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

COST Action E4: Forest Reserves Research Network 99
Growing stock
The growing stock of virgin forest stands has remained practically unchanged over the
past forty years. Between the first full callipering in 1957 and the last, the change was
insignificant. Therefore we could assume that virgin forest stands are in the state of
equilibrium, which means that the increment of trees equals the quantity of dead trees.
Growing stock, however, is not the most appropriate stand parameter for the description
of developmental processes in virgin forest stands. Although tree species composition of
virgin forest stands, d.b.h. structure and the proportion of individual developmental
phases of the virgin forest changed considerably during the analysed period, the growing
stock remained relatively constant in the total area, though it changed substantially in a
smaller area.
Table 1: The growing stock of the virgin forest Rajhenavski Rog in the period 1957 -
1995
Year 1957 1967 1976 1985 1995
Growing stock (m 3 /ha) 783 803 802 799 798
D.b.h. structure
D.b.h. structure is a stand parameter which clearly shows, along with tree species
composition, developmental features of virgin forest stands. During the period 1957-
1995, d.b.h. structure of stands changed substantially in the 51-hectare area of the virgin
forest. Changes that relate to the life cycle of trees and stands are congruent with changes
determined in the horizontal structure of virgin forest stands. The structure and
functioning of virgin forest stands are also influenced by exterior factors. Silver fir
decline, then, is attributed to pollution, while the efficiency of spontaneous regeneration
of stands is adversely affected by big ungulate herbivores.
The most characteristic changes in d.b.h. structure of stands during the period 1957-1995
are as follows: lower density of trees, lower number of medium-size diameter trees, a
slightly higher number of large diameter trees. Recently, however, the number of young,
small diameter trees has risen, exclusively European beech trees.
These changes indicate that virgin forest stands are not in the state of equilibrium, at least
not in such a small area as is the analysed virgin forest. Differences established for d.b.h.
structure of stands suggest ageing of stands, as the study by HARTMAN (1987) has already
shown, and also decaying of stands, which will be even more distinct in the future.