Wind-induced successional changes in pristine boreal Picea abies forest stands: Evidence from long-term permanent plot records

Abstract

We examined the long-term effects of low-to-moderate severity windthrow in 1983 and 1985-1986 on the structure of 11 pristine boreal Norway spruce forest stands. The windthrow events caused varying damage among the studied stands, reducing tree density by 0.6-21.6 per cent and basal area by 0.2-10.4 per cent. The severity increased in proportion to decrease of uneven agedness of spruce and increase of productivity in the stands with share of spruce ≥90 per cent. The mixed stands where tree species composition was changing in favour of spruce dominance were less damaged. Following a disturbance, mortality did not differ among tree species and was influenced by tree size, with probability of mortality increasing with size. In the 20 years after windthrow, growing stock decreased, and stem density and regeneration both increased along with increased wind damage. Successional dynamics of the studied stands depended on the interplay between windthrow severity and stand attributes: age structure, tree species composition and site productivity. Four types of stands have been identified based on decreasing susceptibility to windthrow: even-aged productive spruce stands, uneven-aged low-to-medium productivity spruce stands, all-aged low-productivity spruce stands and even-aged productive mixed stands. © Institute of Chartered Foresters, 2008. All rights reserved.