References of "Hambuckers, Alain"
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See detailStructure and floristic composition of Kibira rainforest, Burundi
Hakizimana, Dismas; Huynen, Marie-Claude ULg; Hambuckers, Alain ULg

in Tropical Ecology (in press), 59(1),

This paper gives the results of the first census of trees in the 32.15 ha plot in order to provide tree species richness in Kibira rainforest (Burundi). All trees ≥ 10 cm dbh were permanently tagged and ... [more ▼]

This paper gives the results of the first census of trees in the 32.15 ha plot in order to provide tree species richness in Kibira rainforest (Burundi). All trees ≥ 10 cm dbh were permanently tagged and their girth measured. The forest structure pattern analysed were diameter at breast height (dbh), basal area, relative dominance, and relative density, Importance Value Index (IVI) and Family Importance Value (FIV). In total, 6504 trees representing 70 species, 67 genera and 37 families were recorded. Tree density was 202 stems/ha, with a basal area of 21.05m²/ha. Seventeen families were represented by a single species each, eleven families were represented by two species each, five families were represented by three species each, and four families were represented by four species each. The most important families in relation to FIV were Euphorbiaceae, Myrtaceae and Araliaceae. Macaranga kilimandscharica, Syzygium guineense and Polyscias fulva were the most important species in relation to IVI. Two tree species were found to be endemic to the Albertine Rift and one species probably endemic to the Albertine Rift. The Shannon-Weiner index (H') and eveness index (J') were respectively 3.18 and 0.75. This study provides a baseline for the management of Kibira National Park. As local communities still depend on forest resources, conservation awareness-raising and education actions have to focus in nearby villages, and growing some fast-growing native trees in the vicinity of the settlement, would be helpful for local communities, this would reduce their dependence on forest resources. [less ▲]

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See detailFruit biomass availability along a forest cover gradiant
Pessoa; Rocca, Larissa; Talora, Daniela et al

in Biotropica (2016)

Habitat loss is the main driver of the current high rate of species extinction, particularly in tropical forests. Understanding the factors associated with biodiversity loss, such as the extinction of ... [more ▼]

Habitat loss is the main driver of the current high rate of species extinction, particularly in tropical forests. Understanding the factors associated with biodiversity loss, such as the extinction of species interactions and ecological functions, is an urgent priority. Here, our aim was to evaluate how landscape-scale forest cover influences fruit biomass comparing different tree functional groups. We sampled 20 forest fragments located within landscapes with forest cover ranging from 2 to 93 percent in the Atlantic Forest of southern Bahia, Brazil. In each fragment, we established five plots of 25 × 4 m and carried out phenological observations on fleshy fruit throughout one year on all trees ≥ 5 cm dbh. We estimated fruit availability by direct counting all fruits and derived fruit biomass from this count. We used spatial mixed linear models to evaluate the effects of forest cover on species richness, abundance, and fruit biomass. Our results indicated that forest cover was the main explanatory variable and negatively influenced the total richness and abundance of zoochoric and shade-tolerant but not shade-intolerant species. A linear model best explained variations in richness and abundance of total and shade-tolerant species. We also found that forest cover was positively correlated with the fruit biomass produced by all species and by the shade-tolerant assemblages, with linear models best explaining both relationships. The loss of shade-tolerant species and the lower fruit production in fragments with lower landscape-scale forest cover may have implications for the maintenance of frugivore, seed dispersal service, and plant recruitment. [less ▲]

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See detailInfluence of frugivore taxa on the generation of plant recruitment foci and on the composition of plant recruits’ communities
Trolliet, Franck ULg; Forget, Pierre-Michel; Doucet, Jean-Louis ULg et al

Conference (2016, June 20)

Frugivores can disperse seeds in a spatially contagious pattern and generate recruitment foci (e.g. under fruiting trees). This process is increasingly explored to understand the influence of frugivores ... [more ▼]

Frugivores can disperse seeds in a spatially contagious pattern and generate recruitment foci (e.g. under fruiting trees). This process is increasingly explored to understand the influence of frugivores on the spatial organization of plant communities, and can also serve as a method to efficiently monitor the consequences of animal extirpation. However, there is limited evidence contrasting the influence of different frugivores taxa on the creation of recruitment foci under fruiting trees, and, similarly, on the overall composition of plant communities. Here, we aimed (i) to compare the role of hornbills and primates in creating recruitment foci, and (ii) to investigate how the presence of hornbills, primates and elephants influence the overall composition of plant recruit’s community in an anthropized forest-savanna mosaic in DR Congo. We firstly compared the community of recruits (0.5-2 m high) in 25-m² plots below hornbill-dispersed trees (Staudtia kamerunensis, N=32), primate-dispersed trees (Dialium spp., N=26), and in control plots located below other tree species (N= 4900 m²). Secondly, we considered all plots to compare the community of recruits in five sites characterized by contrasted levels of hunting and housing different seed disperser communities. Our preliminary results indicate (i) communities of recruits below hornbill-dispersed trees are significantly more dense and richer than in control plots, unlike these below primate-dispersed trees. Also, (ii) recruits in sites less affected by hunting, housing more large frugivores, including elephants, tend to belong to species with longer seeds. We conclude that hornbills generate recruitment foci under fruiting trees, which can serve as an efficient tool to monitor the ecological consequences of their extirpation. Moreover, we discuss the potential influence of the different studied frugivore taxa and the risk of their extirpation from afro-tropical forests on the composition of plant recruits’ community. [less ▲]

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See detailUsing a dynamic vegetation model for future projections of crop yields : application to Belgium in the framework of the VOTES and MASC projects
Jacquemin, Ingrid ULg; Henrot, Alexandra-Jane ULg; Fontaine, Corentin M. et al

Poster (2016, April 22)

Dynamic vegetation models (DVM) were initially designed to describe the dynamics of natural ecosystems as a function of climate and soil, to study the role of the vegetation in the carbon cycle. These ... [more ▼]

Dynamic vegetation models (DVM) were initially designed to describe the dynamics of natural ecosystems as a function of climate and soil, to study the role of the vegetation in the carbon cycle. These models are now directly coupled with climate models in order to evaluate feedbacks between vegetation and climate. But DVM characteristics allow numerous other applications, leading to amelioration of some of their modules (e.g., evaluating sensitivity of the hydrological module to land surface changes) and developments (e.g., coupling with other models like agent-based models), to be used in ecosystem management and land use planning studies. It is in this dynamic context about DVMs that we have adapted the CARAIB (CARbon Assimilation In the Biosphere) model. One of the main improvements is the implementation of a crop module, allowing the assessment of climate change impacts on crop yields. We try to validate this module at different scales: - from the plot level, with the use of eddy-covariance data from agricultural sites in the FLUXNET network, such as Lonzée (Belgium) or other Western European sites (Grignon, Dijkgraaf,. . . ), - to the country level, for which we compare the crop yield calculated by CARAIB to the crop yield statistics for Belgium and for different agricultural regions of the country. Another challenge for the CARAIB DVM was to deal with the landscape dynamics, which is not directly possible due to the lack of consideration of anthropogenic factors in the system. In the framework of the VOTES and the MASC projects, CARAIB is coupled with an agent-based model (ABM), representing the societal component of the system. This coupled module allows the use of climate and socio-economic scenarios, particularly interesting for studies which aim at ensuring a sustainable approach. This module has particularly been exploited in the VOTES project, where the objective was to provide a social, biophysical and economic assessment of the ecosystem services in four municipalities under urban pressure in the center of Belgium. The biophysical valuation was carried out with the coupled module, allowing a quantitative evaluation of key ecosystem services as a function of three climatic and socio-economic scenarios. [less ▲]

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See detailHigh-resolution climate and land surface interactions modeling over Belgium: current state and decennial scale projections
Jacquemin, Ingrid ULg; Henrot, Alexandra-Jane ULg; Beckers, Veronique et al

Poster (2016, April 21)

The interactions between land surface and climate are complex. Climate changes can affect ecosystem structure and functions, by altering photosynthesis and productivity or inducing thermal and hydric ... [more ▼]

The interactions between land surface and climate are complex. Climate changes can affect ecosystem structure and functions, by altering photosynthesis and productivity or inducing thermal and hydric stresses on plant species. These changes then impact socio-economic systems, through e.g., lower farming or forestry incomes. Ultimately, it can lead to permanent changes in land use structure, especially when associated with other non-climatic factors, such as urbanization pressure. These interactions and changes have feedbacks on the climate systems, in terms of changing: (1) surface properties (albedo, roughness, evapotranspiration, etc.) and (2) greenhouse gas emissions (mainly CO2, CH4, N2O). In the framework of the MASC project (« Modelling and Assessing Surface Change impacts on Belgian and Western European climate »), we aim at improving regional climate model projections at the decennial scale over Belgium and Western Europe by combining high-resolution models of climate, land surface dynamics and socio-economic processes. The land surface dynamics (LSD) module is composed of a dynamic vegetation model (CARAIB) calculating the productivity and growth of natural and managed vegetation, and an agent-based model (CRAFTY), determining the shifts in land use and land cover. This up-scaled LSD module is made consistent with the surface scheme of the regional climate model (RCM: ALARO) to allow simulations of the RCM with a fully dynamic land surface for the recent past and the period 2000-2030. In this contribution, we analyze the results of the first simulations performed with the CARAIB dynamic vegetation model over Belgium at a resolution of 1km. This analysis is performed at the species level, using a set of 17 species for natural vegetation (trees and grasses) and 10 crops, especially designed to represent the Belgian vegetation. The CARAIB model is forced with surface atmospheric variables derived from the monthly global CRU climatology or ALARO outputs (from a 4 km resolution simulation) for the recent past and the decennial projections. Evidently, these simulations lead to a first analysis of the impact of climate change on carbon stocks (e.g., biomass, soil carbon) and fluxes (e.g., gross and net primary productivities (GPP and NPP) and net ecosystem production (NEP)). The surface scheme is based on two land use/land cover databases, ECOPLAN for the Flemish region and, for the Walloon region, the COS-Wallonia database and the Belgian agricultural statistics for agricultural land. Land use and land cover are fixed through time (reference year: 2007) in these simulations, but a first attempt of coupling between CARAIB and CRAFTY will be made to establish dynamic land use change scenarios for the next decades. A simulation with variable land use would allow an analysis of land use change impacts not only on crop yields and the land carbon budget, but also on climate relevant parameters, such as surface albedo, roughness length and evapotranspiration towards a coupling with the RCM. [less ▲]

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See detailAssessing the Risk of Ecosystem Disruption in Europe using a Dynamic Vegetation Model driven by CMIP5 Regional Climatic Projections from EURO-CORDEX
Dury, Marie ULg; Hambuckers, Alain ULg; Henrot, Alexandra-Jane ULg et al

Conference (2015, December 18)

While the combination of warmer and drier mean climatic conditions can have severe impacts on ecosystems, extreme events like droughts or heat waves that break the gradual climate change can have more ... [more ▼]

While the combination of warmer and drier mean climatic conditions can have severe impacts on ecosystems, extreme events like droughts or heat waves that break the gradual climate change can have more long-term consequences on ecosystem composition, functioning and carbon storage. Hence, it is essential to assess the changes in climatic variability and the changes in frequency of extreme events projected for the future. Ecosystems could not be in a condition to adapt to these new conditions and might be disrupted. Here, the process-based dynamic vegetation model CARAIB DVM was used to evaluate and analyze how future climate and extreme events will affect European ecosystems. To quantify the uncertainties in the climatic projections and in their potential impacts on ecosystems, the vegetation model was driven with the outputs of different regional climatic models (RCMs), nested in CMIP5 GCM projections for the EURO-CORDEX project. We used the ALADIN version 5.3 (Météo-France/CNRM) and other EURO-CORDEX RCMs. These climatic projections are at a high spatial resolution (0.11-degree, ~12 km). CARAIB simulations were performed across Europe over the historical period 1951-2005 and the future period 2006-2100 under RCP4.5 and RCP8.5 emission scenarios. We simulated a set of 99 individual species (47 herbs, 12 shrubs and 40 trees) representing the major European ecosystem flora. First, we analyzed the climatic variability simulated by the climatic models over the historical period and compared it with the observed climatic variability. None of these climatic models can reproduce accurately the present natural climatic variability. Then, to assess the risk of ecosystem disruption in the future and to identify the vulnerable areas in Europe, we created an index combining several CARAIB outputs: runoff, mean NPP, soil turnover, burned area, appearance and disappearance of species. We evaluated the severity of change projected for these variables (period 2071-2100) relative to their current variability (period 1961-1990). Mean changes were considered severe if they exceed observed variability. The highest values of the index were found in southern Europe, indicating that the amplitude of the expected ecosystem changes largely exceeds current interannual variability in this area. [less ▲]

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See detailEffect of hunting pressure and forest fragmentation on seed dispersal of Staudtia kamerunensis (Myristicaceae) in the Western Congolian forest-savanna mosaic
Trolliet, Franck ULg; Forget, Pierre-Michel; Huynen, Marie-Claude ULg et al

Conference (2015, June 22)

Numerous studies have investigated the impact of hunting and forest fragmentation on seed dispersal processes, but few of them in Africa. The African continent, however, holds the greatest abundance of ... [more ▼]

Numerous studies have investigated the impact of hunting and forest fragmentation on seed dispersal processes, but few of them in Africa. The African continent, however, holds the greatest abundance of large frugivores on Earth and is subject to increasing levels of hunting and forest fragmentation. Frugivory and seed dispersal in the pan-tropical family Myristicaceae has been well studied in the Neotropics, but remain barely known in Afro-tropical forests. Here we investigated how hunting, forest cover, and fruit availability influence the dispersal capacities of Staudtia kamerunensis in a mosaic composed of forest patches and savannas in D.R. Congo. We selected 34 fertile female S. kamerunensis trees distributed, at a landscape scale (300 km²), across 5 sites characterized by a gradient of hunting pressures and density of the study trees. The trees varied in size and surrounding forest cover (patch and corridors). We quantified the percentages of seed dispersal failure using litter trap and fruit remains during the entire 2013 fruiting season, and identified fruit eaters through focal observations. The most frequently observed frugivore was the White-thighed Hornbill (Bycanistes albotibialis). Our GLMM analyses show that increasing hunting pressure, decreasing abundance of B. albotibialis and decreasing forest cover near focal trees significantly increased dispersal failure. The limited forest cover of some patches, resulting from the highly fragmented feature of the landscape, and hunting pressure, are likely to impact negatively the abundance of B. albotibialis. Consequently, we suggest the dispersal system reached saturation because of a lack of effective seed dispersal away from parent trees. [less ▲]

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See detailModelling carbon fluxes of forest and grassland ecosystems in Western Europe using the CARAIB dynamic vegetation model: evaluation against eddy covariance data.
Henrot, Alexandra-Jane ULg; François, Louis ULg; Dury, Marie ULg et al

in Geophysical Research Abstracts (2015, April), 17

Eddy covariance measurements are an essential resource to understand how ecosystem carbon fluxes react in response to climate change, and to help to evaluate and validate the performance of land surface ... [more ▼]

Eddy covariance measurements are an essential resource to understand how ecosystem carbon fluxes react in response to climate change, and to help to evaluate and validate the performance of land surface and vegetation models at regional and global scale. In the framework of the MASC project (« Modelling and Assessing Surface Change impacts on Belgian and Western European climate »), vegetation dynamics and carbon fluxes of forest and grassland ecosystems simulated by the CARAIB dynamic vegetation model (Dury et al., iForest - Biogeosciences and Forestry, 4:82-99, 2011) are evaluated and validated by comparison of the model predictions with eddy covariance data. Here carbon fluxes (e.g. net ecosystem exchange (NEE), gross primary productivity (GPP), and ecosystem respiration (RECO)) and evapotranspiration (ET) simulated with the CARAIB model are compared with the fluxes measured at several eddy covariance flux tower sites in Belgium and Western Europe, chosen from the FLUXNET global network (http://fluxnet.ornl.gov/). CARAIB is forced either with surface atmospheric variables derived from the global CRU climatology, or with in situ meteorological data. Several tree (e.g. Pinus sylvestris, Fagus sylvatica, Picea abies) and grass species (e.g. Poaceae, Asteraceae) are simulated, depending on the species encountered on the studied sites. The aim of our work is to assess the model ability to reproduce the daily, seasonal and interannual variablility of carbon fluxes and the carbon dynamics of forest and grassland ecosystems in Belgium and Western Europe. [less ▲]

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See detailLa menace climatique sur les plantes
Hambuckers, Alain ULg

Conference given outside the academic context (2015)

L’exposé commence par un bref rappel du contexte climatique (évolution de la température globale au cours des 150 dernières années, grandes tendances des changements climatiques prévus par les modèles ... [more ▼]

L’exposé commence par un bref rappel du contexte climatique (évolution de la température globale au cours des 150 dernières années, grandes tendances des changements climatiques prévus par les modèles globaux). Je présente ensuite quelques exemples d’observations de modification de la végétation au cours des décennies passées (enrichissement en espèces de sommets alpins, augmentation de la mortalité de la végétation ligneuse en région sahélienne, variation de la limite altitudinale de présence d’espèces endémiques sur l’île de Ténérife) et les limites de leur interprétation (prise en compte des modifications de l’occupation du sol, de la pollution atmosphérique, des interactions biotiques). On s’intéresse ensuite à la prédiction des changements dans le futur qui nécessite de comprendre les réponses physiologiques des plantes aux facteurs suivants : l’augmentation de la température, les variations du régime de précipitation, les effets des épisodes climatiques extrêmes (canicules, sécheresses), l’augmentation de la concentration en CO2, l’évolution des conditions biotiques. Armé de ces informations, on peut alors examiner des méthodes d’inférences comme l’analyse des distributions présentes, les modèles de niches, ou les modèles dynamiques de végétation et quelques résultats produits par ces méthodes. Pour les espèces tropicales nos résultats donnent plutôt à penser que les aires de distributions s’étendront dans le futur, avec une très large conservation de l’aire originale. Ces résultats sont finalement mis en perspective avec d’autres facteurs d’altération de l’environnement, et en particulier la destruction des habitats. Ceci nous permet de constater que le principal problème contre lequel il faut continuer à agir, en priorité, reste la destruction des habitats naturels et semi-naturels, y compris en Belgique. [less ▲]

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See detailModelling the distribution of key tree species used by lion tamarins in the Brazilian Atlantic forest under a scenario of future climate change
Raghunathan, Poornima ULg; François, Louis ULg; Huynen, Marie-Claude ULg et al

in Regional Environmental Change (2015), 15

We used three IPCC climate change scenarios (A1B, A2 and B1) in a dynamic vegetation model (CARAIB), to determine the potential future distribution of 75 tree species used by two endemic primate species ... [more ▼]

We used three IPCC climate change scenarios (A1B, A2 and B1) in a dynamic vegetation model (CARAIB), to determine the potential future distribution of 75 tree species used by two endemic primate species from the Brazilian Atlantic Forest (BAF). Habitat conservation is a vital part of strategies to protect endangered species, and this is a new approach to understanding how key plant species needed for survival of golden lion tamarins (Leontopithecus rosalia) and golden-headed lion tamarins (L. chrysomelas) might be affected by climate change and what changes to their distribution are likely. The model accurately predicted the current distribution of BAF vegetation types, for 66 % of the individual tree species with 70 % agreement obtained for presence. In the simulation experiments for the future, 72 out of 75 tree species maintained more than 95 % of their original distribution and all species showed a range expansion. At the biome level, we note a substantial decrease in the sub-tropical forest area. There is some fragmentation of the savannah, which is encroached mostly by tropical seasonal forest. Where the current distribution shows a large sub-tropical forest biome, it has been replaced or encroached by tropical rainforest. The results suggested that the trees may benefit from an increase in temperature, if and only if soil water availability is not altered significantly, as was the case with climate simulations that were used. However, these results must be coupled with other information to maximise usefulness to conservation since BAF is already highly fragmented and subject to high anthropic pressure. © 2014 Springer-Verlag Berlin Heidelberg. [less ▲]

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See detailCharacterization of Nest Sites of Chimpanzees (Pan troglodytes schweinfurthii) in Kibira National Park, Burundi
Hakizimana, Dismas; Hambuckers, Alain ULg; Brotcorne, Fany ULg et al

in African Primates (2015), 10

Abstract: Kibira National Park is the only site in Burundi that harbors a large number of chimpanzees (Pan troglodytes schweinfurthii). While information on factors influencing the selection of nest sites ... [more ▼]

Abstract: Kibira National Park is the only site in Burundi that harbors a large number of chimpanzees (Pan troglodytes schweinfurthii). While information on factors influencing the selection of nest sites by chimpanzees is available for other locations of the species’ range, this information is lacking for Kibira National Park. This is mainly due to the political troubles that prevailed in the country from 1993 until 2007, making study there difficult. To better protect this chimpanzee population, it is crucial to survey nest sites to identify the tree species, physical characteristics of the trees and habitat type that chimpanzees preferentially use for nesting. Therefore, in this study, we investigated: 1) the tree species used by chimpanzees for building their nests; 2) nest tree availability in the study area; 3) whether chimpanzee selection of a nest tree is based on physical characteristics such as diameter at breast height, lowest branch height, tree size and crown height; and 4) whether chimpanzees choose their nest sites according to topography and canopy types. We collected data monthly along 16 transects of 3 km each, from September 2011 to February 2013 (18 months). However, data related to the measurements of nests and nest trees were collected for only the last 12 months, from March 2012 to February 2013. We identified tree species used for nesting, and measured physical characteristics of trees used as opposed to surrounding trees unused. The results showed that chimpanzees select certain tree species to build their nests. Among the 32 species of trees bearing nests, chimpanzees used 12 species significantly more frequently than expected and 11 species significantly less frequently than expected. In addition, trees bearing nests were significantly larger and taller than the surrounding trees and had higher lowest branch and bigger canopies. [less ▲]

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See detailThe seed dispersal of the afro- tropical tree species Staudtia kamerunensis (Myristicaceae)
Hambuckers, Alain ULg

Scientific conference (2014, December 27)

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See detailImportance des modèles de distribution de niche potentielle dans la gestion des espèces tropicales exploitées: cas des taxons du genre Guibourtia Benn
Tosso, Dji-ndé Félicien ULg; Daïnou, Kasso ULg; Hambuckers, Alain ULg et al

Poster (2014, September 24)

De la famille des (Fabaceae / Caesalpinioideae) et composé de 13 espèces en Afrique, le genre Guibourtia comporte des taxons à forte valeur culturelle et à forte valeur commerciale. Aujourd'hui, la ... [more ▼]

De la famille des (Fabaceae / Caesalpinioideae) et composé de 13 espèces en Afrique, le genre Guibourtia comporte des taxons à forte valeur culturelle et à forte valeur commerciale. Aujourd'hui, la pression de l'exploitation combinée aux faibles densités de ce genre, fait a priori peser d’importantes menaces sur certaines de ses populations. Un projet de recherche a donc été initié afin de mieux comprendre la structure et la diversité génétique des populations de Guibourtia, en lien avec l'exploitation forestière et les patrons de reproduction spécifiques. Un premier volet de la recherche a consisté à identifier les déterminants climatiques expliquant la distribution des espèces. Nous avons combinée des modèles statiques (Maxent et régression logistique) avec des données du modèle climatique global CNRM CM5, et sur la base de l'occurrence de ces taxons entre 1950 et 2000. Il en ressort que les espèces du genre Guibourtia sont sensibles aux facteurs précipitation (69,2 %) et amplitude thermique (74,3 %). Dans un second temps, il sera utilisé les modèles climatiques des ères géologiques passées afin d'inférer la distribution de l'espèce au cours du Quaternaire, et de faire le lien avec des analyses phylogénétiques et phylogéographiques. Il sera également possible d'évaluer la distribution future de l'espèce tenant compte des modèles d'évolution du climat. Enfin, le projet de recherche s'attèlera particulièrement aux relations phylogénétiques entre espèces morphologiquement similaires en sympatrie ou parapatrie, en caractérisant en détail les flux de gènes entre individus de ces taxons proches, ainsi que leur degré de similarité physiologique. Les résultats de l’étude in fine contribueront à proposer des stratégies de conservation et de gestion durable dans le contexte de l’exploitation forestière d’Afrique centrale et du changement climatique en cours. [less ▲]

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See detailModelling seed dispersal and tropical forest regeneration :application to Staudtia kamerunensis in the WWF Lake Tele-Tumba Landscape in DR Congo
Coos, William ULg; Dury, Marie ULg; Trolliet, Franck ULg et al

Poster (2014, June)

Unsustainable hunting and slash-and-burn farming in tropical forests can lead to the empty forest syndrome. It is characterized by the loss of key species essential in the maintenance and regeneration of ... [more ▼]

Unsustainable hunting and slash-and-burn farming in tropical forests can lead to the empty forest syndrome. It is characterized by the loss of key species essential in the maintenance and regeneration of the forest. Indeed the main mechanism of this regeneration is seed dispersal, which for tropical trees is usually driven by animals, and the alteration of this process through a reduction of the disperser population may have serious consequences on forest composition. Computer models are powerful tools to study these processes, not only towards a better understanding of the key mechanisms controlling tropical forest regeneration, but also with the aim of optimising forest management and exploitation to reach a better equilibrium between tropical tree species and their seed dispersers. This study describes a seed dispersal module ultimately developed to analyze the regeneration of the rainforest in the WWF Lake Tele – Lake Tumba Landscape in RD Congo (BIOSERF project funded by Belgian Science Policy). The module has been developed to upgrade the CARAIB dynamic vegetation model, which is used in the BIOSERF project. Data are derived from a field study in which we analyzed seed dispersal of a common tree species (Staudtia kamerunensis) and we determined the community of its main dispersers (largely dominated by the hornbill Bycanistes albotibialis). Additional data (density of S. kamerunensis, habitat use and retention time in the digestive tract of hornbills to simulate dispersal kernel) were obtained from literature and satellite images. Different simulations were performed to represent seed rain over time and a survival rate was applied to show the regeneration. The module was able to provide a percentage of recolonization of degraded places. In the end, this result was compared to field studies, which provide close percentage of recolonization [less ▲]

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See detailModelling the future range and productivity of African tree species. Perspectives and limits
Hambuckers, Alain ULg; Dury, Marie ULg; Tosso, Dji-ndé Félicien ULg et al

Poster (2014, June)

There remains a lack of information on the future of plant species in many parts of Africa under the threads of climate change with the exception of the mountainous areas. Models are valuables tools to ... [more ▼]

There remains a lack of information on the future of plant species in many parts of Africa under the threads of climate change with the exception of the mountainous areas. Models are valuables tools to examine this problem because they permit to extrapolate basic information as simple as species occurrence coming from a restricted number of localities to the entire continent. Niche-based models, like logistic regression or MaxEnt, easily allow fitting empirical relationships between environmental variables related to climate and possibly to soil properties. They produce probabilities of occurrence for the present with good accuracy (calibration phase). Projections for the future are made by switching the explanatory data set with future conditions. These models however are limited by the fact that it is difficult to integrate physiological response to increasing CO2 air concentration. Dynamic vegetation models (DVMs) are process-based models that simulate plant environment (soil water, light intensity at various heights, etc.) and plant physiology (transpiration, CO2 fixation, photosynthesis, respiration, carbon allocation, etc.) from climate variables, soil properties, and elevation. They could be run at various scales, from global to regional or even local scale, and simulate the growth of plant functional types (PFTs), of biological affinity groups (BAGs) or of species. A model like CARAIB is able to simulate PFTs and BAGs growth (occurrence and productivity) with rather good accuracy for Western Europe. For the future, the simulations confirm that the physiological effect of CO2 concentration change is dramatic but not easily foreseeable because it depends on overall fertility of the sites (Dury et al., iForest – Biogeosciences and Forestry, 4:82-99, 2011). From this conclusion, spatial and temporal variations of fertility would have to be introduced in modelling studies to reach more operational conclusions. Questions arising about the future of ecosystem services in tropical countries highlight particular plant species (BIOSERF project funded by the Belgian Science Policy: Sustainability of tropical forest biodiversity and services under climate and human pressure). In this study, we model a set of 11 selected African tree species including several Congolese species with logistic regression, MaxEnt and CARAIB models. The two niche-based-models rather properly simulate the ranges obtained with the alpha-hull polygon method. CARAIB correctly simulates the range of the evergreen species but not of the deciduous trees. We examine how physiological knowledge could be use to improve the model. IN particular, we conclude that bud dormancy breaking representation has to be upgraded in the model because this process is likely to control the range of the species. It should act in combination with the specific bioclimatic constants controlling the hydrological and thermal stress and the germination. Additionally, we examine the evolution of the ranges at the 2050 horizon using one of the most recent socio-economic scenarios. [less ▲]

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See detailNest grouping patterns of bonobos (Pan paniscus) in relation to fruit availability in a forest-savannah mosaic
Serckx, Adeline ULg; Huynen, Marie-Claude ULg; Bastin, Jean-François ULg et al

in PLoS ONE (2014)

A topic of major interest in socio-ecology is the comparison of chimpanzees and bonobos’ grouping patterns. Numerous studies have highlighted the impact of social and environmental factors on the ... [more ▼]

A topic of major interest in socio-ecology is the comparison of chimpanzees and bonobos’ grouping patterns. Numerous studies have highlighted the impact of social and environmental factors on the different evolution in group cohesion seen in these sister species. We are still lacking, however, key information about bonobo social traits across their habitat range, in order to make accurate inter-species comparisons. In this study we investigated bonobo social cohesiveness at nesting sites depending on fruit availability in the forest-savannah mosaic of western Democratic Republic of Congo (DRC), a bonobo habitat which has received little attention from researchers and is characterized by high food resource variation within years. We collected data on two bonobo communities. Nest counts at nesting sites were used as a proxy for night grouping patterns and were analysed with regard to fruit availability. We also modelled bonobo population density at the site in order to investigate yearly variation. We found that one community density varied across the three years of surveys, suggesting that this bonobo community has significant variability in use of its home range. This finding highlights the importance of forest connectivity, a likely prerequisite for the ability of bonobos to adapt their ranging patterns to fruit availability changes. We found no influence of overall fruit availability on bonobo cohesiveness. Only fruit availability at the nesting sites showed a positive influence, indicating that bonobos favour food ‘hot spots’ as sleeping sites. Our findings have confirmed the results obtained from previous studies carried out in the dense tropical forests of DRC. Nevertheless, in order to clarify the impact of environmental variability on bonobo social cohesiveness, we will need to make direct observations of the apes in the forest-savannah mosaic as well as make comparisons across the entirety of the bonobos’ range using systematic methodology. [less ▲]

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See detailModelling the Congo basin ecosystems with a dynamic vegetation model
Dury, Marie ULg; Hambuckers, Alain ULg; Trolliet, Franck ULg et al

Conference (2014, April)

The scarcity of field observations in some parts of the world makes difficult a deep understanding of some ecosystems such as humid tropical forests in Central Africa. Therefore, modelling tools are ... [more ▼]

The scarcity of field observations in some parts of the world makes difficult a deep understanding of some ecosystems such as humid tropical forests in Central Africa. Therefore, modelling tools are interesting alternatives to study those regions even if the lack of data often prevents sharp calibration and validation of the model projections. Dynamic vegetation models (DVMs) are process-based models that simulate shifts in potential vegetation and its associated biogeochemical and hydrological cycles in response to climate. Initially run at the global scale, DVMs can be run at any spatial scale provided that climate and soil data are available. In the framework of the BIOSERF project (“Sustainability of tropical forest biodiversity and services under climate and human pressure”), we use and adapt the CARAIB dynamic vegetation model (Dury et al., iForest - Biogeosciences and Forestry, 4:82-99, 2011) to study the Congo basin vegetation dynamics. The field campaigns have notably allowed the refinement of the vegetation representation from plant functional types (PFTs) to individual species through the collection of parameters such as the specific leaf area or the leaf C:N ratio of common tropical tree species and the location of their present-day occurrences from literature and available database. Here, we test the model ability to reproduce the present spatial and temporal variations of carbon stocks (e.g. biomass, soil carbon) and fluxes (e.g. gross and net primary productivities (GPP and NPP), net ecosystem production (NEP)) as well as the observed distribution of the studied species over the Congo basin. In the lack of abundant and long-term measurements, we compare model results with time series of remote sensing products (e.g. vegetation leaf area index (LAI), GPP and NPP). Several sensitivity tests are presented: we assess consecutively the impacts of the level at which the vegetation is simulated (PFTs or species), the spatial resolution and the initial land cover (potential or human-induced). First, we show simulations over the whole Congo basin at a 0.5◦ spatial resolution. Then, we present high-resolution simulations (1 km) carried out over different areas of the Congo basin, notably the DRC part of the WWF Lake Tele – Lake Tumba Landscape. Studied in the BIOSERF project, this area is characterized by a forest-savannah mosaic but also by swamp and flooded forest. In addition, forward transient projections of the model driven with the outputs of about thirty global cli- mate models (GCMs) from the new Coupled Model Intercomparison Project Phase 5 (CMIP5) will permit to outline the likely response of carbon pools to changing climate over the Congo basin during the 21th century. [less ▲]

Detailed reference viewed: 56 (5 ULg)
See detailModelling the Congo basin ecosystems with a dynamic vegetation model
Dury, Marie ULg; Hambuckers, Alain ULg; Trolliet, Franck ULg et al

Poster (2014, April)

The scarcity of field observations in some parts of the world makes difficult a deep understanding of some ecosystems such as humid tropical forests in Central Africa. Therefore, modelling tools are ... [more ▼]

The scarcity of field observations in some parts of the world makes difficult a deep understanding of some ecosystems such as humid tropical forests in Central Africa. Therefore, modelling tools are interesting alternatives to study those regions even if the lack of data often prevents sharp calibration and validation of the model projections. Dynamic vegetation models (DVMs) are process-based models that simulate shifts in potential vegetation and its associated biogeochemical and hydrological cycles in response to climate. Initially run at the global scale, DVMs can be run at any spatial scale provided that climate and soil data are available. In the framework of the BIOSERF project (“Sustainability of tropical forest biodiversity and services under climate and human pressure”), we use and adapt the CARAIB dynamic vegetation model (Dury et al., iForest - Biogeosciences and Forestry, 4:82-99, 2011) to study the Congo basin vegetation dynamics. The field campaigns have notably allowed the refinement of the vegetation representation from plant functional types (PFTs) to individual species through the collection of parameters such as the specific leaf area or the leaf C:N ratio of common tropical tree species and the location of their present-day occurrences from literature and available database. Here, we test the model ability to reproduce the present spatial and temporal variations of carbon stocks (e.g. biomass, soil carbon) and fluxes (e.g. gross and net primary productivities (GPP and NPP), net ecosystem production (NEP)) as well as the observed distribution of the studied species over the Congo basin. In the lack of abundant and long-term measurements, we compare model results with time series of remote sensing products (e.g. vegetation leaf area index (LAI), GPP and NPP). Several sensitivity tests are presented: we assess consecutively the impacts of the level at which the vegetation is simulated (PFTs or species), the spatial resolution and the initial land cover (potential or human-induced). First, we show simulations over the whole Congo basin at a 0.5◦ spatial resolution. Then, we present high-resolution simulations (1 km) carried out over different areas of the Congo basin, notably the DRC part of the WWF Lake Tele – Lake Tumba Landscape. Studied in the BIOSERF project, this area is characterized by a forest-savannah mosaic but also by swamp and flooded forest. In addition, forward transient projections of the model driven with the outputs of about thirty global cli- mate models (GCMs) from the new Coupled Model Intercomparison Project Phase 5 (CMIP5) will permit to outline the likely response of carbon pools to changing climate over the Congo basin during the 21th century. [less ▲]

Detailed reference viewed: 69 (14 ULg)
Full Text
Peer Reviewed
See detailDensity estimates and nesting-site selection in chimpanzees of the Nimba Mountains, Côte d'Ivoire and Guinea
Granier, Nicolas ULg; Hambuckers, Alain ULg; Matsuzawa, Tetsuro et al

in American Journal of Primatology (2014)

We investigated nesting behavior of non habituated chimpanzees populating the Nimba Mountains to document their abundance and their criterions of nesting-site selection. During a 19-month study we walked ... [more ▼]

We investigated nesting behavior of non habituated chimpanzees populating the Nimba Mountains to document their abundance and their criterions of nesting-site selection. During a 19-month study we walked 80 km of transects and recces each month, and recorded 764 nests (mean group size = 2.23 nests) along with characteristics of vegetation structure and composition, topography and seasonality. Population density estimated with two nest count methods ranged between 0.14 and 0.65 chimpanzee/km2. These values are lower than previous estimates, emphasizing the necessity of protecting remaining wild ape populations. Chimpanzees built nests in 108 tree species out of 437 identified, but 2.3% of total species comprised 52% of nests. Despite they preferred nesting in trees of 25-29 cm DBH and at a mean height of 8.02 m, we recorded an important proportion of terrestrial nests (8.2%) that may reflect a cultural trait of Nimba chimpanzees. A logistic model of nest presence formulated as a function of 12 habitat variables revealed preference for gallery and mountain forests rather than lowland forest, and old-growth forest rather than secondary forests. They nested more frequently in the study area during the dry season (December-April). The highest probability of observing nests was at 770 m altitude, particularly in steep locations (mean ground declivity = 15.54%). Several of the reported nest characteristics combined with the existence of 2 geographically separated clusters of nest, suggest that the study area constitutes the non-overlapping peripheral areas of 2 distinct communities. This nest-based study led us to findings on the behavioral ecology of Nimba chimpanzees, which constitute crucial knowledge to implement efficient and purpose-built conservation. [less ▲]

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See detailUse of camera traps for wildlife studies: a review
Trolliet, Franck ULg; Vermeulen, Cédric ULg; Huynen, Marie-Claude ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2014), 18(3), 446-454

As human threats continue to impact natural habitats, there is an increasing need to regularly monitor the trends in large vertebrate populations. Conservation efforts must be directed appropriately, but ... [more ▼]

As human threats continue to impact natural habitats, there is an increasing need to regularly monitor the trends in large vertebrate populations. Conservation efforts must be directed appropriately, but field work necessary for data collection is often limited by time and availability of people. Camera traps are used as an efficient method to insure permanent sampling and to work in difficult to access areas. In the present study, we illustrate the way the use of camera traps developed: firstly with the need to monitor tiger (Panthera tigris (Linnaeus 1758)) populations and later as an instrument serving a diverse field of studies, such as animal behaviour and fauna-flora interaction. By looking at the material and technical aspects of various models of camera trap for implementation in different field studies in animal ecology, we highlight the need to choose appropriate camera trap models for the target species and to set up solid sampling protocols in order to successfully achieve study objectives. [less ▲]

Detailed reference viewed: 276 (66 ULg)