References of "Fayolle, Adeline"
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See detailTesting the divergent adaptation of two congeneric tree species on a rainfall gradient using eco-physio-morphological traits
Gorel, Anaïs ULiege; Steppe, Kathy; Beeckman, Hans et al

in Biotropica (in press)

In tropical Africa, evidence of widely distributed genera transcending biomes or habitat boundaries has been reported. The evolutionary processes that allowed these lineages to disperse and adapt into new ... [more ▼]

In tropical Africa, evidence of widely distributed genera transcending biomes or habitat boundaries has been reported. The evolutionary processes that allowed these lineages to disperse and adapt into new environments are far from being resolved. To better understand these processes, we propose an integrated approach, based on the eco-physio-morphological traits of two sister species with adjacent distributions along a rainfall gradient. We used wood anatomical traits, plant hydraulics (vulnerability to cavitation, wood volumetric water content and hydraulic capacitance) and growth data from the natural habitat, in a common garden, to compare species with known phylogeny, very similar morphologically, but occupying contrasting habitats: Erythrophleum ivorense (wet forest) and Erythrophleum suaveolens (moist forest and forest gallery). We identified some slight differences in wood anatomical traits between the two species associated with strong differences in hydraulics, growth, and overall species distribution. The moist forest species, E. suaveolens had narrower vessels and intervessel pits, and higher vessel cell-wall reinforcement than E. ivorense. These traits allow a high resistance to cavitation and a continuous internal water supply of the xylem during water shortage, allowing a higher fitness during drought periods, but limiting growth. Our results confirm a trade-off between drought tolerance and growth, controlled by subtle adaptations in wood traits, as a key mechanism leading to the niche partitioning between the two Erythrophleum species. The generality of this trade-off and its importance in the diversification of the African tree flora remains to be tested. Our integrated eco-physio-morpho approach could be the way forward. [less ▲]

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See detailA sharp floristic discontinuity revealed by the biogeographic regionalization of African savannas [presence data]
Fayolle, Adeline ULiege

Textual, factual or bibliographical database (2019)

Aim. In tropical Africa, savannas cover huge areas, have high plant species richness, and are considered as a major natural resource for most countries. There is, however, little information available on ... [more ▼]

Aim. In tropical Africa, savannas cover huge areas, have high plant species richness, and are considered as a major natural resource for most countries. There is, however, little information available on their floristics and biogeography at the continental scale, despite the importance of such information for our understanding of the drivers of species diversity at various scales and for effective conservation and management. Here, we collated and analysed floristic data from across the continent in order to propose a biogeographic regionalization for African savannas. Location. We collated floristic information (specifically woody species lists) for 298 samples of savanna vegetation across Africa, extending from 18°N to 33°S and from 17°W to 48°E. Taxon. We focused on native woody species. Methods. We used ordination and clustering to identify the floristic discontinuities and gradual transitions across African savannas. Floristic relationships, specificity and turnover, within and between floristic clusters, were analysed using a (dis-)similarity-based approach. Results. We identified eight floristic clusters across African savannas which in turn were grouped into two larger macro-units. Ordinations at species and genus levels showed a clear differentiation in woody species composition between the North/West macro-unit and the South/East macro-unit. This floristic discontinuity matches to the High (i.e., N&W) and Low (S&E) division of Africa previously proposed by White (1983) and which tracks climatic and topographic variation. In the N&W savannas, the floristic gradient determined by rainfall was partitioned into the Sudanian (drier) and Guinean (wetter) clusters. Within the highly heterogeneous S&E savannas and woodlands, six clusters were identified: Ugandan, Ethiopian, Mozambican, Zambezian, Namibian and South-African. Main conclusions. The proposed pan-African classification of savannas and woodlands might assist the development of coordinated management and conservation policies. [less ▲]

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See detailEcosystem services assessment in Southeast Cameroon tropical forests
Lhoest, Simon ULiege; Dufrêne, Marc ULiege; Jamar, Pierre et al

Scientific conference (2019, March 11)

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See detailEcological niche divergence associated with species and populations differentiation in Erythrophleum (Fabaceae, Caesalpinioideae)
Gorel, Anaïs ULiege; Duminil, Jérôme; Doucet, Jean-Louis ULiege et al

in Plant Ecology and Evolution (2019)

Background and aims – The isolation of populations inside forest refugia during past climate changes has widely been hypothesized as a major driver of tropical plant diversity. Environmental conditions ... [more ▼]

Background and aims – The isolation of populations inside forest refugia during past climate changes has widely been hypothesized as a major driver of tropical plant diversity. Environmental conditions can also influence patterns of diversity by driving divergent selection leading to local adaptation and, potentially, ecological speciation. Genetic and phylogenetic approaches are frequently used to study the diversification of African tree clades. However, the environmental space occupied by closely related species or intra-specific gene pools is barely quantified, though needed to properly test hypotheses on diversification processes. Methods – Using species distribution models, we determined the bioclimatic constraints on the distribution of closely related species and intra-specific gene pools. Our study model, Erythrophleum (Fabaceae - Caesalpinioideae), is a tropical tree genus widespread across Africa, and vastly investigated for genetics. Here, we combined the available phylogenetic data with information on niche divergence to explore the role of ecology into diversification at the species and gene pool levels. Key results – Ecological speciation through climate has probably played a key role in the evolution of the Erythrophleum species. The differential climatic niche of the species indicated adaptive divergence along rainfall gradients, that have probably been boosted by past climate fluctuations. At the gene pool level, past climate changes during the Pleistocene have shaped genetic diversity, though within Erythrophleum suaveolens, adaptive divergence also occurred. Conclusions – We believe that ecological speciation is a key mechanism of diversification for tropical African tree species, since such climatic niche partition exist among many other genera. Modeling the environmental niche of closely related taxa, and testing for niche differentiation, combined with divergence dates offered new insights on the process of diversification. [less ▲]

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See detailConservation value of protected and logged tropical forests in Cameroon
Lhoest, Simon ULiege; Fonteyn, Davy ULiege; Daïnou, Kasso ULiege et al

Scientific conference (2019, January 25)

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See detailBiogeography and evolutionary ecology of the woody flora in tropical Africa
Fayolle, Adeline ULiege; Gorel, Anaïs ULiege; Swaine, Michael D. et al

Conference (2019)

Tropical forest and savanna are globally critical biomes and cover the overwhelming majority of the African continent. They support the lives of nearly a billion people, store a huge amount of carbon ... [more ▼]

Tropical forest and savanna are globally critical biomes and cover the overwhelming majority of the African continent. They support the lives of nearly a billion people, store a huge amount of carbon above- and below-ground, and host great biodiversity, including the iconic megafauna. The current extent of tropical forests and savannas, however, remains uncertain, because continental studies are based on remote-sensing products that often fail to distinguish tropical forests and savannas from intermediate vegetation states and in patchy landscapes. Here, we developed a very different approach based on the specific floristics of the forest and savanna biomes, using woody species lists from hundreds of sites scattered across Africa. We specifically propose a biome index based on species affinity to the forest or savanna biome that could be used in the future to predict the distribution of tropical forest and savanna following climate change scenario, or in the past to reconstruct past biomes using palynological or anthracological records. We additionally used the largest ever collation of georeferenced herbarium records made available by the RAINBIO project in association with our biome index, to delineate the distribution of tropical forest and savanna across Africa for circa 1400 tree and shrub species. This allowed us to propose a first map of biome specificity, entirely derived from floristic information, and that could be used as a base map for management and conservation, and specifically for the design of re- and af-forestation programs. Biome specificity was also examined across the phylogeny to identify clades associated with specific biome and environmental conditions, and clades transcending biomes. These results, combining information on species composition in specific sites and on species distribution from herbarium records, provided strong insights into the biogeography and evolutionary ecology of the woody flora in tropical Africa. [less ▲]

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See detailComparative analysis of two sister Erythrophleum species (Leguminosae) reveal contrasting transcriptome-wide responses to early drought stress
Neji, M.; Gorel, Anaïs ULiege; Ojeda, D. I. et al

in Gene (2019), 694

With the ongoing climate change, African rainforests are expected to experience severe drought events in the future. In Africa, the tropical genus Erythrophleum (Fabaceae) includes two forest sister ... [more ▼]

With the ongoing climate change, African rainforests are expected to experience severe drought events in the future. In Africa, the tropical genus Erythrophleum (Fabaceae) includes two forest sister timber tree species displaying contrasting geographical distributions. Erythrophleum ivorense is adapted to wet evergreen Guineo-Congolian forests, whereas E. suaveolens occurs in a wider range of climates, being found in moist dense forests but also in gallery forests under a relatively drier climate. This geographical distribution pattern suggests that the two species might cope differently to drought at the genomic level. Yet, the genetic basis of tolerance response to drought stress in both species is still uncharacterized. To bridge this gap, we performed an RNA-seq approach on seedlings from each species to monitor their transcriptional responses at different levels of drought stress (0, 2 and 6 weeks after stopping watering seedlings). Monitoring of wilting symptoms revealed that E. suaveolens displayed an earlier phenotypic response to drought stress than E. ivorense. At the transcriptomic level, results revealed 2020 (1204 down-regulated/816 up-regulated) and 1495 differentially expressed genes (DEGs) in response to drought stress from a total of 67,432 and 66,605 contigs assembled in E. ivorense and E. suaveolens, respectively. After identifying 30,374 orthologs between species, we found that only 7 of them were DEGs shared between species, while 587 and 458 were differentially expressed only in E. ivorense or E. suaveolens, respectively. GO and KEGG enrichment analysis revealed that the two species differ in terms of significantly regulated pathways as well as the number and expression profile of DEGs (Up/Down) associated with each pathway in the two stress stages. Our results suggested that the two studied species react differently to drought. E. suaveolens seems displaying a prompt response to drought at its early stage strengthened by the down-regulation of many DEGs encoding for signaling and metabolism-related pathways. A considerable up-regulation of these pathways was also found in E. ivorense at the late stage of drought, suggesting this species may be a late responder. Overall, our data may serve as basis for further understanding the genetic control of drought tolerance in tropical trees and favor the selection of crucial genes for genetically enhancing drought resistance. © 2019 Elsevier B.V. [less ▲]

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See detailGrowth determinants of timber species Triplochiton scleroxylon and implications for forest management in central Africa
Ligot, Gauthier ULiege; Fayolle, Adeline ULiege; Gourlet-Fleury, Sylvie et al

in Forest Ecology and Management (2019), 437

The sustainability of the polycyclic logging system in tropical forests has been increasingly questioned for a variety of reasons, and particularly in central Africa as commercial species, mostly light ... [more ▼]

The sustainability of the polycyclic logging system in tropical forests has been increasingly questioned for a variety of reasons, and particularly in central Africa as commercial species, mostly light-demanding long-lived pioneer species, usually fail to recover a stable number of large trees after exploitation. Several factors are known to affect tropical tree demographic processes, like tree growth, survival and recruitment. Tree growth has particularly been showed to depend on ecological conditions, tree genetics, and competition with surrounding vegetation, as well as tree size or ontogeny. Yet, due to the paucity of available data, the importance of such factors is unclear and usually ignored when estimating future timber yields. To fill this gap, we chose to evaluate the variability in growth of one African long-lived pioneer and commercially very important species: Triplochiton scleroxylon K. Schum, gathering a broad dataset composed of tree ring data recorded in one site in Cameroon and periodic field inventory data recorded in seven sites across central Africa. In total, we analyzed 13,225 records of annual tree diameter increments recorded over 920 trees from seven sites in Cameroon, Republic of the Congo and Central African Republic. We evaluated (i) to what extent the average growth of trees that reach harvestable dimensions differs from population average and (ii) to what extent past perturbations influence the growth of remaining trees. We found the diameter growth of T. scleroxylon to be remarkably variable and this study provided an unprecedented quantification of the magnitude of some key growth determinants. In unlogged forests, the diameter increment of T. scleroxylon ranged between 0.40 cm year-1 in Southern Cameroon and 0.83 cm year-1 in South-Eastern Cameroon. The diameter increment was weakly related to tree size but increased twofold from unlogged to logged forests. Perturbation caused by logging stimulates growth of T. scleroxylon for at least 10-15 years. Finally, harvestable timber stock of large-sized T. scleroxylon was found to be constituted by trees that grew in average twice faster than trees of the entire extant population. As more and more inventory data become available, quantifying these effects could be replicated for other timber species and in other sites, to improve the accuracy of future timber resource estimates and improve forest management guidelines. [less ▲]

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See detailRéviser les tarifs de cubage pour prendre en compte l'évolution de la ressource au Cameroun
Ligot, Gauthier ULiege; Dubart, Nicolas; Tchowo Hapi, Mauriad et al

in Bois et Forêts des Tropiques (2018), 338

La connaissance du volume exploitable est une information essentielle tant pour la gestion que pour le contrôle de l’exploitation forestière. En Afrique centrale, l’estimation des volumes repose ... [more ▼]

La connaissance du volume exploitable est une information essentielle tant pour la gestion que pour le contrôle de l’exploitation forestière. En Afrique centrale, l’estimation des volumes repose essentiellement sur l’utilisation de tarifs de cubage à une entrée, spécifique à chaque essence, et prédisant le volume exploitable à partir du diamètre de l’arbre. Or, récemment, de nombreux acteurs de la gestion forestière au Cameroun reportent une inadéquation entre les volumes commerciaux estimés avec les tarifs de cubage imposés par l’administration et les volumes estimés à partir des mesures de la longueur et du diamètre des billes exploitées. Afin de vérifier la justesse des tarifs de cubage imposés par l’administration camerounaise, nous avons réalisé un échantillonnage destructif pour 12 essences jouant un rôle crucial dans le commerce du bois au Cameroun, et développé de nouveaux tarifs de cubage, qui ont été comparés avec les tarifs imposés par l’administration camerounaise et 52 autres tarifs de cubage disponibles dans la littérature. Dans quatre concessions forestières du Cameroun, représentatives des différentes conditions écologiques prévalant dans ce pays, 732 arbres ont été abattus et leur volume a été mesuré par la méthode des billons successifs. Des tarifs de cubage à une entrée, fonction uniquement du diamètre de référence, ont ensuite été ajustés par la méthode des moindres carrés généralisés. Notre étude confirme l’existence de biais entre les volumes mesurés et les volumes estimés en utilisant les tarifs de cubage imposés par l’administration camerounaise. En conséquence, de nouveaux tarifs de cubage et un abaque de correction sont proposés. Enfin, la majorité des tarifs de cubages testés présentaient un biais similaire qui résulte vraisemblablement d’une évolution de la ressource et des pratiques d’exploitation. [less ▲]

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See detailAssessment of mammal biodiversity and bushmeat offtake in the tropical forests of southeastern Cameroon
Lhoest, Simon ULiege; Fonteyn, Davy ULiege; Hette, Samuel et al

Poster (2018, November 27)

Tropical forests of central Africa host an important part of the world’s terrestrial biodiversity and provide numerous provisioning, regulating, and cultural ecosystem services to human populations. Major ... [more ▼]

Tropical forests of central Africa host an important part of the world’s terrestrial biodiversity and provide numerous provisioning, regulating, and cultural ecosystem services to human populations. Major threats hang over those diverse ecosystems, namely land use changes and consumption of bushmeat. Our study aimed to assess mammal diversity and bushmeat consumption in three contrasted and largely represented forest land allocation types in southeastern Cameroon: (i) a protected area, (ii) a FSC-certified logging concession, and (iii) three community forests. Mammal inventories were conducted with 44 camera traps installed for 3 months. Bushmeat consumption was quantified using both tracking of volunteer hunters over 651 kilometers and the daily monitoring of the food bowl of 55 households for 3 months. Though a great part of the mammal diversity is retained inside the logging concession, the protected area holds the richest and most abundant mammal communities, whereas community forests were found to be defaunated and structurally disturbed. The size of the hunting territories is influenced by many factors such as human population density or the presence of alternative protein sources. Although poaching controls in the protected area and, to a lesser extent, in the certified logging concession appear to play a deterrent role, evidence of hunting activities were found in all land allocation types. Bushmeat represents on average 56% of the animal protein consumed by households, the remaining part being mainly fish. Our results demonstrated the ability of the certified logging concession and the protected area in the conservation of wildlife species and the provision of bushmeat for local populations. It remains essential to maintain and develop anti-poaching patrols in those areas, strategically based on geographic data of hunting pressure. Current levels of hunting activities also confirm the need for the development of alternatives to bushmeat. [less ▲]

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See detailSimulating last glacial and postglacial distributions of African tropical trees with a dynamic vegetation model.
Dury, Marie ULiege; Henrot, Alexandra-Jane ULiege; Lézine, Anne-Marie et al

Conference (2018, August 16)

Climate change and human pressure threaten species richness of African tropical forests. Understanding how the past climate changes have shaped the current distribution and composition of African ... [more ▼]

Climate change and human pressure threaten species richness of African tropical forests. Understanding how the past climate changes have shaped the current distribution and composition of African rainforests can certainly help to the ecosystem conservation in the future. This topic is addressed in the framework of the multi-disciplinary AFRIFORD project (Genetic and palaeoecological signatures of African rainforest dynamics: pre-adapted to change?, http://www.ulb.ac.be/facs/sciences/afriford/). In parallel to genetic and palynological analyses, the CARAIB dynamic vegetation model is applied at the level of African tropical plant species to simulate change in their distributions from the Last Glacial Maximum (21,000 years BP) to the present in sub-Saharan Africa. We prepared a set of about a hundred species, mostly composed of tropical tree species (evergreen/deciduous, cool/warm taxa) for which we compiled observed occurrence data (e.g.., RAINBIO database), determined climatic requirements and gathered some specific traits (e.g., TRY database). From LGM to present time, the vegetation model is forced with the 1-kyr snapshot outputs of the HadCM3 climate model. Statistically downscaled at a spatial resolution of 0.5°, we only kept modelled past anomalies that we added to the GSWP3 (20 CR) climate data chosen as the reference for the historical period. Sub-Saharan simulations are performed with CARAIB forced by these climatic projections to simulate the net primary productivity of the species over time and space. We analyse the modelled changes in tropical forest composition and extension as well as in the distribution of individual species whose glacial refugia and postglacial dynamics remain poorly known. [less ▲]

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See detailWhat controls local-scale aboveground biomass variation in central Africa? Testing structural, composition and architectural attributes
Loubota Panzou, Grâce Jopaul ULiege; Fayolle, Adeline ULiege; Feldpausch, Ted R. et al

in Forest Ecology and Management (2018), 429

Tropical forests play a key role in regulating the terrestrial carbon cycle and climate change by storing a large amount of carbon. Yet, there is considerable uncertainty about the amount and spatial ... [more ▼]

Tropical forests play a key role in regulating the terrestrial carbon cycle and climate change by storing a large amount of carbon. Yet, there is considerable uncertainty about the amount and spatial variation of aboveground biomass (AGB), especially in the relatively less studied African tropical forests. In this study, we explore the local-scale variation and determinants of plot-level AGB, between and within two types of forests, the Celtis and Manilkara forests, growing under the same climate but on different geological substrates in the northern Republic of Congo. In each forest site, all trees ≥10 cm diameter were censured in 36 × 1-ha plots and we measured tree height and crown size using a subsample of 18 × 1-ha of these plots. We developed height-diameter and crown-diameter allometric relationships and tested whether they differed between the two sites. For each 1-ha plot, we further estimated the AGB and calculated structural attributes (stem density and basal area), composition attributes (wood density) and architectural attributes (tree height and crown size), the latter being derived from site-specific allometric relationships. We found strong between-site differences in height-diameter and crown-diameter allometries. For a given diameter, trees were taller in the Celtis forest while they had larger crown in the Manilkara forest. Similar trends were found for the sixteen species present in both forest sites, suggesting an environmental control of tree allometry. Although there were some between-site differences in forest structure, composition and architecture, we did not detect any significant difference in mean AGB between the Celtis and the Manilkara forests. The AGB variation was related to the heterogeneous distribution of large trees, and influenced by basal area, height and crown dimensions, and to a lesser extent wood density. These forest attributes have strong practical implications on emerging remote-sensing technologies for carbon monitoring in tropical forests. [less ▲]

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See detailThe importance of stand structure and tree allometry for local-scale variation in aboveground biomass
Loubota Panzou, Grâce Jopaul ULiege; Feldpausch, Ted; Ligot, Gauthier ULiege et al

Poster (2018, March 26)

Aboveground biomass (AGB) plays a critical role in determining the long-term dynamics of carbon in tropical forests. Consequently, understanding what factors are important in controlling AGB in tropical ... [more ▼]

Aboveground biomass (AGB) plays a critical role in determining the long-term dynamics of carbon in tropical forests. Consequently, understanding what factors are important in controlling AGB in tropical forests has major implications for projecting the terrestrial carbon stocks, in the context of an increasingly uncertain future. In this study, we aimed to explore the local-scale AGB variation in two forest sites in northern Congo, representative of two contrasted forest types under the same climate but growing on vastly different soils and parent material (quartzite substrate for CIB and sandstone substrate for Mokabi). Tree diameter was measured in 36 permanent forest plots of 1-ha in each site, and tree allometry (total tree height, height of the first branch and crown dimensions) was measured on a subsample of 18 plots of 1-ha in each site. Allometric data were available for a total of 2202 trees (1040 for CIB and 1162 for Mokabi) covering a large range of diameters (10 – 200 cm). We first developed site-specific allometric models that were then used to estimate AGB at plot level. We then explore the determinants of AGB variation at plot level using multiple regressions and mixed linear models. For a given diameter, trees tended to be taller and to have deeper crown in the Celtis forest of the CIB (rich soil) while they tended to have larger crown in the Manilkara forest of the Mokabi (sandy soil). Similar trends were reported within species for the sixteen species shared by both forest types, suggesting an environmental control of tree allometry. We found that AGB strongly varied between the two forest sites, with greater AGB per hectare in the Celtis forest of the CIB. Within sites AGB variation was positively related to basal area, though between-site allometric attributes (total height and crown radius) were important determinants of AGB variation. These results have strong implications for forest biomass and carbon monitoring. [less ▲]

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See detailState of the art on tropical tree allometry
Fayolle, Adeline ULiege; Libalah, Moses; Medjibé, Vincent P.

Conference (2018)

In the recent decades, a renewed interest has been observed for the estimation and monitoring of forest biomass and carbon worldwide, and specifically in the tropics with the ongoing negotiations under ... [more ▼]

In the recent decades, a renewed interest has been observed for the estimation and monitoring of forest biomass and carbon worldwide, and specifically in the tropics with the ongoing negotiations under the UNFCCC for the implementation of the REDD+ mechanism. Because all methods to estimate biomass and carbon stocks contained in tropical forests rely on an allometric equation to convert inventory data into biomass estimates, tropical tree allometry recently received great attention from scientists and research sponsors. Pantropical allometric models early developed in the 1980s, and 2000s, were recently revised and a global consensus is emerging toward a universal approach to estimate biomass and carbon stocks in tropical forest using generic allometric models. Many local allometric models were also recently established, specifically in places previously under-sampled, such as the forests of the Congo basin. We believe that the newly collected data that have and will have strong practical implications for the estimation of forest biomass and carbon stocks are also extremely important to explore the between-site and between-species variations in tropical tree allometry. Despite major advances in our understanding of tropical tree allometry, an integrative view on tropical tree allometry, its variation and ecological (and evolutionary) significance, is yet to arise. As an introduction to the session, we will present the interest of analyzing between-site and between-species variations in tropical tree allometry, integrating methods and spatial scales, and bridging disciplines and approaches to reach a unifying view. [less ▲]

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See detailPhenological strategies and trends witnessed across Africa
Fayolle, Adeline ULiege

Conference (2018)

Using various data sources, we addressed the diversity of phenological strategies and trends witnessed across Africa, and the consequences for forest management. Using field observations in several sites ... [more ▼]

Using various data sources, we addressed the diversity of phenological strategies and trends witnessed across Africa, and the consequences for forest management. Using field observations in several sites (n=11) across Central Africa, the size at reproduction, a key aspect of species life history, was evaluated for most major timber species (n=31 species). Diameter at reproduction strongly varied among species and was correlated with adult stature (maximum diameter and height). For some species, reproductive diameter thresholds showed substantial variation between sites, and crown exposure to light had a significant positive effect on reproductive status. The majority of minimum cutting diameter limits (MCDLs, imposed by national forest administration) was found to be suitable, trees having high probability for being seed trees at MCDL. Using field and herbarium data, the spatial variation in flowering phenology was examined across the whole range of species, and using remotely-sensed data of vegetation activity (EVI from MODIS satellite), the reversed phenology on both side of the climatic hinge, the area in Atlantic Central Africa where the rainfall seasonality reverses, was specifically examined. Herbarium data can be used to derive phenological information, and specifically the onset of flowering, probably because most central African tree species have a regular and annual phenology. She also found strong support for the spatial variation in tree phenology associated with the shift in rainfall seasonality, for flowering (field and herbarium data) and for forest functioning (EVI seasonality), with however, differences among species. [less ▲]

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See detailRefining species traits in a dynamic vegetation model to project the impacts of climate change on tropical trees in Central Africa
Dury, Marie ULiege; Mertens, L.; Fayolle, Adeline ULiege et al

in Forests (2018), 9(11),

African tropical ecosystems and the services they provide to human society suffer from an increasing combined pressure of land use and climate change. How individual tropical tree species respond to ... [more ▼]

African tropical ecosystems and the services they provide to human society suffer from an increasing combined pressure of land use and climate change. How individual tropical tree species respond to climate change remains relatively unknown. In this study, we refined the species characterization in the CARAIB (CARbon Assimilation In the Biosphere) dynamic vegetation model by replacing plant functional type morpho-physiological traits by species-specific traits. We focus on 12 tropical tree species selected for their importance in both the plant community and human society. We used CARAIB to simulate the current species net primary productivity (NPP), biomass and potential distribution and their changes in the future. Our results indicate that the use of species-specific traits does not necessarily result in an increase of predicted current NPPs. The model projections for the end of the century highlight the large uncertainties in the future of African tropical species. Projected changes in species distribution vary greatly with the general circulation model (GCM) and, to a lesser extent, with the concentration pathway. The question about long-term plant response to increasing CO2 concentrations also leads to contrasting results. In absence of fertilization effect, species are exposed to climate change and might lose 25% of their current distribution under RCP8.5 (12.5% under RCP4.5), considering all the species and climatic scenarios. The vegetation model projects a mean biomass loss of -21.2% under RCP4.5 and -34.5% under RCP8.5. Potential range expansions, unpredictable due to migration limitations, are too limited for offsetting range contraction. By contrast, if the long-term species response to increasing [CO2] is positive, the range reduction is limited to 5%. However, despite a mean biomass increase of 12.2%, a positive CO2 feedback might not prevent tree dieback. Our analysis confirms that species will respond differently to new climatic and atmospheric conditions, which may induce new competition dynamics in the ecosystem and affect ecosystem services. © 2018 by the authors. [less ▲]

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See detailPlant demographic and functional responses to management intensification: A long-term study in a Mediterranean rangeland
Garnier, E.; Fayolle, Adeline ULiege; Navas, M.-L. et al

in Journal of Ecology (2018), 106(4), 1363-1376

Understanding how functional traits, which are key for plant functioning, relate to demographic parameters of populations is central to tackle pending issues in plant ecology such as the forecast of the ... [more ▼]

Understanding how functional traits, which are key for plant functioning, relate to demographic parameters of populations is central to tackle pending issues in plant ecology such as the forecast of the fate of populations and communities in a changing world, the quantification of community assembly processes or the improvement of species distribution models. We addressed this question in the case of species from a Mediterranean rangeland of southern France. Changes in species abundance in response to management intensification (fertilization and increased grazing pressure) were followed over a 28-year period. Probabilities of presence, and elasticities of the changes in the probability of space occupancy to colonization and survival, which are analogues of demographic parameters, were calculated for 53 species from the time series of abundance data using a space occupancy model. Nine quantitative traits pertaining to resource use, plant morphology, regeneration and phenology were measured on these species and related to demographic parameters. The long-term dynamics of species in response to management intensification was associated with major changes in functional traits and strategies. Changes in the probability of occurrence—analogous to population growth rate—were correlated with traits describing the fast-slow continuum of leaf functioning. The elasticity of population growth rate to colonization was significantly related to reproductive plant height and seed mass, and to a lower extent, to leaf carbon isotopic ratio. Synthesis. The functional response of species to management intensification corresponds to a shift along the second axis of a recently identified global spectrum of plant form and function, which maps, to some extent, onto the fast-slow continuum of life-history strategies. By contrast, the elasticity of colonization relates to the global spectrum axis capturing the size of organs. Seed mass contributes to this axis and is assumed to relate to one of the important traits structuring the reproductive strategy axis of life histories as well, namely net reproductive rate. While this mapping between functional and life-history traits is appealing, further tests in contrasting types of communities are required to assess its degree of generality. © 2018 The Authors. Journal of Ecology © 2018 British Ecological Society [less ▲]

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See detailHow do tropical trees cope with drought: the case of Erythrophleum species
Gorel, Anaïs ULiege; Fayolle, Adeline ULiege

Poster (2018)

Understanding the mechanisms used by tropical tree species to cope with drought will be central in predicting forest responses to climate change. The study of plant traits, as wood anatomy and hydraulics ... [more ▼]

Understanding the mechanisms used by tropical tree species to cope with drought will be central in predicting forest responses to climate change. The study of plant traits, as wood anatomy and hydraulics, holds promise for capturing response to drought with the major aim of informing projections of climate impacts. However, the links between wood anatomy, plant hydraulics and species fitness in a given environment are still barely understood for the majority of tropical trees. We proposed to use hydraulics and wood traits to examine adaptation to water availability among congeneric tropical tree species in Africa. We hypothesized that wood anatomy determines tree hydraulics and drought responses which, in turn, influence individual tree performance and fitness. We specifically focused on two congeneric species, Erythrophleum ivorense and Erythrophleum suaveolens, with known phylogeny and occupying contrasting habitats. In the natural habitat of each species, we quantified vulnerability to cavitation, volumetric water content and capacitance and the underlying wood traits in branch and stem. Growth was also examined. A common garden in the natural habitat of E. suaveolens was specifically used to confirm that the observed differences in wood traits and growth are largely genotypic in origin rather than environmentally plastic. While the two species broadly share the same general wood anatomical features (Inside Wood 2004) and are hard to distinguish in the field, we identified some but slight differences in wood traits, particularly in vessel-associated traits, that resulted in strong differences in tree hydraulics, performance and overall distribution. Specifically, the wet forest species, E. ivorense, had wider vessels, lower vessel cell-wall reinforcement and wider intervessel pits than E. suaveolens. These traits allow a high hydraulic conductivity and the fast growth of E. ivorense, but confer high vulnerability to cavitation. [less ▲]

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