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ŠUMARSKI LIST 13/2005 str. 155     <-- 155 -->        PDF

S. Kucbel: THE STRUCTURE AND NATURAL REGENERATION OF A SUBALPINE SPRUCE FOREST ... Šumarski list - SUPLEMENT (2005), 144-153
component of the species composition in the high-elevation
forest, spruce stays the determinant tree species
of these stands and therefore the number and structure
of spruce regeneration has the crucial importance for
the stand renewal. The second reason which does not
allow the direct comparison is the growth rhythm and
ecological demands of these tree species as well as the
different dynamics of the regeneration process.


For the evaluation of the regeneration processes in
the stands especially the height category over 20 cm is
interesting. While the seedlings under 20 cm are only a
very insecure beginning of the next generation and
their numbers per hectare are more the proof of the permanent
breeding in the stands, the individuals over 20
cm (or 50 cm) are relatively secure and able to take part
on the next stand generation. The comparison of the
spruce and rowan representation in table 4 shows the
prevalence of rowan in the height category over 20 cm.
Rowan presents at least 2/3 of the regeneration, on
PRP 1 and 2 even more than 80 % what is the consequence
of her faster growth at the lower age. In the
height category under 20 cm the numbers of spruce and
rowan are approximately equal, excepting PRP 3. The
analysis of the height classes shows relatively high
mortality of rowan individuals especially in higher categories,
where only a minimal number of them reaches
the height over 80 cm. On the contrary, spruce has
a quite balanced ratio in the categories over 20 cm


DISCUSSION AND


In this paper the data acquired from three research
plots were used. The analysis of a structure which is
approximating an ideal stand structure for the high-
elevation forest allowed stating some partial conclusions
regarding the model of the high-elevation forest
structure.


The results can be confronted with the data from
Swiss Alps published by Trepp (1961). According to
this author the most important attributes of the group
selection forest structure on high-elevation sites are
following: cluster or group structure, small-scale regeneration,
middle growing stock (340-380 m3 ha"1) also
on convenient sites, continuous development of the natural
regeneration on ecologically differentiated micro-
sites. On this research plot the tree number was 720 ha,
its distribution into layers: lower 58.3 %, middle 13.8
% and upper layer 27.7 %. The author evaluates the
growing stock on to plot too high and recommends the
maximum growing stock about 350m3 ha"1 even for


what let assume if the spruce seedling has reached the
height of 20 cm we can consider it relatively secure.


The question of sufficient amount of spruce natural
regeneration for high-elevation stand renewal can be
answered according to a calculation of Ott et al.
(1997). The author mentions the area of natural regeneration
in a high-elevation forest should take at least
from 1/6 to 1/3 of the stand area. If we use an average of
1/4 and the usual number of planted spruce (2,500 ha"1),
the approximate reference number should be 600 individuals
per hectare. In the case the real number of spruce
over 20 cm (or 50 cm) is above this limit and there is
a sufficient reserve in the height class under 20 cm, the
dynamics of regeneration process can be considered satisfying.


The comparison of the real numbers with the boundary
value shows a sufficient number of the spruce regeneration
in the classes over 20 cm on PRP 2 and 3.
The amount of the regeneration on the PRP 1 reaches
just the limit 600 ha"1. Generally the amount of spruce
individuals over 20 cm can be considered sufficient.
From the long-term view the number of spruce individuals
under 20 cm is problematic (it lies under 1,500
ha-1 on each PRP). Assuming the high seedling mortality
the number seems to be no sufficient reserve and
the continuous regeneration of the stand could be endangered
in the future.


CONCLUSIONS


most convenient sites. In terms of natural regeneration
he found out 2,160 individuals per hectare in the height
class under 30 cm, in the height class 31-150 cm 1,220
ha"´ and in the class over 150 cm 620 ha"1. Compared
with these results, especially the numbers in the category
under 20 cm from our research plots seem to be
low and as mentioned before they are not a sufficient
reserve for continuous renewal.


Besides the maintenance of the differentiated structure
the silvicultural interventions should be concentrated
on the support of the existing natural regeneration
by means of creating appropriate light and thermal
conditions for their further growth and development.
The best way to do this is to cut several shading trees
from upper layer. On behalf of the increase of the seedling
number in the category under 20 cm it would be
appropriate to leave some of the cutting stems in the
stand and thus create perspective seedbeds for the
seedling emergence.