Ultrasonic acoustic emissions in drought-stressed trees - more than signals from cavitation?

Publication Type:Journal Article
Year of Publication:2008
Alkuperäinen tekijä:Zweifel, Zeugin
Journal:New Phytologist
Volume:179
Numero:4
Pagination:1070 - 1079
Date Published:Jan-09-2008
ISSN:0028646X
Avainsanat: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 (ΔW).
  • Within a low‐dB range (27 ± 1 dB), UAE regularly increased and decreased in a diurnal rhythm in parallel with ΔW 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 ± 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 ΔW and low‐dB UAE.
URL:http://blackwell-synergy.com/doi/abs/10.1111/nph.2008.179.issue-4
DOI:10.1111/nph.2008.179.issue-410.1111/j.1469-8137.2008.02521.x
BioAcoustica ID: 
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith