Detection of xylem cavitation in field‐grown pine trees using the acoustic emission technique

The relationship between the ultrasonic acoustic emission (AE) and the needle water potential in field‐grown Japanese black pine, Pinus thunbergii , and excised‐pine shoots was investigated in summer. The AE technique was employed as a reliable indicator of cavitation events in the water columns of xylem tracheids even under field conditions. In excised shoots. AE events detected when the needle water potential fell below about‐0.9 MPa. In the case of field‐grown pine trees, however, relatively few AE event were detected when needle water potential was lower than‐0.9 MPa. This suggests that the occurrence of cavitation events in Japanese black pine growing under field conditions is comparatively rare, even in summer.