 erg/s, along with spectral and variability measurements. We report 23, 81, 125, and 110 reverberation mapping lags (relative to optical continuum variability) for broad Halpha, Hbeta, MgII and CIV using the SDSS-RM sample, spanning much of the luminosity and redshift ranges of the sample. Using 30 low-redshift RM AGNs with dynamical-modeling black hole masses, we derive a new estimate of the average virial factor of =0.62+-0.07 for the line dispersion measured from the RMS spectrum. The intrinsic scatter of individual virial factors is 0.31+-0.07 dex, indicating a factor of two systematic uncertainty in RM black hole masses. Our lag measurements reveal significant R-L relations for Hbeta and MgII at high redshift, consistent with the latest measurements based on heterogeneous samples. While we are unable to robustly constrain the slope of the R-L relation for CIV given the limited dynamical range in luminosity, we found substantially larger scatter in CIV lags at fixed L1350. Using the SDSS-RM lag sample, we derive improved single-epoch (SE) mass recipes for Hbeta, MgII and CIV, which are consistent with their respective RM masses as well as between the SE recipes from two different lines, over the luminosity range probed by our sample. The new Hbeta and MgII recipes are approximately unbiased estimators at given RM masses, but there are systematic biases in the CIV recipe. The intrinsic scatter of SE masses around RM masses is ~0.45 dex for Hbeta and MgII, increasing to ~0.58 dex for CIV.Comment: 33 pages. Data products available at ftp://quasar.astro.illinois.edu/public/sdssrm/final_result