Natural regeneration of oaks along a climatic drought gradient on limestone

Summary: In central Europe the deciduous oak species Common Oak (Quercus robur), Sessile Oak (Quercus petrea) and in South West Germany Downy Oak (Quercus pubescens) occur. All of these tree species benefit in competition with beech (Fagus sylvatica) from increasing drought. In the face of climate change all three oak species, especially their potential suitable sites and their economic potential attract attention. In this context, it is especially important that the majority of oaks growing in central Europe show a reduced potential to regenerate successfully. In spite of these problems there are habitats, in which regeneration of oaks is less affected. Especially along ecotones oak regeneration and a following successful establishment seems to be favoured.

The topic of this project is to investigate the ecological niche of young oaks along edges of the forest, where oak species are able to regenerate successfully. The investigation takes place in three different study areas. During the dissertation the following questions will be answered:

1. Is there a difference in the ecological niche of young oaks during different stages of development?

2. Does the ecological niche of oak regeneration change along a climatic drought gradient?

For different stages of development of young oaks, habitats will be modelled. For modelling, individual light conditions will be measured and the surrounding vegetation will be recorded (species and cover). To characterize individual water supply, macro-and the microclimate of each individual oak have to be described. In addition, some investigations of the soil will be conducted to obtain information on the individual water storage capacity.

In the project, basic principals for the management of nature reserves as well as for the development of new silvicultural systems will be gathered. Furthermore, precise recommendations for the treatment of nature reserves containing xerotherm oak forests will be given.