Dans la zone de Botambi, au sud de Bangui, en République centrafricaine, la déforestation liée à l’agriculture itinérante sur brûlis entraîne la disparition de la forêt dense humide semi-décidue au profit des jachères envahies par des arbustes exotiques et des savanes herbeuses, poussant les agriculteurs à défricher de nouvelles forêts. La technique de la Régénération Naturelle Assistée (RNA) a été expérimentée dans un paysage forestier dégradé (village de Botéké) et peu dégradé (Salanga). Sur les parcelles RNA, les agriculteurs ont sélectionné et gardé des jeunes arbres utiles dans leurs champs lors des sarclages des cultures entre 2019 et 2021, puis les parcelles ont été laissées en jachère. L’impact de la RNA sur la diversité floristique des jachères post-culturales a été étudié par l’analyse de la cinétique des paramètres de diversité (moment de la première action de RNA, et à 7, 13 et 24 mois après la RNA) et de l’impact sur la biomasse aérienne de la végétation arborée, mesuré par le diamètre quadratique moyen et la hauteur de Lorey à 5, 12, 29 et 53 mois après le brûlis. Dans chaque village, 11 parcelles avec RNA et 10 parcelles témoins sans RNA, d’une surface de 0,231 ha, défrichées et mises en culture au début de 2019, ont été suivies. À chaque inventaire, tous les arbres des parcelles ont été identifiés par leur nom botanique, leur hauteur et leur diamètre à hauteur de poitrine. Pour ce qui concerne la biodiversité, la fréquence relative des espèces ainsi que l’indice de diversité ont été calculés, puis la végétation de chaque parcelle a été classée en fonction de la fréquence des deux espèces dominantes. Enfin, toutes les parcelles appartenant aux mêmes faciès ont été regroupées pour aboutir à 9 « faciès parcellaires ». Pour toutes les parcelles, la diversité est plus élevée à Salanga (Shannon 2,41 et régularité 0,86) qu’à Botéké (Shannon 1,90 et régularité 0,78), et la RNA permet à la végétation d’évoluer très rapidement vers une certaine « stabilité ». À Botéké, la biomasse aérienne à 12 mois était proche de 0, mais à 53 mois, elle est restée à 0,3 t/ha pour les témoins, tandis que pour la RNA, elle a atteint 0,7 t/ha. À Salanga, à 53 mois, la biomasse des témoins était de 0,9 t/ha, tandis que celle du traitement RNA a atteint 3,2 t/ha. La RNA favorise donc une accumulation accélérée et significative de biomasse aérienne des jachères par rapport au témoin, en particulier dans des zones peu dégradées.

ABSTRACT Extensive deforestation and disturbance have reshaped forest landscapes in West Africa, including areas surrounding Taï National Park, the largest remaining block of Upper Guinean rainforest. Although many degraded areas are currently undergoing regeneration, the capacity of these secondary forests to recover their biodiversity attributes remains insufficiently assessed within this park. This study quantifies the multidimensional restoration of biodiversity across 125 secondary forest plots and 15 primary forest plots representing 14,731 inventoried individuals in four sectors of the park. Using a Bayesian modelling framework, we estimate recovery trajectories of Shannon diversity, floristic composition, functional traits (wood density, leaf mass per area, seed mass), and conservation-relevant species. The different biodiversity attributes recovered at contrasting rates. Diversity was restored more rapidly (λ = 0.06) than floristic composition (λ = 0.03), and these recovery varied according to environmental variables. Among these, the presence of remnant trees showed the highest median on diversity (0.53 ± 0.61) and floristic composition (0.37 ± 0.17), promoting the rapid recovery of both attributes, followed by prior land use, particularly cocoa farming which also positively influenced the recovery of alpha diversity (λ = 0.03) and floristic composition (λ = 0.02). Regarding functional traits, they displayed contrasting dynamics: specific leaf area and seed mass recovered rapidly along successional gradients, whereas wood density followed a more gradual recovery trajectory. From a conservation perspective, although the proportion of IUCN Red List species remained stable along the successional gradient, old-growth indicator species were significantly more abundant in primary forests. To ensure the long-term conservation of biodiversity, protecting both primary and regenerating forests is essential to preserve the ecological resilience of this park.

Aboveground carbon (AGC) fluxes from deforestation and subsequent regrowth in tropical moist forest (TMF) are increasingly well characterized, but carbon losses and gains following partial disturbance are uncertain. We synthesized 146 studies quantifying postdisturbance AGC changes relative to undisturbed forests across TMF. Immediate AGC losses (mean ± 1 SD; 2.5 ± 2.3 years after disturbance) following partial anthropogenic disturbances were greatest for forest fires (49 ± 26%), selective logging (34 ± 20%), and edge effects (31 ± 19%). Higher-frequency and -intensity disturbances significantly increased carbon loss. After 20 years of regeneration, AGC stock was higher in recovering degraded forests (41 to 117%) compared to secondary regrowth forests after complete deforestation (1 to 74%), indicating greater regeneration potential when forest structure is preserved. Our compiled database and associated meta-analysis improve accuracy and completeness for carbon inventory reporting and modeling. Substantial AGC losses and gains from distinct degradation and recovery processes are now better characterized, serving as an evidence base for policies to halt degradation and foster recovery for climate mitigation.

L’agroforesterie, souvent présentée comme solution à l’érosion de la biodiversité et aux chocs climatiques, échoue fréquemment lorsqu’elle repose sur des programmes massifs de plantation. Une autre approche, centrée sur la parcelle, valorise la complémentarité entre arbres rémanents, spontanés et plantés. Cette complémentarité renforce biodiversité, carbone, productivité et durabilité des cacaoyères.

Introduction Land degradation severely constrains livelihoods and ecosystem services across the Sahel. Restoration initiatives commonly combine soil and water conservation (SWC) structures with plantings of native woody species, yet outcomes remain highly variable.Objectives We quantified tree survival and aboveground biomass (AGB) across restored sites and tested how SWC structures, geomorphology, post-planting management, and planted-species diversity shape restoration performance and trade-offs between establishment and productivity.Methods We inventoried 2097 trees from six native species across 14 restored sites in three villages of the Tahoua region (Niger). AGB was estimated using allometric models. Drivers of survival and biomass were analyzed using Bayesian logistic and log-normal models, including SWC type, geomorphological unit, management regime, and species diversity.Results Survival and biomass were driven by distinct factors. Survival was primarily controlled by management: sites combining guarding, maintenance, and replanting showed the highest survival, whereas weakly managed or unmanaged sites had high mortality. Biomass was mainly determined by SWC structures: trenches, half-moons, and stone bunds increased biomass, with the strongest effects for trenches. Diversity increased biomass but not survival, and geomorphology played a secondary role. These contrasting responses reveal clear survival-biomass trade-offs.Conclusions Restoration outcomes in Sahelian drylands are structured by trade-offs between survival and biomass. Survival depends mainly on management, whereas biomass depends mainly on SWC structures that enhance resource availability.

Secondary forest succession following agricultural abandonment is a dominant land-use transition across the tropics, yet whether soil microbial communities recover toward old-growth forest reference states remains poorly understood, particularly in West Africa. Here, we investigated the successional dynamics of bacterial and arbuscular mycorrhizal (AM) fungal communities along post-agricultural chronosequences spanning 1 to 43 years across six classified forests in Cote d'Ivoire, using Bayesian hierarchical models applied to amplicon sequencing data. Both guilds attained moderate to high alpha diversity within the first decade of succession; AM fungal diversity showed moderate evidence of age-related increase thereafter while bacterial diversity showed no directional trend. Pairwise turnover analyses revealed progressive internal convergence in AM fungal communities with plots farther apart in successional time becoming more compositionally similar, while bacterial communities showed only a weak and uncertain tendency in the same direction. Beta-dispersion modelling further indicated progressive within-forest homogenisation of AM fungal communities across abundance-weighted metrics, while bacterial assemblages showed no such stabilisation. Despite this internal convergence, compositional distances to old-growth reference plots remained persistently high for both guilds throughout the chronosequence, with no statistical evidence of recovery toward old-growth states across any dissimilarity metric or guild within the 40-year window. Indicator species analysis identified no robust stage-specific taxa after correction for multiple testing. These results indicate that microbial succession in post-agricultural West African forests is characterised by rapid early reorganisation followed by stabilisation into site-specific assemblages that remain persistently distinct from old-growth reference communities. This outcome challenges the direct application of classical vegetation successional theory to soil microbiomes and suggests that passive regeneration alone is unlikely to restore old-growth microbial communities within restoration-relevant timescales.

Predicting which non-native plant species will become established and where is critical for conserving and managing biodiversity. Theory suggests that the mycorrhizal strategy of non-native plants may predict their establishment success. Here we combine a global dataset of 440,788 vegetation plots with data on plant native status and mycorrhizal type to assess mycorrhizal strategy of non-native plants. The mycorrhizal strategy of non-native plants varies strongly across biomes. Across grassland and desert biomes, non-native species are more frequently non-mycorrhizal than native species, whereas in other biomes non-native species are more likely to be mycorrhizal, most commonly arbuscular-mycorrhizal. Disturbance type and intensity are key predictors of mycorrhizal strategy of non-native species, as mycorrhizal species are favoured by landscape modification and non-mycorrhizal species by natural and human-caused disturbance events. Facultatively mycorrhizal species are consistently under-represented among non-native plants compared with natives, suggesting that symbiotic flexibility does not confer an advantage for non-natives as previously expected. Our study shows that non-native mycorrhizal strategy varies across biogeographical contexts and disturbance, highlighting the need for region-specific prevention and management approaches to plant species introductions.

Old-growth tropical forests store vast amounts of carbon in their aboveground biomass (AGB), yet the relative roles of abiotic factors such as climate, soil, and topography in governing its spatial distribution remain poorly understood. In particular, the degree to which climate acts on AGB through forest structure is still poorly quantified at the pantropical scale. Using a pantropical dataset of more than 2,000 old-growth forest plots and a structure-explicit framework, we assess how climate influences AGB through its effects on four structural attributes: basal area, mean diameter, stem density, and basal area-weighted wood density. We find that climate shapes AGB primarily through its effects on forest structure. However, structural attributes respond to climate in opposite directions, so climate’s net effect on AGB largely cancels out, and no clear climate-AGB relationship emerges across tropical regions. Moreover, only wood density responds consistently, decreasing with annual precipitation and increasing with precipitation seasonality, whereas all other attributes respond to climate differently from one region to another. This geographical variation further obscures any global climatic signal on AGB and points to the role of biogeographic history in shaping forest structure. Our findings highlight the central role of the climate-structure nexus in explaining AGB variation, and call for structure-explicit models to improve carbon stock predictions and inform climate adaptation strategies.

In the Sahel, land degradation caused by climate variability and unsustainable human activities has led to soil erosion, declining fertility, and worsening food insecurity. To address this, large-scale restoration initiatives incorporating soil and water conservation (SWC) techniques and drought-resistant tree species have been implemented. This study evaluated the growth of 1564 trees from six species (Acacia nilotica, Acacia raddiana, Senegalia senegal, Vachellia seyal, Bauhinia rufescens, and Ziziphus mauritiana) on rehabilitated lands, using a Bayesian growth model to assess the effects of SWC structures, management practices, and geomorphological conditions. Among the SWC techniques studied-half-moons, trenches, bench terraces, stone bunds, and trenchbund combinations-half-moons proved most effective in enhancing tree growth (+12 %). Pediments provided the best conditions for tree development, outperforming plateaus and slopes. The absence of site management (guarding, replanting, and maintenance of plants and structures) decreased growth (-9 %). Sustainable reforestation in the Sahel requires integrating scientific knowledge with local expertise, adaptive strategies, and community involvement. A holistic approach that prioritizes effective SWC structures, suitable planting sites, and continuous management is crucial for restoring degraded lands, strengthening ecosystem resilience, and ensuring long-term success.

Abstract. Global forest assessments assist climate policy development, ecosystem science, and conservation planning, yet they rely on biomass and canopy data that do not explicitly represent the stand structural attributes derived from tree diameter measurements. This limits the ability to compare size-related structure and within-stand heterogeneity at large spatial scales. Here we present a global, spatially explicit dataset of stand-level tree diameter structure for forest cover in 2020 at 0.027° (~3 km) resolution, based on 1,203,524 georeferenced forest inventory plots comprising 54.6 million trees (≥10 cm DBH) integrated with more than 50 environmental and satellite-derived covariates into machine learning models. The dataset provides the first globally consistent maps of three complementary diameter-based metrics: arithmetic mean diameter (Dmean), quadratic mean diameter (Dqm), and the coefficient of variation of diameter (Dcv), representing average tree size, large-tree dominance, and within-stand size variability, respectively. Model performance of the ecozone-specific Random Forest framework ranged from R² = 0.41–0.82 (RMSE = 3.91–4.63 cm) for Dmean, R² = 0.43–0.83 (RMSE = 4.38–5.27 cm) for Dqm, and R² = 0.47–0.62 with (RMSE = 0.10–0.13) for Dcv across different forest ecozones. By jointly quantifying central tendency and variability in tree size, the dataset revealed spatial patterns of forest structural organization not captured by existing biomass or canopy-height products. It provides a consistent baseline for cross-biome comparison of forest structure, supporting parameterization and evaluation of vegetation and Earth system models, while offering an independent benchmark for remotely sensed structural proxies. Furthermore, it enables spatial assessment of stand structural attributes, including large-tree dominance and structural complexity, facilitating integration of diameter-based structure into global analyses of carbon dynamics and ecosystem functioning.

Amazon rainforests face intensifying water stress due to increases in vapour pressure deficit and changing hydrological regimes. Embolism resistance (Ψ50) is a critical metric of tree survival under drought conditions, it is defined as a plant's capacity to resist disruption of xylem water flow due to air bubble formation from water stress. However, measurements of Ψ50 are only available for a limited number of Amazon locations and species. Conversely, data on forest taxonomic composition are abundant across Amazonia, and if Ψ50 is conserved phylogenetically, these data could provide a way to scale-up drought resistance patterns. Here we evaluate Ψ50 measurements across non-flooded Amazonian tree taxa and reveal a moderate phylogenetic signal, with phylogenetic conservatism evident at the family-level. Notably, Fabaceae is amongst the most embolism-resistant tree families in Amazonia. Leveraging the phylogenetic signal we use species composition and tree size data from 448 forest plots across Amazonia to produce a macroecological assessment of Amazonian vulnerability to embolism. The resulting estimate spatial pattern reveals that forests in the Brazilian and Guiana Shield regions, where Fabaceae abundance is high, show strong resistance to embolism. In contrast, tree communities in Western Amazonia appear more vulnerable to embolism, suggesting a reduced capacity to withstand future drought conditions.

Tree populations have declined substantially in West Africa in recent decades, raising concerns since trees provide numerous ecosystem goods and services. Regional information on the population status of tree species could guide more effective conservation and regeneration of natural vegetation. Here, we report results of the first regional analysis of tree population structure across the Sahel and Sudan zones, a meta-study of vegetation inventories, including 23,586 individual trees sampled across nine countries. We evaluated current status and forecast future trends of 16 species and one genus of trees of ecological and socio-economic importance. Size class distribution (SCD) reflects the population structure of an individual species and can provide early warning of composition change and population decline. SCD is analysed widely at a local scale, but analysis at a regional scale is needed to detect widespread population changes. Many native species lacked trees in the smaller size classes, implying unsustainable populations and future decline. Some species show sound regeneration at the regional scale, but high variation among sites. Eight species, including Adansonia digitata and Afzelia africana, show regional declines in regeneration and risks of future extirpations. Four of these severely lack regeneration. Protected areas show higher tree regeneration, but protected status did not assure good regeneration. Our results identify priority tree species across West Africa, indicate a more urgent need for conservation and regeneration of native tree species, and highlight the benefit of effective conservation. More widespread protection could increase tree populations, conserving biodiversity, and ecosystem services essential for people's livelihoods.

Tropical forest canopies are the biosphere's most concentrated atmospheric interface for carbon, water and energy1,2. However, in most Earth System Models, the diverse and heterogeneous tropical forest biome is represented as a largely uniform ecosystem with either a singular or a small number of fixed canopy ecophysiological properties3. This situation arises, in part, from a lack of understanding about how and why the functional properties of tropical forest canopies vary geographically4. Here, by combining field-collected data from more than 1,800 vegetation plots and tree traits with satellite remote-sensing, terrain, climate and soil data, we predict variation across 13 morphological, structural and chemical functional traits of trees, and use this to compute and map the functional diversity of tropical forests. Our findings reveal that the tropical Americas, Africa and Asia tend to occupy different portions of the total functional trait space available across tropical forests. Tropical American forests are predicted to have 40% greater functional richness than tropical African and Asian forests. Meanwhile, African forests have the highest functional divergence-32% and 7% higher than that of tropical American and Asian forests, respectively. An uncertainty analysis highlights priority regions for further data collection, which would refine and improve these maps. Our predictions represent a ground-based and remotely enabled global analysis of how and why the functional traits of tropical forest canopies vary across space.

Tropical forest restoration is a global priority, yet its success often hinges on seedling survival in degraded landscapes. In West Africa, large-scale restoration is challenged by limited knowledge of how survival drivers interact across diverse native species. This study dissects the "anatomy of survival" by evaluating how planting time, shade, and vegetation competition shape early performance across 21,609 seedlings from 16 native tree species in central C & ocirc;te d'Ivoire-a region marked by seasonal rainfall and widespread land degradation. A large-scale field experiment tested the effects of delayed planting, shade from intercropped banana, and competition from herbaceous cover, Panicum grasses, and the exotic tree Cedrela odorata. Seedling survival was monitored over the first growing season under operational planting conditions. Hierarchical Bayesian survival models were used to isolate species-specific responses to each factor while accounting for environmental variability. The analysis revealed a multidimensional structure to seedling survival. Early planting was generally beneficial, especially for slow-growing species. Banana shade consistently improved survival by buffering temperature and preserving soil moisture. Cedrela had strong negative effects on most species, underscoring its competitive dominance and incompatibility with native restoration. Herbaceous cover also reduced survival, though effects varied by species. Fromager, Kotib & eacute;, Ako, and Asan showed the highest survival probabilities across treatments. This breakdown of survival patterns provides a functional basis for restoration design. We propose species-specific guidelines emphasizing early planting, strategic shading, and targeted weeding. Yet given the complexity and cost of planting, assisted natural regeneration remains the preferred option where viable seed sources persist.

Different regions of the tropics vary in overall tree species diversity, with the tropical Americas exhibiting strikingly higher regional tree species richness than Africa and Southeast Asia. We investigated whether these differences also occur at the local scale and whether the environmental conditions associated with tree species richness are consistent across tropical regions despite highly dissimilar species pools. A spatial random forest model was trained by using a network of 429 1-hectare plots across the tropics, together with 24 environmental variables, to predict plot-level tree α diversity. A combination of climatic, soil and topographical variables explained ∼86% of the variation in richness. Despite differences in regional species pools and the potentially disruptive effects of different geological, climatic and evolutionary histories, the relationship between environmental variables and local-scale tree species richness is closely similar across different continents. Our findings imply a pervasive role of niche-based mechanisms in structuring local tree species richness, regardless of the regional species assemblages. This pantropical convergence in the richness-environment relationship poses a challenge for ecology to explain.

AimGlobal biodiversity loss resulting from anthropogenic land-use activities is a pressing concern, requiring precise assessments of impacts at large spatial extents. Existing models mainly focus on species richness and abundance, lacking insights into ecological mechanisms and species' roles in ecosystem functioning. To bridge this gap, we conducted an extensive analysis of the impact of human land use on vascular plant functional diversity across diverse land-use classes and bioregions in Europe, comparing it to traditional metrics.LocationEurope.Time Period1992-2019.Major Taxa StudiedVascular plants.MethodsIntegrating extensive databases of vegetation plots with spatial data on land use and land cover, we paired plots from areas actively used and modified by humans with plots from natural habitats under similar environmental conditions. Using species occurrences and traits, in each plot we computed three complementary functional diversity metrics (functional richness, evenness and divergence), species richness and abundance. We assessed the impact of land use by comparing the metrics in the paired plots.ResultsOur findings revealed that, compared to natural habitats, anthropogenic land use exhibits lower functional richness and divergence but higher functional evenness across most land-use classes and bioregions. The response of functional richness was more marked than the other two metrics and especially pronounced in croplands and urban areas and in northern bioregions. Functional richness exhibited a pattern that did not fully overlap with the trend in species richness, providing useful complementary information.Main ConclusionsWe provide a large-scale precise assessment of anthropogenic land-use impacts on functional diversity across Europe. Our findings indicate that: (i) human disturbance significantly alters plant functional diversity compared to natural habitats; (ii) this alteration goes in the direction of functional homogenisation within sites; (iii) functional diversity metrics complement traditional metrics by offering deeper insights into the ecological mechanisms in response to anthropogenic land use.

Cocoa cultivation in West Africa has been a major driver of deforestation, leading to increased greenhouse gas emissions and threatening cocoa yields. Agroforestry, which integrates trees from various origins-remnant, spontaneous, and planted-presents a sustainable solution to enhance carbon sequestration and improve farm resilience. However, the specific contributions of these tree origins and the socio-environmental factors shaping their effectiveness remain poorly understood. This study examines carbon dynamics across 150 cocoa fields in Côte d'Ivoire, analyzing a total of 11,568 trees across 15 sites. Using Bayesian modeling, we assess carbon stocks and gains from tree growth to explore how socio-environmental factors influence carbon balance in cocoa fields. Carbon stocks varied widely with remnant having the highest median carbon stocks (6.33 Mg/ha), followed by spontaneous (2.06 Mg/ha) and planted trees (1.53 Mg/ha). Carbon gains are similar for planted and spontaneous trees up to 7 years, but afterward, spontaneous trees grow faster (11.20 ± 0.87 kg/year) than planted ones (3.96 ± 0.5 kg/year). Carbon stocks rose with informed farmers and former forest use, but declined with higher cocoa density. Carbon gains at the tree level is primarily influenced by ownership and previous forest land use with positive effects, while cocoa density and annual temperature have negative effects. To maximize carbon sequestration and ensure the sustainable management of agroforestry systems, interventions should prioritize securing land tenure, enhancing farmer training in tree botany, and promoting the conservation of remnant and spontaneous trees.

Tropical secondary forests play a key role in restoring biodiversity and biomass, yet their recovery dynamics remain poorly understood in West Africa, even within protected areas. In Taï National Park, one of the region’s last major rainforests, we modelled forest recovery trajectories in the past agricultural areas to better understand and support effective conservation strategies. We inventoried 118 plots spanning old-growth undisturbed, old-growth disturbed, and secondary forests. Four structural attributes (aboveground biomass, Lorey’s height, quadratic mean diameter, and structural homogeneity) were modelled using a Bayesian framework. We assessed the influence of past land use, disturbance, and environmental factors on recovery rates. Structural attributes recovered at markedly different rates. Structural homogeneity and mean diameter recovered fastest (∼20–30 years), followed by height (∼30–40 years), while biomass required over a century for near-complete recovery. Recovery was strongly enhanced by the presence of remnant trees and forest connectivity, especially for biomass. In contrast, Marantaceae presence, hydromorphic soils, anthropogenic disturbance, and herbivory slowed recovery. Former cocoa fields showed the highest recovery rates across all attributes, while former gold mining sites exhibited extremely slow regeneration due to severe soil degradation. Our results suggest that forest recovery around Taï National Park will be highly heterogeneous. Cocoa fields with remnant trees offer strong potential for rapid passive recovery, while mined areas may need active restoration. Protecting remnant trees and managing disturbances will be crucial. Overall, passive regeneration holds significant promise, but realistic expectations and adaptive management are essential to support long-term forest resilience in this landscape.