The environmental, social and economic potential of Dinaric uneven-aged forests along with the complex stand dynamics influenced by different long-term management approaches and environmental factors require comprehensive forest monitoring. This study aimed to explore differences in the current status and recent past dynamics of stand structures between unmanaged and managed mixed fir-beech forests in the Croatian part of the Dinaric Alps using large-scale data from an established monitoring system. From the 74 permanent sample plots distributed within the forest type measured in 2008 and re-measured in 2019, we stratified four strata (types of management regimes): (1) forests out of regular management and tree harvest for at least 30 years, (2) managed state forests on carbonate bedrock, (3) managed state forests on non-carbonate bedrock and (4) managed private forests. In each sample plot, 34 structural attributes were computed to assess indicators of their current status and recent past dynamics of stands in the studied forests. An increasing Q shape diameter distribution with a high number of large and very large trees characterize unmanaged forests and managed forests on non-carbonate bedrock. In managed state forests and private forests, variable (rotated sigmoid) and constant (negative exponential) results were obtained, respectively. Principal component analysis (PCA) distinguished managed and unmanaged forests with decreasing harvest volume and recruitment, increasing basal area, number of very large trees, average diameter at breast height (DBH), crown defoliation of firs and basal area of died beech trees. The current structure, recent and expected stand dynamics in the unmanaged forests (accumulation of standing volume, increase of large diameter trees and large snags, large share of beech, large mean DBH) can be recognized as old-growth attributes. The differences between the studied forest types, potential of both unmanaged and state managed fir-beech forests and approaches to sustain multifunctional forest management in the Dinaric region were discussed.

Forest measurements are essential for monitoring stand dynamics and long-term trends. Errors in tree measurement can seriously affect the outcomes of a forest inventory. This study investigates measurement errors from successive measurements on permanent concentric circular plots based on data from 74 plots in Dinaric uneven-aged mixed fir–beech stands. Tree data errors were detected and corrected. Diameter increment was calculated as a difference in DBH from two successive inventories, and linear regression models were developed based on original and corrected data. Measurement errors were identified in 2.57% of trees, some having a substantial impact on tree volume. Volume discrepancies between original and corrected data were generally minor, where 93.2% of plots in the first and 70.3% in the second inventory required no corrections and volume differences in the overall levels were negligible and statistically non-significant: 0.30 m³/ha in the first inventory (p = 0.550) and 0.05 m³/ha in the second (p = 0.974). Although diameter increment models with original and corrected data differed significantly, model choice resulted in minimal impact on volume increment. Since omitting erroneous measurement data would lead to volume underestimation, data correction is preferable. However, when modeling tree increment, excluding incorrect or doubtful data remains a practical and acceptable approach.

European forests face increasing pressure from climate change and a growing number of invasive alien species. This study examines whether growth patterns and climate–growth relationships in pedunculate oak (Quercus robur L.) changed after the appearance of the oak lace bug (Corythucha arcuata; OLB) in the Spačva basin, Croatia. We analyzed 90 cores from 45 trees in young, middle-aged and old stands, comparing growth before and after 2013 (2000–2023). Structural change analysis identified a 2013 breakpoint in all stands, coinciding with the first regional detection of OLB. Growth trends declined significantly in young (p < 0.001) and middle-aged (p < 0.01) stands, but not in the old stand, and increased variability in tree-level slopes indicated heterogeneous individual responses. Declining mean interseries correlation (Rbar) and expressed population signal (EPS) suggested reduced growth synchrony. Positive correlations with precipitation and negative correlations with temperature strengthened in recent years, overlapping the period after OLB appearance. New earlywood signals emerged: a negative correlation with previous December precipitation and a positive correlation with previous October SPEI-3. As the breakpoint also follows the 2011–2012 drought and precedes the 2014 floods, the link to OLB remains correlative. We hypothesize that late-season drought, favoring OLB activity and limiting non-structural carbohydrate (NSC) replenishment, combined with winter waterlogging, may deplete NSC reserves and constrain growth the following year.