DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 7-8/1970 str. 21     <-- 21 -->        PDF

(they are situated in the same stand), i. e. they are not parcelled out, and the system
of management applied to them was completely the same, because the previous
management in these stands was conducted by using compartments.


In order to find out whether there exists a difference between the heights curves
of stands which differ in age by cca 20 years and belong to the same forest community,
we examined by means of null hypothesis their regression coefficients (Tab. 11).
These examinations proved that in forest of Pedunculate Oak and Hornbeam not only
the height curves of 70- and 90-year-old stands differ from one another. Other height
curves of dominant and overall heights differ significantly in both parameters (Tab.
11 and Graphs 5 and 6). In the flooded Pedunculate Oak forest the situation is somewhat
different. Between the height curves of 50- and 70-year-old stands there
exists a significant difference in both parameters. The height curves of 70- and 90-
year-old stands differ only in the position i. e. in parameter In a, while the 90- and
120-year-old stands did not differ at all from one another with respect to their height
curves. Without a detailed investigation of the influence of site factors on the height
curve it is not possible to find out the causse of this phenomenon.


By taking measurements of heights in the area of strips Nos. 4 and 5 we aimed
at eliminating the influence of age, microrelief (forest communities) and system of
management on the height curve. The strips were laid out in stands of the same age,
and they include approximately in an even manner differences of the microrelief,
while the system of management (working plan of Lipovljani) is the same. It was
expected that no significant difference would exist between these height curves,
which was also ^proved for the height curves within the ages of 90 and 120 (Tab. 12).
However, within the ages of 50 and 70 there exists a difference between these height
curves only in parameter b. The occurrence of these differences is not of great probability,
because the differences (A) are hardly greater than the 99"Vo confidence limit.
In addition, it is almost impossible to lay out a sample plot in the manner to eliminate
completely the influence of the microrelief. Accordingly, the stand height curve of
Pedunculate Oak is mainly influenced by the age of the stand, the site quality and
the system of management, without ignoring the influence of other factors such as
groundwater.


On the basis of the results obtained we may draw the following conclusions:


1. The variability of logarithms of heights (slnh, d) around the smoothing line is
significantly different for stands of different ages.
2. There is no difference between the variability (Sinh, a) of dominant heights of
the flooded Pedunculate Oak forest and the forest of Pedunculate Oak and Hornbeam
of the same age.
3. The height curves of Pedunculate Oak of the same forest community embracing
the stands of different ages differ from one another in position (In a) and form (b).
4. The height curves of the dominant part of Pedunculate Oak stands belonging
to the same forest community which includes stands of various ages differ from one
another both in the position (In a) and form (to) of these curves.
5. The height curves of the stands of the same age but belonging to different
forest communities differ significantly as to their position (In a) and form (b). These
differences are more strongly pronounced with respect to the position of the height
curve than its form.
6. The height curves of the dominant storey of stands of the same age, which
belong to different forest communities, differ mainly with respect to their position.
7. Older stands of Pedunculate Oak exhibit mainly steeper height curves, which
is the consequence of a Pedunculate Oak understorey in these stands.
8. According to the author´s investigations the position of height curves of the
same forest community is influenced by age, while its form by the system of management
(understorey of Pedunculate Oak).
From the author´s investigations it is visible that height curves ought to be
constructed separately for each forest community of the same system of management.


Tariffs prepared on the basis of these standard height curves would certainly
possess a satisfactory accuracy, while also the determination of height increment
would be possible from two standard height curves.


It ouhgt to be emphasized that this investigation of Pedunculate Oak height
curves was carried out on a relatively small number of stands, and therefore further
investigations in this direction are expedient.