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Site specific variables

The GLZ below with “site-specific data in Östergötland” showed that pine logs above 25 cm in diameter did not explain presence-absence of the beetle at all. The same is also valid for crown cover less than 25 % and crown cover between 25-50 %. However, there is a strong, highly significant, correlation between presence-absence of T. depsarium and presumed exit holes regardless of their age.

A negative binomial GLZ for the site-specific data in Östergötland County. Pine logs refers to all logs of Scots pine that were not completely decayed, and crown cover was subjectively estimated as an average of the tree canopy cover. Crown cover above 50 % was included in the intercept and thus not shown separately in the table. All parameters were measured within approximately 30 m from each trap.

Explanatory variables

Estimate

SE

z value

p-value

Pine logs, above ø 25 cm

0.085

0.165

0.514

0.607

Pine logs, with exit holes

1.069

0.315

3.394

<0.001

Crown cover < 25 % (compared to crown cover above 50 %)

-1.983

1.839

-1.079

0.281

Crown cover 25-50 % (compared to crown cover above 50 %)

-0.786

0.940

-0.836

0.403
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Last updated: 05/11/15