Can we distinguish between tree-ring eccentricity developed as a result of landsliding and prevailing winds? consequences for dendrochronological dating

The aim of our study was to compare patterns of tree-ring eccentricity developed in Norway spruce trees as a result of landsliding with the one caused by the prevailing wind (in 2 study sites), and with the normal growth of trees (in 2 reference sites). We sampled 20 trees per study site and 10 per reference site. Two cores were taken from each tree (120 cores in total) from the upslope and downslope, windward and leeward sides of stems. Ring widths measured on opposite sides of stems were compared using the method of percent eccentricity index. Graphs of the index obtained for individual trees were analysed. Statistical indicators were calculated for a percent eccentricity index. Disturbance events were dated and the response index was calculated. The results show that the patterns of eccentricity developed as a result of the prevailing winds and due to landsliding differ from one another and from the reference sites. The results suggest that the impact of the prevailing wind on tree growth is more severe than the impact of landsliding. The difference may result from the slow-moving character of the landslide under study. The results, however, indicate that wind impact should be taken into account in dendrogeomorphic research and that the impact of mass movements should be considered in dendroecological studies on wind.