USIFLUX (UB Idex 2014-2016) and (MSC 2016-2018)

Summary

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 (g_s) based on stomatal optimisation theory. However, these models ignore g_s 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 g_s 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 g_s 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 g_s at night to changes in g_s 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 (g_{s, night}).

Objective 2: Quantifying variations of g_{s, night} amongst plant forms and hydric strategy

Here, we will quantify g_{s, 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 g_s. Furthermore, we will simulate future environmental conditions (increased drought and elevated [CO₂]) and assess their impact on g_s 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 g_{s, 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.

Outreach

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.

Local school professors getting to grips with some plants in the lab.

When physicists meet biologists… it can actually work nicely!

COS and CO2 branch fluxes in Finland

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.

The EUC FACE site in Sydney, Australia.

Publications and communications

Peer-reviewed articles

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, 9-13^th 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, 20^th-24^th 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, 6^th-11^th 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, 20^th-24^th 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, 26^th 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, 17^th 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, 2^nd, 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, 12^th-16^th 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, 5^th 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. 17^th International Congress on Photosynthesis Research, Maastricht, Netherlands, 7^th -12^th 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, 17^th -22^nd 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, 17^th -22^nd 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

MSc thesis

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

Project Collaborators

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

Funding Sources

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)

awarded to Teresa Gimeno and Lisa Wingate

Bordeaux Idex Postdoctoral Fellowship USIFLUX