Disturbance dynamics of mountain temperate primary forests of the Western and Southern Carpathians and its effect on forest structure and bird assemblages

Mgr. Ondrej Kameniar

Doctoral thesis

Abstract:

Understanding temporal and spatial variations in historical disturbance regimes, dynamics of forest structure and their impact on forest species across primary forest landscapes is imperative to help forecast forest development and adapt forest management in an era of rapid environmental change. Mountain spruce- and beech-dominated forests are forest communities of major importance in temperate Europe. However, information on the differences between their historical disturbance regimes, structures, and biodiversity from complex primary forest landscapes is still incomplete. In order to evaluate the impact of natural disturbances and forest structure on temperate mountain primary forest biodiversity, we established 〜300 permanent study plots in the best preserved mountain primary forests in the Western and Southern Carpathian Mountains. Our dataset combines disturbance history variables, forest structural variables (forest density, tree diameter distribution, tree height, tree age, tree-related microhabitats, deadwood quantity and quality, regeneration) and breeding bird counts. We selected birds as the model group, because they are an important part of forest biodiversity, sensitive to different aspects of forest structure and contain well known indicator and umbrella species. First, using a tree-ring-based approach, we describe 250 years of historical disturbance regime with the focus on disturbance synchronisation in primary beech- and spruce-dominated forest landscape (Section 5.1). Second, we used birds as a model group to investigate the influence of historical disturbances in spruce-dominated primary forests on forest structure and bird assemblages (Section 5.2). As a last step, we compared the forest structure and bird assemblages’ composition in beech- and spruce-dominated primary forests (Section 5.3). The main findings of this thesis are: i) Synchronised disturbances with higher severity were infrequent but critical as drivers of subsequent dynamics across beech- and spruce-dominated primary forest stands within the largest preserved mountain primary forest landscape in temperate Europe. High-severity disturbances were synchronised across both forest types at the landscape scale, while moderate- and low-severity disturbances were asynchronous and random in both spruce- and beech-dominated primary forests. We detected a peak of canopy disturbance across the region at the end of the nineteenth century. Spruce forests had significantly higher average synchrony and higher between-stand variability of synchrony than the beech-dominated forests (Section 5.1). ii) Bird assemblages were significantly influenced by forest structure which was in turn shaped by disturbance dynamics (disturbance frequency, time since the last disturbance and its severity). Early-successional species associated with more open habitats were positively influenced by disturbance-related structure, while some species responded negatively. At the same time, overall abundance, species richness and Shannon diversity of the bird assemblage remained unchanged under variable disturbance histories (Section 5.2). iii) Differences in the forest structure in beech- and spruce-dominated primary forests supported significantly different bird community compositions among these two forest types. Spruce-dominated primary forest had a higher density of cavities and higher canopy openness, while higher tree species richness and more intense regeneration was found in beech-dominated primary forests. Bird assemblages showed higher species richness in beech-dominated primary forests, but lower total abundance. The majority of bird species which occurred in both forest types were more numerous in spruce-dominated forests, but more species occurred exclusively in beech-dominated forests. Further, some spruce-preferring species were found in naturally disturbed patches in beech-dominated primary forest. High forest age, high standing and downed deadwood volumes an

Abstract:

d multiple tree-related microhabitats provide important habitat opportunities for numerous rare bird species in both forest types (Section 5.3). Our results provide valuable insight into forest dynamics and bird assemblages in spruce- and beech-dominated mountain temperate forests in the Carpathians. We suggest that management efforts should recognize protecting large continuous and altitudinally diversified forest landscapes as a necessary measure to ensure the temporal and spatial structural heterogeneity which is driven by a wide range of disturbances, and thereby provide habitat opportunities for numerous species. The diverse and synchronous disturbance activity among two interconnected forest vegetation types highlights the need for complex spatiotemporal forest management approaches that emulate disturbance synchronicity to foster bird assemblages diversity across multiple forest vegetation types within forest landscapes. Thus, protecting existing primary forests, allowing managed forests to attain older ages, and increasing the heterogeneity and availability of primary forest structures in the landscapes are necessary to maintain diverse beech and spruce forest communities in times of accelerating environmental change.

Keywords

Primary forest, natural disturbances, disturbance synchronisation, beech, spruce, forest structure, birds, Carpathians

Jazyk práce: English

Datum vytvoření / odevzdání či podání práce: 3. 3. 2023

Obhajoba závěrečné práce

• Vedúci: prof. Ing. Miroslav Svoboda, Ph.D.
• Oponent: Grzegorz Mikusiński, externi, Ivana Vašíčková, externi, Simon Thorn, externi

Czech University of Life Sciences Prague

Faculty of Forestry and Wood Sciences

Doctoral programme / odbor:
Forestry Engineering / Forest Biology