Rising atmospheric CO2 concentration, increasing temperature and altered precipitation patterns dramatically impact the terrestrial biosphere with important consequences for all biogeochemical cycles. Predictions of carbon (C) and water exchange between vegetation and the atmosphere require detailed mechanistic understanding of how plants control water loss and C gain through their stomatal pores. Currently, global circulation models incorporate formulations of stomatal conductance (gs) based on stomatal optimisation theory. However, these models ignore gs regulation: (1) during night time, despite clear evidence for significant nocturnal transpiration, (2) in non-vascular plants, (3) during leaf development and (4) in response to endogenous control. To reduce the uncertainty associated with current C and water fluxes in models, we need to incorporate robust predictions of gs in response to novel environmental conditions (higher temperature, decreased water availability and elevated CO2). To fill these gaps, USIFlux, will develop a novel tracing technique to measure gs during the dark, when fluxes are an order of magnitude smaller than during the day. To do so, we will combine measurements of COS (carbonyl sulphide) uptake with CO18O fluxes and changes in the oxygen isotope composition (δ18O) of water in leaves. We will relate the response of gs at night to changes in gs during the day and in response to drought and elevated CO2. These measurements will be coupled to an experiment to investigate stomatal regulation during leaf ontogeny and in different life forms. Here, we will challenge the stomatal optimisation theory in life forms lacking active stomatal control (mosses and brackens) and during leaf development, when leaf construction costs constrain the optimisation of C gain. Empirical formulations arising from these experiments will be incorporated into large-scale soil-vegetation-atmosphere transfer models to explore their impact at larger scales.
Objectives and long-term goal
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 are:
Objective 1: Developing a multi-tracer approach to quantify nocturnal stomatal conductance
Here, we will combine independent measurements of vegetation COS uptake, traditional CO2 and H2O gas-exchange coupled to simultaneous measurements of δ18O of both H2O and CO2 and changes in δ18O of different water pools during the day and night to quantify precisely nocturnal stomatal conductance (gs, night).
Objective 2: Quantifying variations of gs, night amongst plant forms and hydric strategy
Here, we will quantify gs, night amongst various plant forms differing in their evolutionary history and response to drought (iso- vs. anisohydric). We will design an experiment to unveil the underlying regulatory mechanisms of stomata during the night and how those relate to daytime gs. Furthermore, we will simulate future environmental conditions (increased drought and elevated [CO2]) and assess their impact on gs control in mosses, brackens, grasses and angiosperm and gymnosperm trees.
Objective 3: Quantifying variations in stomatal regulation during leaf ontogeny
We will track variations in stomatal regulation during leaf development to challenge the theoretical premise of the stomatal optimisation theory during times when maximisation of C gain is impaired for example, during juvenile growth and periods of leaf expansion and senescence.
Objective 4: Impact of nocturnal stomatal conductance on the CO18O and COS derived budgets of photosynthesis and evapotranspiration at the ecosystem and global scale
We will explore the impact of gs, night on the CO18O- and COS-derived estimates of photosynthesis and evapotranspiration at the ecosystem and global scale. This modelling exercise will integrate the output of objectives 1-3 and will involve collaborations with modellers (Drs. Jerome Ogee, expertise δ18O modelling at the ecosystem scale, and Thomas Launois, expertise COS modelling at the global scale) within the host team.
EGU Session Convener in 2015, 2016, 2017 and 2018
Human activities are altering a range of environmental conditions, including atmospheric CO2 concentration, temperature, precipitation and nutrient availability. Quantifying and predicting the combined effect of these changes on biogeochemical fluxes is challenging because carbon, nutrient, and water cycles are intricately linked in terrestrial ecosystems. Descriptions of ecophysiological, biogeochemical, and hydrological processes in terrestrial ecosystem models are continually being improved,but experimental observations are still required to test these new models.
The European Geosciences Union (EGU) General Assembly is hosted annually in Vienna and constitutes the ideal platform to bring modellers and experimentalists together. With this in mind, I co-convened a joint session in 2015, that turned out to be a huge success. We had many fantastic speakers and one of my most striking memories of this event was how large the aufdience was and how our session actually filled the room with people sitting on the floors and standing in the doorway! It was such a success the co-convenors and I have decided to repeat the same session every year since. In April 2017, J-C Domec and Teresa (from the ECOFUN team), together with Karin Rebel and Maarten Braakhekk (from the University of Utrecht) united forces to put together a session on “Terrestrial ecosystem responses to global change: integrating carbon, nutrient, and water cycles in experiments and models”. This session also turned out to be a great success. We covered all types of biomes, from boreal forest to tropical plantations and all sorts of approaches both experimental and modelling. There is no doubt that we will aim for the same standards in the next EGU edition! By the way, call for abstracts is now open! Check out our session (BG2.14) for the 2018 EGU edition, more information here.
Professors in the Laboratory
In May 2016, the ECOFUN team members had the opportunity to host a science discovery stage for three high school teachers. Our guests came from three local institutions from the region of Aquitaine. All three of them came full of motivation and curiosity and their stay at INRA ended up being a very refreshing exchange of scientific concepts, ideas and experiences that went both directions. This turned out as very positive experience for all our team. It forced us to communicate our science in a more comprehensive way and we all learnt about the difficulties of teaching science to teenagers in France. We really hope that our guests enjoyed it as much as we did! You can read more about this experience here.
When physicists meet biologists… it can actually work nicely!
In September 2016, Teresa travelled to Hyytiälä, a fabulous field station 3 h north of Helsinki (Finland) to meet with about 30 other researchers. At first sight, the group appeared quite heterogeneous, you could find physicists, chemists, mathematicians, atmospheric scientists, plant biologists and microbiologists… but a closer look revealed that we all shared the same interest in one particular molecule: carbonyl sulphide (COS or OCS, I’ll come back to this). COS research has received exponential attention since we figured out we could use it as a proxy to estimate how much carbon our ecosystems are capable of sequestering and storing. Read the whole story here and check out our publications below.
Films publicising our article in Nature Climate Change paper
The publication of our paper in Nature Climate Change (Ellsworth et al., 2017, 7:279-282) received a bit of attention from the media. In this paper, we showed how important it is to take into account nutrient limitations when it comes to estimating the ability of the vegetation to mitigate future climate change. The national TV channel ABC Australia interviewed Prof. David Ellsworth about it (watch the video here) and was highlighted by INRA too, read the story in French here.
Publications and communications
Gimeno, T., Saavedra-Berlanga, N., Ogée, J., Medlyn, B.E. & Wingate, L. (in press) Testing for non-stomatal limitations to optimisation behaviour under drought on contrasting plant functional types. Journal of Experimental Botany Vol 7, Issue 5, 1639-1651 https://doi.org/10.1093/jxb/erz020
Whelan, M., Lennartz, S., Gimeno, T., Wehr, R., Wohlfahrt, G., Wang, Y., Kooijmans, L., Hilton, T., Belviso, S., Peylin, P., Commane, R., Sun, W., Chen, H., Kuai, L., Mammarella, I., Maseyk, K., Berkelhammer, M., Li, K-F., Yakir, D., Zumkehr, A., Katayama, Y., Ogée, J., Speilmann, F., Kitz, F., Rastogi, B., Kesselmeier, J., Marshall, J., Erkkila, K-M., Wingate, L., Meredith, L., He, W., Bunk, R., Launois, T., Vesala, T., Schmidt, J., Fichot, C., Seibt, U., Saleska, S., Saltzman, E., Montzka, S, Berry, J. & Campbell, J.E. (2018) Reviews and Syntheses: Carbonyl sulfide as a multi-scale tracer for carbon and water cycles. Biogeosciences, 15: 3625-3657, https://doi.org/10.5194/bg-15-3625-2018.
Ellsworth, D.S., Anderson, I.C., Crous, K.Y., Cooke, J., Drake, J.E., Gherlenda, A.N., Gimeno, T., Macdonald, C.A., Medlyn, B.E., Powell, J.R., Tjoelker, M.G. & Reich, P.B. (2017) Elevated CO2 does not increase eucalypt forest productivity on a low-phosphorus soil. Nature Climate Change, 7:279-282.
Gimeno, T., Royles, J., Ogée, J, Wohl, S., Jones, S., Sauze, J., West, J., Burlett, R., Griffiths, H. & Wingate, L. (2017) Bryophyte gas-exchange dynamics along varying hydration status reveal significant COS emission in the light. New Phytologist, 215:965-976.
Communications at international conferences
- Gimeno, T. E., Saavedra-Berlanga, N., Ogée, J., Medlyn, B.E. & Wingate, L. Testing for non-stomatal limitations to optimisation behaviour under drought on contrasting plant functional types. Geophysical Research Abstracts, Vol. 20, EGU2018-7659, Vienna, France, 9-13th April 2018
- Likiliki, E., Gimeno T. E., Ogée J. & Wingate L. Acclimation and seasonal coupling of photosynthesis, respiration and carbonyl sulphide exchange in bryophytes. XXI Symposium of Cryptogamic Botany, Aranjuez, Spain, 20th-24th June 2017
- West, J., Ogée, J., Burlett, R., Gimeno, T., Genty, B., Jones, S., Wohl, S., Bosc, A., Cochet, Y., Domec, J.C. & Wingate, L. Partitioning internal diffusion resistances and CO2 isotope exchange in leaves. Proceedings of the annual meeting of the Ecological Society of America (ESA), Portland, Oregon, 6th-11th Aug 2017
- Likiliki, E., Gimeno, T., Ogée, J. & Wingate, L. Acclimation and seasonal coupling of photosynthesis, respiration and carbonyl sulfide exchange in bryophytes. XXI Simposio de botánica criptogámica, Aranjuez, 20th-24th June, 2017
- Gimeno, T., Ogée, J. & Wingate, L. Estimating the contribution of bryophytes to the atmospheric COS budget. Geophysical Research Abstracts, Vol. 19, EGU2017-13117, Vienna, Austria, 26th April 2017
- Wingate, L & Gimeno, T. Using novel approaches to estimate the CO2 sink strength of the terrestrial biosphere. Fédération de recherché biologie intégrative et écologie, Bordeaux, France, 17th Feb 2017 (invited)
- Gimeno, T., Ogée, J., Royles, J., Gibon, Y., West, J., Burlett, R., Jones, S., Sauze, J., Wohl, S., Bernard, C., Genty, B. & Wingate, L. Bryophyte gas exchange dynamics reveal a significant COS sink in the dark and source in the light. XIV Medecos & XIII AEET Spanish Ecology Meeting, Sevilla, Spain, 2nd, Feb 2017
- West, J., Ogée, J., Burlett, R., Gimeno, T., Genty, B., Jones, S., Wohl, S., Bosc, A., Cochet, Y., Domec, J.C. & Wingate, L. Towards improved quantification of internal diffusion resistances and CO2 isotope exchange in leaves. American Geophysical Union (AGU) Fall Meeting, San Francisco, California, USA, 12th-16th Dec 2016
- Gimeno, T., Royles, J., Ogée, J., Jones, S., Burlett, R., West, J., Sauze, J., Wohl, S., Genty, B., Griffiths, H., & Wingate, L. Bryophyte gas-exchange dynamics along varying hydration status reveal significant COS emission in the light. The biosphere-atmosphere exchange and global budget of carbonyl sulfide workshop, Hyytiala, Finland, 5th September 2016
- Gimeno, T., Royles, J., Ogée, J., Jones, S., Burlett, R., West, J., Sauze, J., Wohl, S., Genty, B., Griffiths, H., & Wingate, L. Bryophyte gas-exchange dynamics along varying hydration status reveal significant COS emission in the light. 17th International Congress on Photosynthesis Research, Maastricht, Netherlands, 7th -12th Aug 2016
- Gimeno, T., Royles, J., Ogée, J., Jones, S., Burlett, R., West, J., Sauze, J., Wohl, S., Genty, B., Griffiths, H., & Wingate, L. Investigating the impact of light and water status on the exchange of COS, 13CO2, CO18O and H218O from bryophytes. Geophysical Research Abstracts, Vol. 18, EGU2016-12692, Vienna, Austria, 17th -22nd April 2016
- West, J., Ogée, J., Burlett, R., Gimeno, T., Genty, B., Jones, S., Wohl, S., Bosc, A. & Wingate, L. A new approach to quantifying internal diffusion resistances and CO2 isotope exchange in leaves. Geophysical Research Abstracts, Vol. 18, EGU2016-16367, Vienna, Austria, 17th -22nd April 2016
- Gimeno T. E. (2016) Tracking water use and carbon uptake in a global change scenario: bridging scales and aproaches. Invited seminar at the Department of Environment, Earth and Ecosystems of the Open University, Milton Keynes, UK, February 2016 (invited)
- Wingate L., Wehr R., Commane R., Ogée J. Sauze J., Jones S., Launois T., Wohl S., Whelan M., Meredith L., Genty B., Gimeno T., Kesselmeier J., Bosc A., Cuntz M., Munger B., Nelson D., Saleska S., Wofsy S. & Zahniser M. (2015) The impact of Carbonic Anhydrase on the partitioning of leaf and soil CO18O and COS gas exchange across scales. American Geophysical Union (AGU) Fall Meeting, San Francisco, California, USA, December 2015. (invited)
- Gimeno T. E., Ogée J., Bosc A., Genty B., Wohl S. R., Wingate L. Unveiling stomata 24/7: can we use carbonyl sulfide (COS) and oxygen isotopes (18O) to constrain estimates of nocturnal transpiration across different evolutionary plant forms? European Geosciences Union General Assembly, Vienna, Austria, April 2015
Ms Noelia Saavedra Berlanga (May-December 2015) Effect of ontogeny and water stress on stomatal regulation by different plant functional types. Official MSc. on techniques for biological biodiversity characterization and conservation of the University Rey Juan Carlos (Mósotoles, Madrid). Qualification: Outstanding (9.2/10)
Ms Elise Likiliki (January-June 2017) Acclimation and seasonal coupling of photosynthesis, respiration and carbonyl sulphide exchange in bryophytes Official MSc student from the University of Bordeaux. Qualification: 16/20
- Dr Jessica Royles, The University of Cambridge, Cambridge, UK
- Professor Howard Griffiths, The University of Cambridge, Cambridge, UK
- Professor Fernando Valladeras, The National Museum of Natural Sciences, Madrid, Spain
- Dr Bernard Genty, CEA, Cadarache, France
- Associate Professor Jason West, Texas A & M, Texas, USA
- Mr Regis Burlett, Universite of Bordeaux, Talence, France
- Dr Yves Gibon, INRA, Bordeaux, France
The USIFLUX project has received funding from the European Union’s Seventh framework programme (FP7/2007-2013) Marie Skłodowska-Curie Intra-European fellowship (Grant Agreement No. 653223)
INRA ACCAF Metaprogramme project FORADAPT
awarded to Jerome Ogee