Hydro-geomorphic processes; Dendrogeomorphology; Tree sensitivity; Age/size effects; Growth disturbance; Norway spruce

Dendrogeomorphic reconstructions of debris flows and related hydro-geomorphic processes (i.e. debris floods and flash floods) are widely used in territories with incomplete chronologies and potential future hazards. In recent years, the tree-ring analysis of disturbed trees affected by dangerous geomorphic processes has developed into a discipline with sophisticated methodical approaches and with annual up to monthly accuracy of dating. Field sampling strategies are based on various ranges of sample depth (i.e., different amounts of sampled trees of different age structures). The age and diameter of trees influence the ability of trees to respond to geomorphic processes; therefore, we investigate age-dependent and diameter-dependent tree sensitivity. Our study, for the first time, addresses the sensitivity to hydro-geomorphic processes in detail. We tested 462 individuals of Norway spruce (Picea abies (L.) Karst.) ? a very common species used in the dendrogeomorphic reconstructions ? in the apical part of the medium-high-mountains where there is widespread occurrence of debris flows and debris floods. The tree sensitivity analysis was performed based on the position of growth disturbances within the increment cores of trees (original age and original diameter of the tree before the tree was affected). P. abies shows very high tree sensitivity in the first two decades of the tree lifespan.