DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 1-2/1972 str. 64     <-- 64 -->        PDF

order to answer this question we had to resort to those climatic data which
we have at our disposal from the weather stations Zalesina and Delnice.
These data about the rainfall and temperatures are presented in Tabs. 4 and


5. From these tables we computed that in the course of 5 years, i. e. from
1965 to 1970, the amount of rainfall was 10,660 mm. or annually 2,132 mm.;
for the same time period the rainfall in the course of the growing season
was 5,150 mm. or annually 1,030 mm. During the 1961—1965 period the
amounth of rainfall totalled 10,880 mm. or annually 2,160 mm., while for the
same time in the course of the growing season it was 5,033 mm. or annually
1,066 mm. It is evident that the time intervals of 1961—1965 and 1966—1970
did not differ as regards rainfall. If we study separately the years 1968 and
1969, we see that they did not deviate from the average.
Consequently, we cannot ascribe to the rainfall the reduction of diameter
increment in the last 5 years. Neither are the differences in temperatures
such as to cause the mentioned reduction of increment.


With regard to the management measures (fellings) it ought to be stressed
here that in the management unit of »Belevine« the annual cut is ca. 2.500
cu. m., which is approximately as much as the annual increment. The cutting
is performed under the scientific gudiance of specialists from the Faculty
of Forestry, and thus the management interventions could not be accounted
for the reduction of increment of Fir either, but, what is more, we should
expect it to increase.


Accordingly, it may be said rather reliably that certain pests caused
the reduction of increment which we had established. Entomologists and
those concerned with forest protection have contributed and will contribute
a detailed interpretation of the pests concerned.


And now let us try give an answer to the third query: »How does the
reduction of assimilating apparatus affect the increment?«


In order to be able to give an answer to this query, I sorted the samples
according to the groups: 0%, 10%, 20%, 30%, 40% etc. where 0 means the
samples from Fir trees of the normal assimilating surface, 10% means the
trees in which the assimilating surface was reduced by 10%, 20% means
the trees in which the assimilating surface was reduced by 20%, etc. On
the cores we measured the annual diameter increment during the five-year
period of 1966—1970. After the statistical processing of data, we obtained
the following results:


Loss of


needles 10% 20% 30% 40% 50%


o%


b 326 230 95 33 9 2


d3


50.1 45.8 41.3 45.1 30.8 15.0 cm.
3.82 2.86 2.76 2.38 2.37 1.30 mm.
zs


(b) = number of samples; (ds) = mean diameter b. h. of Fir trees; (Zs) =
average annual diameter increment in the course of the 1966—1970 time
interval.