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Université de Fribourg

Changes in wood anatomy in tree rings of Pinus pinaster Ait. following wounding by flash floods

Ballesteros, J.A. ; Stoffel, Markus ; Bodoque, J.M. ; Bollschweiler, Michelle ; Hitz, Oliver ; Díez-Herrero, A.

In: Tree-Ring Research, 2010, vol. 66, no. 2, p. 93-103

This paper analyzes the anatomical response of Pinus pinaster Ait. following wounding by flash floods. A total of 14 wood samples were taken from 14 different scarred trees located on the river banks of the Arroyo Cabrera torrent (Spanish Central System). In addition, 20 increment cores were collected from undisturbed and healthy P. pinaster trees to build a local reference chronology. For the...

Université de Fribourg

Tree-ring reconstruction of past lahar activity at Popocatépetl volcano, Mexico

Bollschweiler, Michelle ; Stoffel, Markus ; Vázquez Selem, Lorenzo ; Palacios, David

In: The Holocene, 2010, vol. 20, no. 2, p. 265-274

Lahars represent a major threat on the slopes of volcanoes all over the world. In order to realistically assess hazards, knowledge on the occurrence and timing of past lahar activity is of crucial importance. However, archival data on past events is usually scarce or completely missing. Tree-ring records have repeatedly proved to be a reliable data source for the reconstruction of past geomorphic...

Université de Fribourg

Tree-ring reconstruction of past debris flows based on a small number of samples—possibilities and limitations

Stoffel, Markus ; Bollschweiler, Michelle

In: Landslides, 2009, vol. 6, no. 3, p. 225-230

Tree-ring analyses have often been used in the past for the reconstruction of spatiotemporal patterns of previous debris-flow activity, often yielding very precise and extensive data for torrents where information on former activity was largely missing. Unless dendrogeomorphology is slated for multimillion Euro developments, the large sets of tree-ring series that are usually used in these...

Université de Fribourg

Dating past geomorphic processes with tangential rows of traumatic resin ducts

Stoffel, Markus

In: Dendrochronologia, 2008, vol. 25, no. 1, p. 53-60

Past activity of geomorphic processes can be reconstructed on tree-ring series using the presence of injuries, reaction wood or abrupt changes in the annual increment. The analysis of these features provides valuable data on years with process activity. In contrast, an intra-annual dating has so far normally only been possible through the analysis of injuries. In this technical note, it is shown...

Université de Fribourg

Formation and spread of callus tissue and tangential rows of resin ducts in Larix decidua and Picea abies following rockfall impacts

Schneuwly, Dominique M. ; Stoffel, Markus ; Bollschweiler, Michelle

In: Tree Physiology, 2009, vol. 29, no. 2, p. 281-289

After mechanical wounding, callus tissue and tangential rows of traumatic resin ducts (TRDs) are formed in many conifer species. This reaction can be used to date past events of geomorphic processes such as rockfall, debris flow and snow avalanches. However, only few points are known about the tangential spread or the timing of callus tissue and TRD formation after wounding. We analyzed 19 Larix...

Université de Fribourg

Unraveling the patterns of late Holocene debris-flow activity on a cone in the Swiss Alps: chronology, environment and implications for the future

Stoffel, Markus ; Conus, Delphine ; Grichting, Michael A. ; Lièvre, Igor ; Maître, Gilles

In: Global and Planetary Change, 2008, vol. 60, no. 3-4, p. 222-234

Debris-flow activity on the forested cone of the Ritigraben torrent (Valais, Swiss Alps) was assessed from growth disturbances in century-old trees, providing an unusually complete record of past events and deposition of material. The study of 2246 tree-ring sequences sampled from 1102 Larix decidua Mill., Picea abies (L.) Karst. and Pinus cembra ssp. sibirica trees allowed reconstruction of 123...

Université de Fribourg

Wood anatomical changes in roots of European ash (Fraxinus excelsior L.) after exposure

Hitz, Oliver M. ; Gärtner, Holger W. ; Heinrich, Ingo ; Monbaron, Michel

In: Dendrochronologia, 2008, vol. 25, no. 3, p. 145-152

Global changes have distinct influence on fluvial processes in torrents causing erosion on slopes and riverbanks even in forested areas. Continuous as well as discontinuous erosion of riverbanks covered by trees frequently results in destabilisation and finally cause the trees affected to tip over. These uprooted trees may lead to a blockage of the river and, in the case of a collapse of the...

Université de Fribourg

Application of ash (Fraxinus excelsior L.) roots to determine erosion rates in mountain torrents

Hitz, Oliver M. ; Gärtner, Holger W. ; Heinrich, Ingo ; Monbaron, Michel

In: Catena, 2008, vol. 72, no. 2, p. 248-258

Due to the effect of global change, the potential risk of natural hazards occurring in alpine areas is expected to increase to an even higher risk-level than has been recorded during the last century. These global changes potentially also have distinct influences on fluvial processes in torrents causing erosion on slopes and riverbanks in forested areas. Dating the time of root exposure along...

Université de Fribourg

Reconstructing spatio-temporal patterns of debris-flow activity using dendrogeomorphological methods

Bollschweiler, Michelle ; Stoffel, Markus ; Ehmisch, Melanie ; Monbaron, Michel

In: Geomorphology, 2007, vol. 87, no. 4, p. 337-351

Debris flows are a major threat in many parts of the Alps, where they repeatedly cause severe damage to infrastructure and transportation corridors or even loss of life. Nonetheless, the spatial behavior of past debris-flow activity and the analysis of areas affected during particular events have been widely neglected in reconstructions so far. It was therefore the purpose of this study to...