Indeks dekoncentryczności przyrostów rocznych drzew - narzędzie do identyfikacji współczesnych ruchów osuwiskowych

Abstract

Stem shapes and tree-ring width were examined in spruces (Picea abies) growing on landslide-affected slopes in Moravskoslezské Beskydy (Western Carpathians, Czech Republic). In contrast to spruce trees growing on a stable slope, they are tilted upslope – in the upper parts of slopes, while in the near-channel zone they are bent downslope. It was found that on the underside of stems, influenced by gravity, wider tree rings are produced. The first years of tree-ring eccentricity were identified as the period of the initiation/reactivation of landsliding. In order to date them dendrochronologically, the eccentricity index of tree rings [%] and its yearly variation [%] were used. The proposed method of dendrogeomorphic analysis of landslides enables one to obtain the dynamic description of slopes and to study landslide activity, not only contemporary one, but also in the past. Depending on the stand age, it is possible to study the last tens to hundreds of years. Percent eccentricity index enables one to present and compare the intensity of mass movements between individual trees, study sites and landslide slopes – contrary to the reaction wood analyses – so far popular dendrogeomorphic method. Using eccentricity index and its yearly variation, it is possible to determine the presence of contemporary landsliding on slopes, to study its temporal and spatial variability and to outline the zone with domination of mass movements induced by fluvial erosion. The proposed method can be used in practice, in identification of contemporary active landslides, which can threaten existing or planned infrastructure and facilities.