Direkte, indirekte und kombinierte Effekte von Wölfen auf die Waldverjüngung

Abstract

Direct, indirect and combined effects of wolves on tree regeneration The wolf currently returns to its traditional distribution area in central Europe. As a large carnivore, he will change the interactions between the organisms there. The impact of wolves on wild ungulates and on the vegetation cover and its composition is manifold: besides direct, numeric effects of wolves on the abundance and demography of their prey populations (like chamois, roe deer and red deer), indirect functional effects through mediated behavior of ungulates are also reported. In a first phase of wolf recolonization with low population density in a region, the functional effects as changes in the spatio-temporal use of habitats and resources are considered to be dominant because the wild ungulates attempt avoiding to become a prey. Later, in phases with higher wolf densities, direct numeric effects on the abundance of prey species should become more obvious. Such interactions among predator and prey species also have an impact on the browsing of tree regeneration. Since the spatio-temporal habitat use of prey species is mediated by the occurrence and abundance of large predators, we cannot assume that the browsing level will gradually decrease in general. Wild ungulates could more often hide or retreat into steep and rocky terrain or towards human settlement. Hence, trophic interactions between predators, herbivores and forests are complex and multilayered, in particular because forest ecosystems in central Europe are strongly influenced by forestry and hunting practices. This limits the trophic cascading impact of carnivores on forest. Our review demonstrates that the equation “wolf = less ungulates = fewer browsing” is not a general rule.