Estimating survival rates in ecological studies with small unbalanced sample sizes: an alternative Bayesian point estimator

Increasingly, the survival rates in experimental ecology are presented using odds ratios or log response ratios, but the use of ratio metrics has a problem when all the individuals have either died or survived in only one replicate. In the empirical ecological literature, the problem often has been ignored or circumvented by different, more or less ad hoc approaches. Here, it is argued that the best summary statistic for communicating ecological results of frequency data in studies with small unbalanced samples may be the mean of the posterior distribution of the survival rate. The developed approach may be particularly useful when effect size indexes, such as odds ratios, are needed to compare frequency data between treatments, sites or studies

Ecologie comparative des écosystèmes tropicaux (en Afrique)

After a short presentation of my career trajectory in academia, and of the PhD students and post-doctoral fellows I had the chance to supervise, I present a synthesis of the research work I conducted over the last decade on the comparative ecology of tropical ecosystems in Africa. This work is anchored into applied forest sciences and the data that were accumulated to answer practical questions also helped answer more fundamental questions in ecology. In my work, trees are used as the starting point in the understanding of tropical ecosystems, mostly moist forests but also drier formations, such as woodlands and savannas. With a background in community and functional ecology and a position in Gembloux Agro-Bio Tech, University of Liège, targeting tropical tree allometry and forest carbon, I derived two types of comparative approaches in my research activities, I compare either sites (trees or stands) or lineages (species or genera, mostly). For the site comparison, I used either the angle of tree architecture and stand structure or that of diversity and composition, at different spatial and temporal scales, from tree allometry and biomass estimates, up to the landscape scale for the structural approach, and from diversity recovery after logging, the delineation of forest types for management and up to biogeography studies, including cross-taxonomic and cross-continent comparisons for the diversity approach. For the lineage comparison, the concept of functional traits has been central and transversal since it allowed relating the structure and diversity approaches. It was however first adapted to tropical trees for which leaves are difficult to access, and size can vary tremendously over the tree life span and among tree life histories. Allometric or size-controlled traits were notably derived from tree measurements in the field and computed at a certain diameter to compare species of contrasted morphologies. Wood anatomical traits were also investigated and notably related to tree hydraulics. In this line, I finally propose a research project on tree and forest seasonal functioning, and response to drought. Tropical forests of central Africa are indeed found under drier and more seasonal climates than their south-eastern Asian and south American counterparts, and their resilience to climate (change) is a timely topic. These research perspectives will complement ongoing work on (i) the biogeography of Africa using species occurrence derived from herbarium records instead of checklists, (ii) carbon and biodiversity changes over the last decade by re-census a set of existing plots in the Congo basin, and on (iii) the seasonality in tree and forest functioning, using tree dendrometers and phenological cameras (PhenoCams) to monitor in depth how trees cope with the dry season. This project entitled CANOPI has been accepted for founding and offer the opportunity to collect unique ground-based measurements of tree and forest functioning in central Africa.15. Life on lan

Acacia auriculiformis production in the Mampu agroforestry zone on the Batéké plateau, Democratic Republic of Congo

peer reviewedThe Mampu agroforestry zone on the Batéké plateau in the Democratic Republic of Congo, which has been managed with Acacia auriculiformis shade trees for over twenty years by local communities, supplies subsistence products and fuel wood to Kinshasa. Thanks to international grant funding, this agroforestry system, which integrates traditional slashand- burn cultivation, has been replicated in many places across the RDC, but its performance has never been assessed. The aim of this study was to estimate Acacia auriculiformis production in terms of total biomass and usable biomass for charcoal (stems and branches more than 4 cm in diameter) as part of the agroforestry system. To do so, two local allometric equations for total and usable biomass were adjusted from destructive testing data. Using existing inventory data (n = 112 plots), we identified significant structural heterogeneity throughout the rotation period (8-10 years) but also among plots of the same age. Despite this heterogeneity, which may be accounted for by environmental conditions on site and/or by differences in the handling of plot management techniques, production is comparable to that observed at other sites, averaging 145 tonnes per hectare over 10 years. The Mampu agroforestry system has many advantages, including direct services creating rural employment and combined production of subsistence goods and charcoal, but also indirect services such as avoided deforestation and carbon sequestration. The system's sustainability and dissemination should nevertheless be discussed

Rap et politique

Discours identitaire, contestataire et revendicatif, le rap est profondément lié à la structuration sociale de la ville et aux rapports de domination qui lui sont propres. Les chansons des rappeurs témoignent d’une nouvelle énonciation politique construisant une place difficile dans la communauté des Français et un rapport particulier à la langue française.As an anti-establishment discourse based on identity and claims, rap is closely connected to the town’s social structuring and to the power struggle peculiar to urban life. Texts of hip-hop singers convey a new political enunciation resulting in an awkward place within the French community as well as a peculiar relationship with the French language.Discurso identitario, contestatario y revindicativo, el Rap está profundamente ligado a la estructuración social de la ciudad y a los aportes de dominación que le son específicos. Las canciones de los cantantes de Rap testimonian de una nueva enunciación política que constituye un espacio difícil en la comunidad de los Franceses y un relación particular con la lengua francesa

Patterns of tree species composition across tropical African forests and within central African moist forests: the need for adapted management and conservation strategies

Background: Differences in the distribution of biota across Africa have been described for well over 100 years. There is however little information on the forest types at a regional scale. In this study we aimed to identify large-scale variation in tree species composition across tropical Africa, and within central Africa, to detail the structure and functioning of moist forests. Methods: Distribution data were gathered for 1175 tree species in 455 samples from the literature scattered across tropical Africa, from Senegal to Mozambique, and including all types of tropical forests. The value of elevation and 19 climatic variables (BIOCLIM) were assigned to each sample. Management forest inventory data were assembled for 49,711 0.5-ha plots across central Africa, covering an area of more than six million hectares. Using ordinations, we determined the variations in species composition across tropical African forests and for central African moist forests we used both genus composition and forest structure. We defined floristic clusters and identified the characteristic species/genera at both levels of resolution. Results: We found floristic evidence for three main biogeographic regions across the tropical African forests, and described six floristic clusters with particular environmental conditions within these regions: Coastal and Upland for East Africa, Dry and Wet-Moist for West Africa, and Moist and Wet for Central Africa. Within the central African moist forests, we identified 7 forest types based on genus composition and forest structure. Most of these forests were composed of a mosaic of the structural derivatives of the Celtis (Ulmaceae) forest. Secondary Musanga (Moraceae) forest was located along roads and around main cities; mixed Manilkara (Sapotaceae) forest covers a huge area in the Sangha River Interval; and monodominant Gilbertiodendron (Fabaceae) forest was sparsely distributed along rivers. Conclusions: The forest types identified across tropical African forests and within central African moist forests call for adapted management and conservation strategies. Specifically, the old-growth secondary Celtis forests that cover huge areas in central Africa should be managed for future timber productions, possibly complemented by artificial regeneration while the very specific and low productive Manilkara forests should be carefully managed with lower intensity practices. (Texte intégral