EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Disentangling the relative contributions of atmospheric demand for water and soil water availability on the stomatal limitation of photosynthesis

Aliénor Lavergne1, Heather Graven1,2, and Iain Colin Prentice2,3
Aliénor Lavergne et al.
  • 1Imperial College London, Physics, Exhibition Road, London, SW7 2AZ, UK (
  • 2Grantham Institute – Climate Change and the Environment, Imperial College London, Exhibition Road, London SW7 2AZ, UK
  • 3Imperial College London, Life Sciences, Silwood Park Campus, Buckhurst Road, Ascot, SL5 7PY, UK

Plants open and close their stomata in response to changes in the environment, so they can absorb the CO2 they need to grow, while also avoid drying out. Since the activities of leaf stomata determine the exchanges of carbon and water between the vegetation and the atmosphere, it is crucial to incorporate their responses to environmental pressure into the vegetation models predicting carbon and water fluxes on broad spatial and temporal scales. The least-cost optimality theory proposes a simple way to predict leaf behaviour, in particular changes in the ratio of leaf internal (ci) to ambient (ca) partial pressure of CO2, from four environmental variables, i.e. ca, growing-season temperature (Tg), atmospheric vapour pressure deficit (Dg), and atmospheric pressure (as indexed by elevation, z). However, even though the theory considers the effect of atmospheric demand for water on ci/ca, it does not predict how dry soils with reduced soil water availability further influence ci/ca. Recent research has shown that independent of the individual effects of Tg, Dg, ca and z on ci/ca, the model tends to underestimate ci/ca values at high soil moisture and to overestimate ci/ca values at low soil moisture. Here, we will try to disentangle the relative contribution of Dg and soil moisture on changes in ci/ca and test a new implementation of soil moisture effect in the framework of the least-cost hypothesis. To achieve this goal, we will use stable carbon isotopes measurements in leaves and in tree rings at sites with different soil water availability and different evaporative demand. We will then incorporate the improved model based on the least-cost hypothesis into the UK vegetation model JULES and investigate leaf stomatal responses to recent environmental changes across regions.

How to cite: Lavergne, A., Graven, H., and Prentice, I. C.: Disentangling the relative contributions of atmospheric demand for water and soil water availability on the stomatal limitation of photosynthesis, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7190,, 2020

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