Structure, dynamics, and disturbances in the primary forests of eastern and southeastern Europe

MSc. Ruffy Rodrigo

Disertační práce

Abstract:

Forest structure, including tree size distributions such as diameter at breast height (DBH) and age distributions, is a critical indicator of ecological change and forest dynamics. In primary temperate forests, these structural attributes reflect the cumulative effects of historical disturbances and ongoing environmental shifts. Understanding these dynamics is essential for assessing forest resilience and predicting future changes in forest structure and ecosystem functioning. The primary goal of this dissertation is to explore the impact of past disturbances on forest structural attributes—specifically DBH and age distributions—across primary temperate mountain forests in Europe, particularly in the Carpathian Mountains. This dissertation is divided into three major papers. The first paper focuses on how historical mixed-severity disturbances have shaped the DBH distribution in Norway spruce-dominated forests in the Carpathian Mountains. Using a dendroecological dataset from 339 plots across 28 stands (7,845 trees), a linear mixed-effects model was performed to analyze the impact of disturbance parameters, including disturbance severity, timing, and recent disturbances, on DBH distribution. The analysis revealed that historical disturbances had a strong and significant effect on the current diameter distribution shapes at the plot level. High-severity disturbances were associated with unimodal diameter distributions, whereas low-severity disturbances resulted in reverse J-shaped distributions. These findings have important implications for forest management, particularly in terms of tree size heterogeneity, biomass storage, and productivity. The second paper examines the impact of past disturbance severity, including the most recent and maximum disturbance severities, and timing, such as time since the last disturbance and time since the maximum disturbance, on present tree size distributions in beech-dominated forests in the Carpathians. The study utilized a dataset from the REMOTE Network, which includes 238 permanent sample plots across 23 stands (11,755 live trees) in Slovakia and Romania. A two-parameter Weibull function was fitted at the plot level, and linear mixed modeling was applied. The analysis revealed that mixed-severity disturbances historically shaped these forests, with significant variability in both severity and timing observed across different spatial scales. The interaction between the time since the last disturbance and the maximum disturbance severity was identified as the most influential factor driving current tree size distributions. These findings highlight the complex dynamics governing forest ecosystems and suggest that shifts towards more moderate-severity disturbances, as predicted by climate change scenarios, could increase structural complexity at both stand and landscape levels. The third paper investigates the impact of past disturbance regimes on stand-level age distributions in temperate mountain forests across the Carpathian Mountains. Data from 21,727 trees sampled across 590 plots (500 m², 1000 m², 1500 m²) within 55 stands in Romania (23 stands), Slovakia (27 stands), and Ukraine (5 stands) were analyzed. The study examined the influence of disturbance parameters—including maximum and most recent disturbance severities, time since the last disturbance, and time since the maximum disturbance—on stand age distributions across different forest types (beech and spruce) and regions. The results reveal significant variability in age distributions across the Carpathians, with spruce forests exhibiting greater variability compared to the more stable age distributions observed in beech forests. Based on the Akaike Information Criterion, among the disturbance parameters analyzed, time since the last disturbance emerged as the most influential factor, significantly affecting the Weibull shape parameter, which characterizes the stand age distribution. In contrast, the severity of

Abstract:

disturbances—both recent and maximum—showed minimal impact on age distribution, suggesting that while disturbances occur, their timing rather than intensity most profoundly influences forest structure. These findings highlights the importance of incorporating temporal aspects of disturbance into forest management practices to ensure the sustainability and resilience of these temperate mountain forests. This dissertation highlights the profound impact that historical disturbances have had on the structural dynamics of primary temperate forests in the Carpathian Mountains. Across all three studies, it is evident that the severity and timing of past disturbances have shaped the present diameter and age distributions of Norway spruce- and beech-dominated forests. High-severity disturbances tend to create simpler, unimodal distributions, while low-severity disturbances maintain more complex, reverse J-shaped distributions, indicating greater structural heterogeneity. These findings underscore the importance of considering both historical disturbance legacies and future climate change scenarios in forest management strategies. By understanding how past disturbances influence present forest structure, we can better predict and manage the resilience and sustainability of these critical ecosystems in the face of ongoing environmental changes. Tailored management approaches that account for regional and ecological differences will be essential for preserving the diversity, productivity, and stability of Europe's mountain forests

Keywords

Past disturbances, dendrochronology, dendroecology, forest structure, weibull distribution, mixed-modelling, Norway spruce forest, Carpathians mountains, forest dynamics, tree size distribution, primary forests, European beech forests

Jazyk práce: angličtina

Datum vytvoření / odevzdání či podání práce: 3. 10. 2024

Obhajoba závěrečné práce

• Vedoucí: prof. Ing. Miroslav Svoboda, Ph.D.

Česká zemědělská univerzita v Praze

Fakulta lesnická a dřevařská

Doktorský studijní program / obor:
Forestry Engineering / Forest Biology