Data from the eighth National Foest Inventory (NFI) and annual surveys of the vitality of forests was used in this study. Abiotic damage (wind, snow, frost or edaphic factors) was present on 8.4% of forest land, on 1.68 million hectares during 1986-1994. It decreased the silvicltural quality of the stand in 5.2% of forest land. Abiotic damage was more frequent in northern than in southern Finland. Especially snow damage was important in northern Finland in Scots pine stands. The defoliation of conifers and various damage forms showed significant co-occurrence. Temporal and spatial patterns were evident in the occurrence and importance of differenet causal agents. Abiotic damage increased the defoliation in Picea abies more than in Pinus sylvestris, but in the latter species the damage was locally more severe. Sudden changes in defoliation were related to abiotic and biotic damage, and the effect of these injuries can be so remarkable that they mask the possible trend in defoliation. The analysis of these injuries may aid monitoring of forest condition by simplifying interpretation of national and regional patterns of forest damage.
