Tree-ring-based reconstruction of high-magnitude snow avalanches in Piatra Craiului Mountains (Southern Carpathians, Romania)

ABSTRACT Tree-ring analyses were applied in this study, in order to document the spatial–temporal distribution of the past snow avalanche activity along two adjacent avalanche paths in Piatra Craiului Mountains (Southern Carpathians, Romania). The dendrogeomorphic reconstruction performed on 235 Picea abies (L.) Karst. trees is based on the analysis of the effects related to the mechanical impact that snow avalanches had on trees, which resulted in growth anomalies (e.g. scars, callus tissues, onset sequences of tangential rows of traumatic resin ducts, compression wood, growth suppression and release). Tree-growth anomalies found in cores and discs led to the determination of 8 avalanche events within path (1), respectively 10 avalanche events within path (2) spanning the 1950–2016 reconstructed period. Within the paths, a minimum frequency of major snow avalanches was determined and their spatial extent was defined for each reconstructed event. The analysis of weather conditions for two of the events documented in archival records and reconstructed by dendrogeomorphic analyses revealed the role of freezing/thawing periods, combined with heavy snowfalls, in triggering major snow avalanches.