References of "Hubau, Wannes"
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See detailThe global abundance of tree palms
Muscarella, Robert; Emilio, Thaise; Phillips, Oliver L. et al

in Global Ecology and Biogeography (2020), 00

Aim: Palms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and ... [more ▼]

Aim: Palms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and physiologically distinct from other trees, and these differences have important consequences for ecosystem services (e.g., carbon sequestration and storage) and in terms of responses to climate change. We quantified global patterns of tree palm relative abundance to help improve understanding of tropical forests and reduce uncertainty about these ecosystems under climate change. Location: Tropical and subtropical moist forests. Time period: Current. Major taxa studied: Palms (Arecaceae). Methods: We assembled a pantropical dataset of 2,548 forest plots (covering 1,191 ha) and quantified tree palm (i.e., ≥10 cm diameter at breast height) abundance relative to co-occurring non-palm trees. We compared the relative abundance of tree palms across biogeographical realms and tested for associations with palaeoclimate stability, current climate, edaphic conditions and metrics of forest structure. Results: On average, the relative abundance of tree palms was more than five times larger between Neotropical locations and other biogeographical realms. Tree palms were absent in most locations outside the Neotropics but present in >80% of Neotropical locations. The relative abundance of tree palms was more strongly associated with local conditions (e.g., higher mean annual precipitation, lower soil fertility, shallower water table and lower plot mean wood density) than metrics of long-term climate stability. Life-form diversity also influenced the patterns; palm assemblages outside the Neotropics comprise many non-tree (e.g., climbing) palms. Finally, we show that tree palms can influence estimates of above-ground biomass, but the magnitude and direction of the effect require additional work. Conclusions: Tree palms are not only quintessentially tropical, but they are also overwhelmingly Neotropical. Future work to understand the contributions of tree palms to biomass estimates and carbon cycling will be particularly crucial in Neotropical forests. [less ▲]

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See detailTowards improving the assessment of rainforest carbon: Complementary evidence from repeated diameter measurements and dated wood
Ilondea, Bhely Angoboy; De Mil, Tom ULiege; Hubau, Wannes et al

in Dendrochronologia (2020), 62

We explore whether a growth-ring analysis can produce additional information about carbon budgets in tropical forests. Such forests are characterized by a high number of species and by trees that rarely ... [more ▼]

We explore whether a growth-ring analysis can produce additional information about carbon budgets in tropical forests. Such forests are characterized by a high number of species and by trees that rarely have anatomically distinct annual growth rings, which hampers the application of dendrochronological tools in carbon balance assessments in the tropics. We use forest inventory data and archived annual diameter measurements from the Luki Biosphere Reserve in the southwestern margin of the Congo Basin forest massif. In addition, dated wood data are available from the same location thanks to tag nail traces that allow for the measurement of growth increments over a period of 66 years. We find that precise increment measurements based on dated wood are advisable for small subsets of many less abundant species and for functional species groups characterized by slow growth. The dated wood approach shows that many understory trees with non-periodical rings remain in a steady state for long periods of time. These results suggest a dated wood approach is advisable for studies of growth trajectories of individual trees that might be of importance for carbon assessments in degraded forests. [less ▲]

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See detailLong-term thermal sensitivity of Earth’s tropical forests
Sullivan, Martin J.P.; Lewis, Simon L.; Affum-Baffoe, Kofi et al

in Science (2020), 368

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 ... [more ▼]

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. [less ▲]

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See detailAsynchronous carbon sink saturation in African and Amazonian tropical forests
Hubau, Wannes; Lewis, Simon L.; Phillips, Oliver L. et al

in Nature (2020), 579

Structurally intact tropical forests sequestered about half of the global terrestrial carbon uptake over the 1990s and early 2000s, removing about 15 per cent of anthropogenic carbon dioxide emissions1–3 ... [more ▼]

Structurally intact tropical forests sequestered about half of the global terrestrial carbon uptake over the 1990s and early 2000s, removing about 15 per cent of anthropogenic carbon dioxide emissions1–3. Climate-driven vegetation models typically predict that this tropical forest ‘carbon sink’ will continue for decades4,5. Here we assess trends in the carbon sink using 244 structurally intact African tropical forests spanning 11 countries, compare them with 321 published plots from Amazonia and investigate the underlying drivers of the trends. The carbon sink in live aboveground biomass in intact African tropical forests has been stable for the three decades to 2015, at 0.66 tonnes of carbon per hectare per year (95 per cent confidence interval 0.53–0.79), in contrast to the long-term decline in Amazonian forests6. Therefore the carbon sink responses of Earth’s two largest expanses of tropical forest have diverged. The difference is largely driven by carbon losses from tree mortality, with no detectable multi-decadal trend in Africa and a long-term increase in Amazonia. Both continents show increasing tree growth, consistent with the expected net effect of rising atmospheric carbon dioxide and air temperature7–9. Despite the past stability of the African carbon sink, our most intensively monitored plots suggest a post-2010 increase in carbon losses, delayed compared to Amazonia, indicating asynchronous carbon sink saturation on the two continents. A statistical model including carbon dioxide, temperature, drought and forest dynamics accounts for the observed trends and indicates a long-term future decline in the African sink, whereas the Amazonian sink continues to weaken rapidly. Overall, the uptake of carbon into Earth’s intact tropical forests peaked in the 1990s. Given that the global terrestrial carbon sink is increasing in size, independent observations indicating greater recent carbon uptake into the Northern Hemisphere landmass10 reinforce our conclusion that the intact tropical forest carbon sink has already peaked. This saturation and ongoing decline of the tropical forest carbon sink has consequences for policies intended to stabilize Earth’s climate. [less ▲]

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See detailThe persistence of carbon in the African forest understory
Hubau, Wannes; De Mil, Tom; Van den Bulcke, Jan et al

in Nature Plants (2019)

Quantifying carbon dynamics in forests is critical for understanding their role in long-term climate regulation1–4. Yet little is known about tree longevity in tropical forests3,5–8, a factor that is ... [more ▼]

Quantifying carbon dynamics in forests is critical for understanding their role in long-term climate regulation1–4. Yet little is known about tree longevity in tropical forests3,5–8, a factor that is vital for estimating carbon persistence3,4. Here we calculate mean carbon age (the period that carbon is fixed in trees7) in different strata of African tropical forests using (1) growthring records with a unique timestamp accurately demarcating 66 years of growth in one site and (2) measurements of diameter increments from the African Tropical Rainforest Observation Network (23 sites). We find that in spite of their much smaller size, in understory trees mean carbon age (74 years) is greater than in sub-canopy (54 years) and canopy (57 years) trees and similar to carbon age in emergent trees (66 years). The remarkable carbon longevity in the understory results from slow and aperiodic growth as an adaptation to limited resource availability9–11. Our analysis also reveals that while the understory represents a small share (11%) of the carbon stock12,13, it contributes disproportionally to the forest carbon sink (20%). We conclude that accounting for the diversity of carbon age and carbon sequestration among different forest strata is critical for effective conservation management14–16 and for accurate modelling of carbon cycling4. [less ▲]

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See detailField methods for sampling tree height for tropical forest biomass estimation
Sullivan, Martin J.P.; Lewis, Simon L.; Hubau, Wannes et al

in Methods in Ecology and Evolution (2018), 9

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See detailPan-tropical prediction of forest structure from the largest trees
Bastin, Jean-François; Rutishauser, Ervan; Kellner, James R. et al

in Global Ecology and Biogeography (2018)

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See detailDiversity and carbon storage across the tropical forest biome
Sullivan, Martin J.P.; Talbot, Joey; Lewis, Simon L. et al

in Scientific Reports (2017), 7(39102),

Tropical forests are global centres of biodiversity and carbon storage. Many tropical countries aspire to protect forest to fulfil biodiversity and climate mitigation policy targets, but the conservation ... [more ▼]

Tropical forests are global centres of biodiversity and carbon storage. Many tropical countries aspire to protect forest to fulfil biodiversity and climate mitigation policy targets, but the conservation strategies needed to achieve these two functions depend critically on the tropical forest tree diversity-carbon storage relationship. Assessing this relationship is challenging due to the scarcity of inventories where carbon stocks in aboveground biomass and species identifications have been simultaneously and robustly quantified. Here, we compile a unique pan-Tropical dataset of 360 plots located in structurally intact old-growth closed-canopy forest, surveyed using standardised methods, allowing a multi-scale evaluation of diversity-carbon relationships in tropical forests. Diversity-carbon relationships among all plots at 1 ha scale across the tropics are absent, and within continents are either weak (Asia) or absent (Amazonia, Africa). A weak positive relationship is detectable within 1 ha plots, indicating that diversity effects in tropical forests may be scale dependent. The absence of clear diversity-carbon relationships at scales relevant to conservation planning means that carbon-centred conservation strategies will inevitably miss many high diversity ecosystems. As tropical forests can have any combination of tree diversity and carbon stocks both require explicit consideration when optimising policies to manage tropical carbon and biodiversity. [less ▲]

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See detailThe Tervuren xylarium and wood biology to decode the ecological memory of forests and trees
Morin, Julie ULiege; Bourland, Nils; De Ridder, Maaike et al

Conference (2015, October 15)

Presentation of the competences held by the Wood Biology Service members of the Royal Museum for Central Africa, relative to their potential uses in archaeology.

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See detailContributing to wood anatomical databases to improve species identification, phylogeny and functional trait research in Central Africa
Morin, Julie ULiege; Fayolle, Adeline ULiege; De Ridder, Maaike et al

Poster (2015, May 26)

Central African rainforests shelter a high number of woody species that are anatomically very different. Knowledge of taxon-specific wood anatomical features has proven indispensable for scientific and ... [more ▼]

Central African rainforests shelter a high number of woody species that are anatomically very different. Knowledge of taxon-specific wood anatomical features has proven indispensable for scientific and non-scientific applications. The field of wood anatomy and identification has been drastically revolutionized by the development of internationally recognized lists of precisely illustrated microscopic features (e.g. IAWA Committee 1989), together with the launch of InsideWood, an online search database using these features to narrow down identification results (e.g. Wheeler 2011). However, despite these massive efforts, the anatomy of many species or even genera remains in the dark, especially in species-rich regions. Wood anatomy has been formally described for less than 25% of the Central African woody species (Hubau et al. 2012), the focus has been mainly on timber species and variations in wood anatomical structure remain to be explored. Therefore, we are assembling a wood anatomical database of about 800 species covering the Guineo-Congolian region using material from InsideWood and the Tervuren xylarium (new descriptions). As such, we present how large anatomical databases hold interesting perspectives for (i) wood and charcoal identification, (ii) exploring the phylogenetic signal of wood anatomy, and (iii) the relationship between wood anatomical features and functional traits. [less ▲]

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See detailHow Tightly Linked Are Pericopsis elata (Fabaceae) Patches to Anthropogenic Disturbances in Southeastern Cameroon?
Bourland, Nils; Cerisier, François; Daïnou, Kasso ULiege et al

in Forests (2015), 6(2), 293-310

While most past studies have emphasized the relationships between specific forest stands and edaphic factors, recent observations in Central African moist forests suggested that an increase of slash-and ... [more ▼]

While most past studies have emphasized the relationships between specific forest stands and edaphic factors, recent observations in Central African moist forests suggested that an increase of slash-and-burn agriculture since 3000–2000 BP (Before Present) could be the main driver of the persistence of light-demanding tree species. In order to examine anthropogenic factors in the persistence of such populations, our study focused on Pericopsis elata, an endangered clustered timber species. We used a multidisciplinary approach comprised of botanical, anthracological and archaeobotanical investigations to compare P. elata patches with surrounding stands of mixed forest vegetation (“out-zones”). Charcoal samples were found in both zones, but were significantly more abundant in the soils of patches. Eleven groups of taxa were identified from the charcoals, most of them also present in the current vegetation. Potsherds were detected only inside P. elata patches and at different soil depths, suggesting a long human presence from at least 2150 to 195 BP, as revealed by our charcoal radiocarbon dating. We conclude that current P. elata patches most likely result from shifting cultivation that occurred ca. two centuries ago. The implications of our findings for the dynamics and management of light-demanding tree species are discussed. [less ▲]

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See detailCharcoal records reveal past occurrences of perturbations in the forests of the Kisangani region(RDC): vegetation history of the semi-deciduous rainforest
Tshibamba Mukendi, John; Hubau, Wannes; Morin-Rivat, Julie ULiege et al

Poster (2014, April 28)

Introduction. Past disturbances have modified the structure and the floristic composition of Central African rainforests. These perturbations represent a driving force for forest dynamics and they are ... [more ▼]

Introduction. Past disturbances have modified the structure and the floristic composition of Central African rainforests. These perturbations represent a driving force for forest dynamics and they are presumably at the origin of present-day forest mosaics. Fire is a prominent forest disturbance, leaving behind charcoal as a witness of past forest dynamics. The question arises whether quantification, dating and botanical identification of ancient charcoal fragments found in soil layers (pedoanthracology) allows a detailed reconstruction of forest history, including the possible occurrence of past disturbances. Material & methods. We organized pedoanthracological excavations in 6 regrowth sites and 48 sites of primary forests of Yangambi, Yoko, Masako and Kole in the Kisangani (RDC). We performed a detailed sampling in different vegetation types of a semi -deciduous rainforest (Yoko). Charcoal sampling was conducted in pit intervals of 10 cm. The charcoal was quantified whereby pottery fragments were also registered. A selection of charcoal fragments has been dated through AMS 14C measurement. Floristic identifications were conducted using. former protocols based on wood anatomy, which is largely preserved after charcoalification. Results. Charcoal was found in most pit intervals. The anthracomass in the soil of regrowth forests (secondary forests) is much higher than in the primary forest: 27,59 mg/kg for secondary forests et 2,53 mg/kg for primary forests. The specific soil anthracomass of the primary forest of the Yoko reserve is higher (7,7 mg/kg) than in Yangambi (1,9 mg/kg) , Masako (1,7 mg/kg) and Kole (0,8 mg/kg). No systematic differences have been found between soil charcoal content of the different forest type representing different forest histories. Gilbertiodendron dewevrei (De Wild.) J. Leonard forests showed surprisingly a higher concentration of soil charcoal. Discussion. Forest disturbances in the Kisangani region appear to be more recent than those in the Mayombe forest in Western RDC ( 3000-2000 calBP (Hubau, 2013)) and those of the Cameroon forest (2300-1300 calBP) (Morin-Rivat, J et al., 2014). Stratified charcoal conserved in the soil is a useful indicator of past forest disturbances. [less ▲]

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See detailIdentification des charbons de bois pour connaître l'histoire passée des forêts tropicales africaines
Morin-Rivat, Julie ULiege; De Weerdt, Joëlle; Hubau, Wannes et al

Scientific conference (2014, March 26)

Nous présentons ici différents aspects de l’étude des charbons de bois à travers l’exemple de l’Afrique tropicale

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See detailWood charcoal analysis: a relatively new tool for palaeoecology in tropical Africa
Morin-Rivat, Julie ULiege; Biwole, Achille ULiege; Bourland, Nils ULiege et al

Scientific conference (2014, February 14)

This is an introduction about wood charcoal properties, collection and taxonomical identification in the framework of palaeoecological studies in Central Africa through examples of possible applications.

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See detailFrom wood charcoals to trees: pitfalls and successes of the taxonomic identification in tropical contexts
Morin-Rivat, Julie ULiege; De Weerdt, Joëlle; Hubau, Wannes et al

Poster (2014, February 07)

So as to document the past history of tropical forests, several palaeoenvironmental proxies have been used. For instance, charcoals from soil deposits provide a local signal of the evolution of the ... [more ▼]

So as to document the past history of tropical forests, several palaeoenvironmental proxies have been used. For instance, charcoals from soil deposits provide a local signal of the evolution of the vegetation together with snapshots of human interactions with the environment. As charcoal analyses are rare in tropical contexts, here we aim at presenting the different aspects of charcoal studies through their pitfalls and successes as well as the needs for further research. Charcoal analysis (anthracology) is a discipline initially from archaeobotany that consists in the analysis of pieces of charred wood primarily found in archaeological contexts but also in natural soil layers. Its goal is to identified the species that burnt during the past through the observation of the charred wood structure. Indeed carbonization, as the incomplete combustion of the ligneous material, preserves the wood structure. The identifications obtained through microscopic observations allow assessing past uses of wood and human impacts on the forest landscape. However, issues typically tropical exist: difficulties related to fieldwork accessibility, to sampling, to soil processing so as to collect the charcoals, difficulties related to the taxonomic identification because of the huge number of species and of the limited number of anatomical descriptions. New developments are nonetheless emerging for Central Africa with original anatomical descriptions, identification protocols and visual keys. [less ▲]

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See detailHow closely are Pericopsis elata (Fabaceae) patches linked to past human disturbances in South-Eastern Cameroon
Bourland, Nils ULiege; Cerisier, François; Daïnou, Kasso ULiege et al

Conference (2013, June 26)

Studies conducted in the Congo Basin forests concluded that soil parameters and large disturbances induced by human activities since 3000–2000 BP could be the main driver for the persistence of long lived ... [more ▼]

Studies conducted in the Congo Basin forests concluded that soil parameters and large disturbances induced by human activities since 3000–2000 BP could be the main driver for the persistence of long lived light-demanding tall tree species. Today most of the timber species belong to this group, among them Pericopsis elata (Fabaceae). Like many other light-demanding trees, this species suffers from important regeneration problems. While the conditions for its establishment must have been met in the past, they obviously have become unfavourable. Because of ongoing logging activities and a natural decline of its populations, this species is recorded in both the IUCN Red List and the CITES Appendix II listings. Our goal was to investigate the roles of both pedological and anthropogenic factors in the persistence of forest patches characterized by this clustered species. Soil surveys, botanical inventories and anthracological excavations were conducted in three different forest sites located in south-eastern Cameroon. P. elata patches (3.3-14.7 ha) were studied and compared to their close surroundings. No statistical differences were observed between the results of botanical inventories conducted inside and outside the patches (Morisita-Horn indices from 0.69-0.77). Soils only differed in Fe content, but otherwise no significant differences could be observed. Charcoal is widespread and abundant in study sites, mostly inside the patches. Charcoal radiocarbon dating (2,150-195 BP) was consistent with decoration techniques of archaeological materials that we discovered. The average age of P. elata individuals coincides with fire events that occurred in a region where fires rarely occur naturally. We present evidence of past anthropogenic disturbances (human settlement, slash-and-burn cultivation) in the Congolese mixed moist semi-evergreen forest in south-eastern Cameroon. We discuss the potential influence of our findings on the management of light-demanding tall trees populations in a context of logging activities. [less ▲]

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See detailExploring ancient charcoal archives in Central Africa
Hubau, Wannes; Morin-Rivat, Julie ULiege; Van den Bulcke, Jan et al

Conference (2012, July)

Fossil pollen and charcoal fragments are preserved in lake sediments, in forest soils and in ancient human settlements, were they can be accompanied by artifacts. As such, vegetation history is remarkably ... [more ▼]

Fossil pollen and charcoal fragments are preserved in lake sediments, in forest soils and in ancient human settlements, were they can be accompanied by artifacts. As such, vegetation history is remarkably well archived and sometimes closely linked to cultural history. Direct evidence for Central African vegetation history has been mainly derived from pollen analysis, while the charcoal archive remains hardly explored. However, analysis of charred wood remains has proven worthwhile for palaeovegetation reconstructions in temperate and arid regions. One of the main challenges for charcoal identification in tropical regions is species diversity. Therefore we developed and present a transparent charcoal identification protocol within an umbrella database of species names and metadata, compiled from the on-line database of wood-anatomical descriptions (InsideWood), the database of the world’s largest reference collection of Central African wood specimens (RMCA, Tervuren, Belgium) and inventory and indicator species lists. We applied the protocol on radiocarbon dated charcoal collections sampled in the Mayumbe forest (Bas-Congo, DRCongo), in human settlements along the Aruwimi and Lomami rivers (Province Orientale, DRCongo), along the Sangha river (Sangha department, Republic of the Congo) and in Pallisco logging concessions (East Province of Cameroon). First charcoal identification results are promising and sometimes seem to be taxonomically more precise than pollen identification. However, next to opportunities, we also present some pitfalls when exploring ancient charcoal archives. [less ▲]

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See detailForest anomalies and human occupation in Central Africa during the last two millennia
Livingstone Smith, Alexandre; Beeckman, Hans; Cerisier, François et al

Conference (2012, June 23)

Central African rainforests are no longer considered as pristine, but as the outcome of a long history of changes due mainly to climatic variation. For the later part of the Holocene it has been ... [more ▼]

Central African rainforests are no longer considered as pristine, but as the outcome of a long history of changes due mainly to climatic variation. For the later part of the Holocene it has been hypothesised that climate changes together with human activities triggered modifications in terms of distribution and botanical composition. While developing a research project to explore the mechanisms of forest change, new research avenues for the archaeology of rainforests became apparent. In this paper, we outline the results of this approach, implemented on a forest concession (Cameroon). We introduce our methodology based on the analysis of botanical inventories (focused on large trees of human linked species and light demanding species), coupled to systematic core boring and test pits. A sampling strategy for the collection of charcoal and its identification is developed and archaeological remains found in association are analyzed at the Royal Museum for Central Africa. [less ▲]

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See detailCurrent Pericopsis elata (Fabaceae) patches in southeastern Cameroon: remnants of a long and rich Human-rainforest relationship?
Bourland, Nils ULiege; Cerisier, François; Livingstone Smith, Alexandre et al

Poster (2012, June 23)

Pericopsis elata is one of the most valuable African timber species. This IUCN Red Listed tree suffers from a lack of regeneration, thus its current presence provokes questioning. Our work aimed at ... [more ▼]

Pericopsis elata is one of the most valuable African timber species. This IUCN Red Listed tree suffers from a lack of regeneration, thus its current presence provokes questioning. Our work aimed at understanding its origins so as to help securing its future. This study, lead away from engineering works, was conducted in four different sites located within the natural distribution area of the species and taking into account the different growing conditions were the species occurs. Our observations are based on an analysis of charcoal elements and pottery fragments discovered in subsurface layers of soils as well as current botanical and pedological surveys. Evidence of past human activities we found led to the assumption that this part of the Congo Basin was much more inhabited than previously thought. Some of the results obtained for P. elata could apply for other long lived light demanding species growing in the same environment [less ▲]

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