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ŠUMARSKI LIST 5-6/2004 str. 49     <-- 49 -->        PDF

I. Pilaš, N. Potočić: ODNOS UNUTARSEZONSK1H VARIJACIJA PRIRASTA DEBLA, ELEKTRIČNOG ... Šumarski list br. 5-6, CXXVIII (2004). 255-267
The measurements of stem diameter changes were made by the use of a simple
point dendrometer. Differences were measured on a weekly basis by vernier
caliper gauge. Electric resistance ofcambial zone was monitored on average
basis of four longitudinal measurements by Conditiometer. The groundwater
data was collected from four piezometers at numerical depths of 0.5 m, 1.0 m
2.0 m and 7.0 m. The results of measurements were analyzed by Fast Fourier
analysis i. e. similarities of cyclical patterns of data of respective variables
were compared. Differences in stem diameter changes of two groups of trees
were analyzed by cross correlation. The results of measurements showed that
cumulative growth of healthy trees was two times larger than that of damaged
ones i.e 3.88 mm versus 1.85 mm. Weakly tree stem changes were 0.14 mm of
the healthy and 0.07 mm of the damaged group. Electric resistance ofcambial
zone was lower in the healthy group of trees (7,11 kQ on average) than that of
the damaged group (10,09 kQ). The seasonal differences of stem diameter
changes were most obvious in the first half of the growth season either in
quantitative relations or in the existence of weekly time lag delay of stem
changes of damaged trees in respect to healthy ones. Characteristic delay of
stem diameter changes in the first part of the growth season vanished in the
second part due to soil water deficiency caused by decreased groundwater
level below rooting zone. The seasonal pattern of ERCZ showed that the difference
between the two researched groups was constant during growth season.
By use ofFFT (Fast Fourier Transformation), from spectral density plots
identical cyclical pattern of groundwater level measured on 2.0 m depth and
stem diameter changes of healthy trees were most obvious. The identical
peaks of spectral density plots showed that groundwater increase with cyclical
behavior of 4.4 and 5.5 measurements influenced tree stem growth and
changes of ERCZ what was confirmed by the existence of the same periodicity
in these variables. This research showed that by use of easy measurable
variables like stem diameter changes and electric resistance ofcambial zone
one can achieve a quite satisfactory evaluation of tree water status and health
condition. Also, to some extent, the groundwater status can be monitored and
this is useful for forestry practice in drought prevention and as a control of
larger hydro technical activities in lowland common oak forests.
Key words: tree stem diameter changes, electrical resistance ofcambial
zone, groundwater, quercus robur, crown damage
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