DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 1-2/1972 str. 62     <-- 62 -->        PDF

longer individual recruitment times in the last lo years have not come into
evidence. But as the recruitment times did not include the same period
of time, we desisted from further treatment of the recruitment time; we
passed to an analysis and calculation of the diameter increment, first for
the 1961—1970 time interval, then for the 1961—1965 and 1966—1970 time
intervals.


Annual diameter increment of healthy Fir trees as compared
wit the increment of Fir trees whose assimilating surface was reduced


All samples (cores) were divided into two groups or collectives. The
first collective included all samples extracted from healthy Fir trees. The
second collective contained samples extracted from Fir trees whose assimilating
surface was reduced. For the purpose of simplification the first
collective will be called »healthy«, and the second »infested Fir trees«.


The analysis of increment cores was performed in the manner already
mentioned and shown in Fig. 2. The average annual diameter increment was
computed after the formula:


š3 1


Zd - 2 ,


10 b


where (š3) means the width of the last 10 growth-rings, and (b) the number


of samples.


The results of analysis and computation are given in Tab. 2 under


designation (Z) and (Z´), where (Z) means the average annual diameter


increment of healthy and (Z´) of infested Fir trees during the 1961—1970


time interval. In the same table the designations (Zr) and (Z´r) mean the


smoothed average annual diameter increments.


The annual diameter increment of infested Fir trees in the management
unit of »Belevine« may be expressed by equation (1):


Zr = —0.001203 Da + 0.136334 D + 0.800815 (1)


The annual diameter increment of infested Fir trees may be expresse
by equation (2):


Z´r = —0.001311 D2 + 0.131027 D + 0.202656 (2)


In Fig. 4 is represented the course of the annual diameter increment
of healthy and infested trees.
From this figure and from Tab. 2 it is clearly visible that »infested«
Fir trees put on a lower increment.


Taking into calculation the number of cores according to diameter
sub-classes, we found that the increment of infested Fir trees was by 30%
lower than the increment of healthy Fir trees.


This finding is very important, because it gives us an insight into the
economic losses in the forests attacked. But, in addition to such a global