Francisco Maiato Pedro Gonçalves

Accurate mapping of woody biomass and its temporal change is critical for understanding the global carbon balance, informing restoration and supporting evidence‐based policy on climate mitigation and livelihoods. The vegetation of the dry tropics, comprised largely of dry forests and savannas, holds substantial woody carbon stocks, but both stocks and change over time remain uncertain. Where Earth Observation (EO) data have been used to estimate change over time, different products give conflicting results on the direction, magnitude and location of change. We present pan‐dry‐tropical maps of aboveground carbon density (AGCD) and AGCD change at 100 m resolution for the years 2015–2024, developed using ALOS ScanSAR satellite radar observations calibrated with in situ measurements ( n = 237). These maps suggest an aboveground woody carbon pool (AGC) in the dry tropics of 25.3 2.0 PgC, ~13.0% of global AGC. Net AGC has increased by 0.43 0.07 PgC yr ⁻¹ , ~20.0% of the global net land sink. The overall net increase (0.43 PgC yr ⁻¹ ) is comprised of gross losses from deforestation and degradation (0.27 0.05 PgC yr ⁻¹ ) and gains due to densification and extensification of 0.59 0.1 PgC yr ⁻¹ , with the balance accounted for by small changes (change < 20% of AGCD; 0.11 PgC yr ⁻¹ ). Losses are equally split between degradation and deforestation, while gains are divided roughly 2:1 between the densification of woody ecosystems and expansion into previously grass‐dominated areas. These new maps, created with a dry‐tropics‐specific EO method, highlight the importance of tropical dry forests and savannas in the global carbon cycle. The prominent role of degradation‐related losses suggests that climate change mitigation will need to focus much more on reducing losses from overharvesting than at present. The widespread increases in carbon density and the increase in tree biomass into open systems present major challenges for biodiversity conservation, restoration and livelihoods.

Reliable monitoring of leaf phenology across environmental gradients is essential for understanding ecosystem functioning and climate responses, yet existing approaches in African savannas are constrained by either sparse ground-based observations or the limited resolution of satellite products. We evaluated the ability of MODIS (Moderate Resolution Imaging Spectroradiometer), VIIRS (Visible Infrared Imaging Radiometer Suite), and Sentinel-2-derived vegetation indices (Normalised-Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), and Green Chromatic Coordinate (GCC)) to track phenocam-derived phenology across 10 plots along a water-availability gradient in Africa. Satellite vegetation index time series were smoothed using generalized additive models and compared with phenocam-derived GCC, including estimates of transition dates. All satellite datasets estimated longer growing seasons than phenocams, associated with earlier start-of-season (SOS) and later end-of-season (EOS) estimates. MODIS NDVI and VIIRS NDVI most accurately estimated transition dates (SOS root-mean-squared error (RMSE), a standard measure of model accuracy, of 10 and 11 days, respectively; EOS RMSE of 27 days in both datasets). MODIS GCC and VIIRS EVI followed with high estimated transition date accuracy (SOS RMSE of 11 days; EOS RMSE of 32 days, in both datasets). VIIRS EVI and Sentinel-2 (S2) GCC most accurately tracked phenocam temporal fluctuations (r = 0.83 ± 0.08 and 0.83 ± 0.10, respectively), while MODIS GCC and MODIS NDVI also showed high correlations (r = 0.78 ± 0.12 and 0.78 ± 0.15). These MODIS products tracked intraseasonal fluctuations more closely than the VIIRS and S2 datasets. We consider MODIS NDVI the most accurate dataset overall, given its accuracy in estimating SOS and EOS, visible tracking of intraseasonal fluctuations, and high temporal correlation with phenocam phenology. These results support using MODIS and VIIRS for large-scale phenology monitoring and upscaling phenocam observations in African savannas.

Aquatic macrophytes are photosynthetic macroscopic organisms that grow permanently or periodically submerged or floating on the surface of the water. The aim of this study is to compile a checklist of fresh-water aquatic vascular plant macrophytes occurring in Angola, focusing on their origins, life forms, conservation status and distribution throughout the country. The checklist was compiled through a literature review of previous studies carried out in Angola, herbarium collections and online databases. A total of 526 species of macrophytes in 196 genera and 70 families was recorded. Cyperaceae was the most abundant family, followed by Poaceae, Lentibulariaceae, Lythraceae, Eriocaulaceae, Araceae, Podostemaceae, Hydrocharitaceae, Onagraceae and Plantaginaceae. The highest number of macrophytes was recorded from Huíla Province, followed by Moxico and Cuando Cubango Provinces, respectively, while Lunda Norte, Uíge and Zaire were poorly represented. From the aquatic macrophytes recorded, it was possible to identify the category of origin of 511 species. From these, 472 species are native, 23 introduced and 16 are endemic to Angola and the conservation status of these species was also assessed. The results obtained in this study show that there are still some gaps, especially with regard to the distribution of aquatic macrophytes in Angola, since many species are documented as native, but there is a lack of data on their distribution.

Triaspis hypericoides currently comprises three accepted subspecies endemic to woodland savannas of southern continental Africa. After an unusual population belonging to this complex was collected in southwestern Angola, we re‐evaluated the classification of this group. This study was based on the analysis of type specimens, protologues, field photographs and herbarium sheets of all subspecies within T. hypericoides . We reinstate T. canescens , T. hypericoides and T. nelsonii based on differences in leaf, flower and fruit traits. Additionally, the Angolan population is proposed here as a new species of Triapis endemic to the dry miombo woodlands of Bicuar National Park, Huíla Province, southwestern Angola. Triaspis bicuarensis sp. nov. is easily distinguished from T. nelsonii by its alternate (versus opposite) leaves, ovate to widely ovate (versus widely ovate to very widely ovate) leaf laminas, rounded (versus sagittate) leaf base, flat (versus undulate) margins, sparsely white‐tomentose (versus glabrous to glabrescent) abaxial leaf surface, petiole 4–8 mm long (versus 2–3 mm long), compound inflorescences in thyrses (versus corymbs) and bracteoles inserted below apex of peduncles (versus in the middle of peduncles). An identification key to all species belonging to this species complex is presented alongside a complete morphological description for the new species, photographic plates and comments on the distribution, ecology, palynology and taxonomy. These results underline the need for continued revisions of the taxonomy of the neglected African genera of Malpighiaceae.

Four new species are described from central and eastern Angola and adjacent NW Zambia. All occur in Kalahari sand savannas rich in endemic and more widely distributed geoxylic suffrutices. Despite being known from very few collections, the conservation status of one of these new species is assessed as Least Concern, as these grasslands are nutrient-poor, are in remote sparsely populated areas, and are not threatened with conversion to agriculture. The remaining three are treated as Data Deficient. In addition, one new combination is provided for Ancylanthos rubiginosus Desf. under Vangueria as V. rubiginosa (Desf.) Lantz is an illegitimate later homonym. We also make orthographic corrections to specific epithets commemorating Ilse von Nolde, a collector who made important collections from Quela in Malange in the 1930s.

Background and objectives—Podocarpus latifolius (synonym of P. milanjianus) is a key tree representative of Afromontane forests where it is highly threatened by climate and land-use changes. While large populations occur in East Africa, only a few isolated and usually small populations remain in western Central Africa (Cameroon to Angola). Studying the evolutionary history of such relictual populations can thus be relevant to understand their resilience under changing environments. Materials and Methods—we developed nine polymorphic nuclear microsatellites (nSSRs) to estimate genetic variability, (historical) gene flow, and demographic changes among natural populations from Central to East Africa. Results—despite the extended distribution range of P. latifolius, a strong isolation-by-distance pattern emerges at the intra-population scale, indicating low seed and pollen dispersal capacities. Central African populations display a lower genetic diversity (He = 0.34 to 0.61) and are more differentiated from each other (F_ST = 0.28) than are East African populations (He = 0.65 to 0.71; F_ST = 0.10), suggesting high genetic drift in the Central African populations. Spatial genetic structure reveals past connections between East and West Africa but also a gene flow barrier across the equator in western Central Africa. Demographic modelling anchors the history of current lineages in the Pleistocene and supports a strong demographic decline in most western populations during the last glacial period. By contrast, no signature of demographic change was detected in East African populations. Conclusions—in Cameroon, our results exclude a recent (re)colonization from one source population of all mountain ranges, but rather indicate long-term persistence of populations in each mountain with fluctuating sizes. A higher impact of genetic drift and further loss of diversity can be expected by survival through climatically unfavorable periods in such small refugial populations. Tracking the Quaternary legacy of podocarp populations is thus essential for their conservation since there is a temporal gap between environment crises and an ecological/genetic answer at the population level.

Angola is a country in south-central Africa, particularly rich in biodiversity. Despite the efforts recently made to document its biodiversity, there is a need for standardized sampling methods to document and compare the variety of ecosystems and plants occurring in the country. With this database report we aim to document the abundance and diversity of woody species in the woodlands of Huíla province. The database hosts the results of a standardised plot-based vegetation survey, consisting of 448 vegetation plots distributed throughout the 14 municipalities and Bicuar National Park. In total, 40,009 individuals belonging to 44 plant families were recorded and measured, belonging to 193 woody species. Species richness per municipality ranged from 32 to 126. The mean stem diameter (DBH) was 10.9 cm ± 7.5 cm. Small-size classes are increasingly dominated by few species, while the largest trees come from a wider range of species; miombo key-species dominated almost all size classes. Our study represents the first plot-based vegetation survey of any Angolan province and constitutes a useful source of information for conservation and management. Additionally, may constitute a powerful dataset to support future studies on biodiversity patterns and vegetation change over time and facilitate the elaboration of vegetation maps. Taxonomic reference: Checklist of Angolan Plants (Figueiredo and Smith 2008), The African Plant Database (version 3.4.0) and A new classification of Leguminosae (LPWG 2017). Abbreviations: DBH = Diameter at Breast Height; GIVD = Global Index of Vegetation-Plot Databases; LUBA = Acronym of the Herbarium of Lubango

Summary: Positive biodiversity–ecosystem function relationships (BEFRs) have been widely documented, but it is unclear if BEFRs should be expected in disturbance‐driven systems. Disturbance may limit competition and niche differentiation, which are frequently posited to underlie BEFRs. We provide the first exploration of the relationship between tree species diversity and biomass, one measure of ecosystem function, across southern African woodlands and savannas, an ecological system rife with disturbance from fire, herbivores and humans. We used > 1000 vegetation plots distributed across 10 southern African countries and structural equation modelling to determine the relationship between tree species diversity and above‐ground woody biomass, accounting for interacting effects of resource availability, disturbance by fire, tree stem density and vegetation type. We found positive effects of tree species diversity on above‐ground biomass, operating via increased structural diversity. The observed BEFR was highly dependent on organismal density, with a minimum threshold of c. 180 mature stems ha⁻¹. We found that water availability mainly affects biomass indirectly, via increasing species diversity. The study underlines the close association between tree diversity, ecosystem structure, environment and function in highly disturbed savannas and woodlands. We suggest that tree diversity is an under‐appreciated determinant of wooded ecosystem structure and function.

Summary: The miombo region in Africa is covered by a mosaic of woodlands and geoxylic grasslands and is subject to disturbances such as fires, frost and drought, and low nutrient availability. The dominance of Fabaceae Detarioideae species in miombo ecosystems is remarkable but little understood. We therefore compared plant functional traits (PFTs) of common woody species of the Angolan plateau, grouped by life form (trees, geoxyles), lineage (Fabaceae: Detarioideae, non‐Detarioideae) and symbiont association (ectomycorrhiza, rhizobia). PFTs reflect group‐specific adaptations to prevalent environmental conditions. To analyse the impact of environmental drivers, we selected PFTs reflecting ecophysiological aspects of leaf morphology, nutrient content and water transport. Traits were measured following standardized protocols. We found differences in key PFTs between trees and geoxyles reflecting both life form‐specific adaptations to environmental conditions and lineage‐specific strategies to cope with environmental stresses. We interpret higher leaf thickness and higher wood density of geoxyles as responses to harsher open environments. Fabaceae in general and ectomycorrhizal species showed better nutrient status. Symbiotic associations of detarioid legumes with ectomycorrhiza show specific advantages for phosphorous uptake as compared to Rhizobia‐associated Fabaceae and to non‐Fabaceae and thus may be crucial for the stunning dominance of Detarioideae in miombo landscapes.

Significance: We develop a biogeographic approach to analyzing the presence of alternative stable states in tropical biomes. Whilst forest–savanna bistability has been widely hypothesized and modeled, empirical evidence has remained scarce and controversial, and here, applying our method to Africa, we provide large-scale evidence that there are alternative states in tree species composition of tropical vegetation. Furthermore, our results have produced more accurate maps of the forest and savanna distributions in Africa, which take into account differences in tree species composition, and a complex suite of determinants. This result is not only important for understanding the biogeography of the continent but also, to guide large-scaled tree planting and restoration efforts planned for the region.