Regional distibution of standing tree infestation by bark beetle (Ips typographus) following storm damage in Cantone Berne, Switzerland
2003
Gall, R. | Meier, F. (Eidgenoessische Forschungsanstalt WSL, Birmensdorf (Switzerland)) | Meier, A.L. | Forster, B.
After the storm Lothar on December 26, 1999, the forest service of Canton Berne recorded the center- coordinates and the corresponding amount of standing wood infested by spruce bark beetle (Ips typographus). Following the storm, 56% (in 2001) and 58% (in 2002) of these first infestations were identified in areas that were at least 200 m distant from any windthrown area. 33% (2001) and 38% (2002) were found at a distance of 500 m or more. Based on these key data, we computed spatial «hot spots» using GIS. We found geographically separated epidemics. Epidemics at higher elevations (above 1000 m a.s.l.) started later then epidemics at lower elevations. The forest service also recorded the center-coordinates and the corresponding amount of scattered windthrown wood, cleaned in the remaining stands after the storm. As for the beetle-infested trees, 50% of the scattered windthrown wood was found in areas that were at least 200 m and 31% at least 500 m distant from any windthrown area. In addition to beetle-infested wood, we found geographical «hot spots» of cleaned, scattered windthrown wood. The spatial distribution of these «hot spots» neatly corresponded with the spatial distribution of the «hot spots» of beetle-invested wood. Using the spatial distribution and the amount of cleaned scattered windthrown wood as an indicator of local storm intensity, we show the importance of reduced host tree resistance for the spatial occurrence of spruce bark beetle epidemics.
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