The crown class assessment is a key element in forestry practice. It is a traditional method that finds application in thinning plans, assessment of site index, tree competition, or crown condition. Assigning trees into a given class is done during field surveys and requires precision and experience to avoid inaccuracy. Therefore, Kraft’s system has often been criticized and modified. Thus, in our study, we aimed to analyse whether the directly measured traits of trunk and crown of oak trees (Quercus robur L.) can be applied to crown class assessment. For this purpose, we used the principal component analysis (PCA) and nonlinear kernel principal component analysis (KPCA) based on measurable traits of trunk and crown, i.e., the height of the tree, the diameter at breast height, the length of the crown, and the field crown projection area. In total, we measured 286 mature trees in three oak stands located in western Poland. Results indicate that all chosen traits of trunk and crown allowed, though not always perfect, to assign the trees into given crown classes. The greatest contribution to crown class distinction had the diameter at breast height and the parameters of crown, i.e., and the field crown projection area. Furthermore, results show that the best method of assigning the trees into biosocial classes is the KPCA Gauss, considering the percentage explanation of the total variability, and KPCA Laplace, considering the visual division. In the latter, the multivariate analysis resulted in a similar crown class assignment as the field-assigned method. However, its application requires measurements that make it neither cheaper nor faster than a traditional crown class assessment. It indicates that a traditional field-assigned method, despite its subjectivity, should continue to be of great importance in forestry practice. Moreover, the alternative traits of trunk and crown can be a potentially useful statistical substitute for crown class assessment.

Keywords: crown class, oak stand, trunk and crown traits, multivariate methods

   The aim of this study was to assess the quality of Scots pine (Pinus sylvestris L.) wood depending on the age of trees, forest site conditions and social class of tree position in the stand. Analyses were based on the determination of specific density and static bending strength, as well as the strength quality coefficient. It was to determine changes in physical and mechanical properties of timber depending on tree age as well as growth conditions reflected in the forest site such as fresh mixed coniferous forests and fresh mixed broadleaved forests. Experimental plots were established in 6 localities with 30, 40 and 60-year-old trees. In each of the stands, a 1-hectare experimental plot was established. Based on the measured DBH and tree height, dimensions of three mean sample trees were calculated, while the classification of social class of tree position in the stand developed by Kraft (1884) was also applied. Analyses were conducted on wood samples with 12 % moisture content. Strength tests on wood samples were performed on an Instron 33RH204 universal strength testing machine. A detailed analysis showed properties of pine wood are improved with an increase of tree age in both forest sites. Statistically significant differences were observed for wood density and static bending strength. More advantageous properties were observed for wood of pines from the less fertile forest site, i.e., fresh mixed coniferous forests. Density and static bending strength were markedly determined by tree age and growth conditions. The static bending strength quality coefficient from pines growing in the fresh mixed coniferous forests increased between 30 and 40 years, similarly as it was for the fresh mixed broadleaved forests, while between 40 and 60 years, it deteriorated for the fresh mixed coniferous forests. Wood density from the fresh mixed coniferous forests was by 3 % to 7 % greater than pines growing in fresh mixed broadleaved forests. In turn, static bending strength of wood from pines growing in fresh mixed coniferous forests was by 4 % to 10 % greater than trees from the fresh mixed broadleaved forests.

Keywords: Scots pine, wood properties, forest site, Poland

   Quercus pontica K. Koch is a relict plant species which is classified as vulnerable (VU) in Turkey. Within the scope of this study it needed to be investigated are there variations in leaf morphological characteristics within and among Q. pontica populations. Variation in leaf traits in relation to seven different natural provinces was identified. In total, 99 individuals were selected, and 30 leaves were collected from each shrub to determine leaf variations in Q. pontica populations. Mean values for petiole length (1.07 cm), leaf length (17.13 cm), lamina length (16.13 cm), leaf width (8.10 cm), leaf area (93.76 cm²), leaf vein angle (54.22 degree), total number of primary veins (38.72), total number of teeth (40.73), petiole ratio (6.34%), relative length of lamina at largest width (50.50%), and percentage of venation (98.65%) were determined in all populations. The results of the analysis of variance showed significant differences (p < 0.01) among individuals within populations for all leaf characteristics. Variations among populations were detected by cluster analysis and principal components analysis. According to the analysis results, the 11 populations were grouped in three categories. Using correlation analysis, statistically significant relationships between leaf traits were determined. In this study, we detected no significant relationship between environmental factors (altitude, aspect, annual temperature and annual precipitation) and leaf traits.

Keywords: leaf morphology, Quercus pontica, relict, variation

   Canopy gaps play a crucial role in forest dynamic processes and help preserve biodiversity, influence nutrient cycles, and maintain the complex structure of the forests. This study aimed to quantify the gap dynamics, regeneration establishment, and gap closure in a natural old-growth Hyrcanian forest in the north of Iran. We used a repeated inventory of gap size-frequency and fraction in beech (Fagus orientalis) dominant forest over a 9-year interval (2010–2019). The total gap area documented in 2010, 2016, and 2019 was 2,487, 6,890, and 8,864 m², respectively. The gap area ranged from the smallest sizes of 139, 83, and 153 m² to the largest sizes 906, 1,668, and 871 m² in 2010, 2016, and 2019, respectively. Gap fraction significantly increased from 0.52%, 1.93%, and 3.7% in 2010, 2016, and 2019, respectively. The size distribution of gaps was strongly skewed to the medium class (200–500 m²), with approximately 60% of the gaps. Results revealed that total regenerations are not in correlation with gap size. Small gaps were closed within a few years through rapid horizontal canopy expansion of neighboring beech trees. The gap closure rate decreased by increasing the gap size (70% in 71 m 2 to 10% in 1,600 m²). The highest density and greatest regeneration growth occurred mostly along the eastern part of gaps. The spatial distributions of regeneration density demonstrated differences in different gap size classes, which probably resulted from heterogeneity in the microenvironment within the gap and the differences in the regeneration responses to these variations. This investigation provided useful data for managing natural regenerations based on forest sustainability. The changes in gap patterns observed between 2010 and 2019 highlight the high value of repeated gap inventories for better comprehending the disturbance regeneration and dynamics of natural gaps.

Keywords: Gap size, Gap development, Special distribution, Regeneration density, Gap closure