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See detailMiddle Miocene climate and vegetation models and their validation with proxy data
Henrot, Alexandra-Jane ULg; Utescher, Torsten; Erdei, Boglarka et al

in Palaeogeography, Palaeoclimatology, Palaeoecology (2017), 467

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Peer Reviewed
See detailUsing a dynamic vegetation model for future projections of crop yields: simulations from the plot scale to the Belgian and European scales
Jacquemin, Ingrid ULg; Dury, Marie ULg; Henrot, Alexandra-Jane ULg et al

Conference (2016, September 29)

Dynamic vegetation models (DVM), such as CARAIB (“CARbon Assimilation In the Biosphere”) were initially designed to describe the dynamics of natural ecosystems as a function of climate and soil with the ... [more ▼]

Dynamic vegetation models (DVM), such as CARAIB (“CARbon Assimilation In the Biosphere”) were initially designed to describe the dynamics of natural ecosystems as a function of climate and soil with the aim of studying the role of vegetation in the carbon cycle. But their characteristics allow numerous other applications and improvements, such as the development of a crop module. This module can be validated at the plot scale, with the use of eddy-covariance data from agricultural sites in the FLUXNET network. The carbon fluxes (e.g., net ecosystem exchange (NEE), gross primary productivity (GPP)) and the evapotranspiration (ET) simulated with the CARAIB model are compared with the fluxes measured at several sites, in order to cover a maximum number of crop types (winter wheat/barley, sugar beets, potatoes, rapeseed,…) and to evaluate the model for different European regions (Belgium, France, Germany,…). The aim of this validation is to assess the model ability to reproduce the seasonal and inter-annual variability of carbon fluxes. In order to assess the spatial variability of the model, CARAIB will be applied over Belgium and forced with the outputs the regional climate model ALARO (4 km resolution), for the recent past and the decennial projections. To reach the larger scale, we also aim to assess crops yields over Europe and to quantify the uncertainties in the climatic projections. CARAIB will be driven with the outputs of different regional climatic models (RCMs), nested in CMIP5 GCM projections for the EURO-CORDEX project: ALADIN53 (Météo-France/CNRM), RACMO22E (KNMI), RCA4 (SMHI) and REMO2009 (MPI-CSC) RCMs. These climatic projections are at a high spatial resolution (0.11-degree, ≈12 km). The model will be set up for the most common crops in Europe and for simulations tests with marginal and/or new crops. Finally, this simulation ensemble will be used to highlight potential changes in the most productive areas of Europe. [less ▲]

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See detailAssessing the impact of climate change on terrestrial plants in Europe using a Dynamic Vegetation Model driven by EURO-CORDEX projections
Dury, Marie ULg; Hambuckers, Alain ULg; Henrot, Alexandra-Jane ULg et al

Poster (2016, September 26)

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 climate variability and the changes in frequency of extreme events projected for the future. Here, the process-based dynamic vegetation model CARAIB DVM was used to evaluate and analyse how future climate and extreme events will affect European terrestrial plants. To quantify the uncertainties in climatic projections and their potential impacts on ecosystems, the vegetation model was driven with the outputs of different regional climatic models, nested in CMIP5 GCM projections for the EURO-CORDEX project: ALADIN53 (Météo-France/CNRM), RACMO22E (KNMI), RCA4 (SMHI) and REMO2009 (MPI-CSC) RCMs. These daily climatic scenarios are at a high spatial resolution (0.11°, ≈ 12 km). CARAIB simulations were performed across Europe over the historical period 1971-2005 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 analysed the climatic variability simulated by the climatic models over the historical period and compared it with the observed climatic variability. Then, we evaluated change in climatic variability and extreme events projected by the climatic models for the end of the century. Finally, we assessed the change in species productivity and abundance. We evaluated the severity of projected productivity change for the period 2070-2099 relative to their current productivity variability (period 1970-1999). Mean changes were considered severe if they exceed observed variability. The projections of potential shifts in species distributions are directly dedicated to current forest management. [less ▲]

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See detailResponse to droughts and heat waves of the productivity of natural and agricultural ecosystems in Europe within ISI-MIP2 historical simulations
François, Louis ULg; Henrot, Alexandra-Jane ULg; Dury, Marie ULg et al

Conference (2016, June 23)

According to the projections of climate models, extreme events such as droughts and heat waves are expected to become more frequent and more severe in the future. Such events are known to severely impact ... [more ▼]

According to the projections of climate models, extreme events such as droughts and heat waves are expected to become more frequent and more severe in the future. Such events are known to severely impact the productivity of both natural and agricultural ecosystems, and hence to affect ecosystem services such as crop yield and ecosystem carbon sequestration potential. Dynamic vegetation models are conventional tools to evaluate the productivity and carbon sequestration of ecosystems and their response to climate change. However, how far are these models able to correctly represent the sensitivity of ecosystems to droughts and heat waves? How do the responses of natural and agricultural ecosystems compare to each other, in terms of drought-induced changes in productivity and carbon sequestration? In this contribution, we use ISI-MIP2 model historical simulations from the biome sector. Eight dynamic vegetation models have participated in the biome sector intercomparison of ISI-MIP2: CARAIB, DLEM, JULES, LPJ-GUESS, LPJml, ORCHIDEE, VEGAS and VISIT. We focus the analysis on well-marked droughts or heat waves that occured in Europe after 1970, such as the 1976, 2003 and 2010 events. For most recent studied events, the model results are compared to the response observed at several eddy covariance sites in Europe, and, at a lager scale, to the drops in crop productivities reported in national statistics or to the drought impacts retrieved from satellite data (Terra MODIS instrument). [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; François, Louis ULg; Hambuckers, Alain ULg et al

Conference (2016, April 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 climate 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: ALADIN53 (Météo-France/CNRM), RACMO22E (KNMI), RCA4 (SMHI) and REMO2009 (MPI-CSC) 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 2070-2099) relative to their current variability (period 1970-1999). 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. This spatial risk index and the projections of potential shifts in species distributions are directly dedicated to current forest management to guide in planting or in assisted migration. [less ▲]

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See detailMiddle Miocene climate and vegetation models and their validation with proxy data
Henrot, Alexandra-Jane ULg; Utescher, T.; Erdei, B. et al

Report (2016)

The Miocene is a relatively recent epoch of the Earth's history with warmer climate than today, particularly during the middle Miocene Climatic Optimum (MMCO, approximately 17-15Ma). Although the cause of ... [more ▼]

The Miocene is a relatively recent epoch of the Earth's history with warmer climate than today, particularly during the middle Miocene Climatic Optimum (MMCO, approximately 17-15Ma). Although the cause of the warming is probably not only attributable to CO2, but also to changes in orography and configuration of ocean gateways, this time interval represents an ideal case study to test the ability of climate models to simulate warm climates comparable to those that the Earth may experience in the near future. However, even with higher than present-day CO2 concentrations, the MMCO warming inferred from terrestrial proxy data has been difficult to reproduce in climate models.Since fossil flora do not provide direct information on climate, but on flora and vegetation, climate model results are generally compared to climate reconstructions obtained from the fossil flora. In this study, we apply an alternative method by simulating palaeovegetation from the outputs of the climate model, using a dynamic vegetation model. Model vegetation reconstruction can then be compared to the vegetation cover indicated by the fossil flora record at the various localities, provided that a common classification of plant functional types (PFTs) is used for the data and the model. Here, we reconstruct the vegetation of the middle Miocene with the global dynamic vegetation model CARAIB, using the climatologies derived from five atmospheric general circulation models. The reliability of the simulations is examined on a presence/absence basis of PFTs by comparison of vegetation reconstructions to palaeoflora data recorded in the Northern Hemisphere and the Tropics.This comparison provides an overall agreement around 60% between model and data, when all sites and tree types are considered. Three model simulations out of five show to be better at predicting the absence than the presence. The presence of warm-temperate mixed forests in the middle latitudes, dominated by broadleaved deciduous warm temperate and subtropical trees is generally well reproduced in CARAIB simulations. However, poor agreement is obtained for the presence of tropical PFTs out of the Tropics and for warm PFTs at latitudes northward of 50°N, where climate models remain too cold to produce assemblages of trees consistent with the data. Nevertheless, the model-data comparison performed here highlights several mismatches that could result not only from missing feedbacks in the climate simulations, but also from the data. The results of the likelihood analysis on presence/absence of PFTs illustrate the uncertainties in the PFT classification of the Neogene floral records. The coexistence of some PFTs in the palaeovegetation data is impossible to reproduce in the vegetation model simulations because of the climatic definition of the modern PFTs. This result indicates either a bias in the identification of modern analogues for fossil plant taxa, or a possible evolution of environmental requirements of certain plants. © 2016 Elsevier B.V. [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 detailModeling Pacific Northwest carbon and water cycling using CARAIB Dynamic Vegetation Model
Kim, John B; Dury, Marie ULg; Still, Christopher J et al

Poster (2015, December 14)

While uncertainties remain regarding projected temperature and precipitation changes, climate warming is already affecting ecosystems in the Pacific Northwest (PNW). Decrease in ecosystem productivity as ... [more ▼]

While uncertainties remain regarding projected temperature and precipitation changes, climate warming is already affecting ecosystems in the Pacific Northwest (PNW). Decrease in ecosystem productivity as well as increase in mortality of some plant species induced by drought and disturbance have been reported. Here, we applied the process-based dynamic vegetation model CARAIB to PNW to simulate the response of water and carbon cycling to current and future climate change projections. The vegetation model has already been successfully applied to Europe to simulate plant physiological response to climate change. We calibrated CARAIB to PNW using global Plant Functional Types. For calibration, the model is driven with the gridded surface meteorological dataset UIdaho MACA METDATA with 1/24-degree (~4-km) resolution at a daily time step for the period 1979-2014. The model ability to reproduce the current spatial and temporal variations of carbon stocks and fluxes was evaluated using a variety of available datasets, including eddy covariance and satellite observations. We focused particularly on past severe drought and fire episodes. Then, we simulated future conditions using the UIdaho MACAv2-METDATA dataset, which includes downscaled CMIP5 projections from 28 GCMs for RCP4.5 and RCP8.5. We evaluated the future ecosystem carbon balance resulting from changes in drought frequency as well as in fire risk. We also simulated future productivity and drought-induced mortality of several key PNW tree species. [less ▲]

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See detailAnalysing the response of European ecosystems to droughts and heat waves within ISI-MIP2 simulations
Henrot, Alexandra-Jane ULg; Dury, Marie ULg; François, Louis ULg et al

Conference (2015, December 14)

With unprecedented speed and extent, the future climate change can be expected to severely impact terrestrial ecosystems due to more frequent extreme events, such as droughts or heat waves. What will be ... [more ▼]

With unprecedented speed and extent, the future climate change can be expected to severely impact terrestrial ecosystems due to more frequent extreme events, such as droughts or heat waves. What will be the impacts of these extreme events on ecosystem functioning and structure? How far will net primary production be reduced by such events? What will be the impact on plant mortality? Could such events trigger changes in the abundance of plant species, thus leading to biome shifts? In this contribution, we propose to use ISI-MIP2 model historical simulations from the biome sector to analyse the response of ecosystems to droughts or heat waves, trying to understand the differences between several vegetation models (e.g. CARAIB, HYBRID, LPJ). The analysis will focus on Europe. It will compare and assess the model responses for a series of well-marked drought or heat wave events in the simulated historical period, such as those that occurred in 1976, 2003 or 2010. This analysis will be performed in terms of several important environmental variables, like soil water and hydric stress, runoff, PFT abundance, net primary productivity and biomass, fire frequency, turnover of soil organic matter, etc. Whenever possible, the response of the model will be compared to available data for the most recent well-marked events. Examples of data to be used are eddy covariance, satellite data (including leaf area and fire occurrence) or tree rings. [less ▲]

Detailed reference viewed: 74 (11 ULg)
See detailToward modeling Pacific Northwest tree species using CARAIB dynamic vegetation model
Dury, Marie ULg; Still, Christopher J; Kim, John B et al

Poster (2015, November 04)

While uncertainties remain regarding projected temperature and precipitation changes, climate warming is already affecting Pacific Northwest (PNW) ecosystems, notably forest species composition. In this ... [more ▼]

While uncertainties remain regarding projected temperature and precipitation changes, climate warming is already affecting Pacific Northwest (PNW) ecosystems, notably forest species composition. In this research, we use the process-based dynamic vegetation model CARAIB DVM (Dury et al., iForest - Biogeosciences and Forestry, 4:82-99, 2011) to simulate current distribution of common tree species in PNW ecosystems. This DVM includes the influence of soil water content, atmospheric CO2 concentration and disturbances like fires, all essential to consider for reliably predicting present and future plant species distributions. Classically, dynamic vegetation models represent vegetation at the scale of plant functional types (PFTs). However, since they have a narrower bioclimatic spectrum, individual species are probably more vulnerable to climate change than PFTs. Here, we first perform simulations with the CARAIB global vegetation classification based on 26 Plant Functional Types (3 herbaceous, 8 shrubby and 15 arboreal PFTs). Then, we apply the vegetation model at the species level in order to analyse the response of a selected set of plant species to current climate. Representing the European vegetation at the scale of individual species has been successfully performed with CARAIB. The simulated individual species are differentiated by their proper climatic requirements and tolerances. Concerning physiological and structural parameters, species share the traits of the respective PFT, but we progressively improve their characterization by the use of global or local trait databases (e.g., TRY database). The model is driven with climatic observation data over the period 1951-2012 across the PNW region at different spatial resolutions. We test the model’s ability to reproduce the present spatial and temporal variations of carbon stocks and fluxes as well as the observed species and biome distributions over the PNW. We then assess model predictions using a variety of available datasets, including eddy covariance and satellite observations. [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

Poster (2015, April)

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 detailModelling the dynamics of European ecosystems from the early Holocene to the end of the 21st century with the CARAIB dynamic vegetation model
Dury, Marie ULg

Doctoral thesis (2015)

With the current climate change as background, we worked with the dynamic vegetation model CARAIB (CARbon Assimilation In the Biosphere) to study the functioning and dynamics of European ecosystems under ... [more ▼]

With the current climate change as background, we worked with the dynamic vegetation model CARAIB (CARbon Assimilation In the Biosphere) to study the functioning and dynamics of European ecosystems under changing climatic conditions from the beginning of the Holocene to the end of the 21st century. Originally designed to study the role of vegetation in the global carbon cycle and to reconstruct steady state vegetation distributions under current, past and future climatic conditions, we adapt the CARAIB model to perform transient simulations in order to assess vegetation response to changing climate. For this, we improved the demographic processes represented in the model: the conditions for plant establishment, the response to stresses, the competition between species, the species migration, etc. This new version of the model is first described and its main outputs are evaluated using site-based observations, but primarily remote sensing products. The first study carried out with the new version of CARAIB assessed the response of European forest ecosystems to 21st century climate. The classification of the European vegetation in Bioclimatic Affinity Groups (BAGs, Laurent et al., 2008), based on species traits and climatic tolerances and requirements, as well as the fire module recently implemented were for the first time used in future transient projections. The model was first driven by the ARPEGE/Climate model to illustrate and analyse the potential impacts of climate change on forest productivity and distribution as well as fire intensity over Europe under forcing from different IPCC emission scenarios (B1, A1B and A2). The vegetation model projects for the future more frequent and severe droughts in southern Europe. In these areas, the model indicates that interannual variability of net primary productivity might strongly increase as well as wildfire frequency and intensity, which may have large impacts on vegetation density and distribution. In northern Europe and in the Alps, with reduced temperature variability and positive soil water anomalies, NPP variability tends to decrease. The potential CO2 fertilizing effect was studied assuming constant and increasing atmospheric CO2 concentration in the vegetation model. To quantify the uncertainties in the climate projections and in their potential impacts on ecosystems, the vegetation model was also driven by three regional climate models (KNMI-RACMO2, DMI-HIRHAM5 and HC-HadRM3Q0 RCMs) from the European Union project ENSEMBLES. We continued further the analysis representing the European vegetation at the scale of individual species. A set of 99 species (47 herbs, 12 shrubs and 40 trees) have been prepared in such a way that each BAG of plants used in the first part of this work is represented by several of these species. This ensures to provide a full set of species with the major ecosystem functions represented. Like for the BAGs, the bioclimatic limits of the species were obtained by overlapping species distribution from the Atlas Florae Europaeae (AFE) with climatic data. Since the first study highlighted the importance of climatic variability on plant functioning, we used here a 30-yr time series (and not average climate as usually) to determine species establishment and survival conditions. The comparison between the modelled distributions obtained with new climatic thresholds and observed species distribution reveals that taking a longer climatic time series into account improves the predictions of species spatial pattern. Using this improved representation of current species requirements, we projected potential shifts in species distributions for the end of the century. We spatially evaluated the suitability for species establishment and stresses conditions as well as the disappearance and the potential appearance of species. 18% of tree species and 22% of herb and shrub species (respectively 30% and 64% if the CO2 fertilization effect on species is not taken into account) might experience a loss of 30% or more of their current distribution. Finally we combined different model outputs in an original index evaluating the risk of ecosystem disruption to assess the vulnerability of species and ecosystems to future climate change. The highest values of the index are found in southern Europe indicating that the amplitude of the expected ecosystem changes largely exceeds current interannual variability in this area. If climate is one of the main drivers of species dynamics, rapid climate changes as projected for the 21st century might prevent species to track suitable climatic conditions and fill their potential ranges impeded by dispersal capacity. To assess the actual response of vegetation to climate change, we introduced a species migration module in the dynamic vegetation model. Its calibration and evaluation have been performed on the Holocene period considered as an interesting homologue to current climate change, even if the change rate must have been lower. With the module, we studied the postglacial re-colonization of Europe by two tree species Fagus sylvatica and Picea abies. Using maximum potential migration rates (381 and 450 m yr-1 for beech and spruce) calculated by a species distribution model dealing with demographic and dispersal traits, we evaluated with the dynamic vegetation model the involvement of inter-specific competition but also of high climatic variability on species spatio-temporal dynamics. Considering these abiotic and biotic variables in the migration processes resulted in mean migration rates of 91 (± 38) and 131 (± 73) m yr-1 respectively for Fagus sylvatica and Picea abies. If the comparison with palaeorecords demonstrates the ability of such an approach to reasonably replicate the regional features of the species spatio- temporal progressions, the objective was not to reproduce accurately postglacial species history (still not well known and understood) but rather to determine the relative role of some environmental variables on the migration of the two species through different migration scenarii. It appeared that Holocene beech migration might have been strongly affected by interspecific competition while it is climatic conditions and their variability that might have conditioned the spruce migration. With the different scenarios, we showed that mono-causal explanations cannot however explain the observed timing and pattern at the European scale and we rather give preference to a combination of climate, dispersal and competitive factors, the potential role of anthropogenic disturbances being not studied here. [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 ▲]

Detailed reference viewed: 107 (12 ULg)
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: 61 (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: 81 (16 ULg)
Full Text
Peer Reviewed
See detailModelling the Holocene migrational dynamics of Fagus sylvatica L. and Picea abies (L.) H. Karst
Lehsten, Lehsten; Dullinger, Stefan; Hülber, Karl et al

in Global Ecology and Biogeography (2014), 23

Aim: Vegetation dynamics and the competitive interactions involved are assumed to restrict the ability of species to migrate. But in most migration modelling approaches disturbance-driven succession and ... [more ▼]

Aim: Vegetation dynamics and the competitive interactions involved are assumed to restrict the ability of species to migrate. But in most migration modelling approaches disturbance-driven succession and competition processes are reduced to simple assumptions or are even missing. The aim of this study was to test a combination of a migration model and a dynamic vegetation model to estimate the migration of tree species controlled by climate, environment and local species dynamics such as succession and competition. Location: Europe. Methods: To estimate the effect of vegetation dynamics on the migration of European beech and Norway spruce, we developed a post-process migration tool (LPJ-CATS). This tool integrates outputs of the migration model CATS and the dynamic vegetation model LPJ-GUESS. The model LPJ-CATS relies on a linear dependency between the dispersal kernel and migration rate and is based on the assumption that competition reduces fecundity. Results: Simulating potential migration rates with the CATS model, which does not account for competition and disturbance, resulted in mean Holocene migra- tion rates of 435 ± 55 and 330 ± 95 m year−1 for the two species Picea abies and Fagus sylvatica, respectively. With LPJ-CATS, these mean migration rates were reduced to 250 ± 75 and 170 ± 60 m year−1 for spruce and beech, respectively. Moreover, LPJ-CATS simulated migration pathways of these two species that gen- erally comply well with those documented in the palaeo-records. Main conclusions: Our ‘hybrid’ modelling approach allowed for the simulation of generally realistic Holocene migration rates and pathways of the two study species on a continental scale. It suggests that competition can considerably modify spread rates, but also the magnitude of its effect depends on how close climate conditions are to the niche requirements of a particular species. [less ▲]

Detailed reference viewed: 56 (18 ULg)