Timing and spatial extent of snow avalanches inferred from tree rings in Sureanu Mountains (Southern Carpathians, Romania)

Abstract

Snow avalanches (SAs) are one of the debris transfer mechanisms that affect steep slopes of alpine and subalpine belts in the Carpathian Mountains. In remote areas of Carpathians where SA activity is poorly documented, the hazard assessment is hampered by the lack of information about past SA events. This is the case in Sureanu Mountains (Southern Carpathians, Romania), where archival records of the past SAs are missing. There is an urgent need for hazard zonation mapping, as in the last decades, recreational activities attracted an increasing number of tourists reaching the SA-prone slopes in this high mountainous area. This study aims to increase the knowledge on SA history by reconstructing SA events based on tree-ring records in five adjacent avalanche paths in Sureanu Mts. For this purpose, Norway spruce trees (Picea abies (L.) Karst.) exhibiting clear signs of mechanical disturbances caused by the past SAs were sampled. Growth anomalies (e.g., scars, tangential rows of traumatic resin ducts, compression wood and growth suppression sequences) were identified within the annual rings of disturbed trees and served to reconstruct spatial extent, frequency, and return periods of SAs within each of the investigated path. In forested areas of Sureanu Mts. without any monitoring, tree-ring methods allowed to reconstruct spatio-temporal activity of SAs with annual resolution. This information may significantly improve the knowledge of the avalanche regime and contribute to the avalanche hazard zonation in the studied area.