Harald Bugmann

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Bugmann

First Name

Harald

ORCID

0000-0003-4233-0094

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03535 - Bugmann, Harald / Bugmann, Harald

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Publications 1 - 10 of 62

Wildeinfluss auf Waldverjüngung nimmt in der Schweiz weiter zu
Krättli, Sandro; Bugmann, Harald; Conedera, Marco; et al. (2025)
Schweizerische Zeitschrift für Forstwesen
Die Waldverjüngung wird in vielen Regionen durch Wildverbiss stark beeinflusst – Tendenz steigend. Trotz me thodischer Herausforderungen zeigen die Studien in diesem Heft ein einheitliches Bild: Besonders die klima resistenteren Baumarten wie Eiche, Ahorn und Weisstanne sind betroffen. Das gefährdet die Schutzfunktion und verlangsamt oder blockiert sogar die Umwandlung in baumartenreiche Mischwälder und somit die Anpassung an den Klimawandel. Vor allem in den Alpen und teilweise auch im Mittelland können die waldbaulichen Ziele nicht erreicht werden. Die verfügbaren heterogenen Daten erlauben derzeit keine detaillierte, regional differen zierte Beurteilung des Wildeinflusses. Um auch weniger starke Veränderungen ausweisen und vergleichen zu können, ist die Schaffung eines schweizweiten koordinierten Monitoringsystems erforderlich. So wird es auch in kantonsübergreifenden Wildräumen möglich, den Erfolg der Massnahmen zu beurteilen. Jagdlich wie forst lich ist genug Wissen für das Handeln vorhanden. Dringend erforderlich sind gezielte jagdliche Massnahmen zur Senkung der Wildbestände in den betroffenen Regionen, eine aktive Waldbewirtschaftung sowie eine Stär kung des konstruktiven Dialogs zwischen Jagd und Forstdienst. Zudem ist zu prüfen, welche Anpassungen an den jagdlichen und forstlichen Grundlagen, Gesetzen, Managementplänen und Umsetzungspraktiken notwen dig sind, um die Ziele zeitnah zu erreichen.
ModelWorks 2.2: An interactive simulation environment for personal computers and workstations
Fischlin, Andreas; Gyalistras, Dimitrios; Roth, Olivier; et al. (1994)
Systems Ecology Report
ModelWorks is a modelling and simulation environment in Modula-2 specifically designed to be run interactively on modern personal computers and workstations. It supports modular modelling by featuring a coupling mechanism between submodels and an unrestricted number of state variables, model parameters etc. up to the limits of the computer resources. It allows for the formulation of continuous time, discrete time, discrete event models, as well as the free mixing of all these formalisms. Not only does ModelWorks offer the simulationist a handy user interface to experiment interactively with model systems, but also allows the modeller to use ModelWorks' functions via a client interface in any other programming context.
Sensitivities of species compositions of the mixed forest in eastern Eurasian continent to climate change
Shao, Guofan; Yan, Xiaodong; Bugmann, Harald (2003)
Global and Planetary Change
Sensitivities of species compositions of the broadleaf–conifer mixed forest in eastern Eurasian continent to climate change were evaluated with three forest gap models, namely KOPIDE, NEWCOP, and ForClim. Testing sites are located on Changbai Mountain, the middle of the distribution range for the mixed forest. Six climate change scenarios characterizing increase in temperature and increase/decrease in precipitation were used to test the sensitivities of species composition to climate change. Simulations suggest that the mixed forest in temperate Monsoon Asia will face changes in species composition should climate change be almost certain. At the minimum level, the order of dominant species is going to change due to species competition, resulting in the increase in the proportion of broadleaved tree species in the forest. If air temperature increases and precipitation decreases, Pinus koraiensis is going to disappear from the forest and the mixed forest will become hardwood forest. This experiment supports some earlier predictions under other climate change scenarios.
Corrigendum to ’evaluating five forest models using multi-decadal inventory data from mountain forests’
Irauschek, Florian; Barka, Ivan; Bugmann, Harald; et al. (2022)
Ecological Modelling
Perspectives for forest modeling to improve the representation of drought-related tree mortality
Fischer, Rico; Anders, Tim; Bugmann, Harald; et al. (2025)
Journal für Kulturpflanzen
We are currently observing increased tree mortality following multi-year drought events, particularly in low mountain ranges like the Harz Mountains in Germany, where over 70% of spruce stands have died. Forest models are useful tools for understanding the long-term effects of climate change on forest ecosystems, yet struggle to reproduce this massive dieback. In this study, we simulated spruce mortality in the Harz Mountains using five forest models (ForClim, FORMIND, 3-PG-Hydro, LPJ-GUESS, GOTILWA+) of very different complexity. Estimated from the crown condition survey, spruce mortality in the Harz region increased to values above 30% during recent drought years (2018-2020). We found that most models failed to capture these observed high mortality rates, although they showed a clear signal in reduced forest productivity during drought. This discrepancy between the observed high spruce mortality and simulated forest dynamics highlights the need for improved modelling approaches to accurately represent tree mortality processes during and after extreme drought events. We discuss several perspectives for enhancing dynamic forest models by integrating missing processes prospectively. This includes novel (i) process-based drought mortality approaches, (ii) enhanced description of eco-physiological processes like plant hydraulics, (iii) data-driven and AI approaches, and (iv) improved representation of biotic damaging agents (i.e., insects and pathogens). Incorporating these perspectives into forest models has the potential to improve their ability to simulate forest dynamics under extreme drought, ultimately con tributing to the assessment of forest resilience and informing adaptive management strategies in Germany and beyond.
Inter- and transdisciplinary perspective on the integration of ecological processes into ecosystem services analysis in a mountain region
Huber, Robert; Briner, Simon; Bugmann, Harald; et al. (2014)
Ecological Processes
Introduction Ecosystem goods and services (EGS) studies have had little impact on policy processes and real-world decision-making due to limited understanding of the interactions and feedbacks among ecological, social and economic processes. Here we present an inter- and transdisciplinary analysis of global change impacts on EGS provision in a European mountain region. Our aim is to evaluate the projected influence of ecological, economic and social drivers on future EGS provision and to show possible ways to address the predominant limitations of EGS studies. Methods The integrated findings from ecological experiments, mechanistic models of landscape dynamics, socio-economic land-use models, policy analysis and transdisciplinary stakeholder interactions are presented consecutively. Four regionally downscaled global change scenarios, for a case study region near Visp, Switzerland (350 km2), were used to examine the impacts of climate and socio-economic changes on four ecosystem services, i.e., food provision, timber production, net greenhouse gas emissions and protection from natural hazards. Results Our simulation results reveal four key aspects that influence the future provision of mountain EGS. First, we show the high spatial and temporal heterogeneity of EGS provision even in a small case study region. Second, we find that climate change impacts are much more pronounced for forest EGS, while changes to agricultural EGS result primarily from shifts in economic conditions. Third, our modeling results reveal the complex trade-offs associated with the different scenarios. Fourth, simulations illustrate the importance of interactions between environmental shifts and economic decisions. We discuss our simulation results with respect to both existing policy networks and transdisciplinary stakeholder interactions. Conclusion We describe a framework based on experiments and observations that effectively supports the integration of ecological processes into an integrative modeling chain of EGS provision in mountain regions, the political decision-making process and also transdisciplinary stakeholder interactions.
Long-term biomass dynamics of temperate forests in Europe after cessation of management
Idoate-Lacasia, Jokin; Stillhard, Jonas; Portier, Jeanne; et al. (2024)
Forest Ecology and Management
Forests can contribute to climate change mitigation by sequestering carbon when management intensity is reduced. However, there is high uncertainty regarding biomass dynamics in temperate forests after the cessation of management. We used forest inventory data from an extensive network of 224 plots in 37 natural forest reserves (NFR) covering a wide environmental gradient with mean annual temperatures ranging from 1 to 10.4 °C and mean annual precipitation ranging from 901 to 2317 mm. Inventories had been conducted approximately every 10 years during the last 60 years. We used mixed effect models to (i) analyse biomass development, (ii) assess the role of time since the cessation of management (TSCM) and (iii) disentangle the environmental and forest structural drivers of biomass change. After the cessation of management and in the absence of high-severity natural disturbances, biomass accumulated gradually along a saturation curve. There were large differences in biomass among reserves and plots, with values ranging from 101 Mg ha−1 to 851.2 Mg ha−1, with a median of 362.1 Mg ha−1 (SD = 122.5 Mg ha−1). The biomass curve did not yet tend towards an equilibrium, most likely because the majority of the NFRs do not exceed 100 years of TSCM. Compared to higher elevations, forests at lower, warmer sites showed a larger total biomass and higher rates of biomass accumulation. We found a reduction by 148 Mg ha−1 of biomass per 1000 m of elevation gain. The strongest positive rate of change (>8 Mg ha−1 year−1) was found in forests with high basal area (>60 m2 ha−1) and medium to high levels of tree density (1500 to 2000 stems ha−1). Overall, most reserves have not reached a biomass equilibrium yet and continue to act as carbon sinks in tree biomass. This highlights the carbon sequestration capacity of forest reserves and their role as carbon pools.
Tree regeneration in models of forest dynamics – Suitability to assess climate change impacts on European forests
König, Louis A.; Mohren, Frits; Schelhaas, Mart-Jan; et al. (2022)
Forest Ecology and Management
Climate change impacts on Europe's forests are becoming visible much sooner than previously anticipated. The increase in natural disturbances leads to tree mortality and raises concerns about the forest's adaptive potential to sustain vital ecosystem services. In this context, the regeneration phase is crucial and comprises the largest potential to adapt to new environmental conditions with long lasting implications. Yet, forest regeneration is particularly susceptible to climatic changes due to the many directly climate-dependent processes, such as seed production and germination but also seedling and sapling development. Models of forest dynamics (MFDs) are essential to describe, understand and predict the effects of changing environmental and management factors on forest dynamics and subsequently on associated ecosystem services. We review a large variety of MFDs with regard to their representation and climate sensitivity of regeneration processes. Starting with a description of the underlying biological processes, we evaluate the various approaches taking into account specific model purposes, and provide recommendations for future developments. We distinguish between models based on ecological principles and models based on empirical relationships. We found an ample mix of regeneration modelling approaches tailored to different model purposes. We conclude that current approaches should be refined to adequately capture altered regeneration trends. Specifically, refinement is needed for MFDs that rely on ecological principals, as they suffer from knowledge gaps and underrepresented processes, thereby limiting their ability to accurately simulate forest regeneration under climate change. Global vegetation models are strongly constrained by their weak representation of vegetation structure and composition, and need to include more detail regarding structural complexity and functional diversity. Models focused on timber yield often rely on strong assumptions regarding the abundance and composition of the next tree generation, which may no longer hold true with changes in climate and forest management. With the increased utilization of natural regeneration as a source of forest renewal, more dynamic representations of tree regeneration are needed. Our review highlights the necessity to increase the data basis to close knowledge gaps and to enable the adequate incorporation and parameterization of the involved processes. This would allow to capture altered regeneration patterns and subsequent effects on forest structure, composition and, ultimately, forest functioning under climate change.
Sustainable regeneration in uneven-aged mixed deciduous forests managed by selection silviculture: the role of demographic structure
Brüllhardt, Martin; Rotach, Peter; Forrester, David I.; et al. (2022)
Forestry: An International Journal of Forest Research
Selection silviculture aims to create and maintain uneven-aged forests with a diameter at breast height (DBH) structure that is balanced at small spatial scales such that the stem number in each DBH class is high enough to replace the harvested and outgrowing trees over time by ingrowth from the next lower class. In these forests, natural regeneration of shade-tolerant species is at an advantage over shade-intolerant species. This is particularly pronounced in continuous-cover stands dominated by European beech (Fagus sylvatica L.), which develops its crown laterally as a reaction to release events. The conditions necessary to sustain a mixture with less shade-tolerant species, e.g. sycamore (Acer pseudoplatanus L.), have been little studied. Therefore, we explored growth patterns and stand structures in mixed deciduous forests with light availability quantified using vegetation height models. Harvesting and growth patterns were derived from inventory data of beech-dominated selection forests in Thuringia, Germany and long-term forest monitoring plot data from four stands in Switzerland. Based on these data, models of stem number distributions confirmed that stand basal area in deciduous forests dominated by beech should not exceed 21–25 m2 ha−1 to maintain a sustainable structure. In these forests, a total of ~90–120 stems per ha are needed in the ingrowth DBH class (DBH 8–11.9 cm) to ensure demographic sustainability. At canopy light transmittance <10 per cent, total stem number required in the thicket stage (DBH < 8 cm) is 800–1700 ha−1. Under such shady conditions, only a small proportion of sycamore was observed (<25 per cent) in the thicket stage, as the species is likely to require canopy gaps >400 m2 (gap diameter > 22.5 m) to recruit successfully. Selection silviculture with shade-intolerant species therefore requires much lower stocking volume and larger canopy openings created by group selection cutting than what is routinely applied in practical forest management using single-tree selection principles.
Magnitude and timing of density reduction are key for the resilience to severe drought in conifer-broadleaf mixed forests in Central Europe
Zamora- Pereira, Juan C.; Yousefpour, Rasoul; Cailleret, Maxime; et al. (2021)
Annals of Forest Science
Key message We applied a modified forest gap model (ForClim) to depict changes in stand water transpiration via density reduction as a forest adaptation strategy. This approach is the key to analyzing the ecological resilience to drought, stress-induced mortality, and economic efficiency of managed mixed forest stands in Central Europe. The results show that specific geographic conditions and forest composition define the optimal stand density of drought-resilient forests. Context Reducing stand density has been recognized as a valid strategy to increase forest resilience to drought. Moreover, to develop adaptive management strategies (AMS) under climate change, it is crucial to consider not only drought resilience but also the economic efficiency of alternative AMS proposed to alleviate drought effects. Aims To analyze how decreased inter-tree competition among overstorey trees affects stand vulnerability to drought and its expected yield. Methods We integrated experimental thinning data and historical responses to drought years in a climate-sensitive forest gap model, ForClim. We tested a business as usual (BAU) and three alternative AMS (“do-nothing,” low- and high-intensity overstorey removal) in mixed stands of Norway spruce (Picea abies), silver fir (Abies alba), and European beech (Fagus sylvatica) along an elevational gradient of 520–1020 m a.s.l. in Central Europe. Results High-intensity overstorey removal in mixed stands of all three species considerably increased forest volume growth resilience to drought and decreased stress-induced mortality by two-thirds vis à vis a “do-nothing” strategy. In sites including only conifer species, forest resilience was equally improved by high- and low-intensity overstorey removal compared to that in the BAU strategy. Regarding the timber economy, high-intensity overstorey removal resulted in a higher economic revenue of mixed stands (~ 22% higher net present value than other strategies) on the high-elevation sites (> 1000 m a.s.l.). Conclusion Modifying forest density and structure by overstorey removal is principally suitable to increase forest resilience to drought and improve its economic efficiency. The magnitude of the effect however depends on the geographical setting and forest composition.

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Harald Bugmann

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