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Unveiling Stomata 24/7: Using Stable Isotopes and COS to quantify diurnal and nocturnal carbon and water vegetation-atmosphere Fluxes under future climate scenarios

Periodic Reporting for period 1 - USIFlux (Unveiling Stomata 24/7: Using Stable Isotopes and COS to quantify diurnal and nocturnal carbon and water vegetation-atmosphere Fluxes under future climate scenarios)

Reporting period: 2016-04-01 to 2018-03-31

Rising atmospheric CO2 concentration, increasing temperature and altered precipitation patterns dramatically impact the functioning of the terrestrial biosphere with important consequences for carbon, water and nutrient cycling. Predictions of carbon (C) and water exchange between vegetation and the atmosphere require detailed understanding of how plants maintain carbon gain while minimizing water loss. Biosphere-climatic feedbacks have a major impact on future climate predictions, thus we need to reduce the uncertainty associated with current carbon and water fluxes in global models. To do so, robust estimates of carbon and water exchange are required for predicting the response to novel environmental conditions: higher temperature, decreased water availability and elevated CO2. Current global circulation models incorporate formulations of plant carbon and water exchange based on stomatal optimisation theory. However, these models fail at predicting and explaining water loss during night time and ignore the contribution of non-vascular plants, as well as plants with a metabolic pathway different to the predominant types (C3 and C4). In this project (USIFlux), we have developed a novel tracing technique to measure carbon and water exchange during the day, but also during periods of reduced physiological activity or for example at night or in non-vascular plants. This approach combines traditional gas-exchange techniques with online measurements of a trace gas (carbonyl sulphide, COS) and stable isotopes of carbon and oxygen. This novel approach has allowed the tracing of carbon and water exchange in non-vascular plants (mosses and liverworts) and in succulent plants with an opposite metabolic pattern to most vascular plants (CAM), both during the day and at night. Our results contribute to estimating biosphere carbon and water fluxes with functional parameters beyond the classic ecophysiological functioning of vascular plants. Empirical formulations arising from these experiments are going to be incorporated into large-scale soil-vegetation-atmosphere transfer models to explore their impact at larger scales. The results of USIFlux have rendered various publications in high impact journals, contributions to international conferences and the opportunity to develop several MSc. theses, as an example of effective transfer of knowledge (see section 1.3). Also, the work within this project has rendered some unexpected positive outcomes such as the application of this novel measurement approach to track and quantify water and carbon exchange in CAM and non-vascular plants.
Transfer of knowledge: the experienced researcher has gained new skills including the use of stable isotopes and trace gases to infer metabolic and ecophysiological plant processes, pneumatics, programming, biochemical assays, numerical computation and big-data managing, while performing the activities from the various working packages within the host team and in collaboration with other research groups. The candidate has actively engaged in multiple teaching and mentoring activities with INRA’s partner institutions: the Université de Bordeaux (UB) and Bordeaux Science Agro (BSA, the agricultural engineer school); supervision of two master and one PhD students.
Outreach: the work developed within USIFlux has rendered various sound scientific publications (see publications) and the experienced researcher has performed various activities to ensure the outcome and progress of USIFlux reach the specialized scientific community and a broader audience. The experienced researcher promoted the results obtained in USIFlux in various international conferences, meetings and spesialised workshops (the EGU general assembly, the international photosynthesis conferences, the first COS workshop and more).
To achieve an effective outreach and communication beyond the specialised scientific community, we have taken part on a number of initiatives. At the institutional level (INRA), in 2016, Teresa participated in the department seminar series. This series is aimed at sharing project progress with other scientific colleagues, which do not necessary work on the same domain. In 2017, Lisa Wingate (supervisor and project manager) gave a talk, which she prepared with Teresa, to another INRA research unit. Besides academic meetings and seminars, we have also engaged on outreach activities for the broader non-scientific public. Recently, Teresa, together with Jérôme Ogée (project supervisor) and the rest of the ECOFUN team, organized a training workshop for high-school teachers. The aim of this activity was to approach teachers to the reality of how science is done and to help instructors update their teaching material. All participants gave very positive feedback and left our laboratory with a much more realistic idea of what being a scientist is like, which they said would help them encourage students to pursue a career in science. For disseminating and broadcasting of the major achievements and project progress we rely on the press office of the host institution (INRA-Bordeaux). Timely press releases are prepared jointly between the USIFlux project participants and the communication officer. In addition, Teresa maintains an active profile on twitter (@TerefiGimeno), solely devoted to communication in science. Finally, the ECOFUN website hosts a page for the USIFlux project where we publish all our progress.
In addition to the activities directly linked to USIFlux, during this period Teresa, her mentors and the rest of the ECOFUN team have maintained a series of collaborations that have rendered successful results and publications. Since the start of the project, Teresa has published two more papers on the vegetation responses to rising atmospheric CO2 (Ellsworth et al. 2017 Nature Climate Change 7:279-282 and Medlyn et al. 2016 Global Change Biology 22:2834-2851). Furthermore, Teresa is currently finalising one more paper related to this project in collaboration with colleagues in a research institute in Australia. Another collaborative project brought together several members of the ECOFUN team and the BIOGECO unit. This project consisted on a large-scale experimental manipulation to assess the role of carbohydrate content on drought mortality on multiple tree species. The ECOFUN team was involved in the planning and execution of the experiment. Finally, Teresa has continued a series of related scientific activities: hosting visiting academics (Victor Resco in July 2016), review of scientific manuscripts for multiple journals (Functional Ecology, Journal of Plant Ecology, Journal of Arid Environments and Science of the Total Environment, since the start of the project) and she has recently been invited to edit a special issue of forest and global change for the journal Geosciences.
Gas exchange laboratory
Cactus gas exchange
Experimental setup for moss gas exchange
Online gas exchange measurements on liverwort
Research team at the EGU general Assembly in April 2016 with poster
Liverwort samples in the lab