tailieunhanh - Báo cáo lâm nghiệp: "Ultrasound acoustic emission in water-stressed Picea abies Karst"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Ultrasound acoustic emission in water-stressed Picea abies Karst. | 346s Ann. Sci. For. 1989 46 suppl. 346s-349s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA Ultrasound acoustic emission in water-stressed plants of Picea abies Karst. M. Borghetti1 A. Raschi2 and J. Grace3 . IMGPF Via s. Bonaventura 13-50145 Florence Italy . IATA p. le delle Cascine 18-50144 Florence Italy and 3Department of Forestry and Nat. Res. Darwin Building Mayfield Road Edinburgh EH9 3JU . Introduction It is widely known that cavitative events taking place in woody stems can be detected by monitoring acoustic emissions due to the vibrations of the xylem vessel walls. If operating at audio frequencies Milburn and Johnson 1966 noise from the surroundings can mask the faint sounds coming from wood elements. The use of sensors operating at ultrasonic frequencies Tyree and Dixon 1983 overcomes this problem. We report the occurrence of ultrasonic acoustic emissions from the stems of potted saplings of Picea abies Karst during the summer relating these to transpiration rate and water potential since this technique has rarely been used under field conditions and water stress is a major limiting factor of wood production in mediterranean climates. Potted 5 yr old plants of Picea abies were used 10 of them were irrigated on a daily basis while 10 others were assigned to drought treatment witholding water from them during the periods 15-21 July 8-14 August and 16-25 August 1987. Measurements were made from dawn to sunset on July 21 July 30 August 25 and September 10. Xylem water potential was measured with a pressure chamber every 2 h on plants among the 10 belonging to each group. The 6 remaining plants in each treatment were used for measurements of acoustic emission rate using a broad band Bruel and Kjaer model 8312 sensor and a counting device similar to the one described by Sandford and Grace 1985 modified. The transducer was pressed on the stem using a spring-loaded handpiece for a period of 5 min the stem had been prepared by removing