02154nas a2200217 4500008004100000022001300041245009700054210006900151260001600220300001600236490000800252520147100260653001501731653001901746653001301765653002501778653003201803100001601835700001501851856007001866 2008 eng d a0028646X00aUltrasonic acoustic emissions in drought-stressed trees - more than signals from cavitation?0 aUltrasonic acoustic emissions in droughtstressed trees more than cJan-09-2008 a1070 - 10790 v1793 a
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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.
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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).
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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.
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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.
10acavitation10adrought stress10aembolism10atree water deficit10aultrasonicacoustic emission1 aZweifel, R.1 aZeugin, F. uhttp://blackwell-synergy.com/doi/abs/10.1111/nph.2008.179.issue-4