{"data":[{"source":"bio.acousti.ca","id":"57338","type":"article","title":"Ultrasonic acoustic emissions in drought-stressed trees - more than signals from cavitation?","author":"Zweifel, R.; Zeugin, F.","editor":null,"year":"2008","month":null,"journal":"New Phytologist","booktitle":null,"series":null,"howpublished":null,"volume":"179","number":"4","pages":"1070 - 1079","chapter":null,"edition":null,"publisher":null,"organization":null,"institution":null,"school":null,"address":null,"type_of_work":null,"note":null,"isbn":null,"issn":"0028646X","doi":"10.1111\/nph.2008.179.issue-410.1111\/j.1469-8137.2008.02521.x","url":"http:\/\/blackwell-synergy.com\/doi\/abs\/10.1111\/nph.2008.179.issue-4","attachments":"https:\/\/bio.acousti.ca\/sites\/default\/files\/Zweifel_et_al-2008-New_Phytologist.pdf","keywords":"cavitation; drought stress; embolism; tree water deficit; ultrasonicacoustic emission","abstract":"Ultrasonic acoustic emission (UAE) in trees is often related to collapsing water columns in the flow path as a result of tensions that are too strong (cavitation). However, in a decibel (dB) range below that associated with cavitation, a close relationship was found between UAE intensities and stem radius changes. UAE was continuously recorded on the stems of mature field-grown trees of Scots pine (Pinus sylvestris) and pubescent oak (Quercus pubescens) at a dry inner-Alpine site in Switzerland over two seasons. The averaged 20-Hz records were related to microclimatic conditions in air and soil, sap-flow rates and stem-radius fluctuations de-trended for growth (\u0394W). Within a low-dB range (27 \u00b1 1 dB), UAE regularly increased and decreased in a diurnal rhythm in parallel with \u0394W on cloudy days and at night. These low-dB emissions were interrupted by UAE abruptly switching between the low-dB range and a high-dB range (36 \u00b1 1 dB) on clear, sunny days, corresponding to the widely supported interpretation of UAE as sound from cavitations. It is hypothesized that the low-dB signals in drought-stressed trees are caused by respiration and\/or cambial growth as these physiological activities are tissue water-content dependent and have been shown to produce courses of CO2 efflux similar to our courses of \u0394W and low-dB UAE.","type_name":"Journal Article","journal_abbreviation":null,"pmid":null,"info_url":"https:\/\/bio.acousti.ca\/node\/57338"}]}