Influence of Tree Attributes on Silver Fir (Abies alba Mill.) Transitioning to Higher Defoliation Classes Determined by Logistic Regression

The age, size and morphology of trees, including crown dimensions, can influence defoliation. In Croatia, the selection management silver fir (Abies alba Mill.) forests involves pure or mixed stands, either which be affected by various disturbances, resulting in unbalanced stand structures. aim this study was to estimate probability trees transitioning from one defoliation class next, examine tree attributes on that process analyze changes survival over time. conducted a 18-year period (1990–2007) two sites with contrasting structures: uniform dominant share (Site A) an uneven-aged beech–fir B). Logistic regression used model transitions between classes. Uniform structure increased likelihood higher class, limited dependence position. contrast, suppressed central stands were more likely transition due greater competition them. Diameter at breast height (DBH) found significant predictor classes, linear trend increasing DBH. Crown position length also predictors changing observed differences occurring structure. To ensure balanced enhance vitality, careful consideration easily measurable elements such as DBH, length, is imperative when selecting for felling.