J. D. Sauerländer's Verlag, Bad Orb

The forest district “Großer Freeden” is situated in the northwestern Teutoburg Forest (Lower Saxony, northwest Germany) and became a strict forest reserve in 1972. We investigate how the deciduous forest stands in this reserve evolved after the cessation of timber harvesting and which biotic and abiotic factors led to the current status. In this context, forest history is considered as well.
In former times, the investigation area was owned by the prince-bishopric of Osnabrück. Following owners were the Kingdom of Hanover, Prussia and since 1945 the federal state of Lower Saxony. Nowadays, one-storied Fagus sylvatica L. stands are growing on the southern slope that is covered with thick, loess-derived soils. The steep northern slope is dominated by two-storied Fagus sylvatica stands with several secondary tree species, the Rendzina soil is quite shallow (Tab. 1). Even 33 years after the last harvesting operations, it is still apparent how the stands had once been managed. However, tree species that are not site-adapted or less competitive (e.g. Picea abies (L.) Karst. or Ulmus glabra Huds.) are increasingly being replaced by the competitive Fagus sylvatica. Hence, during the observation period (1971–2004), tree-layer diversity decreased, while tree-layer volume increased (Tab. 2, 4, 5, Fig. 2, 3). Besides high tree mortality due to competition, a considerable dieback of Ulmus glabra occurred, which can be explained by the Dutch elm disease temporary drought stress. Regarding Acer pseudoplatanus L., the analysis of a real time series reveals that this tree species grows faster than Fagus sylvatica in early stages (Fig. 4). The difference of rate of growth between these two tree species decreases with increasing age, until finally Fagus sylvatica overgrows Acer pseudoplatanus. In contrast, Fraxinus excelsior L. grows better than Fagus sylvatica. This trend increases during the last two decades of the observation period and can be explained by a combination of site factors and stand history (Tab. 3). The volume of decaying wood amounts in average to 34 m3 per hectare (Tab. 6). Due to the protection of natural processes the abundance of decaying wood will increase in the future. Especially in homogeneous and one-storied Fagus sylvatica stands a considerable number of trees will die back in the next decades. In 2004, we found almost no tree regeneration due to Fagus sylvatica competition and very high population density of fallow deer (Dama dama L.). Since 2005, fallow deer numbers have been reduced by intensified hunting. As a consequence, the forest can develop in a more natural way henceforth. For future stand structure and tree species composition, especially disturbances such as wind throw will be crucial.

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