Modeling olive ecophysiological response to soil water deficit

Objective of the work was to define critical thresholds of soil water status determined according to measured leaf and stem xilematic potentials, as well as tree transpiration. Furthermore, the performance of existing models, simulating the potential transpiration reduction coefficients as a function of the soil water status, was assessed. Soil water retention curve was used to determine soil matric potentials according to measured soil water contents. Transpiration was monitored with Thermal Dissipation Probes, whereas leaf and stem water potentials were measured with the Scholander chamber. An almost constant transpiration value was obtained for soil water contents higher than a critical threshold; lower and lower values of actual transpiration were recognized at decreasing soil water content. A similar threshold was obtained when xylematic potentials were considered. The best performance of models evaluating the potential transpiration reduction coefficient was obtained when non-linear functions are assumed.