Disentangling the impacts of rising temperature and evaporative demand on plants water status

This study focuses on two of the impacts of global warming (increasing temperatures and increasing vapor pressure deficit - VPD) on plants water status. Three different tree species were selected and young three-years-old trees were placed in conditioned chambers. A total of 6 chambers each accommodated 6 plants of each species. This report presents the results of two measurement sessions: a first session (at time t0) before which all the chambers were configured under the same so-called "normal" conditions, then a second session, after 45 days during which each chamber represented a different combination of temperature and VPD. The experimental set-up therefore allowed to decorrelate these two environmental variables which in nature are always positively correlated, making it difficult to understand the specific impacts of each one. A workflow for in-vivo microCT living trees scanning has been defined and improved during this study, and the resulting images allowed to assess correctly the embolism inside the living trees. It has been shown that the three species had a different sensitivity to temperature and VPD increase, and statistical analyses showed a significant effect of temperature and VPD respectively, as well as a significant interaction between those two climatic parameters in certain cases.