Tracking tree growth and tree water status to reveal their intra-annual response to climatic events and to foresee future forest dynamics

Forests play an essential role in maintaining biodiversity and providing ecosystem services. However, the continuity of these ecosystem services is threatened by climate change, which profoundly affects forest structure and composition. It is therefore essential to understand species-specific adaptation to climatic events to model forest evolution under different climate scenarios. Tackling our new project (TreePulser), we aim to understand the annual and intra-annual processes affecting tree growth and mortality in response to different climatic events, to identify the main environmental variables driving intraspecific and interspecific variability in tree response, and to further elucidate the physiological processes involved. Using automated point dendrometers, the growth of 300 trees of 10 species will be monitored at 30 sites in southern Belgium. The list of the study species includes both common tree species and less common species that are thought to be better adapted to future climatic conditions, but whose ecophysiological characteristics are not yet fully known. In addition, soil pits will be analyzed and various sensors for relative soil moisture, air temperature and relative air humidity will be installed to quantify water stress and vapor pressure deficit. The vegetation surrounding each monitored tree will be inventoried. On a sub-sample of 90 trees, in-depth physiological measurements will enable us to understand the processes behind climate-induced growth changes. We will position species along a continuum of hydraulic strategies, defined by the concept of iso-anisohydry. We will assess the sensitivity of species to embolism and explore the risk of mortality linked to hydraulic failure, for both individuals and species, at each site.