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Modeling bark beetle risks

 
 

Current climate change will affect the abiotic and biotic environment for trees and forests. Higher temperatures not only favor tree growth but also the development of pest species such as bark beetles. The most important pest in European coniferous forests is the spruce bark beetle (Ips typographus).
The projected shift of precipitation into wintertime will more often lead to drought stressed trees in summer which makes them susceptible to bark beetle attack. Possibly, storms will become more frequent or severe, providing the defenseless timber where bark beetle populations can build up.
Since spruce makes up 34 % of the growing stock in Switzerland and spruce forests often have protective function in the mountains, this pest insect will probably become even more important in the future.

 

Part I: Statistical modeling

The modeling relies on databases with infested timber volumes from the past two decades from various sites with different climatic, silvicultural and managerial conditions. Using statistical techniques such as point pattern analysis and mixed-effects models the most relevant driving factors of bark beetle outbreaks are analyzed. This modeling is carried out as a PhD study at the professorship of Forest Ecology at ETH Zurich.

Part II: Dynamic modeling

A temperature-driven phenology and population model is developed for this beetle. Furthermore, a predisposition model including site and tree parameters will simulate the susceptibility of spruce stands in Switzerland. This latter model combines statistical and dynamic model components. Our approach will allow developing a short- to long-term infestation risk model for different regions in Switzerland.

Part III: Online risk assessment tool

The risk model (Part II) is used to simulate the development of regional bark beetle populations, their swarming periods and their threats for regional spruce stands. This web tool uses current daily meteorological input and assesses the infestation risk based on simulated bark beetle population development and tree susceptibility. This information will be made available online to the practitioners, together with possible management options.

 

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