Extreme drought events are expected to increase around the world due to global warming. Such events have severe effects on forests, including reduced productivity and increased tree mortality. They are especially worrisome in semi-arid environments, where trees are already limited by low water availability and high evaporative demand during most of the year. Pinus halepensis trees growing at the dry timberline in Yatir forest in Israel offer a superb case study to understand the processes involved in the impacts of extreme drought on tree physiological and hydraulic functioning. One key aspect is the functional damage in the form of tissue loss or enzyme inactivation induced by dehydration, and its impact on the rate at which trees can recover functionality during the following wet season.
Here, we combine extensive field measurements of +10 years with a process-based model (LandscapeDNDC) that captures tree hydraulic responses and functional impairment due to drought stress. The model translates losses in tree hydraulic conductance into stress legacy via a reduction of active sapwood and leaf area. Also, hydraulic stress can result in sudden or delayed tree death, depending on the stress intensity. Flux measurements from Yatir forest and process-driven understanding from controlled studies conducted in Aleppo pine seedlings are providing the necessary data for model calibration and evaluation. In this talk, we will present the results of initial model simulations, to assess to what degree semi-arid pine forests like Yatir can resist and recover from extreme stress under current and future climate conditions.