Implications of spatial distribution of rockfall reconstructed by dendrogeomorphological methods

Abstract

Rockfall is a dangerous geomorphological process. The prediction of potentially threatened areas requires thorough reconstruction of spatial rockfall activity. Dendrogeomorphic methods allow precise determination of both temporal and spatial occurrences of rockfall without the necessity of long-term monitoring. At the case-study site of Taraktash, located among southern slopes of the Crimean Mountains, 114 Crimean pine trees (<i>Pinus nigra</i> ssp. <i>pallasiana</i>) were sampled on a talus slope located under a 150 m high rockwall. Based on their age, the trees were divided into two distinct groups (young and old trees). Considerable disturbance in the age structure of the trees on the talus was probably caused by a series of strong earthquakes. Major differences were identified in the ability of young and old trees to record a rockfall event. We found that in the first decades of their growth, the ability of the studied <i>P. nigra</i> to record rockfall events gradually increased. The trees showed the highest sensitivity at the age of 80 to 90 yr; after that age their sensitivity gradually decreases. Two indicators were selected for the spatial reconstruction of rockfall events (the number of rockfall events per tree and recurrence interval). The highest activity was identified on the talus using selected indicators

Hydrology and hillslope processes explain spatial variation in tree‐ring responses to the 1983 earthquake at Borah Peak, Idaho, USA

“…Although ‘earthquakes can trigger all types of landslides, and all types of landslides triggered by earthquakes can also occur without seismic triggering’ (Jibson, , p. 292), several studies have noted that rockfalls are the most common and spatially synchronous type of co‐seismic mass movement (Keefer, ; Jibson, ; Bull and Brandon, ). Yet, Stoffel () noted that dendrogeomorphic methods had not yet been applied to co‐seismic rockfalls, and contributions since that time have still been rare (Schneuwly and Stoffel, ; Šilhán et al, , ). This study provides further evidence of co‐seismic rockfalls recorded in tree rings via TRDs.…”

“…Although earthquake effects may be recorded in trees located hundreds of kilometers from epicenters (Sheppard and Jacoby, 1989;Veblen et al, 1992;Kitzberger et al, 1995), the damage severity is low over such broad scales (Allen et al, 1999). Moreover, many of these responses could be caused by climatic factors (Kitzberger et al, 1995;Vittoz et al, 2001), and mass movement frequently occurs without seismicity (Jibson, 1996;Šilhán et al, 2013). Overcoming these challenges requires (1) a focus on sites where earthquakes are most likely to produce tree-ring responses, such as those with co-seismic mass movement (Veblen and Ashton, 1978;Carrara and O'Neill, 2003), unstable substrate (Kitzberger et al, 1995;Vittoz et al, 2001), principal block movement (Bekker, 2004), or particularly strong hydrologic control on tree growth (Stahle et al, 1992;Van Arsdale et al, 1998); (2) consideration of the full range of potential effects on tree growth, including positive impacts (Bekker, 2010); and (3) understanding the connection between site conditions and tree response (Jacoby, 1997).…”

Potential of two submontane broadleaved species (Acer opalus, Quercus pubescens) to reveal spatiotemporal patterns of rockfall activity

“…The term recurrence interval has been used traditionally in avalanche zoning (e.g., Schläppy et al, 2014) and only started to occur in rockfall studies over the past few years (Šilhán et al, 2013;;it is defined as the average time period between two successive events at a specific point (or tree). Individual recurrence intervals (Ri) were calculated for each tree T and following Šilhán et al (2013) as:…”

Reconstruction of rockfall activity through dendrogeomorphology and a scar-counting approach

“…Tree-ring analysis can contribute significantly in the following areas (e.g. Stoffel et al, 2005;Perret et al, 2006;Stoffel, 2006;Luckman, 2008;Ciabocco et al, 2009;Lundström et al, 2009;Moya et al, 2010a;Schneuwly, 2010;Stoffel et al, 2010;Guzzeti and Reichenbach, 2010;Šilhán et al, 2013): identifying and dating historical failure events, reconstructing long time series of rockfall events, determining the rates and spatial distri-bution of rockfall activity, investigating the seasonal variation of rockfall occurrences, providing long-term statistics for the geometry of rockfall trajectories in an area, determining the impact probability of rockfall on trees and fostering our understanding of the protective role of forests.…”