ALIEN

Ailanthus altissima (Mill.), commonly known as tree of heaven, is a deciduous tree native to bothnortheast and central China and Taiwan. The tree grows rapidly and is capable of reaching heights of 15 metres in 25 years. However, the species is also short-lived, rarely exceeding ages of 50 years. The tree was first brought from China to Europe in the 1740s. It has become an invasive species due to its ability both to quickly colonise disturbed areas and to suppress competition with allelopathic com-pounds. The tree also resprouts vigorously when cut, making its eradication difficult and time consum-ing. As a consequence, forests, mainly in the warmer, southern parts of the Alps, are increasingly in-vaded by A. altissima trees. Many of these forests play a key role in natural hazard risk management as they have a protective function against rockfall. Decades of fundamental research on both the ecological and mechanical characteristics of forests and trees in the Alps allowed the development of tools which enable quantitative comparisons between technical protective measures and protection forests. The expansion of the invasive species A. altissi-ma in protection forests poses questions on the future development and stability of the affected protec-tion forests and their protective capacity. To answer these questions, both new data and further model developments are needed. The four key goals of this project are therefore: 1. To acquire fundamental ecological knowledge on the long-term development of the structure and stability of forest stands invaded by A. altissima 2. To adapt and calibrate a forest dynamics simulation model for assessing the determinants of A. altissima spread and evaluating the effects of forest management interventions on the future de-velopment of invaded forest stands 3. To develop a model for the mechanical response of A. altissima trees during dynamic impacts 4. To develop methods and models that allow quantifying the current and future protective function of forest stands invaded by A. altissima against rockfall ALIEN will achieve these goals by interdisciplinary fundamental research on A. altissima, tightly cou-pling field data collection and process-based simulation modelling. The novel insights on the dynam-ics of invasive species, their impact on risk prevention related ecosystem services, and on the efficacy of alternative management options will be of high interest to the international research community and eventually also practitioners responsible for the management of protection forests.