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Accurately monitoring tropical forest carbon stocks is an outstanding challenge. Allometric models that consider tree diameter, height and wood density as predictors are currently used in most tropical forest carbon studies. In particular, a pantropical biomass model has been widely used for approximately a decade, and its most recent version will certainly constitute a reference in the coming years. However, this reference model shows a systematic bias for the largest trees. Because large trees are key drivers of forest carbon stocks and dynamics, understanding the origin and the consequences of this bias is of utmost concern. In this study, we compiled a unique tree mass dataset on 673 trees measured in five tropical countries (101 trees > 100 cm in diameter) and an original dataset of 130 forest plots (1 ha) from central Africa to quantify the error of biomass allometric models at the individual and plot levels when explicitly accounting or not accounting for crown mass variations. We first showed that the proportion of crown to total tree aboveground biomass is highly variable among trees, ranging from 3 to 88%. This proportion was constant on average for trees < 10 Mg (mean of 34%) but, above this threshold, increased sharply with tree mass and exceeded 50% on average for trees = 45 Mg. This increase coincided with a progressive deviation between the pantropical biomass model estimations and actual tree mass. Accounting for a crown mass proxy in a newly developed model consistently removed the bias observed for large trees (> 1 Mg) and reduced the range of plot-level error from -23-16 to 0-10%. The disproportionally higher allocation of large trees to crown mass may thus explain the bias observed recently in the reference pantropical model. This bias leads to far-from-negligible, but often overlooked, systematic errors at the plot level and may be easily corrected by accounting for a crown mass proxy for the largest trees in a stand, thus suggesting that the accuracy of forest carbon estimates can be significantly improved at a minimal cost. [ABSTRACT FROM AUTHOR]

Accurate mapping and monitoring of tropical forests aboveground biomass (AGB) is crucial to design effective carbon emission reduction strategies and improving our understanding of Earth's carbon cycle. However, existing large-scale maps of tropical forest AGB generated through combinations of Earth Observation (EO) and forest inventory data show markedly divergent estimates, even after accounting for reported uncertainties. To address this, a network of high-quality reference data is needed to calibrate and validate mapping algorithms. This study aims to generate reference AGB datasets using field inventory plots and airborne LiDAR data for eight sites in Central Africa and five sites in South Asia, two regions largely underrepresented in global reference AGB datasets. The study provides access to these reference AGB maps, including uncertainty maps, at 100 m and 40 m spatial resolutions covering a total LiDAR footprint of 1,11,650 ha [ranging from 150 to 40,000 ha at site level]. These maps serve as calibration/validation datasets to improve the accuracy and reliability of AGB mapping for current and upcoming EO missions (viz., GEDI, BIOMASS, and NISAR)., (© 2024. The Author(s).)

Trees structure the Earth's most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations 1-6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth's 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories 7 , we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world's most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees., (© 2024. The Author(s).)

Introduction: In recent decades, Madagascar has become one of the most important plant hotspots in the world. The country's remaining forests and vegetation are disappearing at an alarming rate, while dozens of new species are discovered each year. Amongst the plant families that have long been studied, Orchidaceae appear as one of the most charismatic, diverse and of high conservation concern. Based on a reviewed, comprehensive herbarium dataset, we have compiled a curated checklist of all orchid species occurring in Madagascar. Based on this complete dataset, we then compiled sampling effort, species diversity distribution and some general statistics on their ecology and IUCN conservation status., Methods: We compiled and standardised a global dataset using five public databases as the main data sources, supplemented by the most recent publications. The database contains ~ 10,000 geolocated records collected between 1816 and 2021. We used GIS software and rarefaction methods to examine sampling and diversity patterns., Results: According to our dataset, there are currently 913 orchid species collected in Madagascar, of which 759 orchid species (83.1%) are endemic. Doubling the sampling effort could lead to the discovery of around 100 more species, bringing the total estimated number of orchid species in Madagascar to between 986 and 1048. About one-third (297 species) of all orchid species are known only by type specimens (189 species) or have not been collected in Madagascar for more than 50 years (214 species). Although the raw data show that the Andasibe-Moramanga area would have the highest orchid species concentration, our analysis of the data, adjusted for bias, shows that the centres of orchid diversity in Madagascar are in the Tsaratanàna Strict Nature Reserve and the Ranomafana National Park. Life-form statistics show that 55.0% of orchid species are strict epiphytes. The main flowering period of orchids in Madagascar is between November and March. To date, 84% of the 226 Malagasy orchid species listed in the IUCN Red List are threatened with extinction (CR, EN or VU)., Conclusion: Despite geographically uneven coverage, the biodiversity of Malagasy orchids appears to be already well documented. We provide maps corrected for sampling bias that indicate priority areas for future surveys. Upcoming efforts should also focus on rediscovery and conservation of rare and/or threatened species and ensure that the protected area network is well aligned with the distribution of priority species for conservation. Finally, the conservation status of 75% of the orchid species found in Madagascar is not yet known and the inclusion of these species must be a top priority in the coming years., Competing Interests: No conflict of interest to declare Disclaimer: This article is (co-)authored by any of the Editors-in-Chief, Managing Editors or their deputies in this journal., (Vincent Droissart, Simon Verlynde, Brigitte Ramandimbisoa, Lalao Andriamahefarivo, Tariq Stévart.)

Tropical forests store 40-50 per cent of terrestrial vegetation carbon 1 . However, spatial variations in aboveground live tree biomass carbon (AGC) stocks remain poorly understood, in particular in tropical montane forests 2 . Owing to climatic and soil changes with increasing elevation 3 , AGC stocks are lower in tropical montane forests compared with lowland forests 2 . Here we assemble and analyse a dataset of structurally intact old-growth forests (AfriMont) spanning 44 montane sites in 12 African countries. We find that montane sites in the AfriMont plot network have a mean AGC stock of 149.4 megagrams of carbon per hectare (95% confidence interval 137.1-164.2), which is comparable to lowland forests in the African Tropical Rainforest Observation Network 4 and about 70 per cent and 32 per cent higher than averages from plot networks in montane 2,5,6 and lowland 7 forests in the Neotropics, respectively. Notably, our results are two-thirds higher than the Intergovernmental Panel on Climate Change default values for these forests in Africa 8 . We find that the low stem density and high abundance of large trees of African lowland forests 4 is mirrored in the montane forests sampled. This carbon store is endangered: we estimate that 0.8 million hectares of old-growth African montane forest have been lost since 2000. We provide country-specific montane forest AGC stock estimates modelled from our plot network to help to guide forest conservation and reforestation interventions. Our findings highlight the need for conserving these biodiverse 9,10 and carbon-rich ecosystems., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

Angraecoid orchids present a remarkable diversity of chromosome numbers, which makes them a highly suitable system for exploring the impact of karyotypic changes on cladogenesis, diversification and morphological differentiation. We compiled an annotated cytotaxonomic checklist for 126 species of Angraecinae, which was utilised to reconstruct chromosomal evolution using a newly-produced, near-comprehensive phylogenetic tree that includes 245 angraecoid taxa. In tandem with this improved phylogenetic framework, using combined Bayesian, maximum likelihood and parsimony approaches on ITS-1 and five plastid markers, we propose a new cladistic nomenclature for the angraecoids, and we estimate a new timeframe for angraecoid radiation based on a secondary calibration, and calculate diversification rates using a Bayesian approach. Coincident divergence dates between clades with identical geographical distributions in the angraecoids and the pantropical orchid genus Bulbophyllum suggest that the same events may have intervened in the dispersal of these two epiphytic groups between Asia, continental Africa, Madagascar and the Neotropics. The major angraecoid lineages probably began to differentiate in the Middle Miocene, and most genera and species emerged respectively around the Late Miocene-Pliocene boundary and the Pleistocene. Ancestral state reconstruction using maximum likelihood estimation revealed an eventful karyotypic history dominated by descending dysploidy. Karyotypic shifts seem to have paralleled cladogenesis in continental tropical Africa, where approximately 90% of the species have descended from at least one inferred transition from n = 17-18 to n = 25 during the Middle Miocene Climatic Transition, followed by some clade-specific descending and ascending dysploidy from the Late Miocene to the Pleistocene. Conversely, detected polyploidy is restricted to a few species lineages mostly originating during the Pleistocene. No increases in net diversification could be related to chromosome number changes, and the apparent net diversification was found to be highest in Madagascar, where karyotypic stasis predominates. Finally, shifts in chromosome number appear to have paralleled the evolution of rostellum structure, leaflessness, and conspicuous changes in floral colour., (Copyright © 2021. Published by Elsevier Inc.)

Tropical Africa is home to an astonishing biodiversity occurring in a variety of ecosystems. Past climatic change and geological events have impacted the evolution and diversification of this biodiversity. During the last two decades, around 90 dated molecular phylogenies of different clades across animals and plants have been published leading to an increased understanding of the diversification and speciation processes generating tropical African biodiversity. In parallel, extended geological and palaeoclimatic records together with detailed numerical simulations have refined our understanding of past geological and climatic changes in Africa. To date, these important advances have not been reviewed within a common framework. Here, we critically review and synthesize African climate, tectonics and terrestrial biodiversity evolution throughout the Cenozoic to the mid-Pleistocene, drawing on recent advances in Earth and life sciences. We first review six major geo-climatic periods defining tropical African biodiversity diversification by synthesizing 89 dated molecular phylogeny studies. Two major geo-climatic factors impacting the diversification of the sub-Saharan biota are highlighted. First, Africa underwent numerous climatic fluctuations at ancient and more recent timescales, with tectonic, greenhouse gas, and orbital forcing stimulating diversification. Second, increased aridification since the Late Eocene led to important extinction events, but also provided unique diversification opportunities shaping the current tropical African biodiversity landscape. We then review diversification studies of tropical terrestrial animal and plant clades and discuss three major models of speciation: (i) geographic speciation via vicariance (allopatry); (ii) ecological speciation impacted by climate and geological changes, and (iii) genomic speciation via genome duplication. Geographic speciation has been the most widely documented to date and is a common speciation model across tropical Africa. We conclude with four important challenges faced by tropical African biodiversity research: (i) to increase knowledge by gathering basic and fundamental biodiversity information; (ii) to improve modelling of African geophysical evolution throughout the Cenozoic via better constraints and downscaling approaches; (iii) to increase the precision of phylogenetic reconstruction and molecular dating of tropical African clades by using next generation sequencing approaches together with better fossil calibrations; (iv) finally, as done here, to integrate data better from Earth and life sciences by focusing on the interdisciplinary study of the evolution of tropical African biodiversity in a wider geodiversity context., (© 2020 The Authors. Biological Reviews published by John Wiley & Sons Ltd on behalf of Cambridge Philosophical Society.)

Forest biomass is key in Earth carbon cycle and climate system, and thus under intense scrutiny in the context of international climate change mitigation initiatives (e.g. REDD+). In tropical forests, the spatial distribution of aboveground biomass (AGB) remains, however, highly uncertain. There is increasing recognition that progress is strongly limited by the lack of field observations over large and remote areas. Here, we introduce the Congo basin Forests AGB (CoFor-AGB) dataset that contains AGB estimations and associated uncertainty for 59,857 1-km pixels aggregated from nearly 100,000 ha of in situ forest management inventories for the 2000 - early 2010s period in five central African countries. A comprehensive error propagation scheme suggests that the uncertainty on AGB estimations derived from c. 0.5-ha inventory plots (8.6-15.0%) is only moderately higher than the error obtained from scientific sampling plots (8.3%). CoFor-AGB provides the first large scale view of forest AGB spatial variation from field data in central Africa, the second largest continuous tropical forest domain of the world.

The sensitivity of tropical forest carbon to climate is a key uncertainty in predicting global climate change. Although short-term drying and warming are known to affect forests, it is unknown if such effects translate into long-term responses. Here, we analyze 590 permanent plots measured across the tropics to derive the equilibrium climate controls on forest carbon. Maximum temperature is the most important predictor of aboveground biomass (-9.1 megagrams of carbon per hectare per degree Celsius), primarily by reducing woody productivity, and has a greater impact per °C in the hottest forests (>32.2°C). Our results nevertheless reveal greater thermal resilience than observations of short-term variation imply. To realize the long-term climate adaptation potential of tropical forests requires both protecting them and stabilizing Earth's climate., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Determining where species diversify (cradles) and persist (museums) over evolutionary time is fundamental to understanding the distribution of biodiversity and for conservation prioritization. Here, we identify cradles and museums of angiosperm generic diversity across tropical Africa, one of the most biodiverse regions on Earth. Regions containing nonrandom concentrations of young (neo-) and old (paleo-) endemic taxa were identified using distribution data of 1719 genera combined with a newly generated time-calibrated mega-phylogenetic tree. We then compared the identified regions with the current network of African protected areas (PAs). At the generic level, phylogenetic diversity and endemism are mainly concentrated in the biogeographically complex region of Eastern Africa. We show that mountainous areas are centres of both neo- and paleo-endemism. By contrast, the Guineo-Congolian lowland rain forest region is characterized by widespread and old lineages. We found that the overlap between centres of phylogenetic endemism and PAs is high (> 85%). We show the vital role played by mountains acting simultaneously as cradles and museums of tropical African plant biodiversity. By contrast, lowland rainforests act mainly as museums for generic diversity. Our study shows that incorporating large-scale taxonomically verified distribution datasets and mega-phylogenies lead to an improved understanding of tropical plant biodiversity evolution., (© 2019 The Authors. New Phytologist © 2019 New Phytologist Trust.)

Phylogenies are a central and indispensable tool for evolutionary and ecological research. Even though most angiosperm families are well investigated from a phylogenetic point of view, there are far less possibilities to carry out large-scale meta-analyses at order level or higher. Here, we reconstructed a large-scale dated phylogeny including nearly 1/8th of all angiosperm species, based on two plastid barcoding genes, matK (incl. trnK ) and rbcL. Novel sequences were generated for several species, while the rest of the data were mined from GenBank. The resulting tree was dated using 56 angiosperm fossils as calibration points. The resulting megaphylogeny is one of the largest dated phylogenetic tree of angiosperms yet, consisting of 36,101 sampled species, representing 8,399 genera, 426 families and all orders. This novel framework will be useful for investigating different broad scale research questions in ecological and evolutionary biology., (Steven B. Janssens, Thomas L.P. Couvreur, Arne Mertens, Gilles Dauby, Leo-Paul M. J. Dagallier, Samuel Vanden Abeele, Filip Vandelook, Maurizio Mascarello, Hans Beeckman, Marc Sosef, Vincent Droissart, Michelle van der Bank, Olivier Maurin, William Hawthorne, Cicely Marshall, Maxime Réjou-Méchain, Denis Beina, Fidele Baya, Vincent Merckx, Brecht Verstraete, Olivier Hardy.)

Despite significant progress made in recent years toward developing an infrafamilial classification of Orchidaceae, our understanding of relationships among and within tribal and subtribal groups of epidendroid orchids remains incomplete. To reassess generic delimitation among one group of these epidendroids, the African angraecoids, phylogenetic relationships were inferred from DNA sequence data from three regions, ITS, matK, and the trnL-trnF intergenic spacer, obtained from a broadly representative sample of taxa. Parsimony and Bayesian analyses yielded highly resolved trees that are in clear agreement and show significant support for many key clades within subtribe Angraecinae s.l. Angraecoid orchids comprise two well-supported clades: an African/American group and an Indian Ocean group. Molecular results also support many previously proposed relationships among genera, but also reveal some unexpected relationships. The genera Aerangis, Ancistrorhynchus, Bolusiella, Campylocentrum, Cyrtorchis, Dendrophylax, Eurychone, Microcoelia, Nephrangis, Podangis and Solenangis are all shown to be monophyletic, but Angraecopsis, Diaphananthe and Margelliantha are polyphyletic. Diaphananthe forms three well-supported clades, one of which might represent a new genus, and Rhipidoglossum is paraphyletic with respect to Cribbia and Rhaesteria, and also includes taxa currently assigned to Margelliantha. Tridactyle too is paraphyletic as Eggelingia is embedded within it. The large genus Angraecum is confirmed to be polyphyletic and several groups will have to be recognized as separate genera, including sections Dolabrifolia and Hadrangis. The recently segregated genus Pectinariella (previously recognized as A. sect. Pectinaria) is polyphyletic and its Continental African species will have to be removed. Similarly, some of the species recently transferred to Angraecoides that were previously placed in Angraecum sects. Afrangraecum and Conchoglossum will have to be moved and described as a new genus., (Copyright © 2018 Elsevier Inc. All rights reserved.)

In the context of producing a revised phylogenetic Linnean taxonomy of angraecoid orchids, the monotypic and narrow-endemic genus Ossiculum is synonymised with Calyptrochilum . Accordingly, a new combination in Calyptrochilum is proposed for Ossiculum aurantiacum . The morphological and DNA-based evidence for this transfer is discussed. Moreover, Calyptrochilum aurantiacum is here firstly reported outside Cameroon, with a record from the Republic of the Congo. The Red List conservation status of this species is reassessed and it is to be downgraded from "Critically Endangered" (CR) to "Endangered" (EN), following the recent discovery of additional subpopulations in Cameroon.

A recent phylogenetic study showed that species assigned to the newly recognised genus Pectinariella Szlach., Mytnik & Grochocka (previously treated as Angraecum Bory sect. Pectinaria Benth.) are polyphyletic, comprising a clade with species primarily in Madagascar and the Western Indian Ocean islands (including the type) and another non-sister clade whose members occur in continental Africa and the Gulf of Guinea islands. In order to render Pectinariella monophyletic, the five continental African species must therefore be removed. A new genus, Afropectinariella M.Simo & Stévart, is described and the following combinations are made: Afropectinariella atlantica (Stévart & Droissart) M.Simo & Stévart, Afropectinariella doratophylla (Summerh.) M.Simo & Stévart, Afropectinariella gabonensis (Summerh.) M.Simo & Stévart, Afropectinariella pungens (Schltr.) M.Simo & Stévart and Afropectinariella subulata (Lindl.) M.Simo & Stévart.

The Red List Categories and the accompanying five criteria developed by the International Union for Conservation of Nature (IUCN) provide an authoritative and comprehensive methodology to assess the conservation status of organisms. Red List criterion B, which principally uses distribution data, is the most widely used to assess conservation status, particularly of plant species. No software package has previously been available to perform large-scale multispecies calculations of the three main criterion B parameters [extent of occurrence (EOO), area of occupancy (AOO) and an estimate of the number of locations] and provide preliminary conservation assessments using an automated batch process. We developed ConR , a dedicated R package, as a rapid and efficient tool to conduct large numbers of preliminary assessments, thereby facilitating complete Red List assessment. ConR (1) calculates key geographic range parameters (AOO and EOO) and estimates the number of locations sensu IUCN needed for an assessment under criterion B; (2) uses this information in a batch process to generate preliminary assessments of multiple species; (3) summarize the parameters and preliminary assessments in a spreadsheet; and (4) provides a visualization of the results by generating maps suitable for the submission of full assessments to the IUCN Red List. ConR can be used for any living organism for which reliable georeferenced distribution data are available. As distributional data for taxa become increasingly available via large open access datasets, ConR provides a novel, timely tool to guide and accelerate the work of the conservation and taxonomic communities by enabling practitioners to conduct preliminary assessments simultaneously for hundreds or even thousands of species in an efficient and time-saving way.

Background: Understanding the patterns of biodiversity distribution and what influences them is a fundamental pre-requisite for effective conservation and sustainable utilisation of biodiversity. Such knowledge is increasingly urgent as biodiversity responds to the ongoing effects of global climate change. Nowhere is this more acute than in species-rich tropical Africa, where so little is known about plant diversity and its distribution. In this paper, we use RAINBIO - one of the largest mega-databases of tropical African vascular plant species distributions ever compiled - to address questions about plant and growth form diversity across tropical Africa., Results: The filtered RAINBIO dataset contains 609,776 georeferenced records representing 22,577 species. Growth form data are recorded for 97% of all species. Records are well distributed, but heterogeneous across the continent. Overall, tropical Africa remains poorly sampled. When using sampling units (SU) of 0.5°, just 21 reach appropriate collection density and sampling completeness, and the average number of records per species per SU is only 1.84. Species richness (observed and estimated) and endemism figures per country are provided. Benin, Cameroon, Gabon, Ivory Coast and Liberia appear as the botanically best-explored countries, but none are optimally explored. Forests in the region contain 15,387 vascular plant species, of which 3013 are trees, representing 5-7% of the estimated world's tropical tree flora. The central African forests have the highest endemism rate across Africa, with approximately 30% of species being endemic., Conclusions: The botanical exploration of tropical Africa is far from complete, underlining the need for intensified inventories and digitization. We propose priority target areas for future sampling efforts, mainly focused on Tanzania, Atlantic Central Africa and West Africa. The observed number of tree species for African forests is smaller than those estimated from global tree data, suggesting that a significant number of species are yet to be discovered. Our data provide a solid basis for a more sustainable management and improved conservation of tropical Africa's unique flora, and is important for achieving Objective 1 of the Global Strategy for Plant Conservation 2011-2020. In turn, RAINBIO provides a solid basis for a more sustainable management and improved conservation of tropical Africa's unique flora.

The tropical vegetation of Africa is characterized by high levels of species diversity but is undergoing important shifts in response to ongoing climate change and increasing anthropogenic pressures. Although our knowledge of plant species distribution patterns in the African tropics has been improving over the years, it remains limited. Here we present RAINBIO, a unique comprehensive mega-database of georeferenced records for vascular plants in continental tropical Africa. The geographic focus of the database is the region south of the Sahel and north of Southern Africa, and the majority of data originate from tropical forest regions. RAINBIO is a compilation of 13 datasets either publicly available or personal ones. Numerous in depth data quality checks, automatic and manual via several African flora experts, were undertaken for georeferencing, standardization of taxonomic names and identification and merging of duplicated records. The resulting RAINBIO data allows exploration and extraction of distribution data for 25,356 native tropical African vascular plant species, which represents ca. 89% of all known plant species in the area of interest. Habit information is also provided for 91% of these species.

Recent field inventories and taxonomic research in Central Africa have resulted in the discovery of many new orchid species. Five specimens of an apparently new Angraecum species were collected in Gabon and Cameroon. They stand out for their hanging habit and short zig-zag stem. Morphology of leaves and habit is somewhat comparable to Angraecum cultriforme and Angraecum stolzii, two species from East Africa. Flowers of the novelty share the general morphology of Angraecum pyriforme from which the new species is distinguished by being smaller and with a different lip-spur ratio. Here we show that these five specimens represent a new species, described here as Angraecum lanceolatum. The distinguishing traits include thin lanceolate leaves, convolute distally, with a rhombic lip shape. Dichotomous key to four Central African species of sect. Conchoglossum and a table of the diagnostic characters of the seven related Continental African Angraecum taxa are included here. A preliminary assessment of the conservation status of Angraecum lanceolatum is provided, using the IUCN Red List Categories and Criteria.

Bulbophyllum leucoglossum, Dendrobium centrosepalum, Dendrobium taeniocaule, and Taeniophyllum pyriforme are here described as new species, based on herbarium specimens collected from the Lengguru fold-and-thrust belt in the West Papua Bird's neck, Indonesian New Guinea. All four novelties were found growing in submontane forest (elevation > 1000 m a.s.l.) on limestone karst. Information concerning the distribution and habitat for these taxa is provided along with diagnostic features, line drawings, high resolution photographs, and a map of collecting localities. More field studies are required to find additional populations of these new species, in order to better characterize their habitat, ecology and conservation status.

While conducting field inventories in South Cameroon, we collected two specimens of a new species that we considered to belong to the genus Angraecopsis. Afterwards, a careful examination of specimens housed at main herbaria, along with the nomenclatural types, allows us to place it in Distylodon, a monotypic genus previously known from East Africa. Distylodon sonkeanum Droissart, Stévart & P.J.Cribb, sp. nov. was collected in the lowland coastal forest of Atlantic Central Africa. It is known from a single locality in the surroundings of the Campo-Ma'an National Park. The species differs from D. comptum, by its several-flowered inflorescences, longer leaves and spur, and shorter pedicel and ovary. The species appears to be rare and is assessed as Critically Endangered [CR B2ab(iii)] according to IUCN Red List Categories and Criteria. New field investigations are required to attempt to find it in the low-elevation parts of the Campo-Ma'an National Park in Cameroon.

We report above-ground biomass (AGB), basal area, stem density and wood mass density estimates from 260 sample plots (mean size: 1.2 ha) in intact closed-canopy tropical forests across 12 African countries. Mean AGB is 395.7 Mg dry mass ha⁻¹ (95% CI: 14.3), substantially higher than Amazonian values, with the Congo Basin and contiguous forest region attaining AGB values (429 Mg ha⁻¹) similar to those of Bornean forests, and significantly greater than East or West African forests. AGB therefore appears generally higher in palaeo- compared with neotropical forests. However, mean stem density is low (426 ± 11 stems ha⁻¹ greater than or equal to 100 mm diameter) compared with both Amazonian and Bornean forests (cf. approx. 600) and is the signature structural feature of African tropical forests. While spatial autocorrelation complicates analyses, AGB shows a positive relationship with rainfall in the driest nine months of the year, and an opposite association with the wettest three months of the year; a negative relationship with temperature; positive relationship with clay-rich soils; and negative relationships with C : N ratio (suggesting a positive soil phosphorus-AGB relationship), and soil fertility computed as the sum of base cations. The results indicate that AGB is mediated by both climate and soils, and suggest that the AGB of African closed-canopy tropical forests may be particularly sensitive to future precipitation and temperature changes.