An Evaluation of Dendroecological Indicators of Snow Avalanches in the Swiss Alps

CASTELLER, A.; STOECKLI, V.; VILLALBA, R.; MAYER, A.C.

Arctic Antarctic and Alpine Research

University of Colorado

Lugar: Boulder, Colorado; Año: 2007 vol. 39 p. 218 - 228

1523-0430

Avalanche records are important for land-use planning and risk management in mountainous areas. Written records on dates, disturbed area, and pressure patterns of past snow avalanches are scarce. Tree rings can be used to complement written records on past avalanche activity. We conducted two case studies at documented avalanche tracks in the Swiss Alps to determine the most valuable dendroecological indicators for reconstructing past avalanche events. Both tracks were impacted by avalanche events in 1951 and 1999, the two most exceptional avalanche years in recent Swiss history. The difference in tree age among the track, border, run-out, and control sectors was a valuable indicator of the area impacted by past avalanches, but not a useful tool to establish dates of avalanche occurrences. Comparisons of reaction wood formation, changes in stem eccentricity, and presence of traumatic resin canals among sectors showed significantly larger values of these indicators after the 1999 event in the track areas, and in minor degree in the border areas. Abrupt growth changes following the 1999 event were identified in most disturbed trees. Growth releases were commonly accompanied by the formation of reaction wood. Tree-ring evidences for the 1951 avalanche event were limited mainly due to the removal of debris by local communities. The intensity of avalanche events was difficult to determine using tree-ring indicators. Although dates and areas impacted by documented avalanche events were sometimes assessed using single indicators, more precise reconstructions result from the combined use of several dendroecological indicators.