Caractérisation de la Biomasse sèche des mosaïques forêt-savane des plateaux Okouma et Bagombé au sud-est du Gabon

Objectif : Quantifier la biomasse sèche de savanes et du sous-bois en forêts dans la mosaïques forêtsavane au Sud-est du Gabon (Okouma et Bagombé).Méthodologie et résultats : La méthode destructive a été utilisée pour l’acquisition des données. En effet, elle a consisté à identifier, mesurer l’aide d’un pied à coulisse et peser les différents arbustes dans une parcelle de 25m2.Pour les arbustes dont les diamètres sont compris entre 1 et 5cm, ont été sectionnés, mesurés et pesés .Les aliquotes prélevés sur chaque échantillon ont permis d’estimer la biomasse en laboratoire .Ainsi, l’analyse statistique réalisée sur ces données a montré que la productivité moyenne de biomasse sèche est beaucoup plus importante en savane (35466760kg/ha) qu’en sous-bois (3442996kg/ha). Par ailleurs, la comparaison statistique «ANNOVA» entre la biomasse sèche produite dans les différents biotopes anthropisés montre que la productivité moyenne de biomasse sèche n’est pas différente d’un biotope à un autre, et afin une estimation des gains perçus par la vente des stockes de carbone dans le cadre du programme REDD a été simulée sur une aire de 3700haConclusion and application : Ce travail a permis de quantifier les stocks de carbone en savane et dans les sous-bois des mosaïque-forêt-savane. Ces travaux sont également d’intérêt capital pour les gouvernants à la fois dans la mise en oeuvre des politiques de réductions des émissions des gaz à effet des serres et d’un impact économique notamment dans le cadre du programme REDD.Mots clés: Carbone, Biomasse sèche, Gabon, savanes, forêt, changement climatiqu

Long-Term Vegetation Change in Central Africa: The Need for an Integrated Management Framework for Forests and Savannas

peer reviewedTropical forests and savannas are the main biomes in sub-Saharan Africa, covering most of the continent. Collectively they offer important habitat for biodiversity and provide multiple ecosystem services. Considering their global importance and the multiple sustainability challenges they face in the era of the Anthropocene, this chapter undertakes a comprehensive analysis of the past, present, and future vegetation patterns in central African forests and savannas. Past changes in climate, vegetation, land use, and human activity have affected the distribution of forests and savannas across central Africa. Currently, forests form a continuous block across the wet and moist areas of central Africa, and are characterized by high tree cover (>90% tree cover). Savannas and woodlands have lower tree cover (<40% tree cover), are found in drier sites in the north and south of the region, and are maintained by frequent fires. Recent tree cover loss (2000–2015) has been more important for forests than for savannas, which, however, reportedly experienced woody encroachment. Future cropland expansion is expected to have a strong impact on savannas, while the extent of climatic impacts depends on the actual scenario. We finally identify some of the policy implications for restoring ecosystems, expanding protected areas, and designing sustainable ecosystem management approaches in the region

Native diversity buffers against severity of non-native tree invasions.

This is the final version. Available from Nature Research via the DOI in this record. Data availability: Data used in this study can be found in cited references for the Global Naturalized Alien Flora (GloNAF) database6 (non-native status), the KEW Plants of the World database5 (native ranges) and the Global Environmental Composite63,77 (environmental data layers). Plant trait data were extracted from Maynard et al.78. Data from the Global Forest Biodiversity Initiative (GFBI) database57 are not available due to data privacy and sharing restrictions, but can be obtained upon request via Science-I (https://science-i.org/) or GFBI (gfbinitiative.org) and an approval from data contributors.Code availability All code used to complete analyses for the manuscript is available at the following link: https://github.com/thomaslauber/Global-Tree-Invasion. Data analyses were conducted and were visualizations generated in R (v. 4.2.2), Python (v. 3.9.7), Google Earth Engine (earthengine-api 0.1.306), QGIS-LTR (v. 3.16.7) and the ETH Zurich Euler cluster.Determining the drivers of non-native plant invasions is critical for managing native ecosystems and limiting the spread of invasive species1,2. Tree invasions in particular have been relatively overlooked, even though they have the potential to transform ecosystems and economies3,4. Here, leveraging global tree databases5-7, we explore how the phylogenetic and functional diversity of native tree communities, human pressure and the environment influence the establishment of non-native tree species and the subsequent invasion severity. We find that anthropogenic factors are key to predicting whether a location is invaded, but that invasion severity is underpinned by native diversity, with higher diversity predicting lower invasion severity. Temperature and precipitation emerge as strong predictors of invasion strategy, with non-native species invading successfully when they are similar to the native community in cold or dry extremes. Yet, despite the influence of these ecological forces in determining invasion strategy, we find evidence that these patterns can be obscured by human activity, with lower ecological signal in areas with higher proximity to shipping ports. Our global perspective of non-native tree invasion highlights that human drivers influence non-native tree presence, and that native phylogenetic and functional diversity have a critical role in the establishment and spread of subsequent invasions.Swiss National Science FoundationSwiss National Science FoundationBernina FoundationDOB Ecolog

The global biogeography of tree leaf form and habit

This is the final version. Available on open access from Nature Research via the DOI in this recordData availability: Tree occurrence data from the Global Forest Biodiversity initiative (GFBi) is available upon request via Science-I (https://science-i.org) or the GFBi website (https://www.gfbiinitiative.org/). Information on leaf habit (evergreen vs deciduous) and leaf form (broadleaved vs needle-leaved) came from the TRY database (https://www.try-db.org). Additional, leaf-type data came from the Tallo dataset (https://zenodo.org/record/6637599). Plot-level soil information came from the World Soil Information Service (WOSIS) dataset (https://www.isric.org/explore/wosis).Code availability: All code is available at https://doi.org/10.5281/zenodo.7967245.Understanding what controls global leaf type variation in trees is crucial for comprehending their role in terrestrial ecosystems, including carbon, water and nutrient dynamics. Yet our understanding of the factors influencing forest leaf types remains incomplete, leaving us uncertain about the global proportions of needle-leaved, broadleaved, evergreen and deciduous trees. To address these gaps, we conducted a global, ground-sourced assessment of forest leaf-type variation by integrating forest inventory data with comprehensive leaf form (broadleaf vs needle-leaf) and habit (evergreen vs deciduous) records. We found that global variation in leaf habit is primarily driven by isothermality and soil characteristics, while leaf form is predominantly driven by temperature. Given these relationships, we estimate that 38% of global tree individuals are needle-leaved evergreen, 29% are broadleaved evergreen, 27% are broadleaved deciduous and 5% are needle-leaved deciduous. The aboveground biomass distribution among these tree types is approximately 21% (126.4 Gt), 54% (335.7 Gt), 22% (136.2 Gt) and 3% (18.7 Gt), respectively. We further project that, depending on future emissions pathways, 17-34% of forested areas will experience climate conditions by the end of the century that currently support a different forest type, highlighting the intensification of climatic stress on existing forests. By quantifying the distribution of tree leaf types and their corresponding biomass, and identifying regions where climate change will exert greatest pressure on current leaf types, our results can help improve predictions of future terrestrial ecosystem functioning and carbon cycling

Les Loranthaceae : un atout pour l’essor de la pharmacopée traditionnelle au Cameroun

La famille des Loranthaceae est largement distribuée dans les zones tropicales en Afrique, Amérique, Asie, Australie et s’étend en zones tempérées. Les Loranthaceae appartiennent à l’ordre des Santalales. Danscette famille sont reconnus 950 espèces et 77 genres. Au Cameroun 26 espèces distribuées dans 7 genres sont citées. L’objectif de ce travail est d’évaluer, l’impact des Loranthaceae dans la pharmacopée traditionnelle des paysans. A travers un questionnaire sémi-structuré, 150 tradipraticiens en activité ont été interviewés en 2008 à Logbessou (quartier périphérique de la ville de Douala). Les réponses de l’enquête mise sur pied révèlent des informations selon lesquelles, les Loranthaceae sont des plantes parasites connues pour les dégâts considérables, occasionnés sur les essences ligneuses sauvages ou cultivées. Cependant, leur intérêt pour lapharmacopée traditionnelle est attesté. Les Loranthaceae fortifient le métabolisme et se présentent comme une panacée. Toutefois, l’ingestion des pseudobaies provoque des vomissements, de l’hypotension et des troubles nerveux. Les parties du végétal utilisées dans le traitement sont les feuilles, les rameaux et la tige sous forme d’extraits aqueux. Les allergies sévères sont rares. Le mode d’action des extraits aqueux des Loranthaceae européennes aux niveaux cellulaire et moléculaire est discuté. Keywords: Loranthaceae, plantes parasites, dégâts, pharmacopée traditionnelle

Author Correction: Native diversity buffers against severity of non-native tree invasions.

Correction to: Nature Published online 23 August 2023 In the version of the article initially published, Stanislaw Miscicki’s name incorrectly appeared as Miscicki Stanislaw. Additionally, the affiliation for Thomas T. Ibanez has been updated to “AMAP, University of Montpellier, CIRAD, CNRS, INRAE, IRD, Montpellier, France”, and the second affiliation for Sharif A. Mukul has been updated to “Department of Environment and Development Studies, United International University, Dhaka, Bangladesh”. The corrections have been made to the HTML and PDF versions of the article

Integrated global assessment of the natural forest carbon potential.

Forests are a substantial terrestrial carbon sink, but anthropogenic changes in land use and climate have considerably reduced the scale of this system1. Remote-sensing estimates to quantify carbon losses from global forests2-5 are characterized by considerable uncertainty and we lack a comprehensive ground-sourced evaluation to benchmark these estimates. Here we combine several ground-sourced6 and satellite-derived approaches2,7,8 to evaluate the scale of the global forest carbon potential outside agricultural and urban lands. Despite regional variation, the predictions demonstrated remarkable consistency at a global scale, with only a 12% difference between the ground-sourced and satellite-derived estimates. At present, global forest carbon storage is markedly under the natural potential, with a total deficit of 226 Gt (model range = 151-363 Gt) in areas with low human footprint. Most (61%, 139 Gt C) of this potential is in areas with existing forests, in which ecosystem protection can allow forests to recover to maturity. The remaining 39% (87 Gt C) of potential lies in regions in which forests have been removed or fragmented. Although forests cannot be a substitute for emissions reductions, our results support the idea2,3,9 that the conservation, restoration and sustainable management of diverse forests offer valuable contributions to meeting global climate and biodiversity targets