Dendrogeomorphogical assessment of snow avalanche activity in Parâng Mountains

Abstract

Abstract-In the alpine area of the Romanian Carpathians in general and Parâng Mountains in particular, snow avalanches play an important role in the landscape and ecosystems dynamics. When the snow masses reach the treeline, they are stopped by forests and cause severe disturbances or even death to the trees. If snow avalanches affect repeatedly the same forest area, an avalanche path takes shape. Inside it, the snow avalanche activity is clearly witnessed by forest vegetation. The trees record in their rings signs of past avalanche activity. In particular forest areas, these are the only avalanche event records that can be investigated in order to improve the knowledge regarding past avalanches. Dendrogeomorphology proved to be the most reliable tool for this scope, allowing yearly reconstructions of avalanche frequency and spatial extension. The present study aims to accomplish tree ring reconstruction of snow avalanche in two avalanche paths located on the southern slope of Parâng Mountains, in the proximity of Păpușa Peak (2135 m a.s.l.), one facing southwest and the other facing southeast. The first mentioned avalanche path is crossed by Transalpina road. Rânca ski resort is placed on a convex slope between these avalanche paths. In the southwestern path, 58 Norway spruces (Picea abies (L.) Karst.) showing severe disturbances caused by snow avalanches were sampled. In the southeastern path, other 52 spruces were sampled. Based on the sampled trees growth disturbances (e.g. scars, tangential rows of traumatic resin ducts, compression wood, growth suppression), the avalanche event chronology was developed for each avalanche path. Then, using a new GIS-based approach, the snow avalanche frequency and return periods were calculated and mapped. The results of this study can contribute to avalanche hazard mapping in the study area and should prevent freeride skiers regarding the snow avalanche risk on southern slopes of Păpușa Peak.