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

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

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.

Data: CORDIS, © European Union