Post-doctoral researcher : Rémi Wortemann
Contract period: Two years (2015-2017)
Research topic — Do adaptive hydraulic mechanisms to drought events change during aging?
Research team and supervising scientists —
Research team: Joint Research Unit (UMR) 1137 – Forest Ecology and Ecophysiology (EEF)
Supervisor : Nathalie Bréda
Context and state of the art — Climate change scenarios predict that in the next ten years, there will be an increase of extreme drought events like those that occurred in 1976 and 2003. Impacts of drought events on forest system productivity and forest health are known, but questions remain unanswered with regards to understanding species’ survival mechanisms and resilience levels. The ecophysiological processes leading to tree mortality have yet to be properly identified. This project will use as a study model a constituent and widespread species in European forests: the European beech (Fagus sylvatica L. ).
It has been established that radial growth of beech is sensitive to soil water deficit but surprisingly, relatively few Beech diebacks have been reported by the ICP Forest (International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests). The strategy of the beech to survive water shortages involving compromises between the growth control, water safety and stomatal control will therefore be investigated.
Objectives and specific questions to be addressed — This project has two main objectives: (1) to identify key parameters involved in survival of trees subjected to extreme and prolonged drought, and (2), to compare resistance levels of 14 natural Beech populations.
Relevant scientific and socio-economic issues — Identifying the parameters involved in Beech survival under severe drought and/or identifying more ‘resistant populations’ of Beech can help forest managers to adapt tree selection methods to maximize productivity and to limit the impact of climate change.
Methodological approaches and expected results — In the Spring of 2014, an experimental site was installed on-site at the INRA Nancy-Lorraine Center. It includes a 500 m2 roof covering more than 1,000 Beech trees (8 years old) from 14 natural populations collected from 7 forests located along a north-south gradient of 250 km in Lorraine. A long-term partial rainfall exclusion system with 30 year old Beech trees will be studied in the Hesse Forest. In both cases, well hydrated (contol) and dry trees will be compared.
Morphological parameters (primary and secondary growth, wood and leaf properties, etc.) and physiological functions (water use efficiency, xylem cavitation resistance, hydraulic properties, stomatal conductance, etc.) will be measured on each stand in drought and control conditions to identify key traits involved in the survival process. All 14 populations will be followed and compared. The hydraulic and morphological adaptations acquired during the long-term rainfall exclusion experiment will be evaluated.