Forest dieback processes in the Central European Mountains in the context of terrain topography and selected stand attributes

Forest dieback of mountainous areas is a common problem in almost all regions of the world. This process is characterized by high variability and is independent of whether the process is caused by climate changes, insect pests or human impact on the environment, particularly environmental pollution. This state of affairs is probably influenced not only by unusual atmospheric conditions, unusual stressors or species composition but also by many factors that have not been identified to date. Even in the case of relatively small mountainous areas in Central Europe with similar species composition, climatic conditions, and stressors, the process of tree dieback might have different characteristics and causes. During the analyses of such phenomena, remote sensing technologies, such as LiDAR and aerial imagery, which have become increasingly popular and precise, are helpful. Additionally, access to geographic information systems has become common by forest owners. Using previous research, as well as airborne laser scanning data, aerial imagery and Polish State Forests IT system (SILP) data, it was possible to analyze almost 200,000 dead trees inventoried in the areas of the Western Sudety, Eastern Sudety, Beskid Slaski and Beskid Zywiecki mountain ranges. Despite the fact these areas are located relatively close to each other, they differ in terms of forest structure and in terms of period of mass deforerstation. The impact of detailed landform, age, and species composition were considered, and complemented many other factors, which eventually enabled the development of three different models for each of the analyzed areas. The models depict the influence of the respective factors of the environment on Norway spruce dieback in the Central Europe mountains. The obtained results show that there are certain factors, such as e.g. age or stocking, which increase the probability of damage in all three areas, but certain ones are significant exclusively for one or two areas, such as e.g. altitude, which has an influence on the likelihood of damage only in the Western Sudety and the Western Beskidy Mountains. What is interesting, the altitude does not impact unequivocally on the share of dead spruces itself, since in the case of the Western and Eastern Sudety, the increase of altitude is positively correlated with the share, whereas in the case of the Western Beskidy Mountains, the correlation is negative. An important fact is that the increase of deciduous species' share impacts positively on the forest dieback of spruces on all analyzed areas.