Projects

Project Bordeaux Idex Fellowship ISOEMB | 2018-2020

The Isotopic signature of drought-induced Embolism: from the leaf to the tree stem

Screen Shot 2018-12-27 at 12.29.49 AMWith climate change drought events are projected to intensify, leading to an increase in tree die-off episodes, particularly in water-limited regions. In this context, species-specific strategies that have evolved to cope with hydraulic failure and carbon starvation will determine the severity of die-off events within ecosystems and lead to changes in community structure and composition. During periods of increasing soil and/or atmospheric drought, leaf water loss is minimised by closing stomata in an attempt by the plant to avoid leaf dehydration and subsequent xylem embolism. Xylem embolism is a dynamic process and until recently traditional methods for embolism assessment could not measure easily how embolism bubbles spread in vivo and at real time. However, it is becoming clearer that embolism of xylem occurs after stomata have closed indicating that non-stomatal water loss and the maintenance of lethal water potentials may govern the rate of embolism and importantly lead to the hydraulic failure of plants. To date, very little attention has been paid to the role of stem transpiration in xylem embolism and tree mortality. However, several studies have measured significant stem transpiration providing clear evidence for gradual evaporative losses from plants when transpiration losses via stomata are minimal. As a result, direct measurement of gas exchange in stems may play a role in the tolerance of different species to stem dehydration and hydraulic failure. IsoEmb will unravel the link between the loss of hydraulic conductance in leaves and in woody stems using novel isotopic techniques. We will measure the isofluxes of water and CO2, to better understand and quantify the mechanisms underlying drought-induced mortality in plants. This project will also contribute to a better understanding of the impact of extreme drought events on plant climate-functional relationships recorded in the annual rings of wood formed by trees.


Project ANR DiPTiCC | 2017-2020

Diversity and Productivity of Trees in the context of Climate Change

B5-PU9_IMGP1347_j132-17 Whereas positive relationships between tree diversity and productivity in forests have been found, little is known about the capacity of mixed forests to sustain biomass production under climate change. The main objective of the project is therefore to quantify the effect of tree species diversity on the temporal stability of forest productivity, tackling the resistance and resilience of mixed forests to extreme climate events. Another major goal is to provide a better understanding of ecological mechanisms at work, addressing linkages between tree growth and above and below ground ecosystem processes, such as light interception, water use, litter decomposition, nutrient uptake and resistance to herbivory. To achieve those targets the project will rely on two existing experimental platforms where tree species diversity and microclimate conditions are both controlled, using irrigation for drought and elevational gradients for temperature. Four teams of expert scientists in forest ecology, ecophysiology, biogeochemistry and entomology will work together in both experimental platforms, using the same methodological approaches and using a common sampling scheme. The outcomes  will be used to improve a process-based model of forest dynamics which can deal with mixed forests and take climate variables into account. More about this project here.


Project Regional Aquitaine Athene | 2017-2020

Attenuation des effets du changement climatique sur la biodiversite et les services ecosystemiques des forets d’Aquitaine

IMG_1435Gallery forests that weave alongside the rivers within the Parc Natural Regional des Landes de Gascogne are corridors of biodiversity that provide many ecosystem services for the region.  These riparian arteries influence the climate of the region, keeping the surrounding areas cool in summer and warmer in winter. This helps sustain the famous wine production in the region (Sauternes) and provides a refugia for the fauna and flora of the region. In this project we will develop techniques to measure and monitor how the climate of the Ciron catchment is regulated by the river and how microclimatic heterogeneity and microbial diversity are linked within tree canopies and how this can affect the decomposition of leaf material in the river. State-of-the-art techniques in microclimate measurements will be developed and deployed in the beautiful Ciron catchment. In addition we will develop drone technology to measure the spatial variability of riparian forest canopy temperatures and phenology and link this to simulations of carbon, water and energy transfer between the canopy and the atmosphere using the SVAT model MuSICA over the growing season. This study is conducted in collaboration with several partners in the region including ECOFUN, INRA UMR BIOGECO, UMR GRETHA, EFI-Atlantic, OASU Ecologie Integrative, PNR Landes des Gascogne. To learn more about the Ciron river take a minute to watch this lovely little movie.


Project Bordeaux Idex Fellowship HYDRO-ECO-REFU | 2018-2020

Ecohydrological relations of a Fagus sylvatica refugial population

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This project will investigate the ecohydrological and ecophysiological mechanisms operating in an emblematic refugial population of beech (Fagus sylvatica L.) trees in the Ciron river gorge in SW France. We will combine high-resolution microclimate and stable isotope data in water pools and tree-ring cellulose with state-of-the-art, isotope-enabled ecophysiological and micrometeorological models. The knowledge gained within HydroBeech will be highly relevant for predicting the performance of refugial forest tree populations under a warmer climate and for developing adequate climate mitigation strategies.


Project Labex COTE MicroMic | 2017-2019

Forecasting changes in microclimate and microbial diversity within tree canopies

stomata_phyllosphereMicro-organisms living within tree canopies experience microclimates that are highly variable in both space and time. Leaf surface temperature can differ by several degrees between the canopies of two adjacent trees, between sun and shade leaves of the same tree, and even between the edge and the center of the same leaf. Foliar microbial communities can also influence tree health (e.g. by fighting pathogens) and contribute to major ecosystem functions such as carbon and nitrogen uptake (e.g. by modulating stomatal closure) and influencing senescence and nutrient cycling (e.g. via litter decomposition). The aim of this project is to understand better how microclimatic heterogeneity and microbial diversity are linked within tree canopies and how this can affect leaf function. Metagenomics and state-of-the-art techniques in microclimate measurements will be compared to microclimate simulations from the canopy SVAT model MuSICA and used to explore how microbial and plant function varies spatially within the canoy and over the growing season. This study is a collaboration between ECOFUN and the INRA UMR BIOGECO.


Project Labex COTE HydroBeech | 2017-2019

Ecohydrological relations of a Fagus sylvatica refugial population

IMG_1435The project HydroBeech will investigate the ecohydrological and ecophysiological mechanisms operating in an emblematic refugial population of beech (Fagus sylvatica L.) trees in the Ciron river gorge in SW France. We will combine high-resolution microclimate and stable isotope data in water pools and tree-ring cellulose with state-of-the-art, isotope-enabled ecophysiological and micrometeorological models. The knowledge gained within HydroBeech will be highly relevant for predicting the performance of refugial forest tree populations under a warmer climate and for developing adequate climate mitigation strategies. More about this project here.


Project Labex ARBRE RootUp | 2017-2019

Root water uptake in ecosystem models constrained by water isotopes and chloride concentrations

Screen Shot 2017-04-15 at 6.40.47 PMPreferential flow, root water uptake and root growth are essential to determine plant available soil water but cannot be examined independently in models. Here we aim to constrain the three processes together in the mechanistic ecosystem model MuSICA by long-term observations of chloride concentrations in precipitation and soil water. The chloride observations will be enhanced by additional observations of water isotopes during one growing season. New observations of root growth will complement the dataset. The study will be conducted at the ICOS ecosystem site Hesse with detailed observations of meteorology and ecosystem fluxes, long-term water balance modelling as well as ancillary data.


Project Marie Curie Fellowship USIFLUX | 2016-2018

 Studying stomatal conductance 24-7: a multi-tracer approach

Screen Shot 2017-04-15 at 9.08.43 PMThe overall objective of the project is to improve our understanding of stomatal regulation in the dark, across plant functional types, over leaf ontogeny and in response to drought and rising CO2. The specific objectives of the project develop a multi-tracer approach to quantify nocturnal stomatal conductance, study its variations amongst life forms, during ontogeny and in response to water limitations. More about this project here.


Project ERC SOLCA | 2014-2019

Identifying the drivers of carbonic anhydrase activity in soils and its impact on soil-atmosphere exchanges of CO18O and COS, two complementary tracers of the global carbon cycle

soil_chamberThe overall goal of SOLCA is to quantify and understand better the environmental and ecological causes behind the spatial and seasonal variability in carbonic anhydrase activity observed in soils from different biomes. As a result of this project we will be able to construct the necessary theoretical and modelling framework for using CO18O, CO17O and COS as additional tracers of global CO2 gross fluxes. This ground-breaking achievement will lead to a revised and well-constrained estimate of the past and present (1977-2015) photosynthetic uptake of the terrestrial biosphere at the global scale. More about this project here.


Project ANR MACCAC | 2014-2017

Modélisation pour accompagner les ACteurs vers l’Adaptation des Couverts agroforestiers aux Changements globaux

forest_sunlight_400This project explores the adaptation potential of agroforestry plantations to global environmental changes: coffee and eucalypt plantations in the tropics and maritime pine plantations in Europe. The project gathers economists, stake-holders, climatologists, ecophysiologists and modellers and evaluates different scenarios using multi-criteria approaches.


Project ANR ORCA | 2014-2018

On the Regulation of Carbonic anhydrase Activity and the COS and CO18O fluxes in terrestrial ecosystems

branch_bagThe overall objective of this project is to produce the necessary process understanding and modelling of carbonic anhydrase (CA) activity in terrestrial ecosystems in order to enable the scientific community working on the global carbon cycle to optimally use COS and the δ18O in atmospheric CO2 as additional tracers of global CO2 budgets, and to increase significantly the accuracy of our large-scale estimates of photosynthesis and respiration over land. More about this project here.


Project Campus France | 2012-2014

Influence of root hydraulic redistribution on the water and nutrient availability in Eucalypts

itatangaThe overall objective of this project is to explore the role played by very deep roots (>10m deep) for redistributing water through the soil column and increasing water and nutrient availability for shallower roots in Eucalypt plantations in Brazil.

 


Project Bordeaux Idex Fellowship USIFLUX | 2014-2016

 Studying stomatal conductance 24-7: a multi-tracer approach

The overall objective of the project is to improve our understanding of stomatal regulation in the dark, across plant functional types, over leaf ontogeny and in response to drought and rising CO2. The specific objectives of the project develop a multi-tracer approach to quantify nocturnal stomatal conductance, study its variations amongst life forms, during ontogeny and in response to water limitations. More about this project here.