Intra-seasonal wood formation is still understudied because the measuring method (analysis of cellular anatomical traits) is labour-intensive and requires important manual skills The last phase of wood formation (lignification) has been particularly neglected, resulting in a lack of understanding of tree autumn dynamics UAntwerp-PLECO and UGent-Woodlab will join forces (in collaboration with dr Fonti, WSL, as key advisor) to address two objectives: (1) develop a new method to study wood formation based on high resolution X-ray Computed Tomography (XµCT) and (2) use the new method to test, at continental scale, the hypothesis that leaf senescence is triggered when wood formation ceases in autumn or, in case of factors limiting growth in summer, when a fixed day of the year is reached (photoperiodic threshold) The first objective will be met by (i) automating the XµCT process, (ii) identifying the degree of lignification, (iii) assessing intra-seasonal wood traits such as cell size and wall thickness etc, and (iv) implementing a time-lapse scanning on small living trees The second objective will be achieved by analyzing data of leaf senescence and wood formation of the 10 most common deciduous species in Europe along several transects of varying environmental conditions (eg photoperiod, temperature, drought) Overall, the project will start a new direction for the study of wood formation and will elucidate autumn dynamics of deciduous temperate trees