Increasing production value in Scots pine plantation through mixing with lodgepole pine

Mixing tree species could be a silviculture model that allows early harvest of short-rotation trees, while longer-rotation crop trees remain in the stand. We examined the effects on growth and tree characteristics in a planted experiment with lodgepole pine (LP) and elite-bred Scots pine (SP) in mixed (50/50) and monospecific plots in three different spacings (at 28 years of age after planting). The future development under different thinning regimes, including net present value for one rotation, was analyzed using the Heureka simulation software. As expected, LP had higher survival and initially more rapid growth than SP, with highest stand productivity and biomass production in LP monoculture during a rotation period as a result. However, intimate mixtures of SP and LP at the two widest spacings could give greater production and economic benefits, compared to SP in monoculture. It seems that elite-bred SP will differ in competitiveness against LP, depending on spacing for growth and some quality traits (branch and bark thickness, height of green crown). The findings support developing management systems for combining sparsely planted, and expensive, elite-bred SP in mixture with other trees that maintains high stem volume production and secures certain properties of trees and stands.