Publications of Alain Hambuckers
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See detailToward a better understanding of habituation process to human observer: A statistical approach in Macaca leonina (Primates: Cercopithecidea)
Gazagne, Eva ULiege; Hambuckers, Alain ULiege; Savini, Tommaso ULiege et al

in Raffles Bulletin of Zoology (2020), 68(2020), 735-749

Habituation allows an observer to closely approach and follow free-ranging animals, as they no longer respond to the observer presence (e.g., through flight, avoidance, display, curiosity). While ... [more ▼]

Habituation allows an observer to closely approach and follow free-ranging animals, as they no longer respond to the observer presence (e.g., through flight, avoidance, display, curiosity). While habituation is implicitly acknowledged as a necessary step before any direct observational studies of primates, there is very little published data on the subject. The aim of this study is to analyse the habituation process over time (17 months) in a wildfeeding troop of northern pigtailed macaques (Macaca leonina) inhabiting a degraded forest fragment of the Sakaerat Biosphere Reserve, Thailand. Based on the number of encounters, contact duration with the studied troop, and behavioural responses to the observer recorded ad libitum and via scan sampling, we found statistical evidence of habituation progress over five stages: early, minimal, partial, advanced, and full. The complete habituation process took nearly 13 months. Factors such as the macaques’ limited experience of human contact, semi-terrestriality, large ranging patterns, fission-fusion dynamics, unpredictable resource use, as well as reduced native fruit availability in this degraded forest fragment may explain the length of the process. It was only possible to collect ranging and behavioural data from the partial habituation stage, although these data were biased toward adult males and sub-adults, while overestimating movement behaviour over inactivity and social behaviours. Our results highlight the importance of analysing behavioural data of fully habituated groups of primates to limit biases of observer presence, and also of not underestimating the habituation process length. This study provides novel information on the habituation process in macaques and proposes an effective methodology to analyse the habituation process across a wide range of primate species. [less ▲]

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See detailNorthern pigtailed macaques rely on old growth plantations to offset low fruit availability in a degraded forest fragment
Gazagne, Eva ULiege; José‐Domínguez, Juan Manuel; Huynen, Marie-Claude ULiege et al

in American Journal of Primatology (2020)

Space‐use and foraging strategies are important facets to consider in regard to the ecology and conservation of primates. For this study, we documented movement, ranging, and foraging patterns of northern ... [more ▼]

Space‐use and foraging strategies are important facets to consider in regard to the ecology and conservation of primates. For this study, we documented movement, ranging, and foraging patterns of northern pigtailed macaques (Macaca leonina) for 14 months in a degraded habitat with old growth Acacia and Eucalyptus plantations at the Sakaerat Biosphere Reserve in northeastern Thailand. We used hidden Markov models and characteristic hull polygons to analyze these patterns in regard to fruit availability. Macaques' home range (HR) was 599 ha and spanned through a natural dry‐evergreen forest (DEF), and plantation forest. Our results showed that active foraging increased with higher fruit availability in DEF. Macaques changed to a less continuous behavioral state during periods of lower fruit availability in DEF, repeatedly moving from foraging to transiting behavior, while extending their HR further into plantation forest and surrounding edge areas. Concomitantly, macaques shifted their diet from fleshy to dry fruit such as the introduced Acacia species. Our results showed that the diet and movement ecology adaptations of northern pigtailed macaques were largely dependent on availability of native fruits, and reflected a “high‐cost, high‐yield” foraging strategy when fresh food was scarce and dry fruit was available in plantation forest. Conversely, wild‐feeding northern pigtailed macaque populations inhabiting pristine habitat approached a “low‐cost, low‐yield” foraging strategy. Our results outline the effects of habitat degradation on foraging strategies and show how a flexible species can cope with its nutritional requirements. [less ▲]

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See detailChapter 4. Multidisciplinary approaches for conservation issues
Cheddadi, Rachid; Sarmiento, Fausto; Hambuckers, Alain ULiege et al

in Frolich, Larry M.; Sarmiento, Fausto (Eds.) The Elgar Companion to Geography, Transdisciplinarity and Sustainability (2020)

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See detailTRY plant trait database – enhanced coverage and open access
Kattge, Jens; Bönisch, Gerhard; Díaz, Sandra et al

in Global Change Biology (2020), 26(1), 119-188

Abstract Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic ... [more ▼]

Abstract Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits—almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives. [less ▲]

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See detailSocial influence on the expression of robbing and bartering behaviours in Balinese long‑tailed macaques
Brotcorne, Fany ULiege; Holzner, Anna; Jorge‑Sales, Lucía et al

in Animal Cognition (2019), 23(2), 311-326

Animals use social information, available from conspecifics, to learn and express novel and adaptive behaviours. Amongst social learning mechanisms, response facilitation occurs when observing a ... [more ▼]

Animals use social information, available from conspecifics, to learn and express novel and adaptive behaviours. Amongst social learning mechanisms, response facilitation occurs when observing a demonstrator performing a behaviour temporarily increases the probability that the observer will perform the same behaviour shortly after. We studied “robbing and bartering” (RB), two behaviours routinely displayed by free-ranging long-tailed macaques (Macaca fascicularis) at Uluwatu Temple, Bali, Indonesia. When robbing, a monkey steals an inedible object from a visitor and may use this object as a token by exchanging it for food with the temple staff (bartering). We tested whether the expression of RB-related behaviours could be explained by response facilitation and was influenced by model-based biases (i.e. dominance rank, age, experience and success of the demonstrator). We compared video-recorded focal samples of 44 witness individuals (WF) immediately after they observed an RB-related event performed by group members, and matched-control focal samples (MCF) of the same focal subjects, located at similar distance from former demonstrators (N = 43 subjects), but in the absence of any RB-related demonstrations. We found that the synchronized expression of robbing and bartering could be explained by response facilitation. Both behaviours occurred significantly more often during WF than during MCF. Following a contagion-like effect, the rate of robbing behaviour displayed by the witness increased with the cumulative rate of robbing behaviour performed by demonstrators, but this effect was not found for the bartering behaviour. The expression of RB was not influenced by model-based biases. Our results support the cultural nature of the RB practice in the Uluwatu macaques. [less ▲]

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See detailFaire face à une faible disponibilité en fruits dans un habitat dégradé : rôle des plantations chez les macaques à queue de cochon (Macaca leonina) en Thaïlande.
Gazagne, Eva ULiege; José Domínguez, Juan Manuel; Huynen, Marie-Claude ULiege et al

Conference (2019, October 04)

Etudier les facteurs impactant l’utilisation de l’habitat ainsi que les stratégies de recherche alimentaire chez les primates résidents dans des habitats dégradés, est indispensable pour pouvoir mettre en ... [more ▼]

Etudier les facteurs impactant l’utilisation de l’habitat ainsi que les stratégies de recherche alimentaire chez les primates résidents dans des habitats dégradés, est indispensable pour pouvoir mettre en place des stratégies de conservation efficaces. Nous avons étudié l’écologie du mouvement, le domaine vital et les stratégies de recherche alimentaire pendant 14 mois, d’une troupe de macaques à queue-de-cochon du nord (Macaca leonina) de 141± 10 individus dans le fragment forestier dégradé de la réserve de biosphère Sakaerat, située au Nord-Ouest de la Thaïlande. Nous avons analysé ces objectifs en utilisant les méthodes récentes suivantes en fonction de la disponibilité en fruit : les modèles d’Hidden Markov et les polygones caractéristiques de Hull. Nos résultats montrent que la troupe étudiée a un domaine vital total de 599 ha qui couvre la Forêt native Sèche Sempervirente (FSS) et de vieilles plantations d’acacias et d’eucalyptus. Lors des périodes de forte disponibilité en fruits natifs, les macaques recherchent activement de la nourriture à l’intérieur de la FSS (i.e. mouvements lents et variables). A l’inverse, lors des périodes de faibles disponibilités en fruits natifs, les macaques passent plus fréquemment d’un état de recherche alimentaire à un état de transit (i.e. mouvements rapides et orientés). Ils élargissent leurs déplacements aux plantations et zone lisières avec une plus faible fidélité au site quotidienne, bien que les domaines vitaux et trajet parcourus journaliers ne soient pas significativement plus grands. En revanche, les macaques adaptent leur régime alimentaire en consommant significativement plus de fruits secs exotiques comme les graines d’acacia. En combinant pour la première fois de nouvelles analyses sur l’écologie du mouvement et le domaine vital, notre étude montre que les macaques à queue-de-cochon adaptent la dynamique de leur mouvement, leur profil de déplacement ainsi que leur régime alimentaire en fonction de la disponibilité en fruit natif. Ces patrons indiquent que les macaques consomment les ressources prédictibles des plantations et ont tendance à suivre la stratégie de maximisation de l’énergie pour faire face à de faibles disponibilités alimentaires. Cette stratégie énergétique est différente de celle utilisé par leurs congénères habitant la forêt pristine du parc national de Khao Yai située près de Sakaerat, qui ont tendance à minimiser leurs dépenses énergétiques lors de faibles disponibilités en fruit, en diminuant leur domaine vitaux et déplacement quotidiens. Ces résultats approfondissent les connaissances sur l’écologie de cette espèce vulnérable et peu connue, et révèlent un des effets potentiels de la dégradation de l’habitat : la modification des stratégies énergétiques chez les macaques. [less ▲]

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See detailUtilisation du modèle dynamique de végétation CARAIB pour simuler les rendements en Belgique : validation et projections à l'horizon 2035
Jacquemin, Ingrid ULiege; Berckmans, Julie; Henrot, Alexandra-Jane ULiege et al

Poster (2019, September)

Le modèle CARAIB (CARbon Assimilation In the Biosphere) est un modèle dynamique de végétation initialement développé pour étudier le comportement de la végétation naturelle, tant son rôle dans le cycle ... [more ▼]

Le modèle CARAIB (CARbon Assimilation In the Biosphere) est un modèle dynamique de végétation initialement développé pour étudier le comportement de la végétation naturelle, tant son rôle dans le cycle global du carbone que sa réponse aux changements de climat et de sol. Afin de pouvoir répondre à de nouveaux challenges (comme l’étude des rétroactions climat-végétation ou encore de l’évaluation des services écosystémiques), le modèle a été doté d’un nouveau module lui permettant de couvrir l’ensemble de la végétation, naturelle et celle dite « managée » comme les cultures. Par conséquent, CARAIB devient un outil intéressant pour l’analyse du risque encouru par la végétation, et tout particulièrement pour les cultures agricoles, dans un contexte de changement climatique. Mais avant toute chose, il convient de procéder à la validation du module culture. Afin d’évaluer la variation temporelle, nous avons confronté les sorties du modèle avec des données de terrain venant des sites de mesure des flux d’eddy-covariance du réseau Fluxnet. Nous avons notamment comparé les flux de carbone (la GPP pour « Gross Primary Production » et la NEE pour « Net Ecosystem Exchange ») et l’évapotranspiration simulés par le modèle, avec les observations venant de plusieurs sites, dont celui de Lonzée en Belgique et de Grignon en France. A eux seuls, ces deux sites permettent de couvrir les 6 cultures proposées par CARAIB, à savoir le froment et l’orge d’hiver, le maïs, les pommes de terre, les betteraves sucrières et le colza. Pour l’évaluation de la variabilité spatiale, nous avons procédé à des simulations sur l’ensemble de la Belgique, où le modèle a été forcé par les sorties du modèle régional ALARO de l’Institut Royal Météorologique pour le passé récent, à 4km de résolution. Finalement, nous avons forcé le modèle CARAIB, toujours avec les sorties du modèle ALARO à 4km, mais cette fois pour les scénarios futurs RCP4.5 et 8.5, pour l’horizon 2035. Au-delà de l’effet fertilisant du CO2 atmosphérique croissant qui impacte positivement les rendements, nous pouvons d’ores et déjà mettre en évidence une variabilité interannuelle plus importante pour l’ensemble des cultures à l’exception du maïs. [less ▲]

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See detailRefining the outputs of a dynamic vegetation model (CARAIB):Research at ULiège, Belgium
Hambuckers, Alain ULiege; Paillet, Marc ULiege; Henrot, Alexandra-Jane ULiege et al

Scientific conference (2019, March 19)

Dynamic vegetation models (DVMs) are process-based models combining the inputs and the outputs of sub-models, possibly in feedback loops, to simulate the plant functions. The sub-models compute conditions ... [more ▼]

Dynamic vegetation models (DVMs) are process-based models combining the inputs and the outputs of sub-models, possibly in feedback loops, to simulate the plant functions. The sub-models compute conditions outside and inside the plant and physiological reactions from the environmental data (climate, light intensity, air CO2 concentration, soil properties). DVMs are tools of choice to predict the future and the past of the vegetation taking into account climatic variations. The emergence of new questions in the context of climate change, particularly on threatened species or on commercial species, compels to apply DVMs to species while the information to parameterize and validate them is largely lacking. Of particular importance are the morpho-physiological traits. These were intensively studied within the hypothesis that they could be used to predict plant performances. This hypothesis finally revealed not very suitable, but it brought to light that important traits controlling photosynthesis and water relationships could strongly vary within each species in response to environmental conditions. We studied the Atlas cedar (Cedrus atlantica (Endl.) Manetti ex Carrière), in Morocco (northern Africa). It is a threatened tree species of important economic value. We also studied the English oak (Quercus robur L.) and the sessile oak (Quercus petraea (Matt.) Liebl.) in eastern Belgium. In a series of localities, we determined several traits (specific leaf area, leaf C/N, sapwood C/N, as well as for the cedar, leaf longevity) and we assessed biomass and net primary productivity as validation data, thanks to forest inventories, dendrochronology analyses and allometric equations combined with leaf area index estimations. We compared the model simulations of the CARAIB DVM when varying the set of traits (direct site estimates or default values) to the field estimates of biomass and net primary productivity. We found that trait default values provide sufficient information for the DVM to compute mean output values but low ability to reproduce between site variations. On the contrary, the in situ traits improve drastically this ability, which indicates that the plant performances are the results of acclimation to the evolving local environmental conditions. [less ▲]

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See detailRefining the outputs of a dynamic vegetation model (CARAIB): the importance of plant traits to improve prediction accuracy at tree species level
Hambuckers, Alain ULiege; Paillet, Marc ULiege; Henrot, Alexandra-Jane ULiege et al

Conference (2019, March 11)

Dynamic vegetation models (DVMs) are process-based models combining the inputs and the outputs of sub-models, possibly in feedback loops, to simulate the plant functions. The sub-models compute conditions ... [more ▼]

Dynamic vegetation models (DVMs) are process-based models combining the inputs and the outputs of sub-models, possibly in feedback loops, to simulate the plant functions. The sub-models compute conditions outside and inside the plant and physiological reactions from the environmental data (climate, light intensity, air CO2 concentration, soil properties). DVMs are tools of choice to predict the future and the past of the vegetation taking into account climatic variations. The emergence of new questions in the context of climate change, particularly on threatened species or on commercial species, compels to apply DVMs to species while the information to parameterize and validate them is largely lacking. Of particular importance are the morpho-physiological traits. These were intensively studied within the hypothesis that they could be used to predict plant performances. This hypothesis finally revealed not very suitable, but it brought to light that important traits controlling photosynthesis and water relationships could strongly vary within each species in response to environmental conditions. We studied the Atlas cedar (Cedrus atlantica (Endl.) Manetti ex Carrière), in Morocco (northern Africa). It is a threatened tree species of important economic value. We also studied the English oak (Quercus robur L.) and the sessile oak (Quercus petraea (Matt.) Liebl.) in eastern Belgium. In a series of localities, we determined several traits (specific leaf area, leaf C/N, sapwood C/N, as well as for the cedar, leaf longevity) and we assessed biomass and net primary productivity as validation data, thanks to forest inventories, dendrochronology analyses and allometric equations combined with leaf area index estimations. We compared the model simulations of the CARAIB DVM when varying the set of traits (direct site estimates or default values) to the field estimates of biomass and net primary productivity. We found that trait default values provide sufficient information for the DVM to compute mean output values but low ability to reproduce between site variations. On the contrary, the in situ traits improve drastically this ability, which indicates that the plant performances are the results of acclimation to the evolving local environmental conditions. [less ▲]

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See detailContrasting climate risks predicted by dynamic vegetation and ecological niche-based models applied to tree species in the Brazilian Atlantic Forest
Raghunathan, Poornima ULiege; François, Louis ULiege; Dury, Marie ULiege et al

in Regional Environmental Change (2019), 19

Climate change is a threat to natural ecosystems. To evaluate this threat and, where possible, respond, it is useful to understand the potential impacts climate change could have on species’ distributions ... [more ▼]

Climate change is a threat to natural ecosystems. To evaluate this threat and, where possible, respond, it is useful to understand the potential impacts climate change could have on species’ distributions, phenology, and productivity. Here, we compare future scenario outcomes between a dynamic vegetation model (DVM; CARbon Assimilation In the Biosphere (CARAIB)) and an ecological niche-based model (ENM; maximum entropy model) to outline the risks to tree species in the Brazilian Atlantic Forest, comprising the habitats of several endemic species, including the endangered primate Leontopithecus chrysomelas (golden-headed lion tamarin; GHLT), our species of interest. Compared to MaxENT, theDVMpredicts larger present-day species ranges. Conversely, MaxENT ranges are closer to sampled distributions of the realised niches. MaxENT results for two future scenarios in four general circulation models suggest that up to 75% of the species risk losing more than half of their original distribution. CARAIB simulations are more optimistic in scenarios with and without accounting for potential plant-physiological effects of increased CO2, with less than 10% of the species losing more than 50% of their range. Potential gains in distribution outside the original area do not necessarily diminish risks to species, as the potential new zones may not be easy to colonise. It will also depend on the tree species’ dispersal ability. So far, within the current range of L. chrysomelas, CARAIB continues to predict persistence of most resource trees, while MaxENT predicts the loss of up to 19 species out of the 59 simulated. This research highlights the importance of choosing the appropriate modelling approach and interpretation of results to understand key processes. [less ▲]

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See detailHighlighting convergent evolution in morphological traits in response to climatic gradient in African tropical tree species: The case of genus Guibourtia Benn.
Tosso, Dji-ndé Félicien ULiege; Doucet, Jean-Louis ULiege; Daïnou, Kasso ULiege et al

in Ecology and Evolution (2019)

Adaptive evolution is a major driver of organism diversification, but the links between phenotypic traits and environmental niche remain little documented in tropical trees. Moreover, trait-niche ... [more ▼]

Adaptive evolution is a major driver of organism diversification, but the links between phenotypic traits and environmental niche remain little documented in tropical trees. Moreover, trait-niche relationships are complex because a correlation between the traits and environmental niches displayed by a sample of species may result from (a) convergent evolution if different environmental conditions have selected different sets of traits, and/or (b) phylogenetic inertia if niche and morphological differences between species are simply function of their phylogenetic divergence, in which case the trait-niche correlation does not imply any direct causal link. Here, we aim to assess the respective roles of phylogenetic inertia and convergent evolution in shaping the differences of botanical traits and environmental niches among congeneric African tree species that evolved in different biomes. This issue was addressed with the tree genus Guibourtia Benn. (Leguminosae and Detarioideae), which contains 13 African species occupying various forest habitat types, from rain forest to dry woodlands, with different climate and soil conditions. To this end, we combined morphological data with ecological niche modelling and used a highly resolved plastid phylogeny of the 13 African Guibourtia species. First, we demonstrated phylogenetic signals in both morphological traits (Mantel test between phylogenetic and morphological distances between species: r =.24, p =.031) and environmental niches (Mantel test between phylogenetic and niche distances between species: r =.23, p =.025). Second, we found a significant correlation between morphology and niche, at least between some of their respective dimensions (Mantel's r =.32, p =.013), even after accounting for phylogenetic inertia (Phylogenetic Independent Contrast: r =.69, p =.018). This correlation occurred between some leaflet and flower traits and solar radiation, relative humidity, precipitations, and temperature range. Our results demonstrate the convergent evolution of some morphological traits in response to climatic factors in congeneric tree species and highlight the action of selective forces, along with neutral ones, in shaping the divergence between congeneric tropical plants. © 2019 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. [less ▲]

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See detailHow complementary are large frugivores for tree seedling recruitment? A case study in the Congo Basin
Trolliet, F.; Bauman, D.; Forget, P.-M. et al

in Journal of Tropical Ecology (2019), in press

Large frugivores provide critical seed dispersal services for many plant species and their extirpation from forested ecosystems can cause compositional shifts in regenerating plant cohorts. Yet, we still ... [more ▼]

Large frugivores provide critical seed dispersal services for many plant species and their extirpation from forested ecosystems can cause compositional shifts in regenerating plant cohorts. Yet, we still poorly understand whether large seed-dispersers have complementary or redundant roles for forest regeneration. Here, to assess the functional complementarity of large-bodied frugivores in forest regeneration, we quantified the effects of varying abundance of hornbills, primates and the forest elephant on the density, species richness and the mean weighted seed length of animal-dispersed tree species among seedlings in five sites in a forest-savanna mosaic in D. R. Congo, while accounting for percentage forest cover and the local presence of fruiting trees. We found that the abundance of primates was positively associated with species richness of seedlings, while percentage forest cover was negatively associated (R 2 = 0.19). The abundance of hornbills, the presence of elephants and percentage forest cover were positively associated with mean seed length of the regenerating cohort (R 2 = 0.13). Spatially explicit analysis indicated that some additional processes have an important influence on these response indices. Primates would seem to have a preponderant role for maintaining relatively high species richness, while hornbills and elephant would seem to be predominantly responsible for the recruitment of large-seeded trees. Our results could indicate that these taxa of frugivores play complementary functional roles for forest regeneration. This suggests that the extirpation of one or more of these dispersers would likely not be functionally compensated for by the remaining taxa, hence possibly cascading into compositional shifts. © Cambridge University Press 2019. [less ▲]

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See detailBrazilian montane rainforest expansion induced by Heinrich Stadial 1 event
Pinaya, Jorge L. D.; Cruz, Francisco W.; Ceccantini, Gregório C. T. et al

in Scientific Reports (2019), 9(1), 17912

The origin of modern disjunct plant distributions in the Brazilian Highlands with strong floristic affinities to distant montane rainforests of isolated mountaintops in the northeast and northern Amazonia ... [more ▼]

The origin of modern disjunct plant distributions in the Brazilian Highlands with strong floristic affinities to distant montane rainforests of isolated mountaintops in the northeast and northern Amazonia and the Guyana Shield remains unknown. We tested the hypothesis that these unexplained biogeographical patterns reflect former ecosystem rearrangements sustained by widespread plant migrations possibly due to climatic patterns that are very dissimilar from present-day conditions. To address this issue, we mapped the presence of the montane arboreal taxa Araucaria, Podocarpus, Drimys, Hedyosmum, Ilex, Myrsine, Symplocos, and Weinmannia, and cool-adapted plants in the families Myrtaceae, Ericaceae, and Arecaceae (palms) in 29 palynological records during Heinrich Stadial 1 Event, encompassing a latitudinal range of 30°S to 0°S. In addition, Principal Component Analysis and Species Distribution Modelling were used to represent past and modern habitat suitability for Podocarpus and Araucaria. The data reveals two long-distance patterns of plant migration connecting south/southeast to northeastern Brazil and Amazonia with a third short route extending from one of them. Their paleofloristic compositions suggest a climatic scenario of abundant rainfall and relative lower continental surface temperatures, possibly intensified by the effects of polar air incursions forming cold fronts into the Brazilian Highlands. Although these taxa are sensitive to changes in temperature, the combined pollen and speleothems proxy data indicate that this montane rainforest expansion during Heinrich Stadial 1 Event was triggered mainly by a less seasonal rainfall regime from the subtropics to the equatorial region. [less ▲]

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See detailAre the climatic ranges of plant species impacted by atmospheric CO2 ? An attempt of quantification with a dynamic vegetation model
François, Louis ULiege; Henrot, Alexandra-Jane ULiege; Dury, Marie ULiege et al

Conference (2018, August 16)

The observed present-day climatic ranges of plant species are frequently used by palaeobotanists and palynologists to reconstruct the climate evolution in the past. This is, for instance, the case of the ... [more ▼]

The observed present-day climatic ranges of plant species are frequently used by palaeobotanists and palynologists to reconstruct the climate evolution in the past. This is, for instance, the case of the widely used “Coexistence Approach” method, which has provided a wealth of palaeoclimatic data on many periods of the Neogene. Such vegetation-based palaeoclimate reconstruction methods rest on the uniformitarian assumption that the climatic tolerances of plant species, or the way their establishment and growth respond to climate parameters, have not changed markedly over time. This hypothesis can be questioned, because climatic tolerances and growth of plant species may depend on many factors likely to change over time. A first example is that other abiotic and biotic factors allowing the plant presence have probably changed in the course of time. Another example is genetic evolution that may affect climate resistance and end up to some adaptation of the populations as climate is changing. Atmospheric CO2 may also modify the plant response. It is not accounted for in the vegetation-based palaeoclimatic reconstruction methods, but may alter the tolerance of plant species to aridity through stomatal closure or stomatal density changes. Moreover, a rise of atmospheric CO2 stimulates photosynthesis through the well-known CO2 fertilisation effect. How far this effect impacts plant growth and how long it can persist is still much debated in the scientific community. It likely depends on the nutrient abundance in the soils. However, if CO2 stimulates growth, it will also facilitate the colonisation of extreme environments by plant species. Indeed, their growth rate between two successive extreme climatic events will be enhanced and, so, the accumulated biomass will be larger and the likelihood to find their signature in the palaeovegetation records will increase. In this contribution, we attempt to quantify this impact of CO2 on the climatic ranges of plant species by using the CARAIB dynamic vegetation model. This dynamic vegetation model can be run at the species level. We use a set of tree species from various climatic zones over different continents, for which the model has proved a good ability to simulate the present-day distribution. The model is run for different levels of atmospheric CO2, but with exactly the same climatic inputs. The simulated tree species distributions versus different climate variables (mean annual temperature, coldest month temperature, mean annual precipitation, precipitation of the driest month, etc) are then analysed and compared among the different CO2 configurations. [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 detailSurviving in a degraded forest environment: foraging strategies and space use of northern pigtailed macaques (Macaca leonina) in Sakaerat Biosphere reserve, Northeastern Thailand
Gazagne, Eva ULiege; Hambuckers, Alain ULiege; Savini, Tommaso ULiege et al

Conference (2018, July 05)

Space-use patterns and foraging strategy in degraded habitat are crucial to understand the ecology, adaptation, and conservation of primates. However, detailed ranging and behavioral data are scarce for ... [more ▼]

Space-use patterns and foraging strategy in degraded habitat are crucial to understand the ecology, adaptation, and conservation of primates. However, detailed ranging and behavioral data are scarce for many species, especially from Southeast Asia. We aimed to determine the northern pigtailed macaques (Macaca leonina) dietary, ranging, and habitat use patterns in the Sakaerat Biosphere reserve in Northeastern Thailand, a degraded habitat with ancient plantations and sub-optimal resources availability. We studied these patterns for eleven months in regard of fruit availability in a wild troop of these macaques. We used Characteristic Hull Polygons (CHP) combined with spatial statistics to estimate home ranges and core areas. We ran a monthly phenology survey to measure fruit availability over the study period. We predicted that macaques would increase their ranging during low fruit abundance to gather enough food (i.e. energy-maximizing strategy) and would use more intensively plantation and edge areas. We found a total home range of 535.5 ha and an average core area of 219.3 ha, with an average daily path length of 2,226 m. During high fruit abundance, macaques spent more time around fruit-tree species in the dry evergreen forest. During low fruit abundance, they extended their home range to plantations forest and edge areas. Fruit consumption was positively correlated to fruit abundance and there was a clear shift from flesh and pulp to dry fruit during low fruit abundance season. While the portion of home range used decreased in period of high fruit availability, daily path length and core area size did not change. Overall, as predicted, our preliminary data shows that the study troop used an energy-maximizing strategy and was able to expand the range of resources consumed in fruit scarcity period. Conversely, a study done using the same method on the same species in the nearby pristine Khao Yai National park found an energy-minimizing strategy, that is, decreased ranging area in periods of food scarcity. In conclusion, as in previous studies, our results show indeed that northern pigtailed macaques adapt their diet, monthly range and habitat use according to food abundance. However, they indicate they adapt it in an opposite way. In a degraded forest environment, the northern pigtailed macaques seem to change their survival strategy by increasing their range in periods of food scarcity to seek additional resources. These findings pose the question of substantial modification of ecological strategies by species constrained by human alteration of their habitat. [less ▲]

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See detailSimulating seed dispersal to reproduce past dynamics and distribution of African tropical trees.
Dury, Marie ULiege; Hardy, Olivier; Migliore, Jérémy et al

Poster (2018, March 28)

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. 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/), this kind of questions is addressed. The CARAIB dynamic vegetation model is applied at the level of representative African tropical tree species to reconstruct their past and present distributions in equatorial Africa. To reproduce fully population dynamics, the results of the vegetation model are combined with a seed dispersal model. At first, we simulate with the CARAIB DVM the changes over time in the potential distribution of the tree species studied in AFRIFORD taking competition between species into account. From Last Glacial Maximum (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° and bias-corrected. The calculated distributions are essentially in equilibrium with climate, except for small delay times associated with biomass growth. These distributions are also compared directly with the potential (no dispersal limitation either) distributions obtained from species distribution modelling (MaxENT) for the same set of tree species and with the same climate forcing. Then, to simulate tree species under limitation by both climate and seed dispersal, the dispersal module is run transiently on a sub-grid at 100 m resolution to reproduce species dynamics over the 20,000 years from their LGM refugia (simulated by the DVM). The dispersal capacities are dependent on species productivity and survival simulated by the DVM for each1-kyr snapshot. The modelled dispersal distances are compared to genetic-based dispersal distances estimated in the project. [less ▲]

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See detailDistribution of Podocarpus latifolius/milanjianus from the Last Glacial Maximum to 2100 in Africa with the dynamic vegetation model CARAIB.
Dury, Marie ULiege; Henrot, Alexandra-Jane ULiege; Lézine, Anne-Marie et al

Conference (2018, March 27)

Podocarpus latifolius/milanjianus (same species according to genetics) is an endemic African species with populations in the western, eastern and southern parts of the continent. The current global ... [more ▼]

Podocarpus latifolius/milanjianus (same species according to genetics) is an endemic African species with populations in the western, eastern and southern parts of the continent. The current global warming threatens the conservation of the relict patches of this mountain evergreen species. During the Last Glacial Maximum (LGM), the species was certainly more largely distributed and present at lower elevations than today according to pollen data. At the beginning of the Holocene, Podocarpus moved upwards due to warmer conditions. The size of the populations might have collapsed abruptly at the end of the ”African Humid Period” at ca. 3,000 BP. Besides this general evolution, the palaeo-distribution of Podocarpus remains relatively unknown. The origin and connections between the eastern, southern and western Podocarpus forests are still not understood. In the framework of two related projects, AFRIFORD and VULPES, we use the CARAIB dynamic vegetation model, in parallel to genetic and palynologic analyses, to simulate the past and future dynamics of Podocarpus and to understand its current distribution. Projections of the HadCM3 climate model are used to reproduce climatic conditions in Africa from LGM (21,000 BP) to present time with a temporal resolution of 1 kyr. For the future (until 2100), several IPCC CMIP5 climate scenarios have been selected according to the quality of their reconstructed climate (temperature and precipitation) over sub-Saharan Africa for historical period. After interpolation to a 0.5° regular grid, we kept only past/future anomalies that we added to the GSWP3 (20 CR) climate data chosen as the reference for the historical period. Sub-continental simulations are performed with CARAIB forced by these climatic projections to simulate the net primary productivity of Podocarpus over time and space. In addition, CARAIB simulations are performed at higher resolution over a restricted region in southwestern Cameroon to identify potential microrefugia. [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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