The effectiveness of dendrogeomorphic methods for reconstruction of past spatio-temporal landslide behaviour

Dendrogeomorphic methods are in fact frequently used for spatio-temporal landslide behaviour reconstruction. However, their real accuracies have not yet been deeply evaluated. The purpose of this study is to evaluate the effectiveness and accuracy of tree ring based methods by comparing them with field monitoring data on landslide behaviours. A total of 876 increment cores have been extracted from 219 P. sylvestris individuals to reconstruct the past spatio-temporal activity of the Lubietova landslide (1977). The landslide re-activation events recorded within the tree ring series of each tree have been spatially interpolated. Those data have been compared with the long-term field monitoring based on the measured changes in the stabilized geodetic point positions. In general, the tree ring based spatio-temporal landslide evolution revealed a higher landslide activity than the monitoring-based one (particularly in the lower part of the landslide). However, higher activity was recorded from the monitoring in the northern part of the upper half of the landslide, while approximately 30% of the studied landslide area revealed highly similar normalized values based on both approaches. The best fit between the results (>80%) was in areas with mean cumulative surface displacements of approximately 200 mm (monitoring based results) and mean event recurrence time of 14.5 years (tree ring based results). The potential sources of uncertainties that should be considered in future dendrogeomorphic research are the irregular spatial positions and spatial density of trees, the physiology of the tree species, the inertia of tree growth responses within tree ring sequences and the type of studied landslide. (C) 2016 Elsevier B.V. All rights reserved.