Tree-ring eccentricity-based dating of landslide movements: Defining a new effective approach

Abstract

Dendrogeomorphic dating of landslide movements is nowadays a frequently used tool for understanding past landslide behaviour. One of the most widespread growth disturbances induced by landslides is tree-ring eccentricity. However, extracting the landslide signal from the time series of its values is a challenge that has suffered from many shortcomings so far. In this study, a new approach based on the detection of changes in tree-ring eccentricity values was developed. The approach, which combines the advantages of previous approaches, was tested on four landslides in different physical-geographical conditions with different tree species of different ages. For all landslides, the year of activity was well known and analyses of the results focused on this year. The tested methodological approach successfully detected all these known years. However, it also detected a higher amount of noise in two cases, which may have been caused by imperfect knowledge of pre-landslide slope activity or creep. An important feature identified in the results obtained by the approach was their potential independence of tree age. As with the use of other macroscopic growth disturbances, this approach does not allow dating with seasonal accuracy. However, compared to previous methodological approaches working with tree-ring eccentricity analysis, the new approach demonstrated significant advantages. The procedure does not truncate the reconstructed time series, does not smooth the landslide signal, and uses exactly defined landslide signal thresholds.