DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 1-2/1972 str. 63     <-- 63 -->        PDF

determination of increment losses, it would be interesting to establish a
functional interdependence between the falling-off of increment and the
degree of infestation, or, properly speaking, of the reduction of assimilating
surface. Before solving this problem, we shall make an attempt at giving
an answer to the query when the falling-off of increment had set in?


Annual diameter increment of Fir at different times


As has already been mentioned in the chapter on the Working Method,
each increment core was analysed four times. The third analysis relates to
the measurement of the average annual diameter increment of Fir for the
1966—1970 time interval. This increment was computed according to the
formula:


ši 1


Zi = 2


5 b


The fourth analysis relates to the measurement of the average annual
diameter increment of Fir for the 1961—1965 time interval. This increment
was computed according to the formula:


Š2 1


Z2 = 2
5 b


The results concerning these increments are found in Tab. 3. (Zi) and
(Zo) mean the measured increments, while (Zir) and (Zar) mean the smoothed
diameter increments.


On the basis of the computation according to the theory of least squares,
I expresed the average diameter increment of Fir for the 1966—1970 time
interval by equation (3), and for the 1961—1966 time interval by aquation (4).


Zlr = —0.000461 D* + 0.060856 D f 2.135759 (3)


Z2r = —0.000402 D2 + 0.073009 D + 1.896828 (4)


These equations are represented in Fig. 5. From data in Tab. 3 and Fig.
5 it is clearly visible that diameter increment of Fir fell off by over 25%
during the 1966—1970 time interval.


Having established that in the past 5 years a marked falling-off of increment
had set in, we are now interested to know what year it was most
marked.


An analysis of the cores showed that the growth rings were narowest
in 1968 and 1969. In fact, at that time the studied forest had a »diseased«
and alarming appearance.


Let us state by the way that to-day the condition of the forest has
improved, and that in the summer of 1971 an unheard-of cone crop was
recorded.


The first query to which we should lend an ear is: »Did the climatic
factors not cause perhaps the reduction of the diameter increment?« In