Target-tailored forest damage inventories (TFDI) aiming at providing data for operational decision making at local level and linked to specific damage events, are undertaken by the Swedish University of Agricultural Sciences.
An annual monitoring of the most important sources of forest damage is carried out by the Swedish National Forest inventory (NFI). The Swedish NFI contributes data to, for example, the European cooperation programme ICP Forests and to Forest Europe.
Although the Swedish NFI is an objective and uniform inventory of forest damage in Swedish forests at national and regional scales, less common or less widespread occurrences of forests pests and pathogens are difficult to survey solely through large-scale monitoring programmes. There is a need for complementary tailored inventories to facilitate timely delivery of relevant information. TDFIs are developed to give a rapid response to requested information on specific damage outbreaks. The TDFIs are carried out in limited and concentrated samples, with flexible but robust methods and design.
Since 2007 inventories have been carried out to assess the damage caused by resin top disease (Cronartium flaccidum), ash tree disease (Chalara fraxinea) and bark beetle attack (Ips typographus; Polygraphus poligraphus) on Norway spruce. During 2015 a repeated inventory of bark beetle attacks in older spruce forests is carried out in the county of Västernorrland and the eastern part of the county of Jämtland.
The results from the inventory in 2016 show that in September there remain nearly 200 000 m³ growing forest killed by European spruce barkbeetle (Ips typographus). The estimated volume is lower than last year, but given the uncertainty of the estimate, we cannot say the volume used by barkbeetles has decreased but has remained at about the same level as last year. The volume spruce used by the four-eyed spruce bark beetle (Polygraphus sp.) is similar to last year’s low levels.
The inventory showed a large amount of new wind-felled trees available for barkbeetles, in total 300 000 m3 raw wind-felled. The largest volumes were found in Medelpad. The newly wind-felled trees where most commonly found in low number near stand edges. Only a low proportion of the wind-felled trees were utilized by spruce barkbeetles.
Damage by barkbeetles on spruce is judged to continue in 2017. Although the level of utilization is uncertain and dependent on the population growth of barkbeatles which is determined by the amount of windfelled trees and the weather. Much points to similar volumes for 2017 and also predominantly in Medelpad.