Ultrasonic acoustic emissions as indicators of tree drought stress in outdoor forest settings: Testing the concept using cut saplings by J. Klaminder, M.M. Rollo Jr, T. Näsholm, J. Viklund, N. Henriksson, S. Jämtgård

“…In this study, we show that microphones mounted on, or adjacent to, stems of young birch (Betula pendula) and Scots pine (Pinus sylvestris), can indeed be used in outdoor environments to detect embolism in the xylem sap. Vapour formation via cavitation in the xylem was artificially generated inside cut saplings by a surfactant that reduced the cohesive forces of water and forced the water column inside the xylem to break. …”
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