Publications of Alexandra-Jane Henrot
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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 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 detailISIMIP2a Simulation Data from Biomes Sector (V. 1.1)
Reyer, Christopher; Asrar, Gassem; Betts, Richard et al

Textual, factual or bibliographical database (2019)

This database collects the results from the ISIMIP2a simulation experiments carried out with from 8 global vegetation models (CARAIB, DLEM, JULES-B1, LPJ-GUESS, LPJmL, ORCHIDEE, VEGAS, VISIT) according to ... [more ▼]

This database collects the results from the ISIMIP2a simulation experiments carried out with from 8 global vegetation models (CARAIB, DLEM, JULES-B1, LPJ-GUESS, LPJmL, ORCHIDEE, VEGAS, VISIT) according to the ISIMIP2a protocol (https://www.isimip.org/protocol/#isimip2a). [less ▲]

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See detailTree mortality submodels drive simulated long-term forest dynamics: assessing 15 models from the stand to global scale
Bugmann, H.; Seidl, R.; Hartig, F. et al

in Ecosphere (2019), 10(2),

Models are pivotal for assessing future forest dynamics under the impacts of changing climate and management practices, incorporating representations of tree growth, mortality, and regeneration ... [more ▼]

Models are pivotal for assessing future forest dynamics under the impacts of changing climate and management practices, incorporating representations of tree growth, mortality, and regeneration. Quantitative studies on the importance of mortality submodels are scarce. We evaluated 15 dynamic vegetation models (DVMs) regarding their sensitivity to different formulations of tree mortality under different degrees of climate change. The set of models comprised eight DVMs at the stand scale, three at the landscape scale, and four typically applied at the continental to global scale. Some incorporate empirically derived mortality models, and others are based on experimental data, whereas still others are based on theoretical reasoning. Each DVM was run with at least two alternative mortality submodels. Model behavior was evaluated against empirical time series data, and then, the models were subjected to different scenarios of climate change. Most DVMs matched empirical data quite well, irrespective of the mortality submodel that was used. However, mortality submodels that performed in a very similar manner against past data often led to sharply different trajectories of forest dynamics under future climate change. Most DVMs featured high sensitivity to the mortality submodel, with deviations of basal area and stem numbers on the order of 10–40% per century under current climate and 20–170% under climate change. The sensitivity of a given DVM to scenarios of climate change, however, was typically lower by a factor of two to three. We conclude that (1) mortality is one of the most uncertain processes when it comes to assessing forest response to climate change, and (2) more data and a better process understanding of tree mortality are needed to improve the robustness of simulated future forest dynamics. Our study highlights that comparing several alternative mortality formulations in DVMs provides valuable insights into the effects of process uncertainties on simulated future forest dynamics. © 2019 The Authors. [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 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 detailEvaluating changes of biomass in global vegetation models: the role of turnover fluctuations and ENSO events
Cantú, Anselmo García; Frieler, Katja; Reyer, Christopher P O et al

in Environmental Research Letters (2018)

This paper evaluates the ability of eight global vegetation models to reproduce recent trends and inter-annual variability of biomass in natural terrestrial ecosystems. For the purpose of this evaluation ... [more ▼]

This paper evaluates the ability of eight global vegetation models to reproduce recent trends and inter-annual variability of biomass in natural terrestrial ecosystems. For the purpose of this evaluation, the simulated trajectories of biomass are expressed in terms of the relative rate of change in biomass (RRB), defined as the deviation of the actual rate of biomass turnover from its equilibrium counterpart. Cumulative changes in RRB explain long-term changes in biomass pools. RRB simulated by the global vegetation models is compared with its observational equivalent, derived from vegetation optical depth reconstructions of above-ground biomass (AGB) over the period 1993–2010. According to the RRB analysis, the rate of global biomass growth described by the ensemble of simulations substantially exceeds the observation. The observed fluctuations of global RRB are significantly correlated with El Niño Southern Oscillation events (ENSO), but only some of the simulations reproduce this correlation. However, the ENSO sensitivity of RRB in the tropics is not significant in the observation, while it is in some of the simulations. This mismatch points to an important limitation of the observed AGB reconstruction to capture biomass variations in tropical forests. Important discrepancies in RRB were also identified at the regional scale, in the tropical forests of Amazonia and Central Africa, as well as in the boreal forests of north-western America, western and central Siberia. In each of these regions, the RRBs derived from the simulations were analyzed in connection with underlying differences in net primary productivity and biomass turnover rate ̶as a basis for exploring in how far differences in simulated changes in biomass are attributed to the response of the carbon uptake to CO2 increments, as well as to the model representation of factors affecting the rates of mortality and turnover of foliage and roots. Overall, our findings stress the usefulness of using RRB to evaluate complex vegetation models and highlight the importance of conducting further evaluations of both the actual rate of biomass turnover and its equilibrium counterpart, with special focus on their background values and sources of variation. In turn, this task would require the availability of more accurate multi-year observational data of biomass and net primary productivity for natural ecosystems, as well as detailed and updated information on land-cover classification. [less ▲]

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See detailHigh-resolution simulations of natural and agricultural ecosystems over Belgium with the CARAIB Dynamic Vegetation Model
Jacquemin, Ingrid ULiege; Dury, Marie ULiege; Henrot, Alexandra-Jane ULiege et al

Conference (2017, November 17)

CARAIB (for CARbon Assimilation In the Biosphere) is a state-of-the-art dynamic vegetation model (DVM), initially designed to study the role of the vegetation in the global carbon cycle and the vegetation ... [more ▼]

CARAIB (for CARbon Assimilation In the Biosphere) is a state-of-the-art dynamic vegetation model (DVM), initially designed to study the role of the vegetation in the global carbon cycle and the vegetation behavior as a function of climate and soil. Motivated by the requirements of ecosystem management and land use planning studies, CARAIB was recently improved so as to deal with both natural and agricultural ecosystems and at a high resolution of 1km over Belgium. A new module, for crops and meadows, was added in the model, which deals with the specific processes (phenology) and management (sowing, harvesting,…) of these ecosystems. The spatial and temporal validation was carried out with different data sources : agricultural statistics, eddy-covariance site, field measurements,… The addition of the crop module has led to the improvement of the surface scheme, from now on including dynamic land use and land cover information. As well as describes the evolution of physical and biological processes, CARAIB has become an interesting tool to assess the sustainability under climate change of the ecological systems, in particular by the approach of the ecosystem goods and services. Indeed, if some model outputs can be directly read as quantitative indicators of ecosystem services (e.g. carbon sequestration), we have translated some of them to get, e.g., the crop yield (from net primary productivity) or an estimation of the soil erosion for simulation at the parcel level (from runoff and parcels characteristics). But whether an ecosystem services or land use planning studies, the crucial point for CARAIB is the landscape dynamics, which is not considered by the model, in the absence of anthropogenic, economic and societal factors in the system. In order to overcome this lack, CARAIB is now coupled with an agent-based model (ABM), to compose a land surface dynamics (LSD) module. The productivity and growth of natural and managed vegetation is given by the DVM to the ABM, which determines the shifts in land use and land cover. The LSD module is able to represent the mutual interactions between ecological and socio-economic systems and thus, to assess the sustainability of the different climate and socio-economic scenarios tested. [less ▲]

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See detailCombining multiple statistical methods to evaluate the performance of process-based vegetation models across three forest stands
Horemans, Joanna A.; Henrot, Alexandra-Jane ULiege; Delire, Christine et al

in Central European Forestry Journal (2017)

Process-based vegetation models are crucial tools to better understand biosphere-atmosphere exchanges and ecophysiological responses to climate change. In this contribution the performance of two global ... [more ▼]

Process-based vegetation models are crucial tools to better understand biosphere-atmosphere exchanges and ecophysiological responses to climate change. In this contribution the performance of two global dynamic vegetation models, i.e. CARAIB and ISBACC, and one stand-scale forest model, i.e. 4C, was compared to long-term observed net ecosystem carbon exchange (NEE) time series from eddy covariance monitoring stations at three old-grown European beech (Fagus sylvatica L.) forest stands. Residual analysis, wavelet analysis and singular spectrum analysis were used beside conventional scalar statistical measures to assess model performance with the aim of defining future targets for model improvement. We found that the most important errors for all three models occurred at the edges of the observed NEE distribution and the model errors were correlated with environmental variables on a daily scale. These observations point to possible projection issues under more extreme future climate conditions. Recurrent patterns in the residuals over the course of the year were linked to the approach to simulate phenology and physiological evolution during leaf development and senescence. Substantial model errors occurred on the multi-annual time scale, possibly caused by the lack of inclusion of management actions and disturbances. Other crucial processes defined were the forest structure and the vertical light partitioning through the canopy. Further, model errors were shown not to be transmitted from one time scale to another. We proved that models should be evaluated across multiple sites, preferably using multiple evaluation methods, to identify processes that request reconsideration. [less ▲]

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See detailHow do individual species and Plant Functional Type responses to environmental change differ in Dynamic Vegetation Models? - A forest stand analysis
Dury, Marie ULiege; Henrot, Alexandra-Jane ULiege; Jacquemin, Ingrid ULiege et al

Poster (2017, October 09)

Originally dedicated to simulate vegetation at the global scale, dynamic (global) vegetation models (D(G)VMs) classify vegetation into Plant Functional Types (PFTs) to represent the largest set of plant ... [more ▼]

Originally dedicated to simulate vegetation at the global scale, dynamic (global) vegetation models (D(G)VMs) classify vegetation into Plant Functional Types (PFTs) to represent the largest set of plant species. PFTs are clusters of species that share common morphological and physiological traits. However, PFT classification becomes surely too coarse to reflect the large diversity in plant species responses to climate and environmental changes, a critical point for biodiversity questions. Thus, some efforts focus now on applying DVMs at the species level refining the definition of morphophysiological parameters from initial PFT traits to specific traits collected or found in trait databases. What are the effects of using species-specific parameters? Do dynamic vegetation models better reproduce historical forest growth and mortality observed in monitored stands? How will individual species respond to future climate compared to PFTs? To study these questions, we used two process-based dynamic vegetation models CARAIB (Dury et al., 2011) as well as LPJ-GUESS (Smith et al., 2001), and compared their outputs. CARAIB has been previously adapted to model a set of 40 European tree species, differentiated by their specific traits, proper climatic requirements and tolerances. LPJ-GUESS features a detailed representation of climate sensitive tree species dynamics, resource competition and canopy structure (Hickler et al., 2012). The respective tree species are distinguished by taking differences in phenology, allometry and bioclimatic limits into account. Model simulations were performed in accordance with the experimental protocol of the COST Action PROFOUND (“Towards robust projections of European forests under climate change”) for several European forest stands selected in the project. We particularly focused on Fagus sylvatica stand in Sorø (Denmark), Picea abies stand in Solling (Germany) and Pinus sylvestris (and Picea abies) stands in Hyytiala (Finland). The experiments include site-specific soil characteristics, management practices (planting, thinning and harvest) and climate conditions. For the historical period (from planting year to 2014), besides local observations, simulations were also run with the original (0.5-degree spatial resolution) and locally bias-corrected (LBC) ISIMIP2B outputs of global climate models for testing the reliance of DVM results to the spatial resolution of climatic inputs. For the future period (2005-2100), vegetation models were driven by the ISIMIP2B climates under different Representative Concentration Pathways. The simulations at the PFT level were performed following the same protocol replacing the locally present species by their representative PFTs. The carbon and water fluxes obtained from the different experiments carried out with the two DVMs were compared with eddy-covariance data from each site. [less ▲]

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See detailLand surface interactions modeling (Agent-Based-Model - Dynamic Vegetation Model) over Belgium: current state and crop yield assessment for future (at the Belgian and European scales)
Jacquemin, Ingrid ULiege; Beckers, Veronique; Henrot, Alexandra-Jane ULiege et al

Poster (2017, May 23)

Agriculture in Europe is under substantial pressure. Farmers need to adapt to an ever-increasing global market, resulting in increasing competition and a high dependency on global food prices. Furthermore ... [more ▼]

Agriculture in Europe is under substantial pressure. Farmers need to adapt to an ever-increasing global market, resulting in increasing competition and a high dependency on global food prices. Furthermore, they have to deal with an increasing urbanization pressure and to comply with increasingly strict environmental rules and policies, sometimes requiring heavy investments. Combined to potential impacts of climate changes on ecosystems functions and structures, these factors could lead to a change in land use structure. In the framework of the MASC project ("Modelling and Assessing Surface Change impacts on Belgium and Western European climate"), we aim at providing a better understanding of these factors, with the final objective of improving regional climate model projections at the decennial scale over Belgium and Western Europe by combining high-resolution models. We propose to combine an agent-base model (ABM) and a dynamic vegetation model (DVM), CARAIB (“CARbon Assimilation In the Biosphere”). The ABM models the farmers as individual agents using a certain number of parcels. They decide on what to plant based on market prices, subsidies, crop rotations, personal preferences and the expected yield, which will be given by CARAIB. CARAIB will be forced over Belgium with the outputs of the regional climate model ALARO (4 km resolution) for the recent past and for the most common crops. As a first attempt to assess the impact of the climate change on crops yields over Europe, CARAIB will be driven with the outputs of several regional climate models (RCMs), from EURO-CORDEX, nested in CMIP5 general circulation model projections: ALADIN53 (Météo-France/CNRM), RACMO22E (KNMI), RCA4 (SMHI) and REMO2009 (MPI-CSC) RCMs (0.11-degree, ≈12 km) [less ▲]

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See detailContinental Climate Gradients in North America and Western Eurasia before and after the Closure of the Central American Seaway
Utescher, Torsten; Dreist, Andreas; Henrot, Alexandra-Jane ULiege et al

in Earth and Planetary Science Letters (2017), 472

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See detailEstimation des bilans hydriques présent et futur ainsi que de leur impact sur les rendements agricoles en Afrique du Nord et de l'Ouest à l'aide d'un modèle de végétation dynamique
Dury, Marie ULiege; Jacquemin, Ingrid ULiege; Henrot, Alexandra-Jane ULiege et al

Conference (2017, March 29)

Climate change is affecting agriculture all over the world with dramatic consequences in developing countries already affected by limited water resources. Unfortunately, the lack of a consistent coverage ... [more ▼]

Climate change is affecting agriculture all over the world with dramatic consequences in developing countries already affected by limited water resources. Unfortunately, the lack of a consistent coverage of hydrological data (precipitation, soil water content, etc.), especially in those regions, makes difficult a good knowledge of the current conditions and, thus, prevents any planning for the future. Therefore, ecosystem process-based models are interesting tools to represent the water balance of terrestrial ecosystems and provide an overview of the current and future hydrological conditions. Here, we use the CARAIB (CARbon Assimilation In the Biosphere; Dury et al., 2011) dynamic vegetation model (DVM) to evaluate current and future soil water availability and assess potential impacts of its reduction on crop yields. CARAIB is a state-of-the-art DVM with various modules dealing with (i) soil hydrology, (ii) photosynthesis/stomatal regulation, (iii) carbon allocation and biomass growth, (iv) litter/soil carbon dynamics, (v) vegetation cover dynamics, (vi) seed dispersal, and (vii) vegetation fires. Climate and atmospheric CO2 are the primary inputs. Within the VOTES project (Fontaine et al., 2014) and the GGCMI intercomparison (Global Gridded Crop Model Intercomparison), the model has been improved to include crops and meadows (Minet et al., 2015), and some modules have been written to translate model outputs into quantitative indicators of ecosystem services (e.g., to evaluate crop yield from net primary productivity, to calculate soil erosion from runoff and slope or to apply irrigation water). In this contribution, we focus on four crop species (maize, rice, soy and spring wheat) over North and West Africa. We use historical climate and future projections from the ISI-MIP2 model intercomparison (Inter-Sectoral Impact Model Intercomparison Project). Historical climate is PGMFD v.2.1 (NCEP/NCAR Reanalysis 1) 1901-2012 time series. Future change in temperature and precipitation are produced over the 21st century by CMIP5 general circulation model simulations that were bias-corrected in the framework of the ISI-MIP2 project. Simulations of the vegetation model are performed at 0.5° spatial resolution under two water scenarios: a water-limited (precipitation only) and a full irrigation (water supplied to reach field capacity). In the model, the soil water available for plant (ASW) is expressed as the fraction between the actual soil water and the water available for plant growth at field capacity (FC): ASW = (SW-WP)/(FC-WP) with SW being the actual soil water and WP the wilting point. Under the first scenario, the soil water deficit and its impacts on crop production are evaluated. The second scenario allows an evaluation of the amount of irrigation water necessary to fulfill crop requirements. This kind of study can help in the identification of agricultural areas currently vulnerable or which might be exposed in the future. It can also be useful to optimise water resource management in African countries. [less ▲]

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See detailImplementation of the MEGAN (v2.1) biogenic emission model in the ECHAM6-HAMMOZ chemistry climate model
Henrot, Alexandra-Jane ULiege; Stanelle, T.; Schröder, S. et al

in Geoscientific Model Development (2017), 10

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See detailQuantification of Calabrian vegetation in Southern Primory'e (far East of Russia) using multiple proxies
Bondarenko, O. V.; Blokhina, N. I.; Bruch, A. A. et al

in Palaeogeography, Palaeoclimatology, Palaeoecology (2017), 467

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See detailRefining plant traits in vegetation models using forest inventory and LAI measurements. An application to the modelling of Cedrus atlantica in the Rif Mountains with the CARAIB model
Henrot, Alexandra-Jane ULiege; Hambuckers, Alain ULiege; François, Louis ULiege et al

Conference (2017)

It appears today established that climate change will alter biodiversity, since the migration speed of many species, especially plants, are presumably too small to follow climate change. Mountain ... [more ▼]

It appears today established that climate change will alter biodiversity, since the migration speed of many species, especially plants, are presumably too small to follow climate change. Mountain ecosystem floras of Mediterranean regions are particularly vulnerable to the climatic threat, because they combine high ecosystem diversity and large proportion of endemic species, with the risk of reaching the summits of the mountains which would limit their migration. Moreover, these environments are often strongly impacted by man. Being able to identify and predict the areas favourable to the species – microrefugia - becomes crucial in view of the fragmentation of the space devoted to their conservation. Dynamic vegetation models (DVMs) are well-designed tools for performing such projections, since they incorporate the physiological effects of CO2. However, they are usually run at the plant functional type level (PFT), whereas conservation studies require specific projections for each individual species. Thus, some efforts focus now on applying DVMs at species level, refining the definition of morphophysiological parameters from initial PFT traits to specific traits collected in the field or found in trait databases. Here we simulated the modern distribution of Cedrus atlantica, an endangered species of the north Africa mountains with the CARAIB DVM (Dury et al., iForest - Biogeosciences and Forestry, 4:82-99, 2011), over the Rif Mountains. Model results in terms of biomass and NPP are evaluated against data coming from forest inventory and LAI measurements. Morphological traits of C. atlantica derived from plant material collected in situ (such as specific leaf area, C:N ratio of leaves, etc) are adapted in the model simulation. CARAIB is run at high resolution using either climatic inputs derived from the Climate Research Unit climate dataset combined with WorldClim climatology at 30 arc sec or the ouputs of a 5 km resolution simulation of the regional climate model MAR (Fettweis et al., The Cryosphere, 7 :469-489, 2013) over the focal area. [less ▲]

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