The ALIEN-Project (2015-2018) aims to assess the long-term effects of invasive tree species on the protection function of forests against rockfall in Switzerland and France. The study species is Ailanthus altissima, the tree of heaven.

Ailanthus altissima (Mill.) Swingle, commonly known as tree of heaven, is a deciduous tree native to China. In the last decades it has become invasive in forests in the southern parts of the Alps. Many of these forests have a protection function against rockfall. The expansion of Ailanthus altissima in protection forests poses questions on the future development and stability of the affected forest stands and their protective capacity. To answer these questions the project has four key parts:


Forest ecology

Acquire fundamental ecological knowledge on Ailanthus altissima

Forest dynamics Forest modelling

Assess the determinants of Ailanthus altissima spread and evaluate the effects of forest management

Mechanical stability Mechanical stability

Assess the mechanical stability of Ailanthus altissima using field experiments

Protection function Protection function

Quantify the current and future rockfall protection function of forest stands invaded by Ailanthus altissima

Forest stand invaded by A. altissima Decayed Ailanthus altissima thrown by wind
Rockfall in a forest stand dominated by Ailanthus altissima in Ticino, Switzerland
(© Simon Knüsel)
Decayed Ailanthus altissima thrown by wind (© Jan Wunder)