DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 5-6/1971 str. 26     <-- 26 -->        PDF

increment according to the check method (»Methode du controle«), and when I established
a »Diminution of increemnt in our valuable Oak forests«, Šumarski list, No
3—4, Zagreb 1969. Taking into consideration that when calculating the increment of
Pedonculate Oak, I retained the same tarif (Algan´s No 17) during the four successive
inventories taking place from 1950 to 1967, i. e. in the course of 17 years, one
could perphaps object that I should have to change the tarif, i. e. to take a higher
one because of the »displacement of the height curve«. Several of my experiments
have proved that the height curves of stands older than 70 years did not differ much
from one another, which would mean that there is no special need to change the
tarif in Oak stands older than 70 years.


This spring — in the month of April — I had the opportunity to verify my
measurements with my assistants Sime Meštrović and Radovan Križanec, graduate
engineers of forestry, as well as with the students of the 8th semester of the Forest
Management Department of the Forestry Faculty, Zagreb.


I instructed the students how to work, explained to them the point in question,
and so I included them into the scientific research work.


In the management unit of Pedonculate Oak »Josip Kozarac« we selected 7
stands or 7 subcompartments as follows: I) 191´c (18 years), II) 184/b (38 years),
III) 187 a (55 years), IV) 164´a (95 years), V) 141/c (77 years), VI) 31/a (111 years) and
VII) 53/a (134 years). Thus we obtained the representatives of 7 age classes with a
20-year period each. We divided the students into 7 groups. Each group of them
obtained a stand where — according to the random sampling — measurements of
total heights on 70 Pedonculate Oak trees with a Blume-Leiss hypsometer had to be
taken.


After making field measuremnts each group constructed a height curve for its
own stands. Thus we obtained 7 height curves for 7 age classes of the Oak in the
forest of »Josip Kozarac«. Data about these height curves are given in Tabl. 1 under
the designation of (h). This is represented in Fig. 1 where the Roman figures
designate the height curves in individual age classes. In this Figure is visible what
we wanted to investigate, i. e. how the height curve shifts with respect to the age
of the stand. A displacement of the height curve from the first age class into the
second one, from the second into the third, and even from the third into the foruth
one is evident. In the other words, the curves of the lrst, 2nd, 3rd and 4th age classes
are mutually fairly separated, as distinct from the curves of the 5th, 6th and 7th
age classes which are nearing mutually. What does this mean? The answer is clear:
The growth rate in the height of young stands is higher than that of the middle-
aged ones which continue to grow show in height, so that the height curves for the
5th, 6th and 7th age classes differ mutually very little. From which it is clep.ry visible
that the displacement of height curves in young stands is great, in middhe-aged
stands small, an´? in old stands insignificant.


In order to see what is the repercussion of this on the tarifs, we constructed
by means of 7 height curves 7 tarifs. We made this by the help of the German
double-entry volume tables for Oak after Schwappach. This constructed tarifs are
found in Tabl. 1 under the designation of (v). If we compare them with Emrović´s or
Algan´s tarifs, we shall see that they coincide very well. From this comparison it
follows that definite tarifs correspond to individual age classes in the following way:


Number of tarif according to
Age class Emrović Algan


I ( 1—20 yr.) 1 8
II ( 21— 40 yr.) 6 13
III ( 41— 60 yr.) 8 15
IV ( 61— 80 yr.) 10 17
V ( 81—100 yr.) 11 18
VI (101—120 yr.) 11 18
VII (121—140 yr.) 12 19


Now, we see how the tarif should be changed when determining the growing-
stock volume. For Oak stands of age class I Emrović´s tarif No 1 (or Algan´s No 8)
is to be taken into consideration, for Oak stands of age class II Emrović´s tarif No 6
(or Algan´s No 13), for age class III Emrović´s tarif No 8 (or Algan´s No 15) for age