Tree mortality after low-intensity prescribed fires in managed Pinus sylvestris stands in southern Finland
Abstract:Tree mortality, its causes, and the input of dead charred wood were studied in 11 managed 30-45-year-old Scots pine (Pinus sylvestris L.) stands 1 year after experimental low-intensity prescribed burnings in southern Finland. First, the relationship between fire-induced tree damage and several external variables, e.g. stand density, within-stand wind speed, open-air wind speed, the Finnish Forest Fire Index (FFI) and flame height, was studied. Secondly, the study examined which damage and morphological characteristics best predicted tree mortality. Tree mortality was very variable in the experimental plots, ranging from 0% to 48% on the basis of stem number and from 0% to 41% in terms of wood volume. The input of dead and charred wood decreased with stand age, being 19.4 m3 ha-1 in 30-35-year-old stands, but only 1.7 m3 ha-1 in 45-year-old stands. The input of dead wood was on average 10 m3 ha-1, representing less than 5% of the mean volume before the prescribed fire. The external variables that best explained fire-induced damage were within-stand wind speed, flame height and FFI. Tree mortality was best predicted by charred stem ratio with bark thickness, and by charred stem ratio with tree diameter. The results indicate that prescribed burning that is conducted downwind increases tree mortality and changes subsequent stand structure with increasing within-stand wind speed.
Document Type: Research Article
Publication date: 2007-01-01