Environmental Engineering Reference
In-Depth Information
changed drastically in central Europe as a consequence
of human impact. Additionally, species have been intro-
duced that did not establish naturally after the last
ice age; for example larch (
Larix decidua
), douglas
fir (
Pseudotsuga menziesii
) and red oak (
Quercus
rubra
), and in some Mediterranean countries eucalypt
(
Eucalyptus globulus
). Some of the introduced species
are spreading now intensively: invasive neophytes (e.g.
Prunus serotina
).
Harvesting procedures influence the
forest structure
.
Tree cutting over an area up to several hectares
followed by seeding or planting of new trees results
in even-aged forest patches in a mosaic of different
age classes. In some countries selective cutting sys-
tems are nowadays common, creating a stand struc-
ture that is not so far from a natural forest structure.
Nevertheless, timber harvesting reduces the proportion
of dead wood in forests drastically.
To improve the soil quality - especially to com-
pensate for former devastating utilizations like litter
harvesting and for soil acidification - carbonate fer-
tilization is sometimes used (1500-4000 kg of calcium/
magnesium carbonate ha
−1
).
Harvesting operations lead to mechanical soil dis-
turbances. Soil compression reduces the growing
potential of the site (water availability, gas exchange);
the influence on biodiversity is discussed in section
10.5.1. Forestry has the option to manage the forests
in a way that is, in principle, not so far from the
natural situation (see section 10.5.1).
an overall goal in land-use management. Growing
conditions for forests as well as quality of timber are
excellent in large parts of Europe. Under the term
close-to-nature forestry (
naturgemäße
or
naturnahe
Waldwirtschaft
) a set of guidelines have been devel-
oped to combine utilization and long-term preserva-
tion of forest ecosystems. Main topics are (i) preferring
native, site-adapted species, (ii) timber harvesting in
(group) selective cutting systems, (iii) using natural tree
reproduction instead of seeding or planting trees and
(iv) leaving dead wood (thick timber, standing as well
as lying) in the forest as an important carrier of species
diversity (a habitat for fungi, insects, and vertebrates,
including birds).
In a recent study on biodiversity in managed and
unmanaged forest stands in the Bavarian Forest,
south-eastern Germany, species diversity (plants,
soil-living beetles and symbiontic as well as soil-
saprophytic fungi) besides dead wood was shown to
depend mainly on the disturbance regime. In forests
a high degree of naturalness is usually not connected
with a high number of species of these organism
groups. Under harvesting that is typical of selective-
cutting systems, plant species number at the plot
level was not different from that of the near-primeval
situation. Activation of the soil seed bank by mech-
anical soil disturbance associated with clear-cutting
is a very important process to increase plant species
diversity significantly at the plot level (Mayer
et al.
2004). Soil-dwelling beetles, too, react with increas-
ing species number after clear-cutting, invading from
surrounding open land. Methods like selective-cutting
combined with the acceptance of leaving a limited vol-
ume of dead timber are able to combine economical
and ecological demands on forests within the same
stand.
Forests are the natural habitat of several ungulates:
in central Europe this means especially wild boar
(
Sus scrofa
) as well as the grazing roe deer (
Capreolus
capreolus
) and red deer (
Cervus elaphus
). The cultural
landscape often provides much better feeding con-
ditions for grazing ungulates than forests do (and
during winter time these animals may be fed by
humans). Therefore their populations today are
usually much larger than expected under conditions
without human impact. A balance has to be found
between the aspects of guaranteeing both survival of
native animal species and natural regeneration of
10.5 Forest restoration: between sterile
substrate and primeval forest
In the following sections, we move gradually from
forest conservation to forest restoration and rehabil-
itation, starting with sustainable use of near-natural
forest as a point of reference, followed by conversions
and transitions back towards formerly existing for-
ests, regeneration after windthrow, reforestation of agri-
cultural land and finally afforestation of post-mining
landscapes (sometimes called reclamation).
10.5.1 Close-to-nature forest management
Seen from a global point of view forest utilization
in central Europe is a must if sustainability is set as
