Disturbance dynamics, stand structure and growth pattern of the primary forest in Europe

Volodymyr Trotsiuk

Doctoral thesis

Abstract:

Disturbances influence forest structure, dynamics, ecosystem function and services. There is widespread concern that climate change is leading to shifts in natural disturbance regimes, and subsequent changes to the structure, composition, and function of forest ecosystems. How past disturbances have shaped forests at the scale of decades or centuries is crucial to understanding long-term forest development and biomass accumulation. This understanding will increase the capacity to manage forests more resilient to climate change. The main objective of the thesis is to reconstruct and characterize historical disturbance regime in the mountain Norway spruce forest and to describe the impact of disturbance legacies on ecosystem services. Analysis of tree-ring widths has been shown to be the only approach to reconstruct forest history with annual resolution over centuries. Thus I first aimed to i) test the efficacy of tree-ring methods for detecting past disturbance events (section 5.1); then ii) access spatiotemporal characteristics of disturbance regime on the plot, stand, landscape, and region level (section 5.2); and finally iii) evaluate the influence of natural disturbances on the magnitude and dynamics of biomass accumulation and maintaining lichen survival and diversity (section 5.3). To achieve first aim I compare each method against a dataset of tree growth with likelihood of a growth release calculated based on competition change from an experimental canopy disturbance mimicking a hurricane in a northern hardwood forest Massachusetts, USA. For the following aims, I compile a globally unique dendroecological dataset, which includes 12000 cored trees sampled over 560 plots located across the Czech Republic, Slovakia, Ukraine, and Romania, to examine regional scale patterns of past disturbance in primary Norway spruce forests, and impact of its legacies on ecosystem services. The main founding of the thesis are: i) Each tree-ring method demonstrated efficacy in the detection of canopy disturbance across experimental and observational data. Recognizing the conditions under which each disturbance detection method performs best will help avoid possible pitfalls related to reconstructing past disturbance histories and facilitate comparisons of forest histories using different methods (section 5.1.1). ii) Evidence of a combination of variable severity disturbances that fails to fit the classical scheme of gap or patch dynamics with sharply defined sizes and borders, but is more consistent with a mixed severity disturbance regime across the landscape (sections 5.2.1 & 5.2.2). Central and Eastern Europe mountain spruce forest has been affected by series of mixed severity disturbances; these events were clustered in a period from 1800 to 1900, resulting in a broad scale peak and associated non-equilibrium of age and biomass across the regional scale under high probability to be disturbed in the near feature (section 5.2.3). iii) The period of time that a tree is in the canopy, and not tree age, modulates the trajectory of tree level AGBI. Time since disturbance and disturbance severity are important co-predictors for stand-level AGBI and AGB (section 5.3.1). Tree age was the strongest variable influencing lichen diversity and composition. Recent (<80 years ago) severely disturbed plots were colonized only by the most common species, however, old trees (>200 years old) that survived the disturbances served as microrefuges for the habitat specialized and/or dispersal limited species (section 5.3.2). To conclude, recognizing the conditions under which each disturbance detection method performs best will help avoid possible pitfalls related to reconstructing past disturbance histories and facilitate comparisons of forest histories using different methods. It is critical to better understand past disturbance legacies over the larger region to assess the potential of future outbreaks and to guide decisions on post disturba

Abstract:

nce management in these key conservation areas. Management should recognize disturbances as a natural part of ecosystem dynamics in the mountain forests of Central Europe, account for their stochastic occurrence in management planning, and mimic their patterns to foster biodiversity in forest landscapes. Even late-seral forests can rapidly regain biomass lost to low intensity disturbance, and additionally survival of old trees after disturbances could maintain and/or recover large portions of epiphytic lichen biodiversity even in altered microclimates.

Abstract:

Disturbances influence forest structure, dynamics, ecosystem function and services. There is widespread concern that climate change is leading to shifts in natural disturbance regimes, and subsequent changes to the structure, composition, and function of forest ecosystems. How past disturbances have shaped forests at the scale of decades or centuries is crucial to understanding long-term forest development and biomass accumulation. This understanding will increase the capacity to manage forests more resilient to climate change. The main objective of the thesis is to reconstruct and characterize historical disturbance regime in the mountain Norway spruce forest and to describe the impact of disturbance legacies on ecosystem services. Analysis of tree-ring widths has been shown to be the only approach to reconstruct forest history with annual resolution over centuries. Thus I first aimed to i) test the efficacy of tree-ring methods for detecting past disturbance events (section 4.1); then ii) access spatiotemporal characteristics of disturbance regime on the plot, stand, landscape, and region level (section 4.2); and finally iii) evaluate the influence of natural disturbances on the magnitude and dynamics of biomass accumulation and maintaining lichen survival and diversity (section 4.3). To achieve first aim I compare each method against a dataset of tree growth with likelihood of a growth release calculated based on competition change from an experimental canopy disturbance mimicking a hurricane in a northern hardwood forest Massachusetts, USA. For the following aims, I compile a globally unique dendroecological dataset, which includes 12000 cored trees sampled over 560 plots located across the Czech Republic, Slovakia, Ukraine, and Romania, to examine regional scale patterns of past disturbance in primary Norway spruce forests, and impact of its legacies on ecosystem services. The main founding of the thesis are: i) Each tree-ring method demonstrated efficacy in the detection of canopy disturbance across experimental and observational data. Recognizing the conditions under which each disturbance detection method performs best will help avoid possible pitfalls related to reconstructing past disturbance histories and facilitate comparisons of forest histories using different methods (section 4.1.1). ii) Evidence of a combination of variable severity disturbances that fails to fit the classical scheme of gap or patch dynamics with sharply defined sizes and borders, but is more consistent with a mixed severity disturbance regime across the landscape (sections 4.2.1 & 4.2.2). Central and Eastern Europe mountain spruce forest has been affected by series of mixed severity disturbances; these events were clustered in a period from 1800 to 1900, resulting in a broad scale peak and associated non-equilibrium of age and biomass across the regional scale under high probability to be disturbed in the near feature (section 4.2.3). iii) The period of time that a tree is in the canopy, and not tree age, modulates the trajectory of tree level AGBI. Time since disturbance and disturbance severity are important co-predictors for stand-level AGBI and AGB (section 4.3.1). Tree age was the strongest variable influencing lichen diversity and composition. Recent (<80 years ago) severely disturbed plots were colonized only by the most common species, however, old trees (>200 years old) that survived the disturbances served as microrefuges for the habitat specialized and/or dispersal limited species (section 4.3.2). To conclude, recognizing the conditions under which each disturbance detection method performs best will help avoid possible pitfalls related to reconstructing past disturbance histories and facilitate comparisons of forest histories using different methods. It is critical to better understand past disturbance legacies over the larger region to assess the potential of future outbreaks and to guide decisions on post disturba

Abstract:

nce management in these key conservation areas. Management should recognize disturbances as a natural part of ecosystem dynamics in the mountain forests of Central Europe, account for their stochastic occurrence in management planning, and mimic their patterns to foster biodiversity in forest landscapes. Even late-seral forests can rapidly regain biomass lost to low intensity disturbance, and additionally survival of old trees after disturbances could maintain and/or recover large portions of epiphytic lichen biodiversity even in altered microclimates.

Keywords

Biodiversity, carbon sequestration, dendroecology, disturbance ecology, Norway spruce, forest dynamics, old-growth forest, tree-rings

Keywords

Biodiversity, carbon sequestration, dendroecology, disturbance ecology, Norway spruce, forest dynamics, old-growth fores, tree-rings

Language used: Czech

Date on which the thesis was submitted / produced: 5. 7. 2017

Thesis defence

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

Czech University of Life Sciences Prague

Faculty of Forestry and Wood Sciences

Doctoral programme / field:
Forestry Engineering / Silviculture