J. D. Sauerländer's Verlag, Bad Orb

In Hainich National Park (Thuringia, Germany), an area with broad deciduous forests rich in tree species, we investigated relationships between tree-layer and regeneration diversity in consideration of deer browsing. In the 21 stands under investigation, which were characterised by closed canopies and a gradient from pure beech (Fagus sylvatica) stands to mixed stands with up to 11 deciduous tree species, we found that tree-layer and regeneration diversity were positively correlated (Tab. 3, Tab. 4, Fig. 4). But the composition of both strata differed considerably. In beech-dominated stands regeneration was more diverse than the tree layer, while in highly diverse stands the situation was contrary (Fig. 2). Main tree species in the regeneration were sycamore (Acer pseudoplatanus), ash (Fraxinus excelsior), Norway maple (Acer platanoides), and beech (Fagus sylvatica) (Fig. 3). Oaks (Quercus spp.), hornbeams (Carpinus betulus), and limes (Tilia spp.), which became more abundant in the canopy with increasing tree-layer diversity, were nearly absent in the regeneration. Quality and quantity of the regeneration were obviously negatively affected by increasing litter layer thickness and soil acidity, which varied due to canopy-species effects. Particularly beech foliage, which decomposes poorly and results in acid soil conditions, had a limiting effect on regeneration. There were no significant correlations between quality and quantity of the regeneration and the irradiance transmitted through the closed canopy (Tab. 5). A secondary stand including higher regeneration was missing between canopy layer and small growing regeneration (Fig. 1). Presumably it was too dark for further growing of regeneration under the canopy of all investigated stands; deer browsing had intensified this effect. Browsing intensity was neither quantitatively nor qualitatively correlated with regeneration supply, but it was strongly related to vertical and horizontal tree-layer diversity (Fig. 5). Particularly former coppices with standards and selection stands with high tree-species richness offer protection from unpleasant weather in winter (thermal cover). This is made possible by suppressed trees with low-set branches, which are a key stimulus for the habitat choice particularly of roe deer (Capreolus capreolus).

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