Dendrogeomorphic chronologies of landslides: Dating of true slide movements?

Abstract

Dendrogeomorphic chronologies of landslide movements are frequently used to investigate past landslide activity. Slide areas are often affected by other slope movements (e.g. creep) simultaneously. Trees growing on landslides record all types of ground movements, which potentially creates significant noise in tree ring based chronologies of landslide movements. The effect of creep movements on dendrogeomorphic landslide chronologies was evaluated in a block-type landslide in the south-western foreland of the Orlické hory Mountains. In total, 272 trees (Picea abies and Fagus sylvatica) were sampled (1088 increment cores) on the sub-horizontal surfaces of rotated slide blocks, which were presumably created only by slide movements, and on the steep internal scarps separating landslide blocks, which were presumably created and affected by a combination of slide and creep movements. Ground movements were dated based on growth disturbances identified in an analysis of eccentric tree growth.The trees growing on the internal landslide scarps separating the rotated blocks exhibited a significantly higher number and frequency of growth disturbances than those growing on the sub-horizontal block surfaces. All eight dated block surface movements were also identified on the internal scarps. Creep-based events represented as many as 70% of the dated movement events on the internal scarps. Varying the I t thresholds did not filter out more than 40% of the noise without significantly reducing the number of true dated slide events. A significant difference was observed between the ability of P. abies and F. sylvatica to record ground movements by eccentric growth. Probably due to its shallower roots (and weaker anchoring of the tree to landslide blocks), P. abies appears to be more sensitive to surficial ground movement, which potentially increases the proportion of dated creep events (noise). Thus, the careful selection of sampled tree species with different physiologies should be considered during dendrogeomorphic field sampling.

Changes in the radial growth of trees in relation to biogeomorphic processes in an old‐growth forest on flysch, Czechia

“…Because the disturbance history of the tree layer is not usually evaluated in geomorphic studies (e.g. Šilhán, 2017; Tichavský et al ., 2019), this factor cannot be separated out, and such situations may mistakenly be interpreted as due only to hillslope processes.…”

Reconstruction of Landslide Activity Using Dendrogeomorphological Analysis in the Karavanke Mountains in NW Slovenia

“…Events of weak intensity have the longest duration (15.7 years on average). The duration of signals could reflect landslide dynamics (e.g., slow-motion slip or creeping), where low intensity and high-frequency events cause signal overlapping [97]. This also indicates that in the reconstruction of Urbas landslide activity, based on the eccentricity signal the prevailing type of geomorphic process was creeping and not landsliding.…”

“…This also indicates that in the reconstruction of Urbas landslide activity, based on the eccentricity signal the prevailing type of geomorphic process was creeping and not landsliding. Inducing noise in the eccentricity signal can be due to root system morphology of P. abies, which seems to be more sensitive to record soil creeping [97]. By selection of higher values of It index, noise can be filtered out, although often on account of not dating true events [97].…”

“…Inducing noise in the eccentricity signal can be due to root system morphology of P. abies, which seems to be more sensitive to record soil creeping [97]. By selection of higher values of It index, noise can be filtered out, although often on account of not dating true events [97].…”

Dendrochronological dating as the basis for developing a landslide hazard map – An example from the Western Carpathians, Poland

“…Dendrochronology has also been used for developing maps of landslide activity (Catani et al, 2005;Lopez Saez et al, 2012). Until now, this method has not only been applied in geomorphology for landslide studies (Stefanini, 2004;Zielonka and Dubaj, 2009;Šilhán, 2017), but also for mapping the frequency of rockfall and debris flow events (Gärtner et al, 2003;Perret et al, 2006;Bollschweiler et al, 2007;Malik and Owczarek, 2009).…”