Trees assimilate carbon dioxide (CO2) through photosynthesis and release approximately half of it

back to the atmosphere through respiration. Photosynthesis is a well-known process that has been

mechanistically described in much detail more than 35 years ago. Contrastingly, respiration remains

poorly understood, especially in woody tissues where measurements of CO2 efflux do not

necessarily reflect respiration rates. TREESPIRE aims to advance in the understanding of respiratory

processes by integrating cutting-edge technologies and mechanistic models that couple water and

carbon transport within the plant. For this goal, manipulative experiments to evaluate how enriched

atmospheric CO2 and drought affect plant growth and woody tissue respiration will be applied.

High-precision and high-time resolution measurements of CO2 exchange between the plant and the

atmosphere will be performed at the leaf and the stem level. Respiration rates will be coupled with

sugar transport flow in phloem obtained with state-of-the-art plant-PET scans. In parallel, a

mechanistic tree model will be developed to elucidate underlying mechanisms that regulate woody

tissue respiration. Conditional algorithms will be implemented to test the sink-limitation hypothesis

under scenarios of climate change. This integrative approach is expected to bring a major

breakthrough in the understanding of woody tissue respiration, which will improve our predictions

of tree carbon cycling.