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Monitoring of forest damage within the National Forest Inventory (NFI) is undertaken using objectively collected data. The NFI has collected data about forest damage such as defoliation since 1984. National inventories of forest conditions are conducted over the whole of Europe since 1985 within the European cooperation programme ICP Forests.
The NFI is the only annual, objective and uniform inventory of forest damage in Swedish forests at both the national and regional scales. NFI collects forest damage data from both individual trees (12000 sample trees in 2009) and stands (600 sample plots in 2009). Defoliation is a key variable used in monitoring forest health. However, different types of damage (symptoms) and causes of damage also are recorded when it can be determined. The types of forest damage included are those which are most common or cause most damage to Sweden's forests. In total over 20 different types of forest damage are registered including fire, climatic damage, moose grazing, deer grazing, other cervidae grazers, beaver, small rodents, Tomicus sp., spruce bark beetle, other bark beetle, defoliators, resin top disease, decay or canker fungi, Scleroderris canker, needle cast fungi, needle rust fungi, pine twisting rust.
Monitoring of forest damage for 2009-2010 is part of the FutMon project (a project within EU Life+ programme). The project aims to create a harmonised forest damage monitoring network at national, regional and EU levels by linking established monitoring projects with new monitoring methods.
Defoliation in pine and spruce is presented annually in the NFI publication Skogsdata. Regular reporting of monitoring the forest condition has lead to a more balanced view of forest damage and the risk of substantial forest dieback. The proportion of trees with needle loss has increased significantly since the middle of the 1980's but has been stable for the last 10-15 years. In more recent years outbreaks of spruce bark beetle have been prominent in southern Sweden, this is in connection with the serve storms of 2005 and 2006. During 2009 a decline in the number of trees affected by spruce bark beetle was seen which indicates a decline in their population again. This situation can however change rapidly with new storms or long warm summers. Other significant regional outbreaks seen are for resintop disease in younger pines in northern Sweden and Chalara fraxinea fungus in ash in southern Sweden. Both these outbreaks have been followed up with extra regional surveys by SLU within the framework of their environmental monitoring and assessment.
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