Armelle Decaulne

Ó Eggertsson

Þ Saemundsson

K Laute

A A Beylich

Olympiu Pop

Emmanuelle Defive

Sébastien Larrue

The EuroDendro project -Snow-avalanche frequency and magnitude in European Middle Mountain unravelled by dendrogeomorphological analyses

niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

  aims to detect the signal of recent snow-avalanche activity within the analyses of tree rings. In mountain areas, even middle mountains, snow avalanches are a common process & pose serious hazards & risks in recently occupied sectors, either for residence or recreation purposes. Where (i) geomorphological evidence of snow-avalanche occurrence are scarce, (ii) historical records are poor & (iii) trees are colonizing part of the slopes, tree-ring analyses appear as a good alternative to reveal the recent snow-broad-leaved trees, which attracted seldom attention in dendrogeomorphology related to snow-avalanche activity: birch (Betula pubescens) in N Iceland birch (Betula pubescens) & alder (Alnus) in W Norway beech (Fagus sylvatica) in NE Cantal -France (ii) coniferous trees in little explored areas where broadleaved trees are unavailable: spruce (Picea abies) Northern Iceland, in the Dalsmynni valley, the Ljósavatnskarð pass & the southern Fnjóskadalur valley, (B) Western Norway, at the bottom of Nordfjord, in Erdalen & Bødalen, (C) Central Romania, in the Southern Carpathians, in the Bâlea valley, Făgărăş massif, (D) Central France, in the Northeastern valleys of the Cantal massifpoor tree cover, even in the distal runout zone Most of the trees are very young (+/-30 years) Reaction wood formation on the downhill side = recurrent stress due to snow-avalanche activity. Oldest trees signal several avalanchy periods, especially from 1920s to early 1950s again during the 1980s. Spatial distribution of major impact areas affecting trees in the Bødalen valley, Norway. Background image is © Norwegian land survey Main dendrogeomorphological investigated paths in the Bødalen valley, Norway. © Katja Laute Map of the tree morphology, reflecting damages due to snow-avalanche occurrence on a colluvial cone in the Dalsmynni valley, Iceland. Background images are © skipulag.is Birches felled by a snow avalanche in the Bødalen valley, Norway. © Armelle Decaulne Topped & tilted spruce in the distal part of the path, Romania. © Armelle Decaulne Asymetric branch distribution on a spruce in Romania. © Armelle Decaulne Scars on the trunk & main branches in the snow-avalanche path. © Armelle Decaulne