Water storage of a typical tree species in the Caatinga biome (Caesalpinia pyramidalis Tul.)

Our understanding of the movement and storage of water in typical Caatinga plants is still limited and often disregarded in water balance calculations. This is why the objective of this work was to evaluate the water storage dynamic in typical trees of the Caatinga biome during the dry, rainy and transition period by gauging the water content levels that cause the onset of leaf emergence. In a preserved Caatinga forest, soil and stem water content of six trees of the representative species catingueira (Caesalpinia pyramidalis Tul.) were monitored with low-cost capacitive sensors. Leaf moisture, leaf area index, leaf and stem water volume, and sap flow density were measured. The emergence of leaves occurred with a stem moisture of 0.32 m(3) m(-3), and the leaf area index was maximum with a stem moisture of 0.34 m(3) m(-3). Catingueira plants are able to absorb water below the soil water potential commonly determined as the permanent wilting point (similar to 1.5 MPa). The volume of water stored in the plants represents 108% of the average volume stored in the Boqueirao reservoir during the study period.