VIRGIN FORESTS AND FOREST RESERVES IN ... - Natura 2000

COST Action E4: Forest Reserves Research Network 105
structure and in intensive developmental dynamics of the virgin forest. Stand dynamics
depends on the proportion of silver fir in the growing stock of a stand, its distribution and
intensity of die-back. The following examples are illustrative (BONČINA 1997):
– if a silver fir tree dies in a stand of the young optimal phase, then remaining trees,
European beech in particular, fill in the vacant space with crown growth. There are
fewer trees but they have larger crowns.
– if the proportion of silver fir is high and it dies uniformly in the area, two-layered
stands are formed, and European beech occupies the lower position;
– if silver fir trees die one after another or in small clusters unevenly in an area,
stand structure is selection,
– if the proportion of silver fir is high and trees die intensively, then regenerating
stands and young uniform European beech stands are formed.
Individual stand structure is dependent on a given tree species composition. Thus the top
layer of two-layered stands consists almost exclusively of silver fir and the lower layer of
European beech. Similarly, selection stand structure depends on the appropriate share of
silver fir or its die-back. The proportion of European beech in the growing stock will
increase more and more, and therefore stand structure will change as well.
CONCLUSIONS
Findings of studies on virgin forest stands contribute to our understanding of the structure
and developmental processes of forest ecosystems. At the same time they give us
information which is useful for close-to-nature forest management. The following should
be underlined in particular:
1. The structure of virgin forest stands is not constant, unchanging or in the state of
balance. We speak about certain intervals, within which stand structure changes.
2. A comparison of d.b.h. structure shows that stands in the virgin forest Rajhenavski
Rog are ageing, since the proportion of large diameter trees has increased, the density
of trees has decreased and, above all, the number of medium-size diameter trees has
fallen. Recently, stands have been regenerating intensively, which results in a higher
number of trees of the second d.b.h. class, (5 - 10 cm).
3. The development of the dominant tree species, silver fir and European beech, is not
parallel, quite the opposite. About a hundred years ago the proportion of silver fir in
the total growing stock accounted for a mere 27%. The available data suggest the
commencement of intensive regeneration of silver fir during that time and a bit earlier
and its gradual ingrowth in the stand canopy, in which European beech dominated.
The proportion of silver fir in the total growing stock was rising till 1967 when it
gradually started to decrease. All indices suggest that the proportion of silver fir will
decrease further in the next decades. The current state, which is just the opposite of
that a hundred years ago, is distinguished by intensive ingrowth of European beech in
the stand canopy, where silver fir still dominates in the growing stock.