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06:58
Isolation, Behavioral Identification, and Pathogenicity Assessment of Entomopathogenic Fungi from a Forest Wood Borer
Published on: September 29, 2023
A resource-depletion model of forest insect outbreaks
Bjørn Okland1, Ottar N Bjørnstad
1Norwegian Forest Research Institute, As, Norway. bjorn.okland@skogforsk.no
Ecology
|April 28, 2006
Summary
This study models bark beetle population dynamics, revealing how resource accumulation and depletion, triggered by wind disturbances, cause transitions between non-epidemic and epidemic phases. The model accurately predicts outbreak patterns observed in spruce bark beetles.
Area of Science:
- Ecology
- Population Dynamics
- Mathematical Modeling
Background:
- Ecological interactions often exhibit threshold dynamics, influencing transitions between different population behaviors.
- Understanding these transitions is crucial for predicting population outbreaks, such as those involving bark beetles.
Purpose of the Study:
- To develop and analyze a threshold model for bark beetle population dynamics.
- To explain the alternation between non-epidemic and epidemic phases based on resource dynamics and disturbance events.
- To parameterize and validate the model using data from spruce bark beetle (Ips typographus) populations in Scandinavia.
Main Methods:
- Development of a threshold model incorporating resource accumulation and depletion.
- Modeling disturbance events (e.g., windthrow) as triggers for regime shifts.
- Analysis of model predictions against historical data of Ips typographus population dynamics.
Main Results:
- The model successfully captures the alternating non-epidemic and epidemic behaviors of bark beetle populations.
- Predicted outbreak lengths align with observed data, while inter-outbreak waiting times show high variability.
- Thresholded resource-depletion dynamics lead to significant variation in periodicity across model simulations.
Conclusions:
- The developed threshold model provides a robust framework for understanding bark beetle outbreak dynamics.
- Windfall events are key drivers of transitions between population regimes.
- While outbreak timing is partly predictable with known disturbances, inter-outbreak periods exhibit low predictability due to inherent variability.
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