Analysis and modelling of tree succession on a recent rockslide deposit

Abstract

Dendroecological methods were combined with vegetation and soil mapping to study recolonisation of European larch (Larix decidua), silver birch (Betula pendula) and Norway spruce (Picea abies) on a recently formed rockslide cone (deposit of 30 × 106 m3) in the Valais Alps (Switzerland). Tree density and tree height were predicted with regression models that we derived using an information-theoretic model selection approach. Results demonstrate that the deposits of the 1991 rockslide have been colonised relatively rapidly with larch (ecesis time 2 years), birch (5 years) and spruce (2 years). Most of the colonisation occurred 5–11 years following the rockslide. Clast size was the primary factor driving tree colonisation with the highest tree densities found on plots with mainly smaller (<30 cm) clast sizes. Tree height was affected by a combination of different influences, with tree age and tree density showing the most obvious effects. This study demonstrates how dendroecological methods allow reconstruction of spatio-temporal patterns of tree succession on rockslides, which may ultimately facilitate a more accurate dating of similar landforms of unknown age.