Extent of abiotic damage and its relation to defoliation of conifers in Finland

Data from the eighth National Forest 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 mill ion hectares during 1986-1994. It decreased the silvicultural quality of th e stand in 5.2% of forest land. Abiotic damage was more frequent in norther n than in southern Finland. Especially snow damage was important in norther n 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 an d importance of different causal agents. Abiotic damage increased the defol iation in Picea abies more than in Pinus sylvestris, but in the latter spec ies the damage was locally more severe. Sudden changes in defoliation were related to abiotic and biotic damage, an d the effect of these injuries can be so remarkable that they mask the poss ible trend in defoliation. The analysis of these injuries may aid monitorin g of forest condition by simplifying interpretation of national and regiona l patterns of forest damage. (C) 2000 Elsevier Science B.V. All rights rese rved.