Seed production of Pinus sylvestris after release cutting

The effects of release cutting on cone, seed production, and seed quality were investigated in 1995-1996 among Scots pine (Pinus sylvestris L.) seed trees in central Sweden. The effects of diameter, height, crown length, and age of trees on cone production were also examined. Cone and seed production were about five times higher in seed trees that had been released for 4 or 5 years, compared with control trees in the unreleased forest. Seed trees released for less than 3 years had about the same level of cone production as the controls. After release, the number of cones increased more in the lower part of the tree crowns than in the uppermost 2 m. The mean 1000-seed weight, seed viability, and number of viable seeds per cone were not significantly different between released and unreleased trees. In 1996, there were about eight times more cones than in 1995, probably because summer temperatures were higher in 1994 than in 1993, the years when the respective flower buds were initiated. Within the investigated range of diameters, 250-430 mm at breast height, a 10-mm increase in diameter was correlated with a 10% increase in mean cone production. However, the variation in cone production between individual trees was considerable. Tree height, length of green crown, and tree age showed no significant correlations with cone production.