water sucked from tree roots ?

[Franz H. Wagner]

I measured water levels in the bank near area of a small river and I
found in two piezometers located near higher trees a clear diurnal
fluctuation: the water level was lower during the day and highest at
mid-night.

Could it be that the reason is that those trees suck water with their
roots ? Are trees able to transport such large amounts of water and
evaporate ist - the sediment is gravel with a rather high hydraulic
connectivity ?

Could anybody of you give me citations which are related to this topic -
activity of trees, measurement of root-sucking pressure e.g. ?

Thanks a lot in advance for any help

Franz


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     Franz H. Wagner, Biological Station Lunz
     3293 Lunz am See, AUSTRIA
     TEL: ++7486  8095 24 FAX: ++7486  8095 31
     e-mail: franz.wagner at oeaw.ac.at