Untersuchungen zur Apophytisierung von Hedera helix : Gelingt dem Efeu die Habitaterweiterung vom Wald zur Stadt?
The ivy (Hedera helix) is one of the rare evergreen forest species in Central Europe and is seen as a relict from the Atlanticum period. It appears in two different forms: as a vegetative floor form and as a climbing and fruiting tree form. In most of the woods in Central Europe the ivy exists only in its floor form. The spreading of the climbing and fruiting form is seen as a climate marker for a possible warming and is therefore often discussed together with “laurophyllisation”, the climatically caused spread of evergreen plants. The spreading and the vitality of the ivy were investigated in the gradient of increasing urbanity using the area of Braunschweig (Germany, Lower Saxony) as an example. It could be shown by the use of a 12 km transect that the tree form of ivy increases from the outskirts to the border of the inner city. Even in the densely built-up inner city fruiting individuals as well as seedlings of Hedera helix are found. Germination investigations with fruits collected in the city of Braunschweig resulted in an average germination rate of 48 % when in dark and 40 % in light. Although ivy is often brought to the cities by man as decorative plant there is no doubt that this species is able to establish itself where this is supported by groups of trees and old walls. Ivy climbes on at least 69 phanerophytic species in Braunschweig. Therefore we classify Hedera helix as an apophyte which succeeded in changing from the forest habitat to anthropogenic habitats like Urtica dioica, Aegopodium podagraria or Campanula rapunculoides. How the period of warmer summers influences the vitality of the ivy could not be estimated at the moment because of lacking comparative data. The basis however is set by our system of plots within the area of Braunschweig. The phenomenon of laurophyllisation is discussed taking into account the possible climate change and short-lived fashions of gardening.