Protection function

We will develop models and tools for quantifying the protective function of Ailanthus altissima invaded protection forests. The models will be validated and calibrated based on traces of past collisions of rocks with trees.

Trees stopping a boulder
Two trees stopping a boulder
(© Luuk Dorren)
Scree in a rockfall protection forest
Scree in a rockfall protection
forest (© Luuk Dorren)
Trace of past rockfall
Traces of past rockfalls in 

trees (© Daniel Trappmann)

Dating of past rockfalls
Freshly cut cross section depicting

characteristic growth reactions that

enable dating of past rockfalls 

(© Markus Stoffel)

Key to this work is the development of a model for the energy dissipative capacity of Ailanthus altissima trees. This capacity determines how much kinetic energy of a falling rock is lost during its impact against a standing tree. To take this effect into account in modelling tools, we have to provide a relationship between the tree diameter and the maximum energy dissipative capacity of Ailanthus altissima trees and one for the relationship between energy loss during impacts and the height of the impact on the tree stem. Further, we will develop a method for describing tree distributions of Ailanthus altissima invaded forests based on the forest simulation model output data that correspond to the Ailanthus altissima invaded forest stands observed in reality. Finally, we will simulate rockfall events given different forest scenarios to eventually describe the protective capacity of Ailanthus altissima invaded forests over time.

To optimize the reproduction of past rockfalls in forests invaded by Ailanthus altissima silent witnesses such as rock impacts in trees will be analyzed externally on the stem surface and internally via tree-ring analysis. This impact data can be compared with simulated rock passages. Comparison will enable validation of model input parameters. Results from a validated model can be used with higher confidence for further investigations.