Dendrochronological methods for reconstructing mass movements — An example of landslide activity analysis using tree-ring eccentricity

Abstract

Dendrochronological methods can be applied to the reconstruction of different types of environmental events such as climate changes, fires, glacier movements, floods, earthquakes, volcano activity. In the field of geomorphology dendrochronology is increasingly frequently used for the absolute dating of different types of mass-movements (rock falls, landslides and debris flows, etc.). Trees growing on slopes transformed by mass-movements are tilted and wounded while their stems and root systems are exposed or buried under sediment. These events are recorded in wood anatomy as eccentric growth, reaction wood, scar overgrowth by callous tissue, changes in cell size or adventitious root production. Dating changes in wood anatomy allows to date and precisely reconstruct the spatial and temporal occurrence of mass-movements with at least one year resolution. The paper provides a review of existing dendrochronological tools used in geomorphology and also an example of the application of eccentric tree-growth to reconstruct landsliding. Using tree-ring eccentricity allows to (1) obtain a dynamic depiction of slopes, (2) study landslide activity, not only contemporary, but also in the last tens of hundreds of years (depending on the stand age).

Coupling between landslides and eroding stream channels reconstructed from spruce tree rings (examples from the Carpathians and Sudetes – Central Europe)

“…specimens. We have applied a dendrogeomorphic method described in detail by Wistuba and Malik (), Malik and Wistuba () and Wistuba et al . ().…”

“…The need to include reference slopes in the dating of landslide activity arises from the fact that eccentricity can also be developed due to factors other than bedrock instability, for instance wind impact, snow creep, asymmetry of the tree crown. The method of dating applied (Malik and Wistuba, ; Wistuba et al ., ) assumes that non‐geomorphic factors influencing eccentricity act in a similar way on both the landslide and reference slopes (fulfilling the criteria described). It also assumes that using a reference slope will allow exclusion from further analysis of geomorphic processes (e.g.…”

“…Both basic methods of dendrochronological dating used in the study are quite new: dating erosion from diagnostic features of root anatomy has been developed over the last 10–20 years (Gärtner et al ., ; Gärtner, ). Dating landsliding from tree ring eccentricity using the per cent index and reference thresholds was developed in the last 2–3 years (Malik and Wistuba, ; Wistuba et al ., ). Also the approach of combining both methods in one valley cross‐section, where landsliding is dated on slopes and erosion on the valley floor is completely new.…”

Human-planted alder trees as a protection against debris flows (a dendrochronological study from the Moxi Basin, Southwestern China)

“…The method has been described in detail by Malik and Wistuba (2012). It is based on the assumption that tilted trees (deformed by a debris flow event) produce wider rings on one side of the stem and narrower rings on the other -i.e.…”

“…Zielonka et al, 2009;Zielonka and Dubaj, 2010;Migoń et al, 2010;Malik and Wistuba, 2012;Šilhán, 2012;Šilhán et al, 2012). The debris flow phenomenon is often investigated by analysing the ring width and wood anatomy of affected trees (Baumann and Kaiser, 1999;Malik, 2004;Stoffel et al, 2005;Hrádek and Malik, 2007;Malik and Matyja, 2008; Malik and Owczarek 2009;Stoffel, 2010;Bollschweiler et al, 2011;Lopez Saez et al, 2011;Procter et al, 2011).…”