Tree-ring eccentricity in the dendrogeomorphic analysis of landslides – A comparative study

Abstract

The chronological aspects of landslide research are of great interest regarding the hazard assessment of landslide triggers. Dendrogeomorphic methods provide a good ratio of chronology length and dating resolution. An alternative to the standard dendrogeomorphic approaches used in landslide research (based on reaction wood analysis – a reaction to stem inclination) is the analysis of tree-ring eccentricity. This study tests three frequently used dendrogeomorphic approaches based on tree-ring eccentricity and verifies the results by comparing them with the results obtained by the standard dendrogeomorphic expert approach. In total, 125 individual Fagus sylvatica L. trees growing on the block-type landslide of Lipová stráň in the foothills of the Orlické hory Mts. (central Europe) were sampled and used for the analysis. The first tested approach identifies landslide signals based on the analysis of mean eccentricity values from two moving windows. The second tested approach determines landslide signals from a series of eccentricity values based on the use of an eccentricity threshold from reference trees. The last tested approach organizes the eccentricity values into categories and identifies landslide signals based on the defined temporal patterns of the individual categories. The limitations of each approach are revealed, and recommendations for increasing the robustness of each approach are presented. Moreover, the sensitivity of F. sylvatica trees to landslide signals was tested using each approach. The obtained results suggest the need for a specific sampling design (regarding tree age) for each tree-ring eccentricity-based approach.