Assessment, Conservation and Sustainable Use of Forest Biodiversity

Conservation and Sustainable Use (sustainable forest management)
Conclusion
Intensified hunting pressure on Roe deer obviously approves growth in young trees. The less numerous
among the browsing-exposed (“appreciated”/palatable) tree species get chances to overcome browsing
pressure during times of higher hunting pressure, only. The number of successful tree species raises
significantly with growing hunting bags.
Whether browsing is considered “tolerable” or “desatrous” depends from forest management goals. As forest
management in Germany decided for the future to rely more on natural regeneration an promote a higher mix
of different tree species than had been done in the past, forest “became defined” more exposed to deer
browsing than before – even without any change in deer population densities or in browsing situation – as
European beech (Fagus silvatica) or spruce (Picea abies), the main tree species for traditional (less close
to nature) forestry in Germany are less intensively browsed – as a rule – in comparison to many other
tree species.
Legends to Figures
Figure 1: Browsing intensity diminishes with growing hunting bag. – Browsing intensity is measured as the
percentage of main shoots browsed during the last winter and before (field work mainly during April).
Hunting bag is the number of Roe deer shot per 100 ha of forest per year. The example is for Sycamore (Acer
pseudoplatanus) of the height calss 20 to 40 cm, a highly palatable tree species for browsing deer and a rather
comfortable height for browsing. The lines in the graph are for different patches of forest, more than 100 ha,
each. They start with 1990 in the upper left and end with 1998 in the lower right. Browsing pressure on this
palatable species went down considerably with raising hunting bags, but still remains high with about 50% -
20 to 30% could be considered tolerable.
Figure 2: Number of young tree indiviuals and browsing intensity per height class, all tree species and forest
patches combined, for 1990 (left column/triangles) and for 1998 (right column/circles). – With growing
height, the number of tree individuals goes down, as a large number of them have to die, not only due to
browsing. Browsing pressure (% of browsed main shoots during the last winter and before) is highest at a
convenient height for the deer (40 to 80 cm) in 1990 as well as 1998, but it is much less intense at the later date
due to an elevated hunting pressure (see Fig. 1). That’s why in the height classes above 40 cm the young tree
individuals (ind/ha) in 1998 outnumber those in 1990: relatively more of them manage to get larger in 1998
due to a lower browsing intensity. (see text).
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