Root sap flow as a tool to establish hydrological thresholds for plant growth and survival

Abstract

Water saving technologies are important for sustainable agriculture and forestry. Recent research indicates that the plant itself may alternate between several natural water sources to survive drought. Therefore, a key issue is how to establish the boundaries of hydrological conditions important for non-stressed tree growth. The smart decision might be to ask the plant itself. Sap flow represents a suitable language to such a talk: it gives long-term automatic records of plant responses to environmental changes. In this work we illustrate how root sap flow can be used to provide information on the thresholds for two sources of tree root water uptake, superficial soil water and groundwater. With this knowledge, a threshold diagram can be constructed which is species and site specific. Such a diagram may help managers of rain fed plantations to follow the current hydrological conditions and apply irrigation as a preventive treatment to avoid growth loss and tree mortality.