Quantitative anatomy or macroscopic parameters of compression wood of Picea abies (L.) H. Karst.? Defining the optimal parameters for dendrogeomorphic purposes

The quantification of the intensities of tree growth responses to the impact of geomorphic processes is a modern research trend in dendrogeomorphology. It enables a more sensitive assessment of the activity of the studied geomorphic process compared to the traditional use of growth disturbances. The advanced definitions of individual intensity classes of growth disturbances are based exclusively on macroscopic observations. This study evaluates the possibility of anatomical quantification of compression wood (CW) intensity in the case of common spruce (Picea abies (L.) Karst.) and compares it with subjective macroscopic evidence of CW with respect to stem tilting intensity. In total, 25 disturbed (tilted) individuals of P. abies occupying a landslide active during July 1997 were sampled, and 21 of them were analysed. The intensity of external disturbance (stem tilting) was compared against the macroscopic (intensity and duration) and microscopic (quantitative change of the tracheid lumen area and the cell wall proportion) parameters of compression wood suitable for practical application in common dendrogeomorphic analysis. Generally, the macroscopic indices of CW were strongly correlated with stem tilting. The intensity of the anatomical growth response was stronger in the earlywood zone than in the latewood zone. Nevertheless, their dependence on stem tilting was not detected. Results suggest that CW classification based on the quantification of anatomical changes is not possible for dendrogeomorphic purposes. Nevertheless, based on the obtained results, the present study suggests preferring the most intensively tilted trees during future dendrogeomorphic research to obtain the most intensive macroscopic and subjective observable anatomical evidence for studying compression wood.