In this perspective, we have developed an optimization model on stomatal behaviour describing gas exchange and stomatal control (Hari et al. 1986, Hari and Mäkelä 2003; Mäkelä et al., 2004). We have also expanded this stomatal optimization model to the whole-tree scale, thanks to Bayesian tools and the powerful data support from the Stations for Measuring Earth surface-Atmosphere Relations (SMEAR) (Liu et al. 2020). In the near future, we will go further to model the detailed hydraulic properties and processes in the tree by system identification and other mathematical tools.

(Up) A 3-level Bayesian hierarchical model containing the stomatal optimization model that estimates ecophysiologically meaningful parameters. See Liu et al. (2020) for details.

(Down) Analogy of the hydraulic system (vessels and parenchymal storages) in the tree trunk to an electric network, where system identification tools may help quantify the properties hard to measure.

Hari, P., & Mäkelä, A. (2003). Annual pattern of photosynthesis in Scots pine in the boreal zone. Tree Physiology 23, 145–155.

Hari, P., Mäkelä, A., Korpilahti, E. & Holmberg, M. (1986). Optimal control of gas exchange. Tree Physiology 2, 169-175.

Liu, Ch., Hölttä, T., Tian, X., Berninger, F., & Mäkelä, A. (2020). Weaker light response, lower stomatal conductance and structural changes in old boreal conifers implied by a Bayesian hierarchical model. Frontiers in Plant Science 11.

Mäkelä, A., Hari, P., Berninger, F., Hänninen, H., & Nikinmaa, E. (2004). Acclimation of photosynthetic capacity in Scots pine to the annual cycle of temperature. Tree Physiology, 24(4), 369-376.