Environmental Engineering Reference
In-Depth Information
native tree species. That large animals contribute to
micro-site diversity of forest stands is obvious (e.g.
digging by wild boars activating the soil seed bank).
The ecological role of large grazers like aurochs
( Bos primigenius ) and tarpan ( Equus przewalskii
gmelini ), which died out centuries ago, are not exactly
known. Although there are current examples of open
woodland resulting from several thousands years
of domestic cattle grazing in forests (Pott & Hüppe
1991, Olff et al. 1999) it is hard to transfer the results
to previous forests because the ecosystem has
changed completely (e.g. it has lost large predators).
forests (original ones as well as those preserved in a
near-natural state or those naturally regenerating;
Schmidt 1998). Most of the stands show increased
susceptibility to damage by snow, ice, wind, drought,
insects, fungi and possibly soil degeneration as com-
pared to forests composed of site-adapted species
due to a low resilience and a lack of ecological
self-regulation.
At present, forest management in many European
countries is changing. Changing demands of society
and an enhanced level of ecological understanding have
given an impetus to a lively discussion and intensi-
fied research regarding the improvement of these sec-
ondary Norway spruce and Scots pine stands (Spieker
& Hansen 2002). Two options for increasing the
resilience of stands are given (Fig. 10.4).
10.5.2 Forest improvement: conversion and
transition of forest stands
Forests in central Europe cover a wide range of site
qualities and stand structures, and were often deeply
influenced by former (mis)use of land due to litter rak-
ing, exploitation and more recently by atmospheric
depositions (Glatzel 1999, Kenk & Guehne 2001; see
also above). Mainly beginning in the 19th century
pine ( P. sylvestris ) or Norway spruce ( P. abies ) plan-
tations were established in areas that had originally
been dominated by deciduous trees. The present com-
mercial forest ecosystems differ widely from natural
1 Conversion , a change in tree species composition,
of secondary coniferous stands into pure or mixed
broad-leaved forests, usually by advanced artificial
regeneration (Hasenauer 2003).
2 Transition , a change in vertical structure, of pure
structured stands in multi-layered stands, for
example by moving from an even-aged to an
unevenaged forest stand and changing the rotation
period (or even to strive for continuous cover
management; see Möller 1921).
FOREST CONVERSION
Initial situation
Silvicultural strategies to
improve horizontal structure
Possible final situation
Acceptance of natural disturbance
Advance planting
Underwood planting
Regulation of mixture
Pure coniferous stand
Broad-leaved and/or
mixed stand
FOREST TRANSITION
Initial situation
Silvicultural strategies to
improve vertical structure
Possible final situation
Acceptance of natural disturbance
Consideration of site locality
Regulation of mixture
Selective cutting system
Continuous forest management
Fig. 10.4 Silvicultural strategies to
improve forest stands that are poor
in structure.
One-layered stand
Multi-layered stand
 
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